Principles of radiotherapy in head

& neck surgery

INTRODUCTION • Head and neck cancer represents the 6th most

common malignancy & accounts for approx. 6% of new cancer cases annually worldwide.

• Treating HNC is often complex• Radiotherapy – definitive, adjuvant and recurrent

disease settings of HNC.• Innovations will continue to improve outcomes by

minimizing toxicity and maximizing organ preservation such as salivation, speech, and swallowing, that are key factors in determining quality of life after treatment through the use of highly conformal techniques.

• The first patient was treated with radiation in 1896, two months after the discovery of the X-ray.

• Back then, both doctors and non-physicians treated cancer patients with radiation.

• Rapid technology advances began in the early 1950s with cobalt units followed by linear accelerators a few years later.

• Recent technology advances have made radiation more effective and precise.

THE BRIEF HISTROY ABOUT RT..

What is Radiotherapy ?....• It is the medical use of ionizing radiation, generally as part of cancer

treatment to control or kill malignant cells by destroying reproductive integrity of the malignant cells.

What is radiation?....• Radiation refers to the propagation of energy through space or a

medium.• If the radiant energy is carried off by a particle that has rest mass, the

radiation is particulate or corpuscular radiation; e.g.-electrons, β-particles protons, neutrons, & heavy charged particles.

• Electromagnetic radiation is a packet of energy (a photon) that propagates through space.

• It has no rest mass and propagates at the speed of light.• This discrete energy (E) is related to its associated frequency (v) as

follows: E = hv where h is Planck’s constant, with a value of 6.626 × 1034 joulesecond (J-s).

Types of Radiation

1] Photon beam (X-ray, Gama –ray) 2] Electron beam 3] Particle radiation (Neutron ,proton, pions)

X ray photons• X rays are produced when electrons decelerate.( hit against a target).• Poor penetration.• Effective depth – 1cm.• Skin tumours.• Exception-Megavoltage beams.

• Gamma rays are emmited by radioactive isotopes from excited nucleus itself.

• Oldest – Radium., Caesium & cobalt.• Cobalt is more widely used : Deep penetration. Low cost and

maintainance.• Disadvantages: Not precise

Gamma rays are more harm to human body than the X- rays.Gamma rays have shorter wavelengths than the X-rays.

Gamma rays

Electron beam• The subject is directly bombarded with electrons. Property :• The depth of penetration of electron beam depends

on energy level of electron.• Hence the beam has a depth limit. Uses :a) In head and neck Ca, where spinal cord is to be spared.b) Primary skin tumour of pinna & cartilage of nose.c) Anterior placed tumour of frontal & ethmoidal sinus

( electron beam for ant field, supervoltage for lateral field)

Proton beam• Heavy positive charged particles.• Advantages:a) Depth dose distribution. Small entry & exit point.b) Maximum dose is depth related- Bragg peak.c) DOES NOT DEPEND ON TISSUE O2.• Application:a) Chondosarcoma of skull base.b) Chondroma of clivus.

• Mechanism : Heavy energy machines produce heavy uncharged paticles.

• Advantage : Cells need to be oxygenated to only 1.5 times(compared to 3 times)

• Uses : Parotid gland tumour.

Neutrons

LINEAR ACCELRATOR (LINAC) a) It is a type of particle accelerator that greatly increases the

kinetic energy of charged subatomic particles or ions by subjecting the charged particles to a series of oscillating electric potentials along a linear beamline.

b) A stream of electrons produced from a filament in an electrically charged field is accelerated through a series of wave guides in conjunction with a radiofrequency pulse to within a fraction of the speed of light.

c) This electron beam can itself be used for treatment or can impact on a target to produce a photon beam of maximum energy between 4 and 20MV according to the design and calibration of the machine.

d) Electron beams are useful for treating superficial lesions because the maximum of dose deposition occurs near the surface.

• USE:- They generate X-rays and high energy electrons for medicinal purposes in radiation therapy, serve as particle injectors for higher-energy accelerators, & are used directly to achieve the highest kinetic energy for light particles (electrons and positrons) for particle physics.

• LIMITATIONS:- a) The device length limits the locations where one may be placed. b)A great number of driver devices and their associated power supplies are required, increasing the construction and maintenance expense of this portion.

Radiotherapy can be given as• External radiotherapy (EBRT or XRT or

Teletherapy)• Internal radiotherapy (Brachytherapy or sealed

source radiation therapy, curietherapy or endocurietherapy)

1] Interstitial implant 2] Intracavitary implanto Systemic radioisotope therapy (or unsealed source

radiotherapy)

Used alone or in combination with other therapies such as

surgery, EBRT & chemotherapy

RADIOBIOLOGY

A] Teletherapy (External Beam Radiation Therapy)• Most widely used • Often uses photon beams.• Used to treat large areas of the body• Usually given daily over several weeks.

