Long-term Outcomes of Stereotactic Body Radiotherapy for Localized Prostate Cancer: A 10-Year Experience at A Single Institution

Abstract

The understanding of radiobiology for prostate cancer suggested hypofractionation might achieve a higher therapeutic benefit. Stereotactic body radiation therapy (SBRT) is able to deliver a high dose per fraction precisely. SBRT for prostate cancer could escalate biological effective doses while without increasing toxicity. Here, we reported our long-term results of SBRT for localized prostate cancer. Between November 2008 and May 2018, a total of 232 patients with clinically localized prostate were analyzed. Patients were low-risk (11%), intermediate-risk (37%), and high-risk (52%). Low- and intermediate-risk patients were treated with SBRT to prostate and proximal seminal vesicles (37.5Gy in 5 fractions). High-risk patients were treated with whole pelvic irradiation (45Gy in 25 fractions) following SBRT boost (21Gy in 3 fractions). The intermediate- and high-risk patients received hormone therapy with different duration. The toxicities of gastrointestinal (GI) and genitourinary (GU) tracts were scored by (CTCAE v3. 0). Patterns of prostate-specific antigen (PSA) response were analyzed. Biochemical failure was defined as Phoenix definition. The initial median PSA was 6.74, 9.87, and 24.22 ng/ml for the low-, intermediate-, and high-risk patients, respectively. After SBRT treatment, median PSA at 60 months was 0.19, 0.11, and 0.07 ng/ml for the low-, intermediate-, and high-risk patients, respectively. In the low-and intermediate risk groups, there were four patients with biochemical failures within a median follow-up of 58 months. For the high-risk patients, eight patients with biochemical failure were noted in the median 48-month follow up. The estimated 10-year biochemical failure-free survival was 96.0%, 94.7%, and 89.9% for low, intermediate-, and high-risk patients, respectively. In the low- and intermediate-risk patients, late Grade 3 GU and GI toxicities were seen in 2% and 0%, respectively. In the whole pelvic irradiation with SBRT boost group, the incidence rate of late Grade 2 GU and GI toxicity was 10% and 2%. There was no late Grade 3 GU toxicity and 1% of Grade 3 GI toxicity. Most acute toxicity effects in all the patients resolved within three to six months of treatment completion. SBRT with or without whole pelvic irradiation for the different risk groups of localized prostate cancer is feasible with minimal toxicity and excellent biochemical failure-free survival. Continued accrual and follow-up would be necessary to confirm this long-term biochemical control and the late toxicity profiles.