CARCINOMA BASE OF TONGUE

CARCINOMA BASE OF TONGUE

ANATOMYBase of tongue Posterior 1/3 rd tongue

Boundaries

- Anterior: Circumvallate papillae - Lateral : Glossotonsillar sulci - Posterior : Epiglottis - Superior : Soft palate - Inferior : Hyoid and epiglottis

Vallecula Transition zone between base of tongue and epiglottis

Muscles : Genioglossus, Styloglossus, Hyoglossus and Palatoglossus

Sensory supply : Glossopharyngeal nerve (IX)

Motor supply: Hypoglossal nerve except for the palatoglossal muscle supplied by the Pharyngeal branch of the vagusArterial supply: Lingual artery

Lymphatic drainage:

Primary drainage Level II (Jugulodigastric nodes)Also to retropharyngeal and parapharyngeal nodesRetropharygeal is divided into lateral (Rouviers) and medial nodesParapharyngeal nodes are called junctional nodes as it occurs on the junction of the spinal accessory (level V) and upper internal jugular lymphatic chains

Risk FactorsTobacco AlcoholHPVGarnaes et al, attributed a rise in eastern Denmark in the incidence of squamous cell carcinomas of the base of the tongue between 2000 and 2010 (by 5.4% per year) to an increase in the number of such tumors (by 8.1% per year) that were positive for human papillomavirus.MarijuanaEnvironmental exposure to PAH, asbestos

Clinical PresentationDysphagiaOdynophagiaSensation of mass in the throatMass/Node in the neckReferred pain to the earHemoptysis

ROUTES OF SPREADLocal: spreads to rest of tongue musculature, epiglottis, pre - epiglottic space, tonsils, faucial pillars, hypopharynx

Lymphatic: Unilateral or bilateral cervical node metastasis in majority of cases. Distant: Lungs, liver , bone

DIAGNOSISRoutine blood investigations( CBC, LFT, RFT)Palpation under anaesthesiaFlexible fibreoptic laryngoscopyChest Xray: Pulmonary metastasis or 2nd primaryCT : Bone invasion and occult nodal disease in the neckPET-CT: Disease recurrence/ persistence after RT and distant metastasisMRI : Soft tissue extension and perineural spreadFNAC of neck nodesBiopsy of the primary lesion

HISTOLOGYMajority squamous cell carcinomasRest are Minor salivary gland tumours - Mucoepidermoid carcinoma - Adenoid carcinoma - Adenoid cystic carcinoma - Clear cell carcinoma

STAGINGPrimary tumour (T)T1: Tumor 2 cm or less in greatest dimension T2: Tumor more than 2 cm but not more than 4 cm in greatest dimension

T3: Tumor more than 4 cm in greatest dimension or extension to lingual surface of epiglottis

T4a: Moderately advanced local disease. Tumor invades the larynx, extrinsic muscle of tongue, medial pterygoid, hard palate, or mandible

T4b: Very advanced local disease. Tumor invades lateral pterygoid muscle, pterygoid plates, lateral nasopharynx, or skull base or encases carotid arter

Regional lymph nodes (N)NX: Regional lymph nodes cannot be assessed N0; No regional lymph node metastasisN1: Metastasis in a single ipsilateral lymph node, 3 cm or less in greatest dimension

N2a: Metastasis in a single ipsilateral lymph node, more than 3 cm but not more than 6 cm in greatest dimension N2b: Metastasis in multiple ipsilateral lymph nodes, not more than 6 cm in greatest dimension N2c: Metastasis in bilateral or contralateral lymph nodes, not more than 6 cm in greatest dimensionN3: Metastasis in a lymph node, more than 6 cm in greatest dimension

Distant metastasis (M) M0: No distant metastasis M1: Distant metastasis

STAGETNMSTAGE IT1NOMOSTAGE IIT2NOMOSTAGE IIIT3NOMOT1/T2/T3N1MOSTAGE IVAT4aNO/N1MOT1/T2/T3N2MOSTAGE IVBAny TN3M0T4bAny NMOSTAGE IVCAny TAny NM1

TREATMENT MODALITIESSurgery As single modality orRadiotherapy in combination

Chemotherapy - Induction CT - Concurrent chemo RT Sequential (ICT concurrent CRT) postoperative adjuvant concurrent chemoRT

Targeted therapy- Alone or combined with RT or palliative CT

GENERAL PRINCIPLES OF TREATMENTStage I and II Early stage disease Stage III and IV Locoregionally advanced disease