• Therapeutic radiation is delivered by two main methods: (1) Electromagnetic radiation (photons) X-rays and gamma rays (2) Particulate radiation in the form of electrons, neutrons, and protons. Ionizing radiation deposits energy at a constant rate as it travels through matter, defined as linear energy transfer (LET).

• “ 4 Rs” principle of RT: - 1) Repair of sublethal damage; 2) Redistribution across the cell cycle; 3) Repopulation; & 4) Reoxygenation.

• Each unit of absorbed radiation is called one gray (Gy) Equivalent to one joule per kilogram of tissue.

• One Gy = 100 centiGy (cGy) or 100 rads. (The rad [radiation absorbed dose] is the previous name for the absorbed dose unit.)

• The relative biological effectiveness (RBE) is a measure of the ability of radiation with different LETs to produce the same biological effect under the same conditions.

• A 250-kV x-ray beam generally is used as the reference source for comparison.

• Beams of 4–6MV are most appropriate for the treatment of HNC.

• The radiation is artificially produced by a LINEAR ACCELERATOR.

• The energy of up to 30MeV & more can be 600-fold higher than this of conventional x-ray machine.

Procedure:-• Position:- Supine position MC It is imp to achieve same alignment

each day.• Simulation:- It is a T/t machine capable of planning a patient for RT,

but can’t give T/t i.e. process in which one tries to copy a procedure.• Beam shaping:- Rectangular beams converted into irregular shapes to

shield normal tissue.• Contour:- The method of transferring the patient across sectional

outline onto paper using wire, plastic, or CT scans.• Beam characteristic:- Photon beams are routinely specified by % dose

depth Since photon energy α surface dose • Portals:- Lateral parallel opposite portals are used to treat HNC.• T/t volume:- It includes the tumor volume + 2-3 cm of surrounding

tissues (target volume) + an adequete margin of tissue to include microscopic extention of the tumor.

• Dosimetry:- After the patient is simulated & the T/t portals are fixed, the dose calculations is made using the T/t planning system.

• MECHANISM :- A stream of electrons produced from a filament in an electrically charged field is accelerated through a series of wave guides in conjunction with a radiofrequency pulse to within a fraction of the speed of light. This electron beam can itself be used for treatment or can impact on a target to produce a photon beam of maximum energy between 4 and 20MV according to the design and calibration of the machine.

• Usually given 5 days a week, for about 5 to 8 weeks. • Electron beams can treat to depths of up to 5 cm or so according to the beam energy used; a 4–6MeV beam would be mostly used to treat skin tumours & a beam of approx. 12MeV to treat neck nodes

Fractionation• It is a technique of administering radiation therapy

in fractions instead of in a single high dose.• Principle :- High total dose can be delivered to the

tumor while sparing adjacent normal tissue.• Conventional schedule 80 to 200 cGy per fraction,

one fraction per day, 5 days per week for 6 to 7 weeks for a total dosage of 6500 to 7000 cGy.

• It depends on (1) Tissue response (2) Duration of treatment (3) Fraction size & number.

Effect consists of four independent processes : (a) Repair of sublethal cellular damage (b) Redistribution of tumor cells from radio-resistant (late S phase) into radio-sensitive (G2-M) portions of the cell cycle (c) Reoxygenation of the hypoxic (and hence radio resistant) portions of tumors (d) migration of normal cells into irradiated areas to repopulate these normal tissues with healthy cells.

• Goal To improve the therapeutic ratio by maximizing the tumoricidal effect and minimizing acute & late toxicities while using readily available low LET radiation.

• Three major categories of altered fractionation schemes are :- 1) Hyperfractionation, 2) Accelerated fractionation, & 3) Hypofractionation

1) Hyperfractionation :- Improves the therapeutic ratio primarily through(1) redistribution of tumor cells into more radiosensitive phases as a result of multiple fractions (2) differential sparing of late-responding normal tissues because of a decrease in the size of the dose per fraction.• Involves use of smaller fractions (i.e.<1.8Gy). • The use of smaller fractions Reduce the risk of late

damage for a given total dose, but the increase in the overall treatment time tends to reduce thE effectiveness of treatment,

• Accelerated fractionations :- The overall treatment time has been shortened.• A greater benefit obtained from combining acceleration with

hyperfractionation & treating two or three times each day.• It reduced risk of normal tissue damage with the benefits of

completing treatment in a shorter overall time.• Min. 6 hr interval between fractions is preferable repair of

sublethal damage.• A good e.g. is the CHART regime (continuous

hyperfractionated accelerated radiotherapy) RT at 1.5Gy per fraction is given 3 times daily & continuously for 12 days to a total dose of 54Gy (i.e. without a weekend break).

