Presentation Authors: Hideyasu Tsumura*, Hiromichi Ishiyama, Ken-ichi Tabata, Yasukiyo Murakami, Akane Sekiguchi, Masashi Kitano, Takefumi Satoh, Masatsugu Iwamura, Sagamihara, Japan
Introduction: We evaluated the efficacy and safety of prostate-directed radiotherapy with or without metastasis-directed radiotherapy in de novo oligometastatic patients who underwent combination of high-dose-rate prostate brachytherapy, external beam radiotherapy, and androgen deprivation therapy.
Methods: Forty patients with bone metastasis and node positive prostate cancer were retrospectively analyzed. Of these, 22(55%), 3(7%), and 15(38%) patients had N1M0, M1a, and M1b, respectively. Eighteen patients (45%) received metastasis-directed radiotherapy to all metastatic sites. All patients initially underwent â‰¥ 6 months of androgen deprivation therapy. Oligometastatic disease was defined as presence of five or fewer metastatic lesions. Median prostate-specific antigen (PSA) at diagnosis and follow-up period was 19.35 ng/ml and 62.5 months, respectively.
Results: Of the 40 patients, the 5-year castration-resistant prostate cancer (CRPC)-free survival rate and cancer-specific survival was 64.4% and 87.9%, respectively. Pre-treatment predictive value including PSA at diagnosis â‰¥ 20 ng/ml (HR 2.722; 95% CI: 1.003-7.392), positive biopsy core rate â‰¥ 51% (HR 4.677; 95% CI: 1.693-12.92), and Gleason grade group 5 (HR 2.993; 95% CI: 1.246-12.34) were significantly associated with worse outcomes for CRPC-free survival. Patients with metastasis-directed radiotherapy had significantly higher probability of achieving a PSA level of < 0.02 ng/ml than those without the therapy (88.8% vs. 54.5%, p = 0.0354) and consequently had a better CRPC-free survival than those without the therapy (HR 0.319; 95% CI: 0.116-0.877) (Figure 1). Prostate-directed radiotherapy with metastasis-directed radiotherapy did not significantly increase the incidences of genitourinary and gastrointestinal toxicities compared to prostate-directed radiotherapy alone.
Conclusions: This single-institutional study revealed the feasibility of combining prostate brachytherapy and metastasis-directed radiotherapy for de novo oligometastatic prostate cancer. This combined approach has potential to prolong CRPC-free survival.