1515P - Maintenance rucaparib after first-line platinum-based chemotherapy in advanced esophagogastric (OG) adenocarcinoma: Interim results from the PLATFORM trial

Background

PLATFORM is a prospective, open-label, multi-centre, adaptive phase II trial assessing maintenance therapy in patients (pts) with OG adenocarcinoma after platinum-based first-line induction chemotherapy. HER2 -negative pts were randomised 1:1 to surveillance or rucaparib.

Methods

After 18 weeks of platinum-based chemotherapy, pts with response or stable disease were randomised, stratified by performance status, region, and disease extent. Pts in the control arm had 4- weekly surveillance visits vs. receiving rucaparib 600mg twice daily every 28 days to progression, death, or toxicity. Interim analysis target accrual of 61 pts was met, the futility endpoint was 12-week progression free rate (PFR). We also report progression-free survival (PFS) from randomisation to progression or death (pre-specified p-value of 0.025) and toxicity.

Results

125 pts were randomised to the control arm and rucaparib. At data cut-off (28 April 2023) median follow up was 41 months (mo). 59 control and 62 rucaparib pts were evaluable for 12-week PFR; 36% in the control arm and 55% in the rucaparib arm had stable disease (Odds Ratio 2.2, 97.5% CI 1.0-5.1, p = 0.035). 39% of all pts had measurable disease at baseline and no responses were seen in either arm. Median PFS was 2.8 mo in the control arm vs. 4.2 mo in the rucaparib arm (HR 0.70, 97.5% CI 0.46 – 1.08, p = 0.063). The 6 mo PFS rate was 20.4% (97.5% CI 9.9 - 33.5) in the control arm vs. 29.5% (97.5% CI 17.4 – 42.8) in the rucaparib arm but there was no difference in median survival (HR 1.15, 97.5% CI 0.73 – 1.82, p = 0.495). Grade ≥3 treatment related adverse events was 19% in the rucaparib arm and no new safety signals identified.

Conclusions

Interim results showed prolonged disease control in pts receiving maintenance rucaparib after first-line platinum-based chemotherapy. Translational biomarker analysis including homologous recombination deficiency testing may identify a subgroup of pts that could derive additional benefit from maintenance rucaparib.

Clinical trial identification

NCT02678182.

Editorial acknowledgement

Legal entity responsible for the study

D. Cunningham.

Funding

Clovis Oncology.

Disclosure

C.Y.K. Fong: Financial Interests, Institutional, Financially compensated role, Honoraria: BMS. P. Das: Financial Interests, Institutional, Advisory Role: Pfizer, BMS, Eisai, Roche; Financial Interests, Institutional, Other: Janssen, AstraZeneca, Ipsen, MSD, Chugai Pharma. T.S. Waddell: Financial Interests, Institutional, Other, Honoraria, Advisory, Research Funding: Pfizer; Financial Interests, Personal and Institutional, Other, Honoraria, Advisory, Research Funding, Travel/accommodation expenses: Ipsen; Financial Interests, Institutional, Other, Honoraria, Advisory, Research Funding, Travel/accommodation expenses: BMS; Financial Interests, Institutional, Other, Honoraria, travel/accommodation expenses: EUSA Pharma; Financial Interests, Institutional, Other, Advisory, Research Funding,: Roche; Financial Interests, Institutional, Other, Advisory, Research Funding: Merck Sharp & Dohme, Eisai Europe. N. Starling: Financial Interests, Personal, Advisory Board: GSK, Novartis, MSD Oncology, Servier, AstraZeneca, Pfizer, Gilead Sciences; Financial Interests, Personal, Invited Speaker: Clinical Options, Eli Lilly, Pierre Fabre, Amgen, Merck, Novartis, MSD Oncology, GSK, Servier, Seagen; Financial Interests, Institutional, Research Grant, Sept 2017 (24m) Paid to institution research: Merck; Financial Interests, Institutional, Research Grant, Nov 2017 (48m) -Paid to institution research fund: AstraZeneca; Financial Interests, Institutional, Research Grant, Jan 2018 - Paid to institution research fund: Pfizer; Financial Interests, Institutional, Research Grant, July 2018 (36m) Paid to institution research fund: BMS; Financial Interests, Institutional, Research Grant, June 2022: Guardant; Non-Financial Interests, Advisory Role, Ad Board uncompensated.: Guardant. I. Chau: Financial Interests, Personal, Advisory Board: Bristol Myers Squibb, Eli Lilly, MSD, Roche, Merck, AstraZeneca, OncXerna, Boehringer Ingelheim, Astellas, Incyte, GSK, Sotio, Daiichi Sankyo, Eisai, Taiho, Seagen, Turning Point Therapeutics, Novartis; Financial Interests, Personal, Invited Speaker: Eisai, Eli Lilly, Servier; Financial Interests, Institutional, Coordinating PI: Cilag-Janssen, Eli Lilly. D. Cunningham: Financial Interests, Institutional, Research Funding: Clovis, Eli Lilly, 4SC, Bayer, Celgene, NIHR EME, Leap, Roche; Financial Interests, Institutional, Advisory Role: Ovibio. All other authors have declared no conflicts of interest.