Radiation planning comparison for superficial tissue avoidance in radiotherapy for soft tissue sarcoma of the lower extremity

Purpose: Three types of preoperative radiotherapy (RT) plans for extremity soft tissue sarcoma were compared to determine the amount of dose reduction possible to the planned surgical skin flaps required for tumor resection and wound closure, without compromising target coverage. Methods and Materials: Twenty-four untreated patients with large, deep, lower extremity STS treated with preoperative RT and limb salvage surgery had their original conventional treatment plans re-created. The same clinical target volume was used for all three plans. The future surgical skin flaps were created virtually through contouring by the treating surgeon and regarded as an organ at risk. The original, conformal, and intensity-modulated RT (IMRT) plans were created to deliver 50 Gy in 25 fractions to the clinical target volume. Clinical target volume and organ-at-risk dose–volume histograms were calculated and the plans compared for conformality, target coverage, and dose sparing. Results: The mean dose to the planned skin flaps was 42.62 Gy (range, 30.24–48.65 Gy) for the original plans compared with 40.12 Gy (range, 24.24–47.26 Gy) for the conformal plans and 26.71 Gy (range, 22.31–31.91 Gy) for the IMRT plans ( p = 0.0008). An average of 86.4% (range, 53.2–97.4%) of the planned skin flaps received ≥30 Gy in the original plans compared with 83.4% (range, 36.2–96.2%) in the conformal plans and only 34.0% (range, 22.5–53.3%) in the IMRT plans ( p = 0.0001). IMRT improved target conformality compared with the original and conformal plans (1.27, 2.34, and 1.76, respectively, p = 0.0001). Conclusion: In a retrospective review, preoperative IMRT substantially lowered the dose to the future surgical skin flaps, sparing a greater percentage of this structure’s volume without compromising target (tumor) coverage.