• Hypofractionation :- It is the administration of high dose per fraction (HDPF) radiation, in which only one or two fractions are given per week.

• Mainly used for radioresistant tumors.• It delivers higher doses of radiation per fraction

(600 cGy twice a week or 800 cGy once weekly)• Aim To overcome the reparative capacity of the

tumor cells by increasing the damage per fraction.SPLIT COURSE

• To prevent mucosal reaction, the radiotherapy course is divided in two halves, seperated by a gap of about 2 weeks.

• This allows the mucosal reaction to settle down

B] Brachytherapy (Internal radiation therapy)• The radiation sources are placed either adjacent to the surface of a

tumor mass or bed or inside the tumor itself.• Types :-a) Interstitial & b)Intra cavitary radiation• Agents :-a) Permanent Radium, Caesium, Iridium b) Temporary Radon, Gold, Iodine.• Methods of implantation:- a) Radium & cesium In needle,

b) Iridium In wire form, c) Iodine & Gold As seeds & grains.Iridium (Ir-192) wire > I-125 is the source of choice in HNC.

• Travels only a short distance to the desired target region, & its dose intensity falls off rapidly with distance according to the inverse square law.

• It permits sharp decrease in the dosage to the surrounding normal tissue Radiation dose is delivered to a relatively small, well-defined volume.

Low-dose rate (LDR) brachytherapy• Delivers continuous radiation @ 40-200 cGy/hr.• Likened to fractionated radiation with an infinite

number of small individual doses Allows redistribution of the tumor cell within the cell cycle, resulting in a greater % of malignant cells in the more radiosensitive phase.

• Allows time for reoxygenation of hypoxic cells during the treatment & thus results in an increase in their radiosensitivity

• Favors late-responding normal tissues relative to tumors, and repopulation does occur, but unfortunately , it benefits tumors more than normal tissues.

High-dose rate (HDR) brachytherapy• Delivers radiation excess of 1200 cGy per hour.• Have a higher risk for complications involving late

responding tissues.• Therefore, it needs to be well fractionated to deliver only 1-

3 fractions/week.Advantage of brachytherapy

a) It provides a means of delivering a high dose to a small area & as the radiation dose falls off rapidly outside the treatment volume, the dose to adjacent normal tissues can be kept within acceptable limits

b) Head and neck tumor sites commonly considered suitable for brachytherapy include the lip, floor of mouth, oral tongue, base of tongue, buccal mucosa, tonsillar region, nasopharynx, skull base, and neck.

a) Radiation at a distance from the source is min. normal tissue damage is min.

b) Localised mucositis, filming on contralateral side in case of parotid tumour is spared.

c) No Dryness of mouth.d) Moist mouth & flexible tongue can be achieved in

early Ca tongue.e) Used in cases of recurrance. Limitations of brachytherapyf) Need for adequate radiation protection and that the

technique is not appropriate where wider field irradiation is required, for example to cover adjacent nodal areas.

Limitations of brachytherapy g) Need for adequate radiation protection and that the

technique is not appropriate where wider field irradiation is required, for example to cover adjacent nodal areas.

IMMOBILISATIONa) Accuracy of delivery of EBRT is dependent on maintaining a

stable target volume.b) Individually moulded thermoplastic shells covering the head and

neck area are used to immobilize patients.c) These are located onto a fixed frame on the treatment couch.d) Reference marks are placed on the outside of the shell, avoiding

the need for any skin marks or tattoos.e) The areas around the eyes and mouth are cut out for patient

comfort and the part of the lower neck field to reduce the surface dose.

f) Standard techniques allow T/t accuracy to within approx 3mm.g) More rigid frames providing accuracy closer to 1–2mm have

been developedfor stereotactic radiotherapy & IMRT) where movement can be more critical to dose delivery.

VOLUMES• GTV = Gross tumor volume (gross disease) We can identify disease

extent• CTV = Clinical target volume (subclinical disease) we can predict

subclinical disease extent• PTV = planning target volume (setup/treatment uncertainty) we

know our precision and accurac• IM = Internal margin variations in size, shape, & position of the

CTV in reference to the patient's coordinate system using anatomical reference points

• ITV = Internal target volume = CTV + IMAlternative is an IGTV that can then be expanded for CTV margins

• SM = Set‐up margin Uncertainties in pt.beam positioning in reference to the T/t machine coordinate system.

