ESTRO 2025 - Abstract Book

S1727

Clinical - Sarcoma & skin cancer & malignant melanoma

ESTRO 2025

4321

Digital Poster Impact of Preoperative Radiotherapy Margin Size on Local Control and Survival in Extremity Soft Tissue Sarcoma. Hideki Minatogawa 1 , Manami Otsuka 1 , Yukiko Nishikawa 1 , Noriaki Nishiyama 1 , Rei Iwata 2 , Tamotsu Souma 2 , Hirokazu Shimizu 2 , Hiroaki Hiraga 2 1 radiation oncology, Hokkaido Cancer Center, Sapporo, Japan. 2 Bone and Soft Tissue Tumor, Hokkaido Cancer Center, Sapporo, Japan Purpose/Objective: The ASTRO guidelines recommend a CTV margin of 3–4 cm along the longitudinal axis from the GTV for preoperative radiotherapy(Pre-RT) in extremity soft tissue sarcomas(STS). However, Pre-RT is known to increase the risk of postoperative wound complications. Additionally, it remains unclear whether wider margins in Pre-RT consistently improve treatment outcomes. This study aims to investigate whether wider margins provide clinical benefits by analyzing various cases of Pre-RT Material/Methods: This retrospective study reviewed treatment plans for 29 cases of primary extremity STS treated with Pre-RT between 2011 and 2022. Radiotherapy modalities included IMRT and 3DCRT. The male-to-female ratio was 17:12. Histological subtypes were undifferentiated pleomorphic sarcoma, myxoid liposarcoma, myxofibrosarcoma, leiomyosarcoma , pleomorphic liposarcoma , synovial sarcoma , rhabdomyosarcoma, spindle cell sarcoma, and unspecified sarcoma .The AJCC staging included stage 1A, 1B, 3A, and 3B. The cases were divided into two groups according to the longitudinal margin. For IMRT, Group 1 included cases with margins <3 cm between the GTV and CTV, while Group 2 included cases with margins ≥3 cm. For 3DCRT, Group 1 included cases where the distance from the GTV to the edge of the radiation field was <4.5 cm, and Group 2 included cases with a distance ≥4.5 cm.Using these longitudinal margins, we compared the groups regarding positive surgical margins, local control rates(LC), and overall survival(OS). Results: Group 1 and 2 comprised 8 and 21 cases, respectively. The age (mean ± SD) was 66.8 ± 12.5 years in Group 1 and 64.0 ± 19.2 years in Group 2. The maximum tumor size was 66.3 ± 12.5 mm in Group 1 and 64.0± 19.2 mm in Group 2 (p = 0.90). The margin from the GTV was 2.6 ± 1.5 mm in Group 1 and 5.20 ± 0.9mm in Group 2 (p < 0.001). The rate of positive surgical margins was 37.5% in Group 1 and 33.3% in Group 2 (p = 1.00). The median follow-up period was 50.5 months. The 5-year LC rate was 100% (95% CI: 100–100%) in Group 1 and 87% (95% CI: 72.4–100%) in Group 2, with no statistically significant difference between the groups (p = 0.3). The 5-year OS was 57% (95% CI: 30–100%) in Group 1 and 51% (95% CI: 33–81%) in Group 2, also showing no statistically significant difference (p = 0.6)

Conclusion: A wider margin in preoperative radiotherapy may not necessarily contribute to better LC.

Keywords: preoperative radiotherapy,margin,

References: Salerno KE, Alektiar KM, Baldini EH, Bedi M, Bishop AJ, Bradfield L, Chung P, DeLaney TF, Folpe A, Kane JM, Li XA, Petersen I, Powell J, Stolten M, Thorpe S, Trent JC, Voermans M, Guadagnolo BA. Radiation Therapy for Treatment of Soft Tissue Sarcoma in Adults: Executive Summary of an ASTRO Clinical Practice Guideline. Pract Radiat Oncol. 2021 Sep-Oct;11(5):339-351. doi: 10.1016/j.prro.2021.04.005. Epub 2021 Jul 26. PMID: 34326023.