Is dose de-escalation possible in sarcoma patients treated with enlarged limb sparing resection?

Abstract

To evaluate the impact of dose de-escalation in a large series of resected limbs soft tissue sarcomas (STS). Data were retrospectively analysed from 414 consecutive patients treated for limb STS by enlarged surgery and radiotherapy at Gustave Roussy from 05/1993 to 05/2012. Radiotherapy (RT) dose level was decided by the multidisciplinary staff and depended upon the quality of surgery and margins size. RT was delivered prior (13%) or after (87%) surgery. Seven patients (2%) had pre- and a postoperative RT boost. Median delivered RT dose was 50 Gy (36-70 Gy), and 33% received ≥55 Gy. At a median follow-up of 6.8 years, the 5-year actuarial local relapse (LR) rate was 7% (95% CI: 4.4-10%). The median time to the first LR was 2.7 years (range: 0.6-11.2 years). The LR was most often located within the irradiated field (26/32; 81%), where the median total applied dose was 56 Gy (range, 40-60 Gy). The 5-year LR rates were 4%, and 15% in patients receiving <55 Gy, and in those who had ≥55 Gy (p < 0.001), respectively. In the multivariate analysis, dose ≥55 Gy (HR [hazard ratio]: 2.9; p = 0.02), certain histological subtypes (HR: 7.8; p < 0.001), and minimal surgical margins <1 mm (HR: 2.9; p = 0.02) were associated to higher LR rates. In the subgroup of patients with "positive" margins <1 mm (n = 102), these histological subtypes (HR: 4.4; p = 0.03), and inadequate initial surgery justifying re-excision (HR: 3; p = 0.048) predicted for an increased LR, whereas dose of irradiation did not (p = 0.2). Patients who had late complications (n = 64; 15%) received higher doses of irradiation as compared with other patients (median: 55 Gy vs. 50 Gy, respectively; p < 0.001). In this retrospective analysis of patients having enlarged surgery and RT, histological subtype is the strongest predictor of LR, whereas dose de-escalation did not lead to worse outcomes. A dose of 50 Gy may be recommended in case of planned enlarged surgery with R0 margins.