Sterotactic Ablative Radiotherapy in a Multicentric Series of Oligometastatic SCLC: The SAMOS Cohort

We conducted a retrospective multicentric analysis of patients with oligometastatic small cell lung cancer (SCLC) treated with stereotactic ablative radiotherapy (SABR) from 2017 to 2022. Our findings suggest that SABR may delay the need for additional treatments and extend ongoing treatment in oligometastatic SCLC, with the need for prospective studies to confirm these results. Aims: SCLC is the most aggressive lung cancer histology with a 5-year OS < 10%. At the diagnosis, almost two-thirds of the SCLC an Extended Disease presentation. Two randomized studies (CASPIAN and ImPower133) demonstrated an OS improvement, when immunotherapy was prescribed as maintenance therapy after standard chemotherapy. To date, SABR has had a limited indication in managing metastatic SCLC, although recent reports proposed it as a valid treatment option in selected patients. We propose a retrospective multicentric analysis of patients treated with SABR for oligometastatic SCLC. Method: Data of patients affected by oligometastatic-SCLC treated with SABR between 2017 and 2022 in 11 Italian centers were collected. Clinical and therapeutic variables together with OS and time to next treatment were analyzed. Univariate analysis with Kaplan-Meier curve were calculated, and log -rank test were applied. Cox proportional hazard model was used for multivariate analysis. Results: Data from 93 patients and 132 metastatic lesions were analyzed. The median age was 64 years (36-86) and all but 1 had Performance Status 0 or 1. Fifty-two patients presented ED at diagnosis. The first line treatment was radiochemotherapy in 42%, CHT alone in 24% and CHTIO in 28%, others treatment accounts for 4% and only 2% of patients underwent best supportive care. Of the 132 lesions treated with SBRT 55 were in brain, 27 in lung, 11 in liver, 10 in lymph nodes, 8 in bones and 20 in adrenal gland. Median OS was 14 months, 1 year -OS and 2 years OS were 53% and 27%, respectively. The median TtNT was 14 months for the entire population. Of all the analyzed variables only, the anatomical site of the metastases and their number showed statistical significance in the univariate analysist, confirmed in the subsequent multivariate. Conclusion: SABR seems to play a role in delaying further systemic lines in oligometastatic disease and to extend the use of ongoing treatment in oligoprogressive state. Prospective studies are needed to confirm these findings.