5-Year Outcomes of a Phase I Dose Escalation Study Using Stereotactic Body Radiosurgery for Patients with Low and Intermediate Risk Prostate Cancer
Mené sur 136 patients atteints d'un cancer de la prostate à risque faible ou intermédiaire de récidive, cet essai de phase I évalue l'efficacité, du point de vue de la récidive biochimique à 5 ans, et la toxicité d'une radiothérapie corporelle stéréotaxique avec hypofractionnement très élevé et escalade de doses
Purpose : To report toxicity outcomes, PSA relapse, and cumulative incidence-post-treatment biopsy results among patients treated on a prospective dose escalation study using ultra-hypofractionated stereotactic body radiotherapy (SBRT) for patients with low/intermediate risk prostate cancer. Methods and Materials : 136 patients were accrued to a Phase I dose escalation study to determine the tolerance of escalating radiation dose levels of SBRT for the treatment of localized prostate cancer. The initial dose level was 32.5 Gy in 5 fractions, and doses were then sequentially escalated to 35 Gy, 37.5 Gy and 40 Gy. Eligibility criteria included only low and intermediate risk patients, and the maximum prostate volume was 60cc. Patients treated with neo-adjuvant androgen deprivation were excluded. The median follow-up in survivors for the 4 dose levels were 5.9, 5.4, 4.1 and 3.5 years, respectively. Results : The incidence of acute grade 2 rectal toxicities for dose levels 1-4 were 0%, 2.9%, 2.8% and 11.4% respectively. No grade 3 or 4 acute rectal toxicities were observed. The incidence of acute grade 2 urinary toxicities for dose levels 1-4 were 16.7%, 22.9%, 8.3% and 17.1% respectively. No grade 3 or 4 acute urinary toxicities were observed. No grade 2 or higher rectal toxicities were observed. The incidence of late grade 2 urinary toxicities for dose levels 1-4 were 23.3%, 25.7%, 27.8% and 31.4% respectively. Only one late grade 3 urinary toxicity (urethral stricture) developed in the 40 Gy dose arm corrected with transurethral resection. No grade 4 late urinary toxicity was observed. The 5-year cumulative incidence of PSA failure for dose levels 1-4 were: 15%, 6%, and 0% and 0%. The incidence of a 2- year positive post-treatment biopsy was 47.6%, 19.2%, 16.7%, and 7.7%, respectively for the 4 dose arms (p=0.013). Conclusions : SBRT doses ranging from 32.5 Gy-40 Gy in 5 fractions were well tolerated without severe urinary or rectal toxicities. Biopsy outcomes suggest improved rates of tumor clearance observed with higher doses.