ASCO GI 2026 | STOPGAP: iterative intraperitoneal paclitaxel and chemotherapy in G/GEJA

As we know, since systemic therapy by itself is not as effective in peritoneal carcinomatosis, there is this constant desire to figure out what additional options can be introduced to improve the outcomes of these patients. And just based on the biology of peritoneal carcinomatosis, it makes sense that maybe regional therapies, addition of regional therapies, might improve the outcomes. And therefore, administration of intraperitoneal chemotherapy, directly putting chemotherapy into the abdominal cavity, is one approach that is tested. And it is tested extensively in Asia because of how common gastric cancer is in Asia. And there are a couple of clinical trials, especially, you know, prior to STOPCAP1, the Phoenix GC trial showed some signal with intraperitoneal paclitaxel administration in gastric PC. Now, with that particular concept is how the STOPCAP1 trial was developed, but there are important modifications to the concept itself. So the STOPCAP1 trial is specifically for patients with gastric or G-junction cancer, cT3 G-junction cancer with cytology-positive disease or gross peritoneal carcinomatosis. The key differences are patients must have received a minimum of three to six months of systemic therapy and must have peritoneal M1 disease. That’s actually the selection because we’re ensuring that the patients who have peritoneally M1 metastases are the ones that are being enrolled into this regional therapy trial. And once they get enrolled in the trial in STOPCAP1, they get bidirectional paclitaxel. So this is important because they’re getting IV and IP paclitaxel. But the great part about the study design is that the patients are still continuing systemic therapy with 5-FU, leucovorin, and any immune checkpoint inhibitors or targeted therapies. And after three months, we are then reevaluating these patients for response. And in select patients, if their peritoneal cancer index is low, we are able to offer surgical treatment, which is cytoreduction. Different from the Asian concept where they use conversion gastrectomy. We are not doing conversion gastrectomy. We are doing actual cytoreduction where all of the disease gets resected. So that is actually how the STOPCAP1 trial has been designed. And we now have enrolled 33 patients in the trial. The trial is now closed for accrual. And we have done 14 cytoreductions. 43% is the cytoreduction rate. And the results show that collectively in patients who have undergone cytoreduction compared to the ones that did not, the median overall survival, it’s still an interim analysis. The median overall survival from diagnosis is about 38 months. And that’s an incredible survival that we have never seen in patients with specifically gastric carcinomatosis. So, you know, I think it’s a very strong signal. The safety and feasibility has been established. So we are excited for the STOPCAP-1 result and even more excited for the STOPCAP-2 trial.

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