Significance of dose in postoperative radiotherapy for soft tissue sarcoma

Purpose: For soft tissue sarcoma, adjuvant postoperative radiotherapy improves the local control rate over surgery alone. However, the issue of a dose-control relationship is controversial and was addressed in this study. Methods and Materials: We retrospectively reviewed the records of 775 consecutive patients who received postoperative external beam radiotherapy and used univariate and multivariate analysis to determine whether a dose-control relationship exists for the whole group and for specific high-risk subgroups. Results: With a median follow-up of 12.3 years, overall local control rates were 82%, 80%, and 79% at 5, 10, and 15 years. Factors adverse for local control were positive resection margins; tumor location in the head and neck and deep trunk; presentation with locally recurrent disease; patient age >64 years; histopathologic subtype of malignant fibrous histiocytoma, neurogenic sarcoma or epithelioid sarcoma; and tumor size >10 cm. In multivariate analysis, radiation dose ≥64 Gy vs. <64 Gy independently correlated with improved local control. Significant interactions were noted between increased effectiveness of a higher dose and presentation with locally recurrent disease, with head and neck and deep trunk tumor sites, and with positive or uncertain resection margins such that local control was specifically improved under these circumstances with doses on the order of 64-68 Gy compared with doses on the order of 60 Gy. Higher dose, however, did not completely abrogate the adverse effect of positive margins. Conclusion: After gross total resection, soft tissue sarcoma with features predictive of a higher than average local recurrence rate benefited from doses of 64-68 Gy compared with 60 Gy.