1589P - Systemic treatment strategies and outcomes of patients with peritoneal metastases of gastric origin

Background

Patients with peritoneal metastases of gastric origin are often underrepresented in clinical studies due to unmeasurable radiological disease. In theory, the efficacy of systemic treatment might be hampered by the peritoneal-plasma barrier. Here, we describe the outcomes of systemic treatment strategies in patients with peritoneal metastases in a real-world setting.

Methods

Patients with gastric adenocarcinoma and peritoneal metastases (with or without other metastases) treated with systemic therapy in the Netherlands between 2015 and 2020 were identified from the Netherlands Cancer Registry. Treatment regimens were classified into groups with one, two or three agents. Median overall survival (mOS) was determined, and multivariable Cox regression analyses were used to compare treatment groups, corrected for relevant tumor and patients’ characteristics.

Results

In 909 patients, a total of 36 different treatment regimens were administered as first-line therapy. Local peritoneal therapies (i.e., HIPEC) was not observed. 5-FU or derivate combined with oxaliplatin (62%) was used most frequently, followed by epirubicin/oxaliplatin/capecitabine (9%) and capecitabine monotherapy (5%). mOS after first-line treatment was 8.1 months. Triplets containing docetaxel (mOS: 10.7 months, HR: 0.68, 95% CI 0.52-0.89) and trastuzumab-containing regimens (mOS: 11.4 months, HR: 0.65, 95% CI 0.50-0.85) had superior mOS compared to doublet therapy with 5-FU/capecitabine + oxaliplatin (mOS: 7.6 months) in multivariable analysis. Monotherapy was associated with a significantly lower mOS of 3.9 months (HR: 2.33, 95% CI 1.69-3.20). Best supportive care had a mOS of only 1.7 months.

Conclusions

In this real-world study, heterogeneity in the first-line treatment for patients with peritoneal metastases of gastric cancer was seen. Triplet therapy with docetaxel and trastuzumab-containing regimens were associated with longer survival. For docetaxel, this result is in contrast to previous meta-analyses in patients with metastases at any location. Whether this is caused by better exposure of peritoneal metastases to docetaxel or results from bias by indication should be the subject of further research.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

R.H.A. Verhoeven: Financial Interests, Institutional, Advisory Board, Consultancy: Daiichi Sankyo; Financial Interests, Institutional, Research Grant: Bristol Myers Squibb; Non-Financial Interests, Member of Board of Directors, The Dutch Upper-GI Cancer Group is the Dutch multidisciplinary research group regarding Upper-GI cancers.: Dutch Upper-GI Cancer Group; Non-Financial Interests, Member of Board of Directors: Internation Association of Cancer Registries. H.W.M. van Laarhoven: Financial Interests, Institutional, Advisory Board: BMS, MSD; Financial Interests, Personal, Invited Speaker: Lilly; Financial Interests, Institutional, Writing Engagement: Nordic Pharma; Financial Interests, Institutional, Invited Speaker: Servier; Financial Interests, Institutional, Research Grant, REPEAT study: Bayer; Financial Interests, Institutional, Research Grant: BMS, Philips; Financial Interests, Institutional, Local PI, FRACTION study: BMS; Financial Interests, Institutional, Research Grant, ACTION study: Celgene; Financial Interests, Institutional, Research Grant, DECO study: Janssen; Financial Interests, Institutional, Local PI, RAINFALL study: Lilly; Financial Interests, Institutional, Local PI, KEYNOTE 062 and KEYNOTE 181 study: Merck/MSD; Financial Interests, Institutional, Research Grant, SOX study: Nordic Pharma; Financial Interests, Institutional, Research Grant, TRAP study, PERFECT study; local PI of JACOB study: Roche; Financial Interests, Institutional, Research Grant, LyRICX study: Servier; Financial Interests, Institutional, Research Grant, TAPESTRY study: Merck; Financial Interests, Institutional, Research Grant, Research money and investigational product: Incyte; Non-Financial Interests, Institutional, Product Samples, For all clinical study mentioned, study medication is provided: See 'research funding'. B. Mostert: Financial Interests, Institutional, Research Grant: Sanofi, Pfizer, BMS; Financial Interests, Institutional, Speaker, Consultant, Advisor: Lilly, Servier; Financial Interests, Personal and Institutional, Speaker, Consultant, Advisor: BMS. B.P.L. Wijnhoven: Financial Interests, Institutional, Research Grant: BMS; Financial Interests, Institutional, Speaker, Consultant, Advisor: BMS. R.H. Mathijssen: Financial Interests, Institutional, Research Grant, Investigator-initiated research: Astellas, Bayer, Cristal Therapeutics, Pfizer, Roche, Sanofi, Servier, Boehringer Ingelheim, Novartis; Financial Interests, Institutional, Coordinating PI: Pamgene. All other authors have declared no conflicts of interest.