Early stage disease Surgery or RT Locoregionally advanced diseaseSurgery followed by RT +/- chemotherapyRT + chemotherapy Recurrent / metastatic disease - Chemotherapy - Palliative or supportive care

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SURGERYLimited role due to inherent morbidity of a near total or total glossectomy needed for large midline tumours

Well lateralized tumours with minimal cervical lymphadenopathy Partial glossectomy

B/L cervical lymph node dissection is done always due to high propensity for occult microscopic nodal involvment

Tumours arising from vallecula which are in close proximity to larynx Supraglottic or total laryngectomy

Surgical approachesMidline mandibulotomy- Splitting the lip, madible and oral tongue midlineLateral mandibulotomy - Dividing the mandible near the angle and approaching the base of tongue from the sideFloor drop procedure - Elevating the inner periosteum from the mandible from angle to angle which releases the entire floor of mouth and oral tongue into the neck exposing the base of tongueTransoral approaches - Laser surgery - Robotic surgery

Radiotherapy BrachytherapyEBRT

BrachytherapyIndicationGiven as boost following EBRT Pre treatment tumour extent should be delineated before EBRT because regression is not always uniformContraindication:- Distant metastasis- Tumors very close to or involving bonePt not suitable for anesthesia

TechniqueClassical Plastic loop techniqueAdvantages:This allows a wider separation between the sources - can be used to treat larger volumes. Remote after-loading that reduces the risk of exposureIn case of local oedema inducing the risk of displacement of the plastic tubes, one can wait for an acceptable local status before loading the iridium wire.Self retaining assembly, no suturing required

Done under general anesthesiaThe loop is formed by passing a hollow stainless steel needle through the skin into the tongue. A parallel stainless steel needle forms the other limb of the loop.A nylon guide wire is introduced to form the loopThe stainless steel needles are then removed.The plastic tube that has to be implanted is tied to guide wire and pulled through, ultimately forming the loop.Plastic or Lead button are introduced at skin end of tube to fix it.

On completion of the implant orthogonal radiographs are taken to show the position of the plastic tube loops.GTV is defined.CTV is drawn giving a margin of 1-1.5 cmPTV is same as the CTVBasal dose between the sources calculated.Mean basal dose calculated from basal dose.85% isodose volume of mean basal dose should ideally cover the PTV( reference volume) and get the prescribed dose for adequate tumor control

Brachytherapy guidelinesABS guidelinesEBRT of 45 to 60 Gy followed by HDR boost of 3-4 Gy per fraction for 6 to 10 doses

GEC and ESTRO guidelinesEBRT of 45 to 50 Gy followed by HDR boost of 30 to 35 Gy

EBRTIndication - Sole modality in early stage tumours - Adjuvant to surgery - Concurrent chemotherapy - Palliative EBRT

EBRTRadiotherapy Simulation CT based with IV contrast - Patients are positioned supine with a rigid head holder - Extended head position is used - Shoulder traction to position it as caudally as possible to allow adequate neck exposure - Tongue immobilization - Bite blocks - Head immobilized with a tight thermoplastic mask - Images are taken from the calvarium to carina

Conventional techniqueIrradiation portals should encompass the primary tumor and its local and regional extensions, with a margin for the CTV (approximately 0.7 cm) and for the PTV(approximately 0.5 cm).Neck portals should extend superiorly until C1 for N0, and the base of skull (retrostyloid space) in case of N+ diseaseThe primary tumor and both sides of the upper neck are irradiated using a conventional lateral parallel-opposed technique for the upper neck in case of a T2N2b BOT tumor. Both sides of the lower neck are generally irradiated through a single anteroposterior field, sometimes with a midline block.

Standard beam arrangments (3DCRT) - Parallel opposed lateral upper fields - Low neck/Supraclavicular field treated with single anterior or AP-PA fields

DEFINITIVE RT

High risk - 66 to 70 Gy/ 35F/ 7 weeksConcomitant boost accelerated RT - 72 Gy /6 weeks( 1.8Gy/F for large field; 1.5 Gy boost as second daily fraction during the last 12 treatment days)Hyperfractionation - 81.6 Gy/7 weeks(1.2 Gy/F twice daily)Low risk - 44 to 50 Gy/ 25F/5 weeks

DOSE CONSTRAINTSTemporal lobe: < 60 GyOptic nerve and chiasma : < 50 GyBrainstem : < 54 GySpinal cord :< 45 GyMandible :< 70 GyParotid gland :