Actual area of delivery of radiation

PTV = GTV + CTV + Margin

PTV Pale blue area

Planning target volume = Gross Tumour Volume + Clinical target volume + a margin around it to account for the

systematic and random errors plus physiological organ changes that occur during the treatment planning and

delivery process.

Mechanism of action • Rates of cellular proliferation of most tumours exceed that

of most normal tissues.• In HNC, Potential doubling times (Tpot) range from 2 to 67

days (median 6.4 days).• Cancer cells Generally less differentiated, More stem cell-

like, Reproduce more than most healthy differentiated cells, & Have a diminished ability to repair sub-lethal damage.

• Cells are most sensitive to radiation-induced damage during the G2 and M phases of the cycle.

• After exposure to ionizing radiation, surviving cells undergo partial synchronization as a consequence of G2 arrest, which delays cells in a more radiosensitive phase.

• Malignant cells within the center of bulky tumors are relatively hypoxic and therefore are relatively radioresistant by virtue of the fact that they are more than 150 μm away from a blood vessel, which is the maximum diffusing distance of oxygen from a capillary

• Radiation therapy works by damaging the DNA of cancerous cells.

• There is Direct damage to DNA of cancerous cells.• Single-strand DNA damage is then passed on through cell

division; damage to the cancer cells' DNA accumulates, causing them to die or reproduce more slowly.

• Generally, it takes up to 4–6 weeks after the end of a course of radiotherapy for maximum tumour response to become evident.

Basis of radiation energy• The energy of diagnostic and therapeutic gamma- and X-rays is

expressed in kilovolts or megavolts (kV or MV).• Energy of therapeutic electrons –Megaelectronvolts (MeV).• 1 MV beam will produce photons of no more than about 1 MeV.• X-rays are produced when electrons are accelerated to a high energy• The mean X-ray energy is only about 1/3 of the maximum energy.• Beam quality and hardness may be improved by special filters,

which improve the homogeneity of the X-ray spectrum.• Bragg peak - The dose increases while the particle penetrates the

tissue, up to a maximum (the Bragg peak) that occurs near the end of the particle's range & it then drops to

(almost) zero. • The advantage of this energy deposition

profile is that less energy is deposited into the healthy tissue surrounding target tissue.

Some examples of X-ray energies used in medicine

• Diagnostic X-rays – 20 to 150 kV• Superficial X-rays – 50 to 200 kV• Orthovoltage X-rays – 200 to 500 kV• Supervoltage X-rays – 500 to 1000 kV• Megavoltage X-rays – 1 to 25 MV

Megavoltage X-rays are by far most common in radiotherapy. Orthovoltage X-rays do have

limited applications, and the other energy ranges are not typically used clinically

A] Orthovoltage radiotherapy: 200-500 kv• Maximum dose is deposited at the skin surface and

dose falls to 90% at ~2 cm of depth in the tissue.• Primarily suited for treatment of superficial tumors

that do not involve adjacent bone. • Applications include primarily skin tumors, and

nasal cavity tumors after cytoreductive surgery. relatively short source-to-skin distance (usually 50 cm) limiting the size of the treatment field

• Bone, cartilage necrosis is common Osteoradio necrosis, laryngeal cartilage necrosis.

2] Supervoltage : 500 kV to 1 MV Most frequently used in head and neck cancers Greater penetration and skin sparing effect.3] Megavoltage : Most frequently used.(1-4 MV)• Machines – linnear accelerator. Advantages :-a) Greater penetration.b) Absorbtion does not depend on atomic no.c) Forward scatter effect - Incident skin recieves

smaller dose.d) Homogenous beam distribution: no damage to

bone and cartilage.•

• Brass Filters – thick end absorbs more radiation. So used to turn the main axsis of the beam.

• 4 Mev and 10 MeV- Head and neck. Disadvantages :- a) Long distance machinb) Beam does not arise from a point.- penumbra-

gamma rays

Special ways to deliver external beam radiation

• Three-dimensional conformal radiation therapy (3D-CRT)

• Intensity modulated radiation therapy (IMRT)• Image-guided radiation therapy (IGRT)• Intensity modulated proton therapy (IMPT)• Stereotactic radiosurgery (SRS) and

fractionated stereotactic radiotherapy• Intraoperative radiation therapy (IORT) • Electromagnetic-guided radiation therapy

Three-dimensional conformal radiation therapy (3D-CRT)

• This technique uses imaging scan pictures and special computers to map the location of a tumor very precisely in 3 dimensions.

