In contrast to other recent studies, androgen deprivation therapy (ADT) had no link to dementia in a observational cohort study of more than 45,000 men with prostate cancer who received definitive radiotherapy, investigators have reported.
No significant associations were found between ADT and Alzheimer’s disease or vascular dementia, or between shorter or longer courses of ADT and any dementia studied, according to Rishi Deka, PhD, of Veterans Affairs San Diego Health Care System, La Jolla, Calif., and coinvestigators.
“These results may mitigate concerns regarding the long-term risks of ADT on cognitive health in the treatment of prostate cancer,” Dr. Deka and colleagues wrote in JAMA Oncology.
Two other recent studies showed strong, statistically significant associations between ADT and dementia in prostate cancer. However, those studies combined patients with local and metastatic disease, receiving ADT in the upfront or recurrent settings, while the present study looked specifically at men with nonmetastatic prostate cancer who received radiotherapy.
“Different treatment modalities and disease stages are associated with substantial selection bias that may predispose results to false associations,” noted Dr. Deka and coauthors.
Their observational cohort study comprised 45,218 men diagnosed with nonmetastatic prostate cancer at the U.S. Department of Veterans Affairs who underwent radiotherapy with or without ADT. The investigators excluded men who had a diagnosis of dementia within 1 year of the prostate cancer diagnosis or who had prior diagnoses of dementia, stroke, or cognitive impairment.
A total of 1,497 patients were diagnosed with dementia over a median of 6.8 years of follow-up: 404 with Alzheimer disease, 335 with vascular dementia, and 758 with other types or unclassified dementias.
The investigators found no significant association between use of ADT and development of any dementia, the primary outcome of the analysis (subdistribution hazard ratio [SHR], 1.04; 95% confidence interval, 0.94-1.16; P = .43).
Likewise, there was no association between ADT and vascular dementia, specifically, with an SHR of 1.20 (95% CI, 0.97-1.50; P = .10) or Alzheimer’s disease, with an SHR of 1.11 (95% CI, 0.91-1.36; P = .29).
Duration of ADT longer than 1 year was not significantly associated with dementia, nor was duration shorter than 1 year, with SHRs, of 1.08 and 1.01 respectively, the analysis shows.
The SHRs in these and other analysis reported ranged from 1.00 to 1.21. That is substantially lower than hazard ratios of 1.66 to 2.32 in one previous study linking ADT to dementia, according to the investigators, suggesting that the results of the current analysis were not due to inadequate power to detect differences.
Nevertheless, the findings may not be generalizable to some other populations, they cautioned, since it was focused demographically on veterans, and was limited to radiotherapy-treated patients.
Dr. Deka and coauthors reported no conflict of interest. Their study was funded by grants from the University of California San Diego Center for Precision Radiation Medicine.
SOURCE: Deka R et al. JAMA Oncol. 2018 Oct 11. doi: 10.1001/jamaoncol.2018.4423.