Is seminal vesicle implantation with permanent sources possible? A dose–volume histogram analysis in patients undergoing combined 103Pd implantation and external beam radiation for T3c prostate cancer

Combined brachytherapy and external beam radiation therapy (EBRT) of the prostate and seminal vesicles (SVs) is evolving as a successful treatment option for high-risk prostate cancer. Dose–volume histogram (DVH) analysis of the SV was performed in patients with biopsy-positive SV who received implantation of the SV and prostate. Fifteen consecutive patients with high-risk features (prostate-specific antigen [PSA] ≥ 10 ng/mL, Gleason score ≥7, or clinical stage ≥T2b) and a positive SV biopsy were treated with a 103Pd implant of the prostate and SV followed by 45 Gy of EBRT. DVHs were generated for the prostate and total SV volume (SVT). In addition, the SV was divided into 3-mm-thick volumes identified as SV1, SV2, SV3, SV4, SV5, and SV6 starting from the junction of the prostate and SV and extending distally. Delivered dose was defined as the D 90 (dose delivered to 90% of the organ on DVH). The median number of seeds implanted into the prostate and the SVT was 59 (41–94) and 9 (4–21), respectively. The median D 90 values for the prostate, SVT, SV1, SV2, SV3, SV4, SV5, and SV6 were 103.2 (87.4–137.1), 46.2 (4.0–69.4), 76.0 (31.2–147), 63.4 (25.1–145.9), 49.7 (15.3–118), 27.4 (9.3–135.1), 14.2 (2.3–100.3), and 3.9 (0–61.5) Gy, respectively. Implantation of the SV using a real-time intraoperative approach is technically feasible and results in higher doses to the SV than has been reported with implantation of the prostate alone. Although dose distribution in the SV can be variable and unpredictable, these doses, in combination with 45 Gy of EBRT, may be adequate to control disease spread in these organs.