P11.35.B SURVIVAL OF PATIENTS WITH LD-SCLC FOLLOWED WITH BRAIN-MRI INSTEAD OF THE PROPHYLACTIC CRANIAL IRRADIATION (PCI) - RESULTS OF A PROSPECTIVE ONE-ARM STUDY

Abstract BACKGROUND The primary end-point was the assessment of patients’ overall survival at 24 months after starting chest chemoradiotherapy. We assumed that follow-up with brain-MRI (every 3-months) and the use of stereotactic radiotherapy(SRT) for early brain metastases will not worsen survival in LD-SCLC patients without PCI. The other endpoints were intracranial tumor control at 12 and 24 months; the risk of brain metastases without PCI; the feasibility and efficacy of SRT (stereotactic radiotherapy). MATERIAL AND METHODS It was a prospective, two-center one-arm study (NCT04168281). We included 87 patients who responded to radical chest chemoradiotherapy and had no brain involvment on brain MRI and any progression after completion of chemoradiotherapy. The group included 46 females and 41 males aged 52-84 (median=67). PS of 80% patients was very good of good (WHO 0 or 1), in 20% WHO=2. The first patient was enrolled 03.09.2019, the last 20.09.2024. The median and the average follow-up was 545 days and 650 days (range: 960-2097). The patients had brain MRI and chest-abdomen CT every 3 months. The brain metastases were treated with SRT or WBRT or chemotherapy. RESULTS 29 (33%) of patients progressed in the brain. 61 (70%) had any progression. The median OS was 22 months, 2-y OS was 44% (95% CI= 32%-55%); the median OS of pts with brain metastases was 19 months and 2-y OS was 24%; for patients without brain metastases median OS was 27 months and 2-y OS 56%. 14 (48%) patients with brain progression were treated with SRT, 11 (38%) patients with WBRT, 3 (10%) patients with chemotherapy and one (3%) with surgery as the first treatment. The median PFS was 10 months for all patients, 8 months for brain metastases vs 15 months for progression outside the brain. CONCLUSION The progresssion rate in the brain was lower than expected. It confirms than most patients with LD-SCLC do not need PCI. The OS of the whole group was close to the pre-study assumption and comparable to published results in PCI-treated cohorts, however the OS of brain metastases patients was significantly shorter. The progression in the brain was observed early -most patients progressed during the first 12 months and almost all in 18 months. A MRI (not CT) before starting radical chemoradiotherapy should be done in all patients. The significant proportion of patients with brain progression can be treated with SRT instead of WBRT. Better ways to identify patients with high risk of brain involvement are urgently needed to offer them PCI instead of treating the whole LD-SCLC population as per current clinical guidelines.