Oncological impact of neoadjuvant hormonal therapy on permanent iodine-125 seed brachytherapy in patients with low- and intermediate-risk prostate cancer

Impact of neoadjuvant androgen deprivation therapy on postimplant prostate D90 and prostate volume after low-dose-rate brachytherapy for localized prostate cancer

OBJECTIVE

Higher quality of postimplant dosimetric evaluation is associated with higher biochemical recurrence-free survival rates after low-dose-rate brachytherapy for localized prostate cancer. Postimplant prostate D90 is a key dosimetric parameter showing the quality of low-dose-rate brachytherapy. In this study, to improve the quality of low-dose-rate brachytherapy for localized prostate cancer, we investigated pre-implant factors affecting the reduction of postimplant prostate D90.

METHODS

A total of 441 patients underwent low-dose-rate brachytherapy monotherapy and 474 patients underwent low-dose-rate brachytherapy with external beam radiation therapy. Logistic regression analysis was carried out to identify predictive factors for postimplant D90 decline. The cut-off value of the D90 decline was set at 170 Gy and 130 Gy in the low-dose-rate brachytherapy monotherapy group and low-dose-rate brachytherapy with external beam radiation therapy group, respectively.

RESULTS

On multivariate analysis, neoadjuvant androgen deprivation therapy was identified as an independent predictive factor for the decline of postimplant D90 in both the low-dose-rate brachytherapy monotherapy group (P < 0.001) and low-dose-rate brachytherapy with external beam radiation therapy group (P = 0.003). Prostate volume changes and computed tomography/transrectal ultrasound prostate volume ratio were significantly and negatively correlated with the postimplant D90. The prostate volume changes and computed tomography/transrectal ultrasound prostate volume ratio were significantly higher in patients with neoadjuvant androgen deprivation therapy than those without neoadjuvant androgen deprivation therapy (P < 0.001).

CONCLUSIONS

Neoadjuvant androgen deprivation therapy decreased postimplant D90 with substantial prostate gland swelling after low-dose-rate brachytherapy. When neoadjuvant androgen deprivation therapy is required to reduce prostate volume for patients with large prostate glands and offer adequate local control for patients with high-risk prostate cancer before low-dose-rate brachytherapy, intraoperative D90 adjustment might be necessary.

Biochemical outcomes and predictive factors by risk group after permanent iodine-125 seed implantation: Prospective cohort study in 2,316 patients

PURPOSE

To evaluate the biochemical freedom from failure (bFFF) by risk group and treatment modality and the predictive factors of bFFF by risk group in patients with prostate cancer undergoing permanent seed implantation (PI) with or without external beam radiation therapy (EBRT) in a nationwide prospective cohort study (Japanese Prostate Cancer Outcome Study of Permanent Iodine-125 [I-125] Seed Implantation) in Japan during the first 2 years.

METHODS AND MATERIALS

The analyses included 2,316 participants in 42 institutions; bFFF was evaluated using the Phoenix definition and calculated using the Kaplan-Meier method, and the Cox proportional hazards model was used to identify the factors associated with bFFF.

RESULTS

Median followup period was 60.0 months. The 5-year bFFF rates in all patients, 1,028 low-risk patients, 1,114 intermediate-risk patients, and 133 high-risk patients were 93.6%, 94.9%, 92.7%, and 91.1%, respectively. The 5-year bFFF rates in the PI group and EBRT combination therapy group were 93.7% and 93.3%, respectively. In a multivariate analysis, younger age, higher Gleason score (GS), higher percent positive biopsies (%PB), and lower prostate V₁₀₀ (p = 0.0012, 0.0030, 0.0026, and 0.0368) in all patients; younger age, higher pretreatment prostate-specific antigen, and lower prostate V₁₀₀ (p = 0.0002, 0.0048, and 0.0012) in low-risk patients; higher GS, higher %PB, and no hormonal treatment (p = 0.0005, 0.0120, and 0.0022) in intermediate-risk patients; and higher GS and higher %PB (p = 0.0329 and 0.0120) in high-risk patients were significantly associated with bFFF.

CONCLUSIONS

PI with or without EBRT resulted in excellent short-term biochemical outcomes in all risk groups, especially in high-risk patients. Age, pretreatment prostate-specific antigen, and prostate V₁₀₀ in low-risk patients; GS, %PB, and hormonal treatment in intermediate-risk patients; and GS and %PB in high-risk patients were independently affected bFFF.