This trial is a European, multicenter, open-label, randomized, Phase II trial using a pick-the-winner design aiming to the clinical and biological activity of anti-PD-L1 (atezolizumab) in a population of operable localised soft tissue sarcomas (STS) patients to be treated with radiotherapy.~Following inform consent signature and validation of eligibility criteria, patients will be randomized (1:1:1) into one of the 3 study arms:~Arm A: Pre-operative radiotherapy followed by 2 cycles of atezolizumab then surgery~Arm B: 2 cycles of atezolizumab followed by surgery then post-operative radiotherapy~Arm C: Pre-operative radiotherapy followed by surgery then 2 cycles of atezolizumab.~The sequence of treatment is different between the study arms, but the regimen of study treatments are the same. All randomized patients will received:~The conventionally fractionated radiotherapy regimen of 2 Gy, 5 days a week up to a total dose of 50 Gy over 5 weeks. Radiotherapy will be either pre-(Arms A and C) or post-(Arm B) operative.~Two cycles of atezolizumab (1200mg, IV, Q3W)~Surgery will be performed as per institutional practice.~Randomisation will be stratified according to histological subtypes as follows~Group 1: Leiomyosarcoma [LMS], Undifferentiated Pleomorphic Sarcoma [UPS], Liposarcoma [LPS], myxofibrosarcoma, angiosarcoma versus~Group 2: all translocation sarcoma except Ewing, rhabdomyosarcoma RMS and myxoid LPS.~Following this sequence of treatment, all patients will be followed-up 2 weeks after the end of the treatment period then W18, W24 (=M6) then every 3 months until disease relapse, death, loss to follow-up. The minimal follow-up will be 1 year for the last randomized patient.~During the study period, the following tumor samples will be also collected for all randomized patients:~A de novo tumor biopsy before study treatment start (pre-treatment tumor sample)~A fragment of the surgery specimen.
This multicentric, randomised, Phase II trial will use a pick-the-winner design in order to evaluate the clinical and biological activity of atezolizumab when combined with pre-operative or post-operative radiotherapy in STS patients.~Following Inform Consent Form (ICF) signature, eligible patients will be randomised (1:1:1) to receive:~Arm A: Radiotherapy followed by atezolizumab then surgery.~Arm B: Atezolizumab followed by surgery then radiotherapy.~Arm C: Radiotherapy then surgery followed by atezolizumab.~The sequence of the study treatments is different among the 3 study arms. However, the dose regimens will be the same:~Atezolizumab will be administered to all patients at the dose of 1200mg, by IV injection, for 2 cycles (Q3W).~Radiotherapy will be administered to all patients at the dose of 2Gy/day, 5 days per week, for a total of 5 weeks and 50Gy.~Surgery will be performed as per institutional practice.~Randomisation will be stratified according to histological subtypes as follows:~Group 1: Liposarcoma (LPS), Undifferentiated Pleomorphic Sarcoma (UPS), Leiomyosarcoma (LMS), myxofibrosarcoma, angiosarcoma versus Group 2: all translocation sarcoma except Ewing, rhabdomyosarcoma (RMS) and myxoid LPS.