In The Last of Us, the scary part was fungi hijacking bodies; in gastric cancer, the scarier everyday version is tumor cells quietly convincing your immune system to act like it “didn’t see anything.”
That is the basic plot of PD-1 and PD-L1 biology. Your immune cells have brakes so they do not go full action-movie on healthy tissue. Tumors, being cellular opportunists with no respect for zoning laws, can exploit those brakes. PD-L1 is one of the “please ignore me” signals. PD-1 drugs try to cut through that nonsense and let immune cells notice the problem again.
The new ASTRUM-006 trial asks a very practical question: if a stomach or gastro-oesophageal junction cancer can still be removed by surgery, should doctors bring immunotherapy into the room earlier, before and after the operation, rather than waiting until the cancer has had more time to misbehave?
The Usual Plan Has Been Chemo, Surgery, More Chemo
For locally advanced but resectable gastric cancer, surgery is the main chance at cure. But surgery alone can leave behind microscopic disease, the sort of invisible leftover problem epidemiologists politely call “residual risk” because “tiny chaos confounder” sounds less professional.
That is why perioperative chemotherapy exists. “Perioperative” just means treatment around surgery: some before, some after. The idea is to shrink the tumor, attack stray cancer cells, and improve the odds that the operation is not fighting yesterday’s battle with tomorrow’s recurrence.
ASTRUM-006 tested whether adding serplulimab, a PD-1 inhibitor, to pre-surgery SOX chemotherapy and then continuing serplulimab after surgery could improve outcomes compared with perioperative SOX chemotherapy alone.
What ASTRUM-006 Found
This was not a tiny “we tried it in six people and everyone looked hopeful under fluorescent lighting” study. It was a randomized, double-blind, phase 3 trial. Researchers screened 1,646 patients and randomly assigned 588 patients at 57 hospitals in China. All had PD-L1-positive, locally advanced, resectable gastric or gastro-oesophageal junction adenocarcinoma, with PD-L1 combined positive score, or CPS, of at least 5.
The main result: event-free survival improved with serplulimab.
In patients with PD-L1 CPS of at least 10, median event-free survival was not reached in the serplulimab group versus 42.0 months in the placebo group. The hazard ratio was 0.65, meaning the relative risk of an event was lower with serplulimab. In the full intention-to-treat population, median event-free survival was also not reached with serplulimab versus 35.9 months with placebo, with a hazard ratio of 0.73.
Translation without the statistical tuxedo: fewer patients had recurrence, progression, or death during follow-up when serplulimab joined the treatment plan.
The safety finding was also interesting. Grade 3 or worse treatment-related adverse events occurred in 47% of patients receiving serplulimab and 59% receiving placebo plus chemotherapy. That does not mean immunotherapy is harmless. Immune drugs can cause the immune system to start filing complaints against normal organs. But in this trial, the serplulimab strategy did not look like it added a giant toxicity tax.
Why This Is a Big Deal, With Appropriate Error Bars
Gastric cancer remains a major global burden, with especially high rates in parts of East Asia. Risk patterns are not random: age, sex, geography, Helicobacter pylori, diet, and socioeconomic context all crowd into the causal diagram like they were invited to a very nerdy dinner party.
That population lens matters because ASTRUM-006 enrolled patients in China, and the trial population was mostly male, with a median age of 61. The results are strong, but they still need careful interpretation across other regions, surgical practices, chemotherapy backbones, and patient groups. Generalizability is where good ideas go to get stress-tested.
The trial also lands in a fast-moving neighborhood. KEYNOTE-585 tested perioperative pembrolizumab plus chemotherapy and improved pathological responses, but its event-free survival result did not cross the prespecified statistical boundary. MATTERHORN, meanwhile, showed that adding durvalumab to perioperative FLOT improved event-free survival in resectable gastric and gastroesophageal junction cancer. So ASTRUM-006 is not a lonely data point. It is part of a broader pattern: immunotherapy is moving earlier, when tumors may be more vulnerable and the immune system has not yet been through the cancer-treatment equivalent of airport security.
The Catch: We Still Need the Long Game
Event-free survival is meaningful. Nobody wants recurrence penciled onto the calendar. But overall survival data are still immature, and that matters. A treatment can delay bad events without always proving that people live longer. Oncology has learned this lesson often enough to keep a statistical helmet nearby.
Still, the idea is compelling: use chemotherapy to damage the tumor, use surgery to remove it, and use immunotherapy to help the immune system recognize what is left. If future follow-up confirms a survival advantage, this could offer a new perioperative option for PD-L1-positive resectable gastric cancer, especially for patients whose tumors seem immunologically targetable.
Cancer cells are not masterminds. They are more like rule-breaking tenants who found the building’s maintenance loopholes. ASTRUM-006 suggests serplulimab may help close one of those loopholes before the tumor gets another chance to redecorate.
References
-
Shen L, Zhang X, Ji K, et al. Perioperative serplulimab with neoadjuvant chemotherapy versus perioperative chemotherapy in PD-L1-positive gastric cancer (ASTRUM-006): a randomised, double-blind, multicentre, phase 3 study. Lancet. 2026. https://doi.org/10.1016/S0140-6736(26)00974-8
-
Al-Batran SE, et al. Perioperative durvalumab in gastric and gastroesophageal junction cancer. New England Journal of Medicine. 2025. https://doi.org/10.1056/NEJMoa2503701
-
Shitara K, Rha SY, Wyrwicz LS, et al. Neoadjuvant and adjuvant pembrolizumab plus chemotherapy in locally advanced gastric or gastro-oesophageal cancer (KEYNOTE-585). Lancet Oncology. 2024;25:212-224. https://doi.org/10.1016/S1470-2045(23)00541-7
-
Haverkamp L, et al. Neoadjuvant atezolizumab plus chemotherapy in gastric and gastroesophageal junction adenocarcinoma: the phase 2 PANDA trial. Nature Medicine. 2024;30:519-530. https://doi.org/10.1038/s41591-023-02758-x
Disclaimer: The image accompanying this article is for illustrative purposes only and does not depict actual experimental results, data, or biological mechanisms.