Clinical Variables Predict Radiographic Progression in mCRPC
Extent of disease and change in PSA were the strongest predictors of disease progression in men with chemotherapy-naïve mCRPC treated with abiraterone.
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SAN FRANCISCO—Extent of disease and change in PSA are among the clinical variables that can predict radiographic progression in men with chemotherapy-naïve metastatic castrate-resistant prostate cancer (mCRPC) treated with abiraterone. Antonio Finelli, MD, MSc, of Princess Margaret Cancer Center, University of Toronto, presented the findings in a podium session at the American Urological Association 2018 annual meeting.
Within the abiraterone treatment group of the phase III randomized trial COU-AA-302, 546 patients experienced 301 episodes of radiographic progression in bone or soft tissue. The median time to radiographic progression was 16.6 months. Using a multivariable Cox proportional hazards model with a concordance of 0.71, the team studied the predictive power of baseline variables (including extent of disease, ECOG status, pain, PSA, lactate dehydrogenase, alkaline phosphatase, and albumin), as well as change in PSA and alkaline phosphatase at 8 weeks.
Extent of disease at baseline and change in PSA at 8 weeks were the strongest independent determinants of radiographic progression-free survival (RPFS), Dr Finelli reported. Based on risk stratification, men with bone disease only at baseline and with halving of PSA or more were considered low risk. Their RPFS was 93% at 6 months and 80% at 12 months. In contrast, high-risk men with bone and soft metastasis and less decline in PSA had worse RPFS: 55% at 6 months and 34% at 12 months.
“Patients with chemo-naive mCRPC treated with abiraterone can be divided into groups with significantly different risks of radiographic progression based on a few clinically available variables,” Dr Finelli told Renal & Urology News. “That means the frequency of imaging could be individualized by risk. For example, in the absence of symptoms, it is unnecessary to image for at least 1 year the one-third of patients who fall into the very low-risk group with bone disease only and a PSA decline of 50% or more after 8 weeks. The highest-risk group with bone and soft tissue disease who do not experience a PSA decline of more than 50%, which represents 15% of patients, would benefit from starting imaging as early as 3 and certainly by 6 months.”
The next step is external validation of the model, and examination with other treatments.
Martin L, Alibhai S, Komisarenko M, Timilshina N, and Finelli A. Predictors of radiographic progression in metastatic castration-resistant prostate cancer patients treated with abiraterone: Retrospective analysis of COU-AA-302. Presented at: American Urological Association meeting. May 18-21, 2018. San Francisco. PD10-07.