• The patient is fitted with a plastic mold or cast to keep the body part still during treatment.

• The radiation beams are matched to the shape of the tumor and delivered to the tumor from several directions.

• Careful aiming of the radiation beam may help reduce radiation damage to normal tissues and better fight the cancer by increasing the radiation dose to the tumor.

• Photon beams or particles (like protons) can be used in this way.• Drawback :- It can be hard to see the full extent of some tumors

on imaging tests, & any part not seen will not get treated with this therapy.

3D – CRT Images.

AXIAL VIEW SAGGITAL VIEW

Intensity-Modulated Radiation Therapy. (IMRT) • High-precision radiotherapy that uses computer-controlled linear

accelerators to deliver precise radiation doses to a malignant tumor or specific areas within the tumor.

• The intensity (strength) of the beams can be adjusted. This gives even more control over the dose, decreasing the radiation reaching sensitive normal tissues while delivering higher doses to the tumor

• A variation of IMRT is called volumetric modulated arc therapy. It uses a machine (called RapidArc®).

• It delivers the radiation quickly as it rotates once around the body. This allows each treatment to be given over just a few minutes. Although this can be more convenient for the patient, it’s not yet clear if it’s more effective than regular IMRT.

• A special cast or mold may be made to keep the body in place during treatment. Again, miscalculations in tumor size and exact location can mean missed areas will not get treated.

• Because IMRT uses a higher total dose of radiation, it may slightly increase the risk of second cancers later on.

• The drawback with FPMS is that optimization is done using manual iteration (trial and error) by the planning dosimetrist or physicist.

• With proper placement and weighting of beam angles, the number of iterations can be significantly reduced.

• Treatment with IMRT is slightly longer that with 3DCRT, but generally produces

• IMRT allows for the radiation dose to conform more precisely to the three-dimensional (3-D) shape of the tumor by modulating—or controlling—the intensity of the radiation beam in multiple small volumes.

• IMRT also improves the ability to conform the treatment volume to concave tumor shapes for example when the tumor is wrapped around a vulnerable structure such as the spinal cord or a major organ or blood vessel.

• IMRT also allows higher radiation doses to be focused to regions within the tumor while minimizing the dose to surrounding normal critical structures.

Preoperative Radiation Therapy• Dose of approx. 5000 cGy using conventional fractionation of 180 -

200 cGy / fraction is delivered 5 days / week for a total of up to 5 weeks.

• A 4-6 week period of rest is allowed for the patient to recover and the acute inflammatory reaction to subside before surgical excision.

Advantages• No treatment-related delay in surgery, limitations to the dose of

radiation, local and/or regional control • Allows complete surgical, HP & biological evaluation of the tumor

& LN. • Reduces tumour bulk, Oxygenation to tissues adequate.• Lymphatics are blocked by radiation so dissemination of tumour is

less.• Eliminates microscopic spread beyond palpable tumour mass

Disadvantagesa) Potential for delay in initiation of radiation therapy

if recovery from surgery is complicated flap necrosis or fistula formation or other wound problems

b) Scarring and vascular modifications from surgery may decrease tissue

c) Oxygenation and thus adversely affect radiation tumor cell kill.

d) Reduces vitality of tissues thus delays healing.

Postoperative Radiation Therapy• It is indicated when the estimated risk of local-regional recurrence

of disease is <=20%.• It should be initiated within 6 weeks of surgery to maximize the

benefits.• PORT dose for the primary tumor site &/or the neck region using

conventional fractionation consists of a 180 - 200 cGy fraction/day administered 5 days/wk up to a total dose of 6000 - 6300 cGy for high-risk areas & 5000 - 5400 cGy for elective nodal irradiation.

Indicationsa) Primary tumor factors :-Locally advanced T3 or T4 lesions, High-

grade histology, Presence of perineural or vascular invasion, Concern with respect to the adequacy of the procedure irrespective of the histological status of the surgical margins, Infiltrating rather than pushing borders of the tumor, Positive or close margins of surgical resection

a) Cervical nodal factors :- N stage higher than N1, Surgical contamination (e.g., excisional or incisional biopsy) prior to definitive surgery, Presence of gross extracapsular extension

Advantagesb) No treatment-related delay in surgery ,No limitations to radiation.c) Allows complete surgical, histopathological and biological

evaluation of the tumor and lymph nodesd) Residual microscopic disease can be effectively sterilized with

improved local and/or regional controle) More effective bulk of mass removed, post op healing betterf) Extent of tumour is known so radiation given to suspected area.Disadvantagesg) Potential for delay in initiation of radiation therapy if recovery

from surgery is complicated by fistula or other wound problemsh) Scarring & vascular modifications from surgery may decrease

tissue oxygenation & adversely affect radiation tumor cell kill.

