ESTRO PT 2018

Phase I trial of pre-operative intensity modulated proton radiation (IMPT) with simultaneous boost to high risk margin for retroperitoneal sarcomas DeLaney et al. MGH – Adv Radiat Oncol 2017 2:85-93 Goal: selectively escalate retroperitoneal sarcoma (RPS) preoperative radiation dose to tumor volume (CTV2) judged at high risk for positive margins, aiming to reduce local recurrence(LR). ➢ Patients > 18 years with primary or locally recurrent RPS ➢ preoperative IMPT, 50.4 GyRBE/28 fractions, to CTV1 (GTV and adjacent tissues) with integrated boost to CTV2 to doses of 60.2, 61.6, and 63.0 GyRBE in 28 fractions of 2.15, 2.20, and 2.25 GyRBE respectively. ➢ Phase I study primary objective was determination of maximum tolerated dose (MTD) to CTV2, to be further tested in subsequent phase II. Results: ➢ 11 patients were accrued to increasing IMPT dose levels without acute dose limiting toxicities preventing dose escalation to MTD. ➢ Acute toxicity mild. No radiation interruptions. No unexpected perioperative morbidity. ➢ 8 months postoperatively, one patient developed hydronephrosis treated by stent; Ureter received 57.5 GyRBE. Subsequently constrained to 50.4 GyRBE. ➢ With 18-month median follow-up, there were no LRs.

Conclusions: IMPT dose escalation to CTV2 to 63 GyRBE achieved without DLT; phase II IMPT study started to accrue to that dose.