115 - Stereotactic Radiotherapy in 3 Fractions for Localized Prostate Cancer
Presenter(s)
G. Sanguineti1, A. Farneti1, A. Faiella1, M. Rotondi2, S. Gomellini3, M. Bottero1, E. Moretti4, V. Landoni1, D. Giannarelli5, I. Farina1, and A. Magli2; 1IRCCS Regina Elena National Cancer Institute, Rome, Italy, 2Azienda Sanitaria-Universitaria Giuliano Isontina, Trieste, Italy, 3San Giovanni Addolorata Hospital, Rome, Italy, 4Azienda Sanitaria-Universitaria Friuli Centrale, Udine, Italy, 5Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
Purpose/Objective(s): To assess the oncologic outcomes after stereotactic body radiotherapy (SBRT) in 3 fractions for low to favorable-intermediate risk prostate cancer.
Materials/Methods: This is a prospective, multicenter study (NTC02623647) on SBRT to 40 Gy in 3 fractions to the whole prostate gland. Patients had to have the pathological diagnosis of prostate carcinoma at low or favorable-intermediate risk according to NCCN criteria. Patients with prostate volume =80 cc or with baseline IPSS score =15 were excluded. All patients underwent both 3-4 fiducials and rectal spacer gel placement before simulation. The target as identified on MRI was uniformly prescribed 40 Gy in 3 fractions (every other day) while the dose to the urethra was limited to 33 Gy with the highest priority. Treatment was planned and delivered with an empty rectum while bladder filling was controlled via a Foley catheter. Toxicity was prospectively scored with the Common Terminology Criteria for Adverse Events version 4.0 while biochemical control with the Phoenix definition. The feasibility at 1 year of this novel schedule has been published earlier on a preliminary group of 59 patients. We expanded the patient population to assess its efficacy and here we report the results at a median follow up of 59.8 months (IQR: 48.0-64.1 mths).
Results: From November 2015 to March 2023, 159 patients were enrolled. Median PSA value and prostate volume at diagnosis were 5.6 ng/ml (IQR: 3.6-8.3 ng/ml) and 45 cc (IQR: 33.9-61.5 cc), respectively. Ninety (56.6%) and 69 (43.4%) patients had low risk and favorable-intermediate risk disease, respectively. All enrolled patients completed the treatment as planned. Four patients showed biochemical failure for an estimated survival free of biochemical failure of 97.6% at 5 years (95%CI: 94.9-100%). All patients with biochemical failure developed recurrent disease (1 isolated local, 2 isolated nodal and 1 nodal+distant failures). None of the patients died of disease and overall survival is 89.5% (95%CI: 84.4%-94.6%) at 5 yrs. Thirteen grade 2 late GU toxicity events have been observed in 17 (10.7%) patients, while no grade 3+ GU toxicity event has been recorded. Regarding late GI toxicity, 4 grade 2 and 2 grade 3 events have been observed in 6 (3.8%) patients. Results of prostate biopsy at 2 yrs after SBRT as well as QoL longitudinal data will be presented as well.
Conclusion: Stereotactic radiotherapy to 40 Gy in 3 fractions is highly effective in patients with low- to favourable-intermediate-risk prostate cancer.