Radiotherapy and Sarcomas

Wendy Ella

University College London Hospitals

NHS Foundation Trust

Introduction

• Rare malignant tumours arising from mesenchymal tissue

• <1% malignant tumours

• 78% originate from soft tissue, remainder from bone

• Diverse group

Heterogenous group of tumours

• Malignant Fibrous histiocytoma 28%• Liposarcoma 15%• Leiomyosarcoma 12%• Synovial sarcoma 10%• MPNST 5%• Rhabdomyosarcoma 5%• Fibrosarcoma <5• Ewings sarcoma • Angiosarcoma• Osteosarcoma• Clear cell sarcoma• Alveolar soft part sarcoma• Hamangiopericytoma• Chondrosarcoma

Introduction

• Increasing frequency with age

• Most commonly arising in the limbs– Extremities 50%– Trunk and retroperitoneal space 40%– Head and neck region 10%

Heterogenous group of tumours

Heterogenous group of tumours

Heterogenous group of tumours

Heterogenous group of tumours

Principles of management: soft tissue sarcomas

Surgery

+/- Radiotherapy

+/- Chemotherapy

Radiotherapy for soft tissue sarcoma

• Radiotherapy – role optimise local control

• Local control rates for combination of surgery + radiotherapy similar to amputation without affecting patient survival (Potter et al; 1986).

• Yang et al, J Clin Oncol, 1998, looked at high grade extremity lesions: Surgery vs Surgery + EBRT (63Gy in 1.8Gy), - increased local control from 70% to 99%, No difference in OS.

• Summary: Post operative radiotherapy is highly effective in preventing local recurrence.

Pre- or Post-Op Radiotherapy?

O’Sullivan et al; Five year results of randomised phase III trial of pre-op vs. post-op radiotherapy in extremity STS; JCO 2004 190 patients (94 pre-op/96 post-op) 5 year local control 93% v 92%, metastatic relapse free 67% v 69%, recurrence free survival; 58% v 59%, overall survival 73% v 67%

• Pre-op and post-op radiotherapy equally effective, normal tissue complication rate varies for both - therefore need to take in to account anatomical site

Indications for Post Operative Radiotherapy;

• Consider for all high grade sarcomas.

• Consider for low-intermediate grade with marginal excision/positive margins if further surgery not possible

• Following removal of recurrent tumour

Indications for pre-operative radiotherapy

• If tumour adjacent to or involving critical structures.

• Likely difficult resection.

• Tumour initially inoperable at diagnosis

Planning post-operative radiotherapy

• Immobilisation

• Definition of target volume

• Phase I & II

• Field arrangements

• Implementation of plan

Immobilisation

• Impression of limb with patient in the optimum treatment position -sheet of thermoplastic (Orfit) moulded around limb – clipped onto baseboard

• Immobilise limb• Same position every day• Reduce marks being drawn on skin

Immobilisation: Lower limb

Immobilisation: Upper limb

Phase I Volume definition

• GTV reconstructed from pre-op imaging.• Consider compartment at risk of microscopic spread.

Should include biopsy site and scar

CTV (length) = GTV + 4-9cm (usually ~5cm)PTV = CTV + 5-10mm (depending on departmental set up) or 1 cm beyond scar

Trans-axial CTV - treat width of compartment or GTV + 2-3cm

Phase II Volume definition

• Length

PTV = GTV +2-3cm

• Width

PTV is usually the same as phase I in axial plane

Sparing a “corridor”

• Leaving an area of normal tissue within the circumference of the limb can reduce risk of lymphoedema

Vortex

• CTV1 = axial 2cm or fascia• Longitudinal 2cm

• CTV2 = axial 2cm or fascia• Longitudinally 2cm

• CTV- PTV = 5mm

Margin calculation

• Van Herk, Seminars in Radiation Oncology, 14, 2004, 52-64

• Margin = (2.5 X SD of group systematic error) + (0.7 X SD of random error)

Systematic/Random errors

Group systematic

error

Group SD of random error

Margins calculated

L-R on AP

0.2 mm

+/- 1.4 SD

+/- 1.1mm 4.3 mm

S-I on AP

-0.2 mm

+/- 1.7 SD

+/- 1.7mm 5.3 mm

A–P on Lat

0.3 mm

+/- 1.5 SD

+/- 0.8mm 4.4 mm

Margin = (2.5 X SD of group systematic error) + (0.7 X SD of random error) - Van Herk, 2004

Implementation of Plan

• 6MV photons• Prescribed to 100%• Given isocentrically treating all fields daily• Limbs 2 phase technique;

phase I 50Gy in 25# over 5 weeksphase II 10 -16Gy in 5# over 1 week

• 60Gy is standard post op dose, 66Gy if positive margin

MRI Scan

Planning

Planning

Radiotherapy for soft tissue sarcoma

• Complex radiotherapy

• Highly individualised

• Requires good anatomical knowledge

Questions?

University College London Hospitals

NHS Foundation Trust