61P Treatment patterns and outcomes of patients with RET fusion-positive non-small cell lung cancer (NSCLC) treated with selpercatinib in Europe: Final results from the SPRINT-RET study

Background: Selective RET tyrosine kinase inhibitors (TKIs) have become standard treatment for advanced/metastatic RET-altered solid tumours.Efficacy was seen in LIBRETTO-001 and ARROW.Late presenting adverse events (LPAEs) are not well described.Real-world data (RWD) can be utilized on these issues not addressed in clinical trial.We presented RWD on resistance mechanisms and post progression treatment outcomes at an earlier conference (Cheung et al.ESMO 2025).Here, we report in detail LPAEs and its management strategies.Methods: Consecutive pts with advanced RET-altered solid tumours followed prospectively receiving >=1 RET TKI through clinical trial or Expanded Access Programme from a single centre were eligible.Natural history of LPAEs and its management were reviewed.Results: 53 pts (48 selpercatinib, 1 BOS172738, 1 selpercatinib & pralsetinib, 3 BOS172738 & pralsetinib) started RET TKI in Mar 2018 -Sep 2023 were included: 47 NSCLC (98% fusion; 2% exon 11 intron), 6 thyroid cancer (50% M918T, 33% fusion, 17% G634R/G533C).Median age = 61.42% = male.Median duration of RET TKI (1L 32%, 2L 43%, 3L+ 25%) = 799 days.Chylous effusion (CE) (4 thorax, 2 ascites) was most common LPAE seen in 6 patients (11%).Median time to CE = 651 days (range: 502 -1134).Efficacy was maintained in pts with CE managed with drainage, dose reduction (DR) and initiation of octreotide treatment.Details of management strategies will be highlighted in the presentation.Conclusions: This is one of the largest prospectively recruited RWD cohort to date.LPAEs like CE were manageable with supportive measures and DR without compromising efficacy.There is a need to be vigilantly recognized to differentiate from PD.