105P - The efficacy of nivolumab monotherapy for advanced gastric cancer depends on the HER2 status

Background

The ATTRACTION-2 trial demonstrated the survival benefits of nivolumab in heavily treated advanced gastric cancer. Moreover, nivolumab has been approved for third- or later line treatment regardless of the human epidermal growth factor receptor 2 (HER2) status. However, there is limited information about variations in the efficacy of nivolumab according to the HER2 status. This study aimed to assess the differences in the efficacy of nivolumab between HER2-positive and -negative population for advanced gastric cancer.

Methods

We identified patients with advanced gastric or gastro-oesophageal cancers who received nivolumab monotherapy from September 2018 to April 2022. The HER2 levels were documented as positive (HER2+) (3+ scores on an immunohistochemical analysis or 2+ scores with positive results on in situ hybridization) or negative (HER2-) (other than the above). We assessed their clinicopathologic and molecular characteristics as well as the efficacy of nivolumab. We retrospectively evaluated their progression free survival (PFS) and overall survival (OS).

Results

We obtained the data of 101 patients who met the inclusion criteria. Twenty-four patients were HER2+, whereas 77 were HER2-. The baseline characteristics of the HER2+/HER2- group were as follows: median age, 73/68 years; men, 71%/58%; Eastern Cooperative Oncology Group performance status 0-1, 58%/70%; previous gastrectomy, 41%/54%; intestinal type, 66%/38%; and peritoneal metastasis, 20%/55%, respectively. The median progression-free survival and median overall survival of the HER2+/HER2- group was 2.0 (95% confidence interval, CI: 1.5 to 2.9)/2.5 (95% CI: 1.9-3.2) months (p=0.0945) and 8.3 (95% CI: 3.9-18.9)/8.2 (95% CI: 5.5-10.9) months (p=1.0000), respectively. We observed the progression free survival at 24 months in seven cases in the HER2- group, whereas no cases in the HER2+ group achieved 24 months of disease control.

Conclusions

Our data analysis did not reveal statistically significant differences in the PFS or OS between the groups. However, consistent antitumor activity of nivolumab >2 years was only observed in few participants of the HER2- group, thus necessitating further studies to confirm these results.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.