Carbon-Ion Radiation Therapy for Adenocarcinoma of the Uterine Cervix: Clinical Outcomes of a Multicenter Prospective Registry-Based Study in Japan (2016-2020).

PURPOSE: Cases of adenocarcinoma of the uterine cervix (AUC) have poorer prognoses than those of squamous cell carcinoma. Carbon-ion radiation therapy (CIRT) outcomes for AUC have been reported in retrospective or single-institutional prospective studies but not prospective multicenter studies. We present the results of CIRT for AUC in a prospective multicenter study using a nationwide hospital-based registry in Japan. METHODS AND MATERIALS: Patients with locally advanced untreated AUC who received CIRT at 4 Japanese centers between June 2016 and April 2020 were included in this study. In the absence of organ dysfunction, up to 5 weekly 40 mg/m cisplatin courses were administered. The primary endpoints were 2-year overall survival and local control rates. The secondary endpoints were 2-year disease-free survival rate and late adverse events (AEs). RESULTS: Forty-two patients were enrolled with a median age of 54 years (range, 34-76 years). Patients were diagnosed with stage IIB n = 26, IIIB n = 12, or IVA n = 4 disease. The median follow-up period was 24 months. The 2-year overall survival, local control, and disease-free survival rates were 97.5% (95% CI, 92.7%-100.0%), 80.9% (95% CI, 66.9%-94.8%), and 64.3% (48.1%-80.4%), respectively. Two patients developed grade 3 rectum/sigmoid AE. One patient required urinary diversion surgery during a salvage operation for local tumor recurrence (grade 3 genitourinary AE). No other grade 3 or worse toxicities were reported. CONCLUSION: CIRT is an effective treatment for locally advanced AUC. Further research is required to validate the safety and efficacy of CIRT for AUC.