Sandwich radiation therapy• Preoperative RT followed by surgery, which is

followed by postoperative RT.• A type of split course irradiation with a break in the

irradiation during which the surgery is performed.• The major objective of this sequence is the

opportunity it provides for a rapid regeneration of carcinoma during postop. recorative phase.

Reirradiation• It is considered if adequate salvage surgery is not feasible or

if concerns exist about margins after salvage surgery.• The important factors that have an impact on the feasibility

of reirradiation are (1) previous dose, volume, & tumor response, (2) tolerance of normal tissues to additional radiation, (3) radiation dose to adjacent vital structures, (4) the feasibility of delivering a tumoricidal additional dose of radiation, & (5) the need for bringing in nonirradiated vascularized tissue to protect vital structures.

• One frequently encountered situation is recurrent metastatic disease in a previously irradiated neck requiring salvage neck dissection.

• In this setting, tumor invasion of the carotid sheath is quite common.

RADICAL & PALLIATIVE RADIOTHERAPY• Radical RT:- Used for highly radiosensitive tumors such as sq. cell ca.

of the nasopharynx & oropharynx, early-staged ca.larynx, Basal cell carcinomas & superficial sq. cell ca of skin.

• In most instances, therapeutic doses of radiation > 6000 cGy and may be >7000 cGy depending on them site, histology, and stage of the tumor.

• Palliative RT:- Rt is an effective means of palliation of symptoms in patients with incurable HNC.

• USES:- 1) Control of pain due to tumor shrinkage or necrosis by relieving pressure on neural structures. 2) Lesions that obstruct the airway can be palliated effectively when tumor shrinkage is achieved with RT. 3) Control of hemorrhage from bleeding tumors

• Dose in the range of 4000 cGy usually is used for palliation.

Radical RT should commence within 4 weeks of the decision to treat & Palliative RT within 2 weeks.

FACTORS INFLUENCING THE EFFECTIVENESSOF RADIOTHERAPY

• Total dose.• Concurrent treatment with chemotherapy or biological

agents• Delays in starting treatment Has a relative risk of

locoregional recurrence of 1.15/month of delay for radiotherapy as primary treatment & 1.28 for postop T/t.

• Treatment interruptions Local control falls by 1.4 % per extra day when it is prolonged.

• Anaemia Hb should be>=12g/dL. Loss of local control of disease by approx. 10–15 % for a 2 g/dL fall in Hb.

• Smoking Reduces T/t effectiveness by inhaled CO displacing oxygen from Hb.

HNC : a) Laryngeal cancers.Immobilization:- For all ca. larynx, patients should be in the supine position with the cervical spine straight.

GLOTTIC CANCERa) Most stage T1/T2,N0 –radical radiotherapy with surgery reserved for

salvage after radiotherapy failsb) Local control rate- T1-90%, T2-70 -80%c) Given through irradiation as it preserves natural voice and avoids

tracheostomyFor T1,Ant- Field border should be in air,Post-Anterior part of vertebral bodySup- Lower border of hyoid boneInf- lower border of cricoid cartilage

Radiotherapy for a T1/T2 N0 carcinoma of theglottis.

• FOR T2- depends upon its supraglottic and subglottic extension

• Elective nodal irradiation is not needed as there is extremely low incedence of cervical metastasis

• Dose depending upon field size by 5 fraction/weeka) -<36 cm2- 50 Gy in 16 fraction b) 36 -42 cm2-55 Gy in 20 fractionc) >42 cm 2 -64-66 Gy in 2Gy per fraction

SUPRAGLOTTIC TUMOURS• For T1/T2,N0 supraglottic tumor Rich in lymphaticshigher LN

metastasis rate Requires elective nodal irradiation• Achieved through two-phase technique• Phase I= Primary tumour, whole larynx, pre epiglottic space &

cervical lymph nodes b/l in levels Ib,II,III ant spinal cord.• Phase II= primary tumour & larynx• Total dose = 66–70Gy in 2Gy/fraction, treating daily, 5 fractions a

week, to macroscopic disease & 44–50Gy in 2Gy/fraction, treating daily, 5 fractions a week, to microscopic disease;

Subglottic tumors• Subglottic tumours are rare present with locally advanced disease

requiring surgery followed by adjuvant RT. However, for patients with early-stage disease,

• Incidence of cervical LN metastases is rare, involvement of paratracheal nodes is estimated at 50 per cent, & treated electively.

