Radiotherapy technique shows promise
In one of the first longer-term follow up studies using this technology, Sunnybrook researchers show that for low-risk localized prostate cancer, stereotactic ablative body radiotherapy is well tolerated with potential cancer control similar to standard image-guided radiotherapy, as published in Radiotherapy and Oncology.
"Our goal is to improve quality of life for patients, to improve treatments with greater accuracy and to reduce treatment time without compromising treatment effectiveness," says Dr. Andrew Loblaw, radiation oncologist, Odette Genitourinary Cancer Care team, lead author and the study's co-principal investigator with Dr. Patrick Cheung, radiation oncologist, Odette Genitourinary Cancer Care team.
"We continue to strive for greater accuracy with these high-precision, high-dose approaches so that we can decrease treatment time for patients and spare more healthy tissue to help reduce side effects," says Dr. Cheung.
The researchers followed 84 patients, median age 67 years, with localized low-risk prostate cancer who completed stereotactic ablative body radiotherapy (SABR) to a dose of 35 Gy in 5 fractions, delivered once per week. Five-year tumor control rate was 98%.
With 5 years of follow-up, the Odette group went on to compare low-risk patients treated with SABR to those getting standard image-guided radiation therapy (76-78 Gy in 38-39 treatments delivered daily, over 8 weeks) or low dose rate (LDR or "seed") brachytherapy. Results showed equal tumour control (97% at 5 years for all treatments) and slightly lower risks of complications for SABR and standard radiation. Results were presented in abstract at the 2013 American Society of Clinical Oncology annual meeting.
The research team included Dr. Geordi Pang and other medical physicists of Sunnybrook's Odette Cancer Centre who specifically commissioned linear accelerators, normally used for standard image-guided radiotherapy, to deliver stereotactic ablative body radiotherapy (SABR).
The researchers continue to refine the optimal SABR technique and recommend more studies to compare SABR to standard, or hypofractionated image-guided radiotherapy, or brachytherapy in a large, randomized controlled trial.