Low-dose-rate, high-dose-rate, and pulsed-dose-rate intra-cavitary brachytherapy for cervical cancer: The very first comparison study

Purpose:
For cervical cancer patients, intra-cavitary brachytherapy (ICBT) is utilized with various dose-rate systems, such as low-dose-rate (LDR), high-dose-rate (HDR), and pulsed-dose-rate (PDR). This retrospective analysis aimed to compare the therapeutic outcomes of cervical cancer patients treated with either LDR-, HDR-, or PDR-ICBT.

Material and methods:
A total of 613 patients were treated with pelvic external beam radiation therapy (EBRT), followed by either LDR- (271 patients), HDR- (259 patients), or PDR- (83 patients) ICBT. Point-based planning was performed according to orthogonal radiographs in LDR patients, and computed tomography (CT) imaging in HDR and PDR patients. ICBT prescribed dose was as follows: for LDR treatment, 30 Gy in a single-session; for HDR: 7 Gy × 3 fractions (once a week fraction); and for PDR: 27 Gy in an hourly pulse of 70 cGy, with all the doses prescribed at point A. Radioactive source used was cesium-137 for LDR, and iridium-192 for HDR and PDR treatments.

Results:
Loco-regional control (LRC) rate was 74%, 75%, and 77% in LDR, HDR, and PDR groups, respectively (p = 0.80). The 5-year overall survival (OS) in the three groups, i.e., LDR, HDR, and PDR was 63%, 64%, and 68%, respectively (p = 0.77). Severe late toxicity (RTOG grade ≥ 3) rate in the three groups was comparable (LDR, 12%; HDR, 8%; and PDR, 8.9%, p = 0.36).

Conclusions:
Our study revealed comparable LRC, 5-year OS, and late toxicity rates using three dose-rate systems. Lower OS rates were observed in LDR group for stage III patients compared with patients in HDR and PDR groups. Therefore, we suggest that LDR should be used with caution while treating stage III patients.