[A case of superior sulcus tumor treated with carbon ion radiotherapy].

Superior sulcus tumor( SST) is a rare type of lung cancer. Treatment usually consists of surgical resection after chemoradiotherapy. We report a case of a woman in her fifties who underwent carbon ion radiotherapy for SST. The patient complained of left shoulder pain, and imaging studies revealed a 5.2×3.5-cm local solid tumor at the apex of the left lung, invasion to the ribs, and no lymph node swelling. The level of tumor marker, carcinoembryonic antigen (CEA), was 5.7 ng/mL. Needle biopsy specimen revealed adenocarcinoma. The diagnosis was SST, T3N0M0, stage IIB. We did not detect Horner syndrome. Carbon ion radiotherapy at 66 Gy equivalent dose per 10 fractions was administered to the SST site. Subsequently, the tumor size decreased to 4.5×1.9-cm. The adverse effect was Grade 1 skin and pulmonary toxicity. Six months later, Grade 2 left shoulder connective tissue toxicity was observed; it was difficult to differentiate this from tumor recurrence. After 2.5 years from radiotherapy, the patient is free from recurrence. Carbon ion radiotherapy is effective and safe and can be considered as an important treatment option for SST.