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PSA nadir value following radiation, ADT may predict prostate cancer mortality risk
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A PSA nadir value greater than 0.5 ng/mL following radiation and androgen deprivation therapy identified men at high risk for death prior to PSA failure, according to a secondary analysis of a randomized clinical trial published in JAMA Oncology.
“This study’s results can have practice-changing implications on how future prostate cancer trials are designed in terms of identifying the men for these studies who are at high risk for early death due to ineffective initial treatment for their prostate cancer,” Anthony Victor D’Amico, MD, PhD, chief of genitourinary radiation oncology at Brigham and Women’s Hospital, said in a press release.
Trailing only lung cancer, prostate cancer is the second-leading cause of cancer death among American men, with an estimated 26,000 deaths in 2016. Researchers noted that although several markers for prostate cancer mortality exist, it is unknown if those markers identify which men are likely to die from any cause and whether they may benefit from more aggressive forms of treatment.
“By identifying and enrolling these men in clinical trials immediately, the hope is to take a prostate cancer that appears to be incurable and make it curable,” Trevor J. Royce, MD, senior resident in the department of radiation oncology at Brigham and Women’s Hospital, said in the release.
Researchers randomly selected 206 men with unfavorable-risk prostate cancer who were seen at a Harvard-affiliated academic hospital or an associated community hospital between Dec. 1, 1995 and April 15, 2001. Those patients were randomly assigned to radiation therapy alone or with 6 months of ADT. Researchers followed patients for a median of 16.62 years.
For this subgroup analysis, researchers evaluated data from 157 (median age, 72.43 years) of the men who had minimal or no comorbidities. Median follow-up was 16.49 months.
Risk for all-cause mortality was the main outcome measure of the subgroup analysis.
Researchers used the four Prentice criteria for surrogacy to evaluate candidate surrogates.
Three tested metrics met all four criteria: PSA nadir greater than 0.5 ng/mL (adjusted HR = 1.72; 95% CI, 1.17-2.52); PSA doubling time less than 9 months (adjusted HR = 2.06; 95% CI, 1.29-3.28); and interval to PSA failure less than 30 months (adjusted HR = 1.76; 95% CI, 1.06-2.92).
The proportion of treatment effect values were 103.86% for PSA nadir greater than 0.5 ng/mL, 43.09% for PSA doubling time less than 9 months, and 41.26% for interval to PSA failure less than 30 months.
Despite selecting men with minimal or no comorbidities, researchers did not find that PSA failure was a strong surrogate for all-cause mortality (adjusted HR = 1.76; 95% CI, 1.06-2.92)
“The clinical importance of this finding is that it provides an opportunity for patient selection for clinical trial entry at a time when the patient is still responding to but has not yet declared as having failed primary therapy,” D’Amico and colleagues wrote. “This could be used to select men for entry at the time of PSA nadir onto randomized trials evaluating the impact on survival of salvage ADT with or without agents shown to prolong survival in men with castrate-resistant metastatic prostate cancer.” – by Chuck Gormley
Disclosure: Researchers report no relevant financial disclosures.
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