[A Case of Perianal Squamous Cell Carcinoma with Left Inguinal Lymph Node Metastasis That Showed a Complete Response More Than Five Years after Chemotherapy and Concomitant Proton Beam Therapy].

We report a case of perianal squamous cell carcinoma and left inguinal lymph node metastasis that showed a complete response more than 5 years after chemotherapy and concomitant proton beam therapy. A 34-year-old woman was referred to our hospital for an anal tumor and a left inguinal tumor. A digital rectal examination revealed a tumor in the anterior wall of the anal canal. In addition, the left inguinal lymph nodes were swollen, leading us to suspect metastases. Biopsy specimens confirmed poorly differentiated squamous cell carcinoma. We made a diagnosis of squamous cell carcinoma T4bN2M0, Stage III b. The patient was treated with chemotherapy consisting of 5-FU(700mg/m / 2/day; continuous intravenous administra- tion)on days 1-5, and CDDP(70mg/m / 2/day)on day 1, along with concomitant proton beam therapy. A total of 45 Gy of X-ray irradiation was administered to the primary lesion, pelvis, and groin area. Furthermore, 24.2 Gy of proton beam therapy was administered to the primary lesion, and 28.6 Gy to the left inguinal lymph nodes. The patient tolerated this treatment with no severe adverse effects. The tumor disappeared completely 1 month after this treatment, and biopsy specimens confirmed the absence of any viable cancer cells. The patient has been alive with no sign of recurrence for 5 years.