Radiation treatment for clinically localized prostate cancer (PCa) is associated with an increased risk of cardiac and skeletal-related events compared with surgery, according to study findings presented at the Canadian Urological Association 2016 annual meeting in Vancouver.
In a population-based cohort study, a team led by Christopher J.D. Wallis, MD, and Robert K. Nam, MD, of the University of Toronto, found that, patients treated with radiation had a significant 18% increased risk of coronary heart disease, 20% increased risk of myocardial infarction (MI), 28% increase risk of sudden cardiac death, and 16% increased risk of both fracture and fracture requiring hospitalization compared with men who underwent radical prostatectomy (RP).
Results showed that patients receiving androgen-deprivation therapy (ADT) had an increased risk of coronary heart disease, sudden cardiac death, fractures, and fractures requiring hospitalization, but not MI. The investigators found no evidence of a significant interaction between local treatment and ADT.
For the study, the investigators used the Surveillance, Epidemiology and End Results (SEER)-Medicare linked databases for men aged 65 to 79 years to examine outcomes from 14,403 patients who underwent RP and 45,753 who underwent radiation treatment. A significantly higher proportion of radiation therapy patients than RP patients received ADT (52% vs. 12%). The cohort had a median follow-up of 6 years.
As for what might explain the study’s findings, Dr Wallis told Renal & Urology News:
“There is biologic rationale for radiotherapy to increase cardiovascular and skeletal-related events. Work in testis cancer has shown that abdominal radiotherapy, without mediastinal radiotherapy, increases rates of cardiovascular disease.”
In addition, mechanistically, radiotherapy has been shown to cause damage to the vasculature, including fibrosis, intimal thickening, proteoglycan deposition, inflammatory infiltration and radiation-nephropathy-induced hypertension, all of which may contribute to cardiovascular disease, Dr. Wallis pointed out. Similarly, radiotherapy has been shown to induce damage and occlusion of the periostic microcirculation, leading to increased bone fragility.