ESTRO 2022 - Abstract Book

S120

Abstract book

ESTRO 2022

replace time-consuming manual counting allowing large scale quantitative assessment of the DNA damage response after photon and proton therapy in tumor tissue slices.

Mini-Oral: 04: Sarcoma, skin cancer, malignant melanoma

MO-0145 Prospective single-arm trial of preoperative 42.75 Gy in 15 fractions for soft tissue sarcoma

B.A. Guadagnolo 1 , D. Mitra 1 , A. Farooqi 1 , C. Hempel 2 , C. Dorber 1 , R. Mathai 1 , T. Willis 1 , W. Wang 3 , R. Ratan 4 , N. Somaiah 4 , K. Torres 5 , K. Hunt 5 , C. Scally 5 , E. Keung 5 , R. Satcher 6 , J. Bird 6 , P. Lin 6 , B. Moon 6 , V. Lewis 6 , C. Roland 5 , A. Bishop 1 1 MD Anderson Cancer Center, Radiation Oncology, Houston, Texas, USA; 2 MD anderson Cancer Center, Radiation Oncology, Houston, Texas, USA; 3 MD Anderson Cancer Center, Pathology, Houston, Texas, USA; 4 MD Anderson Cancer Center, Sarcoma Medical Oncology, Houston, Texas, USA; 5 MD Anderson Cancer Center, Surgical Oncology, Houston, Texas, USA; 6 MD Anderson Cancer Center, Orthopedic Oncology, Houston, Texas, USA Purpose or Objective The standard pre-operative radiation therapy (RT) dose of 50 Gy in 25 daily fractions for soft tissue sarcoma (STS) contributes to excellent local control and is associated with major wound complications (MWC) in approximately 35% of patients. We sought to prospectively investigate whether a radiobiologically equivalent dose given in a 3-week course of 42.75 Gy in 15 daily fractions confers a higher risk of MWC. Materials and Methods We conducted a prospective, single-arm, non-randomized trial of hypofractionated pre-operative RT consisting of 42.75 Gy in 15 once-daily fractions followed by surgery 4-8 weeks after RT completion for adult patients with biopsy-confirmed, non- metastatic, previously un-irradiated STS of the extremity or superficial trunk. Patients (n=120) were enrolled from December 2018 to January 2021. The primary outcome of the study was to determine the rate of MWC within 120 days of surgery among patients treated with the trial regimen. Safety was monitored using a Bayesian stopping rule One-Arm Time- To-Event Simulator which compared development of MWC at 120 days post-surgery among patients on study to the historical rate of 35%. The Kaplan-Meier method and Cox proportional hazards regression was used to estimate outcomes. Results Median follow-up from surgery was 20 months (interquartile range [IQR] 11-33). Median age was 60 years (IQR 48-69) and median maximum tumor size was 7.6 cm (IQR 4.5-12.8). A majority of the patients had lower extremity (LE) tumors (n=78, 65%; upper extremity (UE), n=20, 17%; trunk, n=22, 18%). Tumor grade was: high in 51% (n=61), intermediate in 23% (n=27), low in 8% (n=9), or not gradeable in 19% (n=23). All patients received 42.75 Gy (or CGE) in 15 once-daily fractions with either: IMRT (n=57, 48%), 3D-RT (n=55, 46%), electrons (n=5, 4%), or protons (n=3, 3%). None experienced acute skin toxicity of CTCAE v4.0 ³ grade 3. Thirty-seven (31%) patients developed MWC within 120 days of surgery. Adjusted analyses showed UE tumor was less likely to be associated with MWC (OR: 0.08, 95% CI: 0.01-0.69) and diabetes mellitus had a higher likelihood of MWC (OR: 3.06, 95% CI: 1.35-6.98). Six patients (5%) developed local recurrence at a median 16 mos (IQR 7- 17); 4 in the RT field, 1 at the field margin, and 1 wide of field. Actuarial 2-year local control is 92% (95% CI: 82-96%). Conclusion Our prospective non-randomized clinical trial revealed that a hypofractionated pre-operative radiotherapy dosing regimen of 42.75 Gy in 15 once-daily fractions resulted in a MWC rate that was not higher than accepted historical rates. Early analyses show rates of local recurrence that are consistent with those observed with standard fractionation. These data support that this 3-week regimen may offer a safe, effective, and more convenient alternative to 50 Gy in 25 daily fractions for patients undergoing pre-operative RT for STS. 1 Maria Sklodowska-Curie National Research Institute of Oncology, Department of Soft Tissue/Bone Sarcoma and Melanoma, Warsaw, Poland; 2 Maria Sklodowska-Curie National Research Institute of Oncology, Department of Soft Tissue/Bone Sarcoma and Melanoma , Warsaw, Poland; 3 Maria Sklodowska-Curie National Research Institute of Oncology, Department of Pathology and Laboratory Medicine, Warsaw, Poland; 4 Maria Sklodowska-Curie National Research Institute of Oncology, Department of Radiology, Warsaw, Poland; 5 Maria Sklodowska-Curie National Research Institute of Oncology, Department of Soft Tissue/Bone Sarcoma and Melanoma , Warsaw, Poland Purpose or Objective The role of perioperative treatment in radiation-induced and in-field recurrent sarcomas (RIS/IFRS) is unknown. Reirradiation may be associated with a risk of significant toxicity; thus, it is rarely used. We hypothesized that the combination of preoperative or definitive 12x 3 Gy radiotherapy (RT) with or without integrated 3.5 Gy to 42 Gy boost combined with regional hyperthermia twice a week will enable satisfactory local control without significant late toxicity in patients with RIS/IFRS. Materials and Methods A prospective phase II, single-arm clinical trial was conducted. We included patients with locally advanced RIS/IFRS without distant metastases. Treatment combined three weeks of radiotherapy, four fractions per week, 3 or 3.5 Gy per fraction, with regional hyperthermia, followed by surgery or observation. The choice of the boost or no-boost regimen was based on MO-0146 RT with hyperthermia in recurrent and radiation-induced sarcomas: preliminary results of NCT04398095 M. Spa ł ek 1 , A. Borkowskia 2 , M. W ą grodzki 3 , P. Castaneda-Wysocka 4 , P. Rutkowski 5