Evaluation of IMRT for Ewing’s Sarcoma of the Chest wall

Purpose. Radiotherapy has been shown to play a vital role in the treatment of Ewing’s Sarcoma of the chest wall, however the need for bilateral or unilateral lung irradiation makes the delivery of a high dose boost to the primary tumour bed challenging. The current study aimed to evaluate the use of Intensity Modulated Radiotherapy (IMRT) in the treatment of this site.

This study supports the conference aim in the technical innovations category by proposing an innovative new method of treating a challenging cancer site.

Methods. Four consecutive patients who had received conformal radiotherapy (CRT) between 2009 and 2011 were re-planned using multiple beam arrangements to determine an IMRT class solution. Three patients had received a two-phase technique (lung bath plus boost to GTV) and one patient a single phase. The optimal IMRT plan for each patient was compared against the delivered CRT plan in terms of dose to the target volumes and organs at risk.

Results. The IMRT and CRT plans provided similar coverage of the whole lung volume in phase 1 (V95 ± 5 %) The IMRT plan provided 39 % better coverage of the high dose PTV in one patient, comparable coverage in three patients (± 5 %). The lung V20 was reduced in one patient (-4 %) and increased in 3 patients (+2 %, +62 %, +63 %) to a maximum of 43.6 %.

Conclusions. The low dose bath delivered by IMRT has led to an unacceptable increase in the lung dose for three of the four patients in this cohort, making the plan un-deliverable. IMRT may provide a solution in individual cases, but it is felt that further research is required to develop a technique suitable for this patient group as a whole. Studies in the use of proton therapy look promising.