• The radiation portal should extend from the top of the thyroid cartilage sup. to the mid-trachea inf.

• This requires the use of either an ant oblique beam arrangement or a coronal tech.in order that good coverage of the inf. most area is achieved.• Dose prescription:- total dose is 66–70Gy in 2Gy per fraction, treating daily,5 fractions a wk, to macroscopic disease & 44–50Gy in 2Gy per fraction, treating daily, 5 fractions a wk, to microscopic disease

Oropharygeal tumours (tonsil, tongue base, soft patate, PPW) • Small T1/T2,N0 total dose is 66–70Gy in 2Gy/fraction, treating

daily, 5 fractions a wk, to macroscopic disease & 44–50Gy in 2Gy per fraction, treating daily, 5 fractions a wk, to microscopic disease.

• Immobilization is in the supine position with the cervical spine straight.

• Radiotherapy technique using parallel opposed feilds

Hypopharyngeal tumours (Pyriform fossa ,Postcricoid region,PPW)

• Have high incidence of nodal metastases with submucosal spread Elective nodal irradiation is necessary.

• Ca. hypopharynx have a tendency to present with locally advanced disease Treated with radical chemoradiation.

• Immobilization: supine position with the cervical spine straight.• Pyriform fossa: Target volume includes the primary tumour & levels

Ib–V LN B/l.• Postcricoid region, PPW: CTV includes the primary tumour with a 2

cm (PPW) or 5 cm (post-cricoid) margin craniocaudally & levels Ib–V LN B/l.

• Total dose: 66–70Gy in 2Gy/fraction, treating daily, 5 fractions a wk, to macroscopic disease & 44–50Gy in 2Gy per fraction, treating daily, 5 fractions a wk,to microscopic disease.

NASAL CAVITY • Best treated with a combination of surgery with radiation and/or

chemotherapy.• Definitive radiation for occasional early tumour.• It may also be offered for advanced unresectable disease, although 5 yr

survival rates for the latter do not usually exceed 10 %.• Advanced lesions Radical radiation by using altered fractionation regime.

NASAL COLUMELLA / VESTIBULE• Radiation is often undertaken in the first instance to avoid deformity.• Small lessions may be treated with appositional electrons, with the CTV including

the primary tumour with a 2 cm margin.• With more locally advanced lesions, CT planning is recommended, with the CTV

including the primary tumour with a 1 cm margin & the entire nasal septum.• Dose prescription• 1) For small lesions confined to the columella or vestibule = 55Gy in

20 fractions, treating daily, five times a week and• 2) For more advanced lesions, with extension up the nasal

septum/cavity = 66–70Gy in 2Gy per fraction, treating daily, five times a week.

MAXILLARY SINUS• Immobilization Supine position with the cervical spine straight & a

mouth bite in place to exclude the tongue & lower part of the oral cavity from the radiation field.

• CTV maxillary sinus,ethmoid sinus,nasal cavity, pterygoid fossa & lateral pharyngeal node Achieved using a heavily weighted anterior field in combination with 1-2 lateral fields.

• Total dose 66–70Gy in 2Gy per fraction, treating daily, five fractions a week.

Anterior field Lateral field

ETHMOID SINUS• Immobilisation & total dose same as maxillary sinus.• CTVBoth ethmoid sinuses,nasal cavity,

medial half of the maxilla on the I/L side & pterygoid fossa.

• A 3 field plan,using a heavily weighted 2 ant. field & lat. fields achieves the best dose homogeneity.

ORAL CAVITY• Best treated with surgery, followed by adjuvant radiation with or without

chemotherapy.• Small (T1/T2), superficial (<5mm thickness) lesions of the oral tongue &

floor of mouth should be considered for interstitial brachytherapy.• Oral tongue :- a) Small superficial lesions may be treated with interstitial

brachytherapy. (2-3iridium-192 hairpins). b)The CTV includes the primary lesion with a 1 cm margin. c) The dose prescription for interstitial brachytherapy = 60Gy over 6 days with iridium-192 LDR.

• Buccal mucosa, alveolus & small hard palate tumours These sites are almost invariably treated in the postoperative setting

Complications HNC radiotherapyEarly

1) Fatigue, hair loss, Radiation sickness.

2) Mucositis, loss of taste, xerostomia.

3) Dryness of mucous membranes.

