The presence of lymph node metastasis (OR 0.52, 95% CI 0.40–0.66), higher tumour grade (e.g. OR 0.60, 95% CI 0.48–0.74 for grade III compared to I) and HER2-positive tumours (OR 0.61, 95% CI 0.45–0.82) were associated with lower odds of non-adherence to ET. Here, ERBB2 is linked to metastatic malignant neoplasm in the lymph nodes.