Locoregional recurrence after preoperative radiation therapy for retroperitoneal sarcoma: adverse impact of multifocal disease and potential implications of dose escalation.

BACKGROUND: Locoregional recurrence (LRR) rates following preoperative radiation therapy (RT) and radical resection for retroperitoneal sarcoma (RPS) are high. Targeted radiation dose escalation has been proposed as a means to decrease LRR, but is applicable only if LRRs are confined to within the RT field. We analyzed predictors for LRR and examined LRR locations to determine the potential benefit of dose escalation.
METHODS: For 33 patients treated with preoperative RT and radical resection, we determined high-risk tumor volumes appropriate for boost and identified the number of recurrences within this volume. Clinical and pathologic variables predictive of overall survival (OS), freedom from progression (FFP), LRR, and distant recurrence (DR) were evaluated.
RESULTS: Median follow-up was 32.9 months. At 1 and 3 years, OS was 87 and 64 %, FFP rates were 71 and 45 %, cumulative incidences of LRR were 19 and 37 %, and of DR were 13 and 21 %. On multivariate analysis, multifocal disease was a significant predictor of increased incidence of LRR. At first relapse, 6 patients had isolated LR, 2 isolated RR, 6 isolated DR, 1 synchronous LR and RR, and 1 synchronous LR, RR, and DR. Ultimately, 4 patients (25 % of those who recurred) had isolated in-field recurrences within the hypothetical high-risk dose-painting boost volumes and that thus might have been prevented with dose-escalation.
CONCLUSION: Following preoperative RT and resection, LRR rates are high and associated with multifocal disease. Preoperative dose escalation to high-risk tumor volumes may perhaps benefit only a limited subset of patients, and therefore strategies are needed to select appropriate patients for consideration of this approach.