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e17598 Background: Rucaparib is a PARP inhibitor (PARPi) approved as maintenance therapy for platinum (Pt)-sensitive recurrent high-grade ovarian cancer (HGOC), and as treatment for BRCA-mutant HGOC patients. To date, there is little evidence about the efficacy and safety of rucaparib after prior exposure to PARPi. This subanalysis aims to describe the patients’ characteristics and treatment outcomes with rucaparib in women who were included in the rucaparib early access program (RAP) in Spain and had received a prior PARPi. Methods: A retrospective study was conducted by GEICO at 22 hospitals in Spain to analyze data of 51 women treated within the RAP (600 mg BID). Adult women with HGOC, fallopian tube, or primary peritoneal cancer, who had received at least one prior PARPi before rucaparib were analyzed. Patients’ characteristics, medical history, safety, efficacy, and dosing data were collected. Results: A total of 14 women, with a median age of 63 years old (42-78) were included in this subanalysis. Of them, 92.9% were diagnosed of epithelial ovarian cancer and 78.6% had mutations in BRCA1/ 2 genes. The median number of lines before rucaparib was 5 (3-8), while the number of lines before the first PARPi was 3 (2-5). Except for one woman who had received 2 prior PARPis before rucaparib, the others had received just 1. Most patients were given olaparib as the first PARPi (n = 12, 85.8%), while niraparib was the initial PARPi in the remaining cases (n = 2, 14.3%). The outcomes of the treatment with rucaparib in these patients are outlined in table 1. Rucaparib was given as maintenance therapy in 1 patient and as treatment in 13 patients, 12 of them being Pt-resistant. The progression-free survival (PFS) ranged from 0.23 to 9.12 months. Adverse events (AE) of any grade were detected in 78.6% of patients, whereas AE of grade ≥3 affected 28.6% of women. Rucaparib dose was interrupted in 57.1% and reduced in 42.9% of patients. Only 1 patient discontinued rucaparib due to toxicity. No new safety signals were detected. Conclusions: This is one of the first real-word studies reporting the use of rucaparib after treatment with another PARPi. Even in these heavily pre-treated patients who had received prior PARPi, rucaparib efficacy has been notable in some cases, and its safety profile is consistent with that reported in previous clinical trials. Future studies should focus on the selection of patients who could benefit from rucaparib after prior PARPi exposure. [Table: see text]

e17562 Background: Rucaparib is a PARP inhibitor approved for the treatment of high-grade ovarian cancer (HGOC). Clinical trials have demonstrated its benefit both as maintenance therapy (MTN) for platinum (Pt)-sensitive recurrent HGOC, and as treatment (Tx) in BRCA-mutated relapsed or recurrent HGOC patients. Here we analyze real-world data from the rucaparib early access program (RAP) in Spain with focus in the long-term responder patients (LTR). Methods: A retrospective observational study was performed by GEICO at 22 hospitals in Spain that had treated patients within the RAP. Adult women with HGOC, fallopian tube, or primary peritoneal cancer were included and received rucaparib (600 mg BID) in the MTN, Tx Pt-sensitive or Tx Pt-resistant setting. Patients’ characteristics, medical history, safety, efficacy, and dosing data were collected. In this analysis, long-term response was defined as progression-free survival (PFS) ≥12 months for the MTN group and ≥6 months for the Tx group. LTR were stratified based on the rucaparib indication (MTN/Tx). Results: Between July 2020 and February 2021, 51 patients were recruited: 18 received rucaparib as MTN and 33 as Tx. In the MTN group, 6 patients (33.3%) were LTR, with a median age of 65 years (54-79). Of them, 2 patients (33.2%) harbored BRCA or RAD51C mutations. The median number of prior lines was 3 (2-6), being ≥5 in 33.2%, and 50.0% received prior bevacizumab. ECOG PS was ≤1 in all these patients, 66.6% had measurable disease and 50.0% achieved a partial response to