Stereotactic body radiation therapy for low-, intermediate- and high-risk prostate cancer: Disease control and quality of life at 9 years.

摘要

20 Background: Stereotactic body radiation therapy (SBRT) takes advantage of the prostate’s low α/β ratio to deliver a large radiation dose in a few fractions. This prospective study expands upon prior studies to further evaluate SBRT efficacy and QOL for a large patient population that includes low-, intermediate- and high-risk patients with prostate cancer. Methods: 515 patients with organ-confined prostate cancer (471 T1c and 44 T2a, all N0M0) received robotic SBRT. The median age was 69 years and the median PSA was 6.48 ng/ml. By NCCN criteria, 324 patients were low-risk, 139 were intermediate-risk, and 52 were high-risk. Androgen deprivation therapy was administered to 70 patients for up to one year. 158 patients with Gleason scores < 4+3 received 35 Gy delivered in 5 daily fractions. The remaining patients, from all risk groups, received a total dose of 36.25 Gy in 5 daily fractions. The proximal seminal vesicles were treated except in low-risk cases. Biochemical failure was assessed using the Phoenix criterion and QOL was assessed with EPIC scoring. Results: At a median follow-up of 84 months, 74 patients died (72 from unrelated causes). The median PSA at 78 months was 0.11 ng/ml. The actuarial 9 year freedom from biochemical failure was 95%, 89%, and 66% for the low-, intermediate- and high-risk groups (p = 0.01). For patients with Gleason scores < 4+3, there was no difference in terms of median nadir or biochemical control between doses of 35 and 36.25 Gy. Late RTOG toxicity was mild with 4% grade 2 rectal, 9.5% grade 2 urinary, and 1.9% grade 3 urinary. Late grade 2-3 urinary toxicity was 6.9% for 35 Gy vs. 13.2% for 36.25 Gy (p = 0.01). Mean EPIC urinary and bowel QOL declined at 1 month post-treatment and returned to baseline by 2 years where it remains. EPIC sexual QOL declined by 29% at 78 months. Conclusions: SBRT alone produces excellent biochemical control rates at up to 9 years with mild toxicity and minimal impact on quality of life. These long-term results appear superior to standard IMRT with lower cost and are strikingly similar to HDR therapy. These results also strongly suggest that 35 Gy is as effective as 36.25 Gy for patients with Gleason < 4+3, with less urinary toxicity.