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    Original Investigation
    December 12, 2019

    Association Between New Unconfirmed Bone Lesions and Outcomes in Men With Metastatic Castration-Resistant Prostate Cancer Treated With Enzalutamide: Secondary Analysis of the PREVAIL and AFFIRM Randomized Clinical Trials

    Author Affiliations
    • 1Division of Medical Oncology and Urology, Duke Cancer Institute Center for Prostate and Urologic Cancers, Duke University, Durham, North Carolina
    • 2Biostatistics, Pfizer Inc, Cambridge, Massachusetts
    • 3Biostatistics, Pfizer Inc, San Francisco, California
    • 4Clinical Development, Pfizer Inc, San Francisco, California
    • 5Biostatistics, Astellas Pharma Inc, Northbrook, Illinois
    • 6Clinical Development, Astellas Pharma Inc, Northbrook, Illinois
    • 7Division of Urology, Cliniques Universitaires Saint-