Which patients benefit from post-implant CT dosimetry after real-time intraoperative planning for low dose rate prostate brachytherapy? Case series and systematic literature review.

INTRODUCTION: At present, post-implant CT-based dosimetry is a standard quality assurance practice following low dose rate (LDR) prostate brachytherapy. However, it rarely influences management and involves radiation exposure, costs and inconvenience. The purpose of our study was to assess the need for post-implant CT-based dosimetry through correlation with pre-implant and real-time dosimetry and review its place in the management of patients treated with LDR brachytherapy, so that it could be undertaken more selectively. METHODS: The real-time dosimetry parameters of 34 consecutive patients who underwent LDR brachytherapy were compared with day 30 post-implant CT-based dosimetry. To validate our results against the world practice, we performed a meta-analysis of six relevant published studies, which combined data from 699 patients. The Student's t-test was performed to verify whether our dosimetric parameters significantly differ from the results of the meta-analysis. RESULTS: In our case series, the mean target volume on real-time-planned US and post-implant CT was 33.9 and 32.7 cc, respectively (P > 0.05). The dose-volume histogram (DVH) parameters were significantly different between real-time-planned and post-implant dosimetry, but re-implantation was not needed for any patients. The literature review demonstrated that there is no consensus on measures being reported. Comparison showed that our cohort had significantly smaller prostate volumes, but the DVHs were similar to other series. CONCLUSIONS: Post-implant CT and dosimetry did not alter patients' management after real-time intraoperative planning. However, we recommend that it still be employed for difficult cases or if there are any concerns identified in real-time planned dosimetry.