Efficacy of Curvilinear Needle Implantation for Prostate HDR Brachytherapy

Abstract

High-dose-rate (HDR) brachytherapy is gaining popularity due to better dose distribution, good clinical outcomes, and convenience of the procedure. Conventionally, Rectilinear (straight needle) Method (RLM) is utilized for HDR procedure. However, the efficacy of a newly developed technique, the Curvilinear (curved needle conforming the prostate shape) Method (CLM), for HDR brachytherapy has not yet been explored. In this study, efficacy of the CLM is evaluated. The CLM technique is expected to significantly improve the radiation dose distribution with small number of needles that will potentially improve the clinical outcomes. Randomly 16 prostate cancer patients were selected (median age: 68.3 yrs, Stage: T1-T2a) from an IRB approved pool of patients. Prostate and OARs (urethra, rectum and bladder) were contoured on T2-weigthed MRI for all the patients. Thirty-two HDR plans, 16 for RLM and 16 for CLM, were prepared using Oncentra treatment planning software with Ir-192 isotope and were optimized using Hybrid Inverse treatment Planning Optimization (HIPO) tool. Prescription dose was 15 Gy in single fraction. Data for relevant parameters (V100, V200, D90, D10, Dmax, etc.) for prostate and OARs were collected using the dose-volume histogram. P-value less than equal to 0.05 was considered statistically significant. Average prostate volume was 33.1cc (range 17.7-51.3cc, median 30.6cc). In CLM technique the target coverage and dose constraints for OARs were improved by 0.3%-6.4% and 1.6%-34.2%, respectively (see Table below). Certain dose constraints were difficult to meet for some cases with RLM (prostate V100 (4 pts) and V200 (5 pts); rectum Dmax (5 pts) and D12 Gy (10 pts). On average, over 44.6% (average 17.5 vs 9.7 needles) reduction of needles was achieved with CLM (p-value < 0.001). The CLM technique generated significantly improved dosimetric plans using less number of needles. Reduction in number of needles would be associated with potential decrease in toxicity and improved clinical outcomes. Future plan includes clinical implementation of the CLM technique.