Histology and outcome in localized high-risk soft tissue sarcomas (STS) treated with preoperative chemotherapy (CHT) with or without radiation therapy (RT) within a phase III trial from the Italian Sarcoma Group (ISG) and the Spanish Sarcoma Group (GEIS).

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10089 Background: We reported on a phase III trial comparing 3 versus 5 cycles of preoperative CHT in high-grade localized STS of the extremities and trunk wall. We explored to which extent histological subtype was prognostically relevant in such an adjuvant series. Methods: 311 pts were eligible. All received 3 cycles of preoperative Epirubicin + Ifosfamide, followed by surgery. Local RT was administered before or after surgery. 136 pts were randomized to receive 2 more cycles of adjuvant CHT. In 222 (71%) cases, centralized pathological review was performed. Histology was categorized into 4 groups: MFH/undifferentiated pleomorphic sarcoma and spindle cell sarcoma NOS (Group 1 = 125 pts), leiomyosarcoma (Group 2 = 41 pts), synovial sarcoma (Group 3 = 68 pts), other (Group 4 = 77 pts). The influence of histology OS and RFS was retrospectively assessed through a univariate Cox regression model. Besides, responses to the preoperative treatment according to RECIST (78% evaluated pts of those with measurable disease) and CHOI criteria (50% evaluated pts) were retrospectively recorded. Results: Group 1, Group 2 and Group 3 accounted for about 75% of cases. At a median follow-up of 60 months (range = 24-102), the OS probability was 0.76, 0.48, 0.64 and 0.73, and the RFS probability was 0.61, 0.48, 0.59 and 0.65, respectively, for Groups 1, 2, 3, 4. For both OS and RFS, a trend in favour of a better outcome was observed in Group 1. On the contrary, a diagnosis of leiomyosarcoma correlated with both a worse OS (Group 1 vs Group 2: HR 2.88, 95%CI 1.63 – 5.01) and a worse RFS (Group 2 vs Group 1: HR 1.72, 95%CI 1.03-2.88). Leiomyosarcoma was marked by the highest number of PD according to both RECIST and CHOI criteria, and Group 1 had the highest RR, when changes in tumor density were accounted for with CHOI criteria. Conclusions: In this series of localized high-risk limb and trunk wall STS, leiomyosarcoma performed worse than the other types. This may be the product of the combination of natural history and chemosensitivity. At least in part, the latter may correlate with the outcome.

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