Early outcomes and decision regret using PSMA/MRI guided focal boost for prostate cancer SBRT.

SBRT is a recognised treatment for low and intermediate risk prostate cancer with 36.25Gy in 5 fractions the most commonly used regimen. We explored the preliminary efficacy, patient recorded toxicity and decision regret in intermediate and high risk prostate cancer receiving SBRT with PSMA/MRI guided focal gross tumor volume (GTV) boost to 45Gy.

Between July 2015 and June 2019, 120 patients received SBRT across 2 institutions with a uniform protocol. All patients had fiducial markers and hydrogel, MRI and PSMA PET scan. All patients received a questionnaire asking the degree of urinary, bowel and sexual bother experienced at set time points, including questions about treatment choice and decision regret.

112 of 120 patients consented, their median age was 72 years and median follow up was 2.3 yrs. As per National Comprehensive Cancer Network guidelines, 78% had intermediate risk and 20% high risk. Androgen deprivation was combined with radiation in 6 patients. Most patients (74%) reported that receiving SBRT significantly influenced their choice of treatment. Five men (4%) expressed "quite a lot" (n=4) or "very much" regret (n=1) regarding their choice of treatment, whilst 89% expressed "no regret". Similar to pre-treatment levels, "Quite a lot" or "Very much" urinary or bowel bother was expressed in 8% and 6% of patients respectively. Two patients experienced nadir +2 biochemical failure, both found to have bone metastases. A 3rd patient underwent PSMA PET at nadir + 1.7, and had disease at the penile bulb, which was out of field. Three year estimated freedom from biochemical failure was 99% for intermediate and 85% for high risk groups.

We have demonstrated promising efficacy and low toxicity with PSMA/MRI guided SBRT focal boost. Less than 5% of patients expressed significant decision regret for their choice of treatment.

Practical radiation oncology. 2021 Oct 04 [Epub ahead of print]

Thomas Eade, Andrew Kneebone, George Hruby, Jeremy Booth, Edward Hsiao, Andrew Le, Carol Kwong, John Atyeo, Chris Brown, Julia Hunter, Francina Wade

Northern Sydney Cancer Centre, Radiation Oncology Unit, Royal North Shore Hospital, St Leonards, Sydney, NSW, Australia; Northern Clinical School, University of Sydney, Royal North Shore Hospital, St Leonards, Sydney, NSW, Australia; Genesis Care, Mater Hospital, North Sydney, Sydney, NSW, Australia. Electronic address: ., Northern Sydney Cancer Centre, Radiation Oncology Unit, Royal North Shore Hospital, St Leonards, Sydney, NSW, Australia; Northern Clinical School, University of Sydney, Royal North Shore Hospital, St Leonards, Sydney, NSW, Australia; Genesis Care, Mater Hospital, North Sydney, Sydney, NSW, Australia., Northern Sydney Cancer Centre, Radiation Oncology Unit, Royal North Shore Hospital, St Leonards, Sydney, NSW, Australia; Northern Clinical School, University of Sydney, Royal North Shore Hospital, St Leonards, Sydney, NSW, Australia., Department of Nuclear Medicine and PET, Royal North Shore Hospital, St Leonards, Sydney, NSW, Australia., Northern Sydney Cancer Centre, Radiation Oncology Unit, Royal North Shore Hospital, St Leonards, Sydney, NSW, Australia., Northern Sydney Cancer Centre, Radiation Oncology Unit, Royal North Shore Hospital, St Leonards, Sydney, NSW, Australia; National Health and Medical Research Council, Clinical Trials Centre, The University of Sydney, Sydney, NSW, Australia., Genesis Care, Mater Hospital, North Sydney, Sydney, NSW, Australia.