Abstract 517P
Background
Phase II-III trials have demonstrated lasting clinical efficacy with Immune Checkpoint Inhibitors (ICI) in metastatic Gastrointestinal Tumors with Mismatch Repair Deficiency or Microsatellite Instability (dMMR/MSI-H). The GAIN study evaluates ICI effectiveness and safety in real-world dMMR/MSI-H Gastrointestinal Tumors.
Methods
A multicenter, retrospective observational study on dMMR/MSI-H gastrointestinal tumors treated with ICI was conducted at 6 university hospitals in Northwest Spain.
Results
A total of 112 patients treated with ICI between November 2015 and August 2023 were analyzed. Median age was 69.4 years (range 29-89), with 52.7% males. Colorectal cancer (CRC) comprised 57.1% of cases, mainly right-sided (67.2%) and BRAF V600mt (37.5%), followed by gastroesophageal adenocarcinoma (31.3%). Prior treatments included: no previous treatment (33%), only adjuvant chemotherapy (20.5%), and first-line treatment (33%). At ICI initiation, 22.3% had an ECOG PS0, 58% had ECOG PS1, and 18.8% had ECOG PS2. 17% had ≥3 metastatic sites, with liver metastases in 30.4%. Pembrolizumab was the predominant ICI (92%), administered at fixed dosing in 59.8% of cases. Overall, 92.9% were evaluable, achieving an ORR of 76% and a DCR of 90.4%. For CRC and non-CRC, ORR was 74.6% and 77.8%, and DCR was 89.8% and 91.1%, respectively. Median OS was 55.1 months (95% CI 42.4-60.6), and PFS was 50.7 months (95% CI 33-68.4). OS for CRC and non-CRC was 60.9 months (95% CI 46.9-75) and 39.8 months (95% CI 17.9-61.6), with corresponding PFS of 60.9 months (95% CI 39.3-82.6) and 34.8 months (95% CI 15.9-53.6). Grade 3-4 treatment-related adverse events included nephritis (3.6%), pneumonitis (1.8%), asthenia (1.8%), and hepatitis (1.8%), with no treatment-related deaths.
Conclusions
Our series confirms the efficacy and safety of immune checkpoint inhibitors in advanced dMMR/MSI-H gastrointestinal tumors, both colorectal and non-colorectal.
Legal entity responsible for the study
Galician Research Group on Digestive Tumors (GITuD).
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.