Clival Chordoma Case Clival Chordoma Case in Pediatric Patientin Pediatric Patient

Radiation Oncology Case Radiation Oncology Case with Pre-RT Imageswith Pre-RT Images

••RT and IMRT slides RT and IMRT slides courtesy of Paul Read, MDcourtesy of Paul Read, MD

Clival Chordoma – OverviewClival Chordoma – Overview

••CCongenital tumors believed to originate from notochordal ongenital tumors believed to originate from notochordal cell restscell rests

••Rare in childhood, more common in 3Rare in childhood, more common in 3rdrd and 4 and 4thth decades decades

••Chordomas generally occur in 3 locations: the sacrum, the Chordomas generally occur in 3 locations: the sacrum, the clivus, and along the spinal axisclivus, and along the spinal axis

••For clival tumors, diplopia, headache, widening sutures, For clival tumors, diplopia, headache, widening sutures, and enlarging head size areand enlarging head size are most common sx most common sx

••About ½ patients haveAbout ½ patients have cranial nerve palsies (VI, V, III) cranial nerve palsies (VI, V, III)

Clival Chordoma – OverviewClival Chordoma – Overview

••Male predominance in pediatric population for unclear reasonsMale predominance in pediatric population for unclear reasons

••10 month average time from the onset of sx to dx 10 month average time from the onset of sx to dx

••Tumors usually large in size at dx with innocuous presenting sxTumors usually large in size at dx with innocuous presenting sx

• •CT exam often reveals a midline soft tissue mass around the clivus CT exam often reveals a midline soft tissue mass around the clivus associated with osteolytic bone destruction and intralesional associated with osteolytic bone destruction and intralesional calcifications. calcifications.

•• MRI delineates the exact site and extension, but also defines neural MRI delineates the exact site and extension, but also defines neural and vascular relationship for planning surgand vascular relationship for planning surg

• • Location of these tumours proximal to vital neural and vascular Location of these tumours proximal to vital neural and vascular structures makes surgical removal difficult and the ultimate clinical structures makes surgical removal difficult and the ultimate clinical course malignantcourse malignant

Clival Chordoma – OverviewClival Chordoma – Overview

••Combination of a ‘radical debulking’ operation followed by Combination of a ‘radical debulking’ operation followed by high dose radiation therapy appears to be an effective mode high dose radiation therapy appears to be an effective mode of treatment in older childrenof treatment in older children..

••Chemotherapy appears to be of no valueChemotherapy appears to be of no value

•• Survival for 4‑11 years without recurrence is recorded in Survival for 4‑11 years without recurrence is recorded in children under 10 years of age who received such a children under 10 years of age who received such a combination of treatmentcombination of treatment

•• The 5-year survival 51%, 10-year survival 35%The 5-year survival 51%, 10-year survival 35%

•• Good prognostic factors are young age, complete Good prognostic factors are young age, complete resection, and the addition of radiation therapyresection, and the addition of radiation therapy

Clival Chordoma CaseClival Chordoma Case

•Pediatric patient with an extremely Pediatric patient with an extremely aggressive atypical chordoma that locally aggressive atypical chordoma that locally destroyed the clivusdestroyed the clivus

•Tumor extension to brainstem, upper Tumor extension to brainstem, upper spinal cord, nasopharynx, cavernous sinus, spinal cord, nasopharynx, cavernous sinus, retropharyngeal space, left parapharyngeal retropharyngeal space, left parapharyngeal spacespace

•Plan high dose RT to tumor (65-70 Gy) Plan high dose RT to tumor (65-70 Gy) while respecting CNS tolerancewhile respecting CNS tolerance

Axial and Sagittal CT views of an Atypical Chordoma

Axial view Sagittal view

What is Radiation Therapy?

• Radiation therapy is the treatment of cancer using energy in the form of high voltage radiation.

• Radiation Oncologists prescribe a radiation dose in units of Gray (Gy) like other physicians prescribe drugs in units of milligrams.

• A Gray is defined as an amount of energy deposited per unit mass of tissue.

• Radiosurgery uses 10-40 Gy per treatment.

• Fractionated Radiotherapy uses 1.8-2.0 Gy per treatment.

patient

tumor

Standard Parallel Opposed Radiotherapy Isodose Distribution

The high dose isodose lines span the entire patient volume damaging normal tissues.

patient

tumor

Conformal Isodose Distribution

The high dose isodose lines conform to the target volume and spare normal tissues.

Improved Dose Conformality

Goals to maximize the dose of radiation delivered to target volume and minimize dose to surrounding tissue

Each normal tissue has its own inherent threshold dose for irreparable damage

Three-dimensional conformal therapy was the first application of improved dose conformality

IMRT furthers this concept

Standard Linear Accelerator (Linac):produces megavolt x-rays for 3D Conformal

radiotherapy and IMRT

What is Intensity Modulated Radiotherapy (IMRT) ?

• Intensity modulated radiotherapy is very complex radiotherapy in which the radiation beam is “modulated” by blocking part of the beam using a motorized array of paired tungsten blocks called a multi-leaf collimator within a linear accelerator.

• With radiation beam modulation and the use of multiple radiation beam angles one can achieve conformal radiotherapy with a standard linear accelerator (linac).

• IMRT is usually delivered with fractionated radiotherapy with 25-35 treatments of 1.8-2.0 Gy of radiation each.

• Currently UVA has a linear accelerator (linac) based IMRT program which is described below.

Linear Accelerator Multi-Leaf Collimator Based IMRT

Multi-leaf Collimator

The multi-leaf collimator is inside the linear accelerator. It is comprised of multiple 1 cm thick metal radiation blocks each driven by an independent motor and controlled by a central computer. The multi-leaf collimator allows for multiple blocking patterns in each radiation field which in turn allows for intensity modulation of the radiation dose.

9 field IMRT conformal treatment plan for an atypical chordoma

IMRT in Practice Physician outlines areas of interest on each slice

Then describes desired doses to CTV and restraints to structures.

Then assigns numerical priority score to these goals.

There are several trade-offs and some of them are more important in pediatric patients…

IMRT conformal plan for an atypical chordoma (55-100% isodoses)

Isodoses Sagittal viewAxial view

3D view of the dose intensity of IMRT plan for an atypical chordoma

Isodoses Right-inferior 3D view

3D view of dose intensity of IMRT conformal radiotherapy plan for an

atypical chordoma

Isodoses 3D Inferior view

ACR CODE:ACR CODE:

Presented by Tim Showalter, Class of 2004Presented by Tim Showalter, Class of 2004

Many of the RT and IMRT slides courtesy of Paul Read, MD Many of the RT and IMRT slides courtesy of Paul Read, MD of UVA Department of Radiation Oncologyof UVA Department of Radiation Oncology