Pelvic radiotherapy may lead to decreased bone mineral density (BMD) and increased risk of fracture which could be of particular concern in prostate cancer (PCa) patients who also receive androgen deprivation therapy (ADT). We performed exploratory analysis of a randomized, double-blind, placebo-controlled trial to determine if exposure to prior pelvic external beam radiotherapy (XRT) affects BMD and risk of fracture in PCa patients treated with ADT.
Non-metastatic PCa patients with age ≥70 years or <70 years with low BMD (T-score < -1) or osteoporotic fracture, on ADT for ≥12 months, were randomly assigned to receive densoumab versus placebo every 6 months for 3 years. BMD was measured at baseline, and at months 1, 3, 6, 12, 24, and 36. We applied multivariable linear mixed effect models with an interaction term between the treatment arm and exposure to prior pelvic XRT to evaluate differential XRT effect on percent BMD change between the two treatment arms.
Among 1407 eligible patients, 31% (n=447) of patients received prior pelvic radiotherapy. There was no difference in any clinical fractures among patients with (5.8%, 26 out of 447) or without (5.2%, 50 out of 960) prior pelvic radiotherapy (p=0.42). Receipt of prior pelvic XRT was associated with a significant 0.54 percent improvement in BMD (95% CI: 0.05 to 1.02) in the placebo group and a non-significant 0.04 percent decline in BMD (95% CI: -0.47 to 0.35) in the denosumab arm, respectively. (interaction p=0.007). There was no significant difference in pelvic radiotherapy effect on percent BMD change in lumbar spine (p=0.65) or total hip (p=0.39) between the two treatment groups.
We did not find sufficient evidence to suggest any detrimental impact of pelvic XRT on the treatment effect from denosumab on percent BMD change with only about 5% incidence of clinical fractures.
International journal of radiation oncology, biology, physics. 2023 Nov 02 [Epub ahead of print]
Soumyajit Roy, Shawn Malone, Yilun Sun, Nicholas G Zaorsky, Daniel E Spratt, Scott C Morgan, Robert T Dess, Christopher J D Wallis, Amar U Kishan, Deborah E Citrin, Fred Saad
Department of Radiation Oncology, Rush University Medical Center, Chicago, IL, USA. Electronic address: ., Division of Radiation Oncology, The Ottawa Hospital Cancer Centre, University of Ottawa, Ottawa, ON, Canada., Department of Population and Quantitative Health Sciences, School of Medicine, Case Western Reserve University, Cleveland, OH, USA., Department of Radiation Oncology, University Hospital Seidman Cancer Center, Case Western Reserve University, Cleveland, OH, USA., Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA., Department of Urology, Mount Sinai Hospital and University Health Network, University of Toronto, Toronto, ON, Canada., Department of Radiation Oncology, University of California Los Angeles, Los Angeles, CA, USA., Radiation Oncology Branch, National Cancer Institute, Bethesda, MD, USA., Department of Surgery, Université de Montréal, Montreal, QC, Canada.