The influence of time and implants in high-dose rate image-guided adaptive brachytherapy for locally advanced cervical cancer.

Purpose: To compare the clinical outcomes of two different schedules of modern image-guided adaptive brachytherapy (IGABT) in patients underwent chemoradiotherapy (CCRT) and high-dose rate (HDR) brachytherapy (BT) for locally advanced cervical cancer treated (LACC) METHODS AND MATERIALS: Data from medical records of all consecutive patients with histologically proven cervical cancer (FIGO 2018 stage IB-IVA) treated by HDR-BT after CCRT at our institution between 2016 and 2021 were reviewed.

Results: Two hundred and 8 patients with LACC FIGO 2018 stages (IB 20.7%; II 26.5%, III 51%, IVA 1.9%) underwent brachytherapy at our institution. Depending on initial clinical features of disease and the clinical response to CCRT, HDR-BT was delivered with one implant (BT1i) or two implants (BT2i) in 39% and 61% of patients respectively. FIGO stages (≥IIB) were 63% vs. 78% for BT1i and BT2i patient group respectively. Combined brachytherapy technique [endocavitary/interstitial (IC/IS)] was required in 14.8% vs. 68.5% for BT1i and BT2i respectively. With a median follow-up of 32.5 months (95% confidence interval, [29.7-35.8]), local relapse was observed in sixteen patients: 8 patients (3.8%) had local (exclusive) relapse and 8 patients (3.8%) had locally persistent and progressive disease, without significant difference for each BT modality group (p = 0.27), even if BT2i group had more aggressive initial disease. The estimated 3-year disease free survival and overall survival for the entire population was 69% (95% confidence interval, [62-75%]) and 88% (95% confidence interval, [82-92%]) respectively. There was a significant difference in the incidence of global toxicity grade G≥2 in favour to the BT2i group (p = 0.026).

Conclusions: HDR brachytherapy delivered with a long time interval between fractions, two implants, and combined IC/IS brachytherapy is the best way to ensure local control and to perform IGABT with low toxicity, even in advanced stages of disease.