prior Pt-based chemotherapy. In the Tx group, 10 patients (30.3%) were LTR, with a median age of 71 years (47-86). All of them harbored BRCA and/or RAD51C mutations. The median number of prior lines was 6 (2-9), with 60.0% receiving ≥5 prior lines, and 50.0% received prior bevacizumab. Regarding Pt-status, 40.0% of patients were Pt-sensitive and 60.0% were Pt-resistant. The ECOG PS was ≥1 in 30.0% of patients and 60.0% had measurable disease. The median PFS of LTR was not achieved in the MTN group and was 10.9 months (95% CI: 7.0-16.7) in the Tx group. Adverse events (AE) of any grade were reported in 66.6% of LTR within the MTN group and in 100.0% within the Tx group, while AE of grade ≥3 occurred in 16.6% and 50.0%, respectively. Rucaparib dose was reduced in 50.0% of LTR in the MTN group and 80.0% in the Tx group. Discontinuation rate due to rucaparib toxicity was 20.0% in the Tx group and there were no discontinuations due to toxicity in the MTN group. No new safety signals were detected. At present, 3 and 1 patients are still receiving rucaparib as MTN and Tx, respectively. Conclusions: A durable response was achieved in a notable proportion of patients, even despite their unfavorable conditions at treatment initiation (heavily pre-treated patients, partial response or resistance to Pt, or high volume of disease). The safety profile of rucaparib in this real-world setting is consistent with that reported in clinical trials.

e17550 Background: In epithelial ovarian cancer (EOC), the identification of mutations in homologous recombination repair (HRR) genes on tumor is prognostic, predictive of response to PARP inhibitors, and a tool to identify individuals at genetic cancer risk. The aim of this study is to compare the concordance between two laboratories in identifying and classifying genetic variants in HRR genes. Methods: In a multicentre ambispective series of unselected, non mucinous EOC of all stages formalin-fixed and paraffin embedded tumors were collected. These samples underwent the same mutational analysis of 15 HRR genes ( ATM, BARD1, BRCA1, BRCA2, BRIP1, CDK12, CHEK1, CHEK2, FANCL, PALB2, PPP2R2A, RAD51B, RAD51C, RAD51D, RAD54L) in two different Laboratories (Lab1, Lab2) that used their own validated multi-gene NGS panels. Variant allele frequency (VAF) threshold was 5% for single nucleotide polymorphism and 10% for indels. Large rearrangements were not analyzed. Variants were classified into three categories based on ACMG criteria: non-mutated (class 1-2), Variants of Uncertain Significance (VUS: class 3) and likely pathogenic/pathogenic (class 4-5). Results: A total of 81 cases were sent for the analysis. One had low DNA quality and therefore 80 cases were finally studied (85% high grade serous and 74% FIGO stage III-IV). Results reported by Lab1 and Lab2 (lab1/Lab2) were the following: 21/19 (26%/24%) cases had BRCA1/2 mutations, 7/8 (8.7%/10%) mutations on other HRR genes including two in ATM and RAD51D, one in CHEK1, CHEK2, and FANCL and one RAD51C reported in Lab2 only while the rest were either VUS 23/27 (29%/34%) or non-mutated 29/26 (36%/33%). Concordance between laboratories in classifying patients was 93.75% (kappa coefficient 0.86). Discrepancies (DC) on variants were classified into arbitrary categories, namely 0= complete concordance, category 1 meaning DC in detection assumed to be due to tumor heterogeneity (VAF nearby the threshold) or technique (1A), or caused by laboratories performance and avoidable (1B) and the category 2 identified DC in interpretation without clinical relevance (2A) or clinically relevant (2B), the results of total number of variants are shown in table. Overall, regarding clinically relevant DC in HRR genes, 9 DC in variants were observed including six 2B, two 1A and one 1B and they affect 5 (6.3%) patients since some were overlapping. Conclusions: In our EOC series the concordance of two Laboratories in the identification of clinically relevant HRR mutations on tumor is high but discrepancies in interpretation remain a challenge that needs further harmonization.[Table: see text]