Dr Kohei Shitara talks to ecancer at ESMO 2026 about the second interim analysis of the phase III HERIZON-GEA-01 trial, evaluating zanidatamab plus chemotherapy with or without tislelizumab in patients with previously untreated HER2-positive advanced or metastatic gastroesophageal adenocarcinoma.

The study randomised 914 patients to receive zanidatamab-based treatment or trastuzumab plus chemotherapy.

After a median follow-up of 35.3 months, zanidatamab plus chemotherapy significantly improved median overall survival compared with trastuzumab plus chemotherapy (22.9 versus 19.6 months; HR 0.76).

Adding tislelizumab further extended median overall survival to 27.0 months, although the improvement over zanidatamab plus chemotherapy alone did not reach statistical significance.

Three-year overall survival was highest with the triplet combination (39.8%), and safety remained consistent with previous findings.

Dr Shitara suggests that these results support zanidatamab-based regimens as a first-line treatment option for HER2-positive advanced gastroesophageal cancer.