P-253 Single agent immunotherapy in advanced oesophago-gastric (OG) cancer: An option for frail patients

The management of oesophago-gastric (OG) cancers has rapidly evolved over the last three years with the introduction of immune checkpoint inhibitors into the treatment landscape. Nivolumab monotherapy is currently used in the UK as a second-line treatment option in advanced oesophageal squamous cell carcinomas (SCC). Additionally, since August 2020, it has been funded for mismatch repair deficient (MMRd) advanced OG cancers to avoid immunosuppressive toxicity associated with chemotherapy during the COVID pandemic. Limited real-world data on long term safety and outcomes. using immunotherapy in this population exist. We present our experience of delivering single agent nivolumab at a tertiary UK cancer centre, reporting on real-world adverse events (AEs) and outcomes. This was a retrospective review of patients with advanced OG cancers who received treatment with single-agent nivolumab, between June 2018 – December 2022, from a large London Cancer Centre. Data was recorded on a prospectively collected database. Electronic records were reviewed for data on demographics, histological subtype, biomarker profile and AEs. The data was analysed for maximal response, median progression free survival (PFS) and overall survival (OS). Subgroup response and survival analysis was performed on the MMRd patients. Thirty-three patients received single agent nivolumab between June 2018 and December 2022. The total population was made up of 20 (61%) oesophageal, 10 (30%) gastric and three (9%) gastro-oesophageal junction tumours. Nineteen (58%) patients were SCC and 14 (42%) were adenocarcinomas (AC), of which 10 were MMRd. Of the total population, the median age was 67 years. Most patients (n=30, 91%) had a baseline performance status of 0-1, and received nivolumab as second line treatment or more (n=23, 70%). Of the MMRd population, the median age was 73.5 years. Most MMRd patients (n=8, 80%) had a baseline performance status of 1, and received nivolumab as first-line treatment or more (n=8, 80%). In terms of AEs in the overall population, grade (G) 1/2 AEs were reported by 32 (97%) patients. One patient had a G3 toxicity, which was an endocrinopathy. Two (6%) patients stopped treatment due to toxicity – myocarditis (G2) and nephrotoxicity (G2). A partial or complete response was documented in 12 (36%) of the total population; of those 67% were MMRd. Median PFS across the whole population was 7.6 months, and 13.6 months in the MMRd adenocarcinoma population. Median OS across the whole population was 14.5 months, and 17.0 months in the MMRd adenocarcinoma population. The use of immunotherapy in OG cancers is expanding. Our experience suggests nivolumab was well tolerated in patients with OG cancers with only one patient experiencing G3 toxicity. In our cohort the MMRd group, who were older, had a favourable survival outcome compared to published trial data, exploring reduced-intensity chemotherapy in older patients with advanced oesophago-gastric cancers. Similarly, most patients with a radiological response were MMRd. The benefit of single agent nivolumab seen in this subgroup highlights the importance of MMR testing, and its potential role as a first line treatment, in older patients with MMRd oesophago-gastric cancers.