ESTRO 2024 - Abstract Book

S2325

Clinical - Urology

ESTRO 2024

454

Mini-Oral

SABR for favourable-risk prostate cancer: 10-year outcomes and second malignancies

Thomas AC Kennedy 1,2 , Wee L Ong 3 , Harvey Quon 4 , Aldrich Ong 5 , Patrick Cheung 1,2 , William Chu 1 , Hans Chung 1,2 , Danny Vesprini 1,2 , Amit Chowdhury 5 , Dilip Panjwani 6 , Yasir Alayed 7 , Geordi Pang 1,8 , Renee Korol 1,8 , Melanie Davidson 1,2 , Ananth Ravi 9 , Boyd McCurdy 5 , Liying Zhang 1 , Meghan Kulasingham-Poon 1 , Alexandre Mamedov 1 , Andrea Deabreu 1 , Andrew Loblaw 1,2 1 Sunnybrook Health Sciences Centre, Odette Cancer Centre, Toronto, Canada. 2 University of Toronto, Department of Radiation Oncology, Toronto, Canada. 3 Monash University, Alfred Health, Radiation Oncology, Melbourne, Australia. 4 Tom Baker Cancer Centre, Department of Radiation Oncology, Calgary, Canada. 5 University of Manitoba, Department of Radiology, Winnipeg, Canada. 6 BC Cancer, Abbotsford Centre, Abbotsford, Canada. 7 King Saud University, Radiation Oncology, College of Medicine, Riyadh, Saudi Arabia. 8 University of Toronto, Department of Medical Physics, Toronto, Canada. 9 Molli Surgical, CEO, Toronto, Canada

Purpose/Objective:

Stereotactic ablative radiotherapy (SABR) offers an effective treatment option for clinically localized prostate cancer. Two non-inferiority randomized controlled trials have demonstrated non-inferiority of SABR vs conventional fractionation for patients with favourable risk localized prostate cancer [1, 2]. These studies, however, only have medium term follow-up, with approximately 5 years median duration. There are few prospective studies reporting long-term oncologic outcomes and to our knowledge, none documenting the risk of second malignancies (SM). We report the 10-year outcomes and describe the incidence and patterns of second malignancy after SABR for low and intermediate risk prostate cancer in three prospective trials.

Material/Methods:

Patients with low and intermediate risk prostate cancer who received SABR as part of pHART3 (NCT01578902), pHART6 (NCT01146340), and PATRIOT (NCT01423474) were included. Patients received prostate SABR, 35 or 40 Gy in 5 fractions, over 11 – 29 days. PSA nadir, distant metastasis, and vital status were recorded. Biochemical failure was based on Phoenix consensus guidelines. Occurrence of SM after treatment was assessed by electronic chart review and classified using a modification of Cahan’s criteria to reflect the likelihood they were related to prior radiotherapy. Freedom from biochemical failure (FFBF), overall survival (OS), prostate-cancer specific survival (PCSS), and metastasis-free survival (MFS) are reported by Kaplan-Meier estimation.

Results:

267 patients enrolled in three trials (n = 84 (pHART3), n = 31 (pHART6), and n = 152 (PATRIOT)) from 11/2006 to 11/2013 were included in the analysis. Median follow up at time of reporting was 10.13 years (IQR 6.72 – 12.35 years). 10-year FFBF was 92.6% (95% CI: 89.1 – 96.2%). 10-year OS, PCSS, and MFS were 84.1% (79.3 – 89.1%), 99.2% (98.1 – 100%), and 83.8% (79.1 – 88.9%), respectively. 27 of 267 (10.1%) patients experienced a SM, with a median