Certainly, the goal of ADT is to reduce serum testosterone to castrate levels, inducing regression of androgen-sensitive prostate cancer cells. The objective of this study was to determine whether continuous ADT users achieving testosterone levels <0.7 nmol/L demonstrate subsequent testosterone level elevations on follow-up and whether such events predict worse oncologic outcomes.
The authors identified a random, retrospective sample of 514 prostate cancer patients treated with continuous ADT and having serum testosterone levels <0.7 nmol/L between 2007-2016. Patients were followed from date of first testosterone level <0.7 nmol/L till progression to castrate resistance, death, or end of study period. Study outcomes were occurrence of testosterone level elevations >0.7, >1.1, and >1.7 nmol/L and progression to a castrate-resistant state. Survival curves were used to determine rates of occurrence of testosterone level elevations. Multivariate Cox regression analysis was used to assess whether occurrence of elevations predicts progression to castrate-resistance. The median age of men included in the study was 74 years of age and median follow-up was 20.3 months. 82% of patients had testosterone levels of >0.7 nmol/L, 45% >1.1 nmol/L, and 18% of patients had subsequent testosterone levels >1.7 nmol/L within five years of follow-up. Interestingly, 96-100% of such patients subsequently re-established levels <0.7 nmol/L within five years. None of the patient baseline characteristics were associated with occurrence of elevations. Occurrence of elevations was not a significant predictor of progression to a castrate-resistant state.
In conclusion, continuous ADT users having initial testosterone levels <0.7 nmol/L frequently exhibit subsequent elevations in serum testosterone levels. As such, these occurrences should not trigger an immediate response from physicians as these events are prognostically insignificant with regards to oncologic outcomes, and patients eventually re-establish levels <0.7 nmol/L. Frequent testosterone level re-assessment (eg. at 3 or 6 month intervals) in patients who achieve an appropriate nadir is likely unwarranted.
Presented by: Rashid Sayyid, MD, MSc¹
Co-Authors: Abdallah Sayyid BSc², Zachary Klaassen MD², Kamel Fadaak MD², Hanan Goldberg MD², Thenappan Chandrasekar MD², Ardalanejaz Ahmad MD², Ricardo Leao MD², Nathan Perlis MD, MSc², Karen Chadwick MSc², Robert Hamilton MD, MPH², Girish Kulkarni MD, PhD², Antonio Finelli MD, MSc², Alexandre Zlotta MD, PhD² and Neil Fleshner MD, MPH²
Affiliation: ¹Medical College of Georgia, Augusta University, Augusta, GA; ²Department of Surgical Oncology, Division of Urology, University Health Network, University of Toronto, Toronto, ON, Canada
Written by: Zachary Klaassen, MD, Society of Urologic Oncology Fellow, University of Toronto, Princess Margaret Cancer Centre @zklaassen_md at the 18th Annual Meeting of the Society of Urologic Oncology, November 20-December 1, 2017 – Washington, DC