High dose (54 Gy) pre-operative helical tomotherapy for retroperitoneal liposarcoma: Results of a phase II multicenter study

Purpose: To evaluate efficacy and feasibility of high-dose intensity-modulated radiotherapy (RT) with pre-operative helical tomotherapy, delivering 54 Gy/30 fractions in patients with retroperitoneal liposar-comas (RPLS).Materials and Methods: Patients with operable, biopsy-proven, RPLS were included in this phase II mul-ticenter study (ClinicalTrials.gov: NCT01841047). The primary objectives were to analyze loco-regional relapse free survival (LRFS), overall survival (OS) and toxicities, graded according to CTCAE V3.0. Results: From April 2009 to September 2013, 48 patients were included. Histological types were: 20 well differentiated and 28 dedifferentiated liposarcomas. Median clinical target volume (CTV) was 2570 cc (range, 230-8734 cc). The radio-surgical schedule was completed as planned in all patients apart from one. A monobloc wide excision was achieved for all patients. Surgical margins were R0 (16; 34%), R1 (28; 60%), R2 (2; 4%) or missing (1, 2%). With a median follow-up of 5.5 years, 3-year LRFS rate was 74.2% (95%CI: [59.1%; 84.5%]). At 5 years, cumulative incidence of loco-regional relapse for well differen-tiated and dedifferentiated RPLS was 10% and 18%, respectively. The 5-year OS was 73.9% [95%CI: 58.7- 84.3%]. During RT, the most common grade 3-4 adverse events were hematological (N = 20; 41.6%). After surgery and during follow-up, 17 patients (35.4%) presented a grade 3-4 toxicity. Two patients (4.1%) died due to a duodenal toxicity. Nine second cancers were observed.Conclusion: From this phase II trial of preoperative RT in RPLS patients, the dose level proposed cannot be considered safe, leading to non-negligible toxicity and second cancers rates. Our results, combined with STRASS-1 study, suggest that the ideal indication of RT for patients with RPLS still remains to be determined.& COPY; 2023 Elsevier B.V. All rights reserved. Radiotherapy and Oncology 186 (2023) 109791

Automated summary

This study evaluated the efficacy and feasibility of high-dose intensity-modulated radiotherapy in patients with retroperitoneal liposarcomas. The results showed significant toxicity and rates of second cancers associated with this treatment regimen. Therefore, the optimal indication of radiotherapy for patients with retroperitoneal liposarcomas still needs to be determined.