- Design
- Post hoc landmark analysis of 2 phase 3 trials
- Population
- 564 (LATITUDE) and 578 (ARASENS) men with metastatic hormone-sensitive prostate cancer on intensified therapy
- Primary outcome
- Overall survival after the landmark
- Effect
- LATITUDE HR 1.49 (95% CI 1.07 to 2.08); ARASENS HR 1.18 (0.85 to 1.62)
A post hoc analysis of the experimental arms of two phase 3 trials asked whether a serum testosterone rising above 35 ng/dL during treatment predicted worse outcomes. LATITUDE added abiraterone and prednisone to androgen deprivation; ARASENS added darolutamide and docetaxel.
In LATITUDE, about 560 men were analysed; breakthrough was associated with worse overall survival, with about 1.5 times the hazard of death. Progression-free survival pointed the same way but was not statistically significant. In ARASENS, about 580 men were analysed, and associations with survival and time to castration resistance were not significant.
The authors stress that these findings are exploratory, do not show cause, and do not establish a testosterone target on intensified therapy. They do suggest that checking testosterone during treatment — standard practice on androgen deprivation alone — remains worthwhile, and that breakthrough may prompt a check of adherence or the adequacy of castration.
- Continue measuring serum testosterone periodically in men on intensified therapy for metastatic hormone-sensitive disease.
- When testosterone exceeds castrate levels, check injection timing and adherence before changing therapy.
- Do not switch or escalate treatment on testosterone breakthrough alone; this analysis does not support that.
- Interpret any association as specific to the regimen studied; the two trials disagreed.
Why it matters
It keeps a simple blood test relevant in an era when most men get combination therapy.
Don't overread it
This post hoc analysis found inconsistent results between trials and cannot establish causation or a testosterone threshold for action.
The statistics, in plain English
A hazard ratio of 1.49 (95% CI 1.07 to 2.08) in LATITUDE means about 50% higher risk of death at any time after the landmark. In ARASENS, the interval for overall survival (0.85 to 1.62) crossed 1.0.
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