Intensity-modulated radiotherapy for synchronous cancer of the anal canal and cervix.

Due to recent advancements in diagnostic techniques, the incidence of multiple primary cancer has increased; however, synchronous cancer of the anal canal and cervix (SCACC) is rare, and no previous studies have investigated the treatment of this disease. The present study reports a case in which intensity-modulated radiotherapy (IMRT) was used to treat a 64-year-old female with SCACC, inguinal lymphadenopathy and anal pain. The patient was diagnosed with cT3N3M0 stage IIIb anal canal squamous cell carcinoma and cT1b1N0M0 stage Ib1 cervical squamous cell carcinoma, based on biopsy and imaging study data. According to the definitive treatment for advanced-stage anal canal cancer, outpatient treatment with chemoradiotherapy (CRT) using S-1 for SCACC was recommended, as the patient did not want to undergo resection of the anus. Considering the lymph node regions involved in SCACC and the necessary doses, the treatment plan was as follows: Whole pelvis and inguinal lymph node region radiation (36 Gy/20 fractions); a first booster radiation dose (9 Gy/5 fractions) for the whole pelvis; and a second booster radiation dose (14.4 Gy/8 fractions) for the primary lesions. The patient was prescribed S-1 at a dose of 60 mg/m2/day twice daily on days 1-14 and 29-42. The patient experienced grade 2 diarrhea and anal mucositis, but CRT was completed without discontinuation and hospitalization. The patient exhibited a complete response and remained disease-free without any treatment-associated complications at the 6-month follow-up. In conclusion, SCACC was successfully treated with IMRT in the present case. It is important to determine the treatment strategy for synchronous cancer types, taking into consideration the tumor stage, tumor location and patient situation.