ESTRO 2024 - Abstract Book

S2084

Clinical - Sarcoma, skin cancer, melanoma

ESTRO 2024

899

Mini-Oral

Long-term safety of hypofractionated RT combined with AI in marginally resectable sarcomas

Mateusz Jacek Spałek 1,2 , Anna Małgorzata Czarnecka 1 , Piotr Błoński 1 , Maria Krotewicz 1 , Iga Płachta 1 , Klaudia Bobak 1 , Aneta Borkowska 1 , Michał Wągrodzki 3 , Hanna Koseła -Paterczyk 1 , Piotr Rutkowski 1 1 Maria Skłodowska -Curie National Research Institute of Oncology, Soft Tissue/Bone Sarcoma and Melanoma, Warsaw, Poland. 2 Maria Skłodowska -Curie National Research Institute of Oncology, Radiotherapy I, Warsaw, Poland. 3 Maria Skłodowska -Curie National Research Institute of Oncology, Pathology and Laboratory Diagnostics, Warsaw, Poland

Purpose/Objective:

There is no consensus on optimal treatment for marginally resectable soft tissue sarcomas (STS) of the extremities and trunk wall that would enable R0 limb-sparing/conservative en-bloc surgery. Based on our phase II trial finished in November 2019 we implemented the proposed preoperative radiochemotherapy regimen in marginally resectable STS into clinical practice. The regimen consists of the first course of chemotherapy - doxorubicin 75 mg/sqm and ifosfamide 10 g/sqm (AI regimen) followed by 5x5 Gy and, after radiotherapy, two additional courses of AI. The treatment is finished with surgery. However, there is a fear of significant toxicity due to several factors, i.e., hypofractionation, combination with chemotherapy, and large tumor size. Thus, we aim to describe the long-term safety and efficacy of this treatment approach.

Material/Methods:

The patients were treated within a single-arm prospective clinical trial and routine clinical practice according to the same regimen afterward. Treatment combined 1 cycle of AI with subsequent 5 × 5 Gy radiotherapy within 1 week, followed by 2 cycles of AI and surgery. Adult patients with locally advanced or lung oligometastatic disease were treated with definitive intent. The primary endpoint was to assess the number of patients in whom R0 radical en bloc resection was achieved. The secondary endpoint was to describe the safety of treatment. Patients with STS were enrolled in the study with the exclusion of Ewing sarcoma, rhabdomyosarcoma, gastrointestinal stromal tumor, dermatofibrosarcoma protuberans, angiosarcoma, and aggressive fibromatosis patients. Patients treated with other chemotherapy than AI, other fractionation, or in a palliative setting were not eligible for analysis. Common Terminology Criteria for Adverse Events (CTCAE) 4.0 was used to describe the toxicity. Descriptive statistics were used to summarize the demographic and clinical characteristics. Median follow-up was estimated by Kaplan Meier analysis with the reversed meaning of status indicator. Local relapse-free survival (LRFS) was calculated from the day of resection to the last follow-up, death without local relapse, or confirmed local relapse. Clinical local recurrence was confirmed with CT or MRI and biopsy. Overall survival (OS) was calculated from the enrollment to the last follow-up or death. The data cut-off was the 24th of June 2023. All statistical analyses were performed using R version 4.2.3.

Results: