[An Abscopal Effect after Palliative Radiotherapy in a Patient with a Locally and Lymph Node Recurrent Gastric Cancer].

Radiotherapy is known to have a high local effect for cancer treatment. However, several reports that radiotherapy could stimulate the anti-tumor effect by releasing endogenous signals and cytokines, increasing the presentation of tumor associated antigens on dendritic cells, and proliferating tumor antigen-specific cytotoxic T lymphocytes have been shown. A tumor regression in both non-irradiated and irradiated fields have observed, which is called"abscopal effect". We report a case of the abscopal effect in adenocarcinoma of the stomach with locally and lymph node recurrence after surgery. A 59-year-old Japanese male was diagnosed with residual stomach cancer and underwent total gastrectomy and distal pancreatectomy. Three months after the surgery, a local recurrence and the involvement of para-aortic lymph node were diagnosed using computed tomography. The chemotherapy treatment(S-1, cisplatin, trastuzumab)was prescribed. However, the disease has progressed. Paclitaxel and ramucirumab were given for second-line, nivolumab for third-line and irinotecan for fourth-line. During that, tumor at local recurrent site invaded to the portal vein. The patients received 50 Gy in 25 fractions of radiotherapy. A remarkable reduction of the mass was shown. In addition to this, we observed that spontaneous shrinking of the para-aortic lymph node metastasis, which was located out of the radiation field. We observed a rare radiation-induced abscopal effect. Radiotherapy might represent a potential candidate for a combination with immunotherapy. A combination of immunotherapy as well as chemotherapy with radiotherapy represents a promising therapeutic strategy.