Nivolumab in combination with radiotherapy for unresectable advanced or recurrent gastric cancer (CIRCUIT trial): A 5-year update of the progression-free survival and local control outcomes.

[BACKGROUND AND PURPOSE] We have previously reported a single-arm, phase 1/2 trial against unresectable advanced or recurrent gastric cancer (GC) treated with a combination of radiotherapy and nivolumab (CIRCUIT trial). We present the 5-year updated results of the progression-free survival (PFS) and local control (LC) rates.

[MATERIALS AND METHODS] We enrolled 41 patients with unresectable advanced or recurrent GC who developed progression after the primary and secondary chemotherapies with more than one tumor assessable by diagnostic imaging. Thirty-three patients had five or more tumors and 34 had two or more organs with cancer. The largest or symptomatic tumors were irradiated in 22.5 Gy/5 fractions/5 days. Three patients had multiple sites irradiated. Ten patients underwent irradiation of additional newly appeared tumors after the first irradiation. A total of 65 irradiated fields were evaluated.

[RESULTS] The median survival time and time to progression were 7.3 and 3.0 months, respectively. The overall survival and PFS rates were 29.6% and 7.5% at 1 year, 16.2% and 7.5% at 2 years, and 10.8% and 5.0% at 5 years, respectively. Two patients have lived without disease progression for >5 years. The median LC period was 49.8 months. The LC rates at 1, 2, and 5 years for the irradiated tumor were 84.8%, 71.8%, and 57.5%, respectively. Severe adverse events related to radiotherapy were not observed.

[CONCLUSION] The addition of radiotherapy to nivolumab therapy was safe and seemed to be beneficial for survival. Furthermore, a good LC rate was observed even with administering a palliative irradiation dose.