Impact of brachytherapy technique (2D versus 3D) on outcome following radiotherapy of cervical cancer

Purpose
The purpose of this study was to analyze the effect of 2D conventional brachytherapy (CBT) compared to 3D MRI-guided brachytherapy (IGBT) with and without the use of interstitial needles on local control, overall survival, and toxicity in patients treated for cervical cancer with radiation or chemoradiation.

Material and methods
A retrospective analysis was performed of biopsy-proven FIGO IB-IVA cervical cancer patients, treated with primary radiation or chemoradiation, followed by brachytherapy (BT) between January 1997 and July 2016. Endpoints were local control, overall survival, and toxicity.

Results
Of 126 patients included, 35 have been treated with CBT, 31 with IGBT without needles (IC), and 60 with IGBT with needles (ICIS). External beam radiotherapy (EBRT) had mostly been delivered concurrently with chemotherapy (weekly cisplatin). Overall local control was 93% after 1 year, and 88% after 3 years. Overall 3-year survival was 75%, and 5-year survival was 66%. The 3D technique (IGBT cohorts) showed a trend for an improved local control and overall survival (p = 0.05) compared to the 2D technique (CBT cohort). A decrease in toxicity was observed from 17% (2D cohort) to 12% (3D cohort). The use of interstitial needles was associated with a higher high-risk clinical target volume (HR-CTV) dose (11.3 Gy vs. 9.9 Gy) and a lower D2cc bladder dose (10.9 Gy vs. 14.7 Gy, both p < 0.01).

Conclusions
In cervical cancer treatment, the use of a 3D brachytherapy technique (MRI-guided with or without interstitial needles) showed a trend towards an increased local control and improved overall survival with reduced toxicity, compared to the conventional 2D brachytherapy technique. The use of interstitial needles allowed dose sculpting, resulting in delivery of higher doses to the HR-CTV, while reducing radiation doses to organs at risk, such as the bladder.