Definitive radiotherapy consisting of external beam radiotherapy without central shielding and 3D image-guided brachytherapy for patients with cervical cancer: feasibility for Japanese patients and dose-response analyses for local control in the low-dose range.

Objective: To assess the feasibility of external beam radiotherapy without central shielding in definitive radiotherapy for Japanese patients with cervical cancer.
Methods: We retrospectively analysed the data of cervical cancer patients treated with definitive radiotherapy consisting of external beam radiotherapy without central shielding and three-dimensional-image-guided brachytherapy.
Results: The study included 167 patients (T1 + 2 = 108, T3 + 4 = 59) from eight Japanese institutions. For three-dimensional-image-guided brachytherapy, intra-cavitary and interstitial brachytherapy was utilized in 33 patients (20%). The median follow-up was 26.6 months (interquartile range, 20-43.2). The maximum rectal D2 (75 Gy)/bladder D2 (90 Gy) constraints were deviated by 6%/10% and 10%/5% for T1 + 2 and T3 + 4, respectively. The 2-year incidence of ≥grade 3 proctitis/cystitis was 4%/1% for T1 + 2 and 10%/2% for T3 + 4. The 2-year local progression-free survival was 89% for T1 + 2 and 82% for T3 + 4. For T1 + 2, the 2-year local progression-free survival for the high-risk clinical target volume D90 ≥ 68 Gy (indicated by receiver operating characteristic analysis; area under the curve = 0.711) was 92% versus 67% for <68 Gy (log-rank; P = 0.019). Cox multivariate analysis indicated that the high-risk clinical target volume D90 was one of independent predictors of local failure (P = 0.0006). For T3 + 4, the 2-year local progression-free survival was 87% for the high-risk clinical target volume <82 cm3 (area under the curve = 0.67) and 43% for ≥82 cm3 (P = 0.0004). Only the high-risk clinical target volume was an independent predictor of local failure (P = 0.0024).
Conclusions: Definitive radiotherapy consisting of external beam radiotherapy without central shielding and three-dimensional-image-guided brachytherapy was feasible for Japanese patients with cervical cancer. Dose de-escalation from the current global standards is suggested for patients with T1 + 2 disease.
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