4) Skin reaction(erythema, dry or wet desquamation).

5) Candida infection.6) Haematopoietic suppression.7) Acute transverse mylitis.

Late1) Permanent xerostomia.2) Skin changes(atrophy of skin &

fibrosis).3) Decaying of teeth.4) Osteoradionecrosis.5) Trismus, pharyngeal stenosis6) Transverse myelitis, carotid artery

stenosis.7) Radiation retinopathy, cataract.8) Hypothyroidism, hypopitutarisim,9) Radiation induced malignancy-

thyroid cancer, osteosarcoma of orbit.

10) Carotid blowout syndrome.11) Oropharyngocutaneous fistula.

Precautions that has to be taken….During RT

1) Maintenance of good oral hygiene.

2) Eat balanced & healthy diet.3) Brushing 2-4 times daily with

soft-bristled brush.4) Flossing daily Daily topical

fluoride Custom trays,5) Brush-on prescription-strength

fluoride 6) Frequent saline rinses, lip

moisturizer (non-petroleum based)

7) Passive jaw Opening exercises to reduce trismus

Just After RT• Complete dental work that was

deferred during radiotherapy• Maintain integrity of teeth

especially those in radiation fields

• Frequent follow-up

CYBERKNIFE• Frameless robotic radiosurgical device that has been developed to treat

mainly extracranial lesions.• The two main elements of the CyberKnife are : (1) The radiation produced from a small linear particle accelerator. (2) A robotic arm which allows the energy to be directed at any part of the

body from any direction.• To correct for patient misalignment, the device provides both translational as

well as rotational corrections.• RapidArc allows for very fast treatment. CK allows for very accurate

treatment.• The robotic mounting allows very fast repositioning of the source, which

enables the system to deliver radiation from many different directions without the need to move both the patient and source as required by current gantry configurations.

• This imaging system allows the CyberKnife to deliver radiation with an accuracy of 0.5mm. Uses 6D reconstruction.

• Corrections are made for the 3 translational motions (X,Y and Z) and three rotational motions.

PARTS

GAMMAKNIFE • One of the most widely known stereotactic radiosurgery systems.• Radiosurgery is a neurosurgical procedure whereby radiation is

delivered using stereotactic principles.• The GammaKnife system uses 201 Cobalt-60 sources located in a

ring around a central treatment point ("isocenter"). • The Gamma Knife system is equipped with a series of 4 collimators

of 4mm, 8mm, 12mm and 16mm diameter, and is capable of submillimeter accuracies.

• The Gamma Knife system does however require a head frame to be bolted onto the skull of the patient, and is only capable of treating cranial lesions.

• As a result of frame placement, treatment with Gamma Knife does not require real time imaging capability as the frame does not allow movement during treatment

IMPANOVALIS

ADVANCED BRACHYTHERAPY

Few tips that may help to manage HNC RT problems…..• Avoid strong spices & coarse foods, such as raw vegetables, dry crackers,

and nuts.• Do not eat or drink very hot or very cold foods or beverages.• Do not smoke, chew tobacco, or drink alcohol – these can make mouth sores

worse.• Stay away from sugary snacks.• Ask doctor or nurse to recommend a good mouthwash. • Rinse mouth with warm salt and soda water every 1 to 2 hours as needed.• Sip cool drinks often throughout the day.• Eat sugar-free candy or chew gum to help keep mouth moist.• Moisten food with gravies & sauces to make it easier to eat.• Ask doctor or nurse about medicines to help treat mouth sores & control

pain while eating.• Clean teeth & gums with a very soft brush after meals & at least one other

time each day.• Use fluoride toothpaste that contains no abrasives.

Radiopharmaceuticals

• Drugs that contain radioactive materials called radioisotopes

• Travel to various parts of the body put out radiation, mostly in the form of alpha and beta particles

• Eg: Treatment of bone pain Strontium 89 ,samarium 153,Radium- 223

• Treatment of thyroid cancer: radioactive iodine (also known as radioiodine or iodine 131)

Organ Normal tissue tolerance (2Gy/fraction)

Lens 6

Cornea 40

Retina 50

Optic nerve 50

Optic chaisma 50-55

Spinal cord 44-48

Brain stem 48-54

Parotid gland 30

Lacrimal gland 30

What’s new in radiation therapy?....

• Hyperthermia is the use of heat to treat cancer• Hyperbaric oxygen therapy - Helps to increase the

sensitivity of certain cancer types to radiation• Radiosensitizers:- Oxygen, Metronidazole etc..• Radioprotectors: Amifostine