578 Ca125, HE4 and systemic immune inflammation index during maintenance with PARPi in ovarian cancer patients: three markers, two markers, or usual ca125?

Introduction/Background Serum Ca125 level is systematically evaluated during maintenance therapy with PARP inhibitors (PARPi) to early detect an ovarian cancer relapse. This study aimed to evaluate whether HE4 or the Systemic Immune Inflammation Index (SII) can anticipate the relapse diagnosis in this setting, when compared to Ca125 alone. Methodology Data from all the patients who had an ovarian cancer relapse during PARPi therapy at S.Anna Hospital in Torino (2017–2023) were collected prospectively. Ca125, HE4, and the blood count were assessed the day before each cycle of PARPi therapy. SII was estimated as (platelet count × neutrophil count)/lymphocyte count. Results Among 76 patients treated with PARPi, 22 relapses (29%) occurred during PARPi therapy, (7–14-1 during Olaparib-Niraparib-Rucaparib, respectively). In these patients, PARPi were used in 64% as a maintenance therapy after first-line chemotherapy and in 36% as maintenance after second-line chemotherapy. Ca125 was elevated in 90% of the relapses and HE4 in 68%. In 7 patients, HE4 started to rise before Ca125 (with a lead time of 1–12 months) and in 1 patient without Ca125 elevation, HE4 anticipated the diagnosis of relapse. A SII index peak was shown in almost all the relapses (19/22), and in 63% this peak coincided (+/- 2 months) with the first rise of Ca125 and/or HE4 Conclusion Our data support the use of both Ca125 and HE4 during maintenance therapy with PARPi and SII index peak seems useful to reinforce the suspicion of a relapse when Ca125 and HE4 start to rise. These data should be confirmed on a larger scale trial. Disclosures The authors have no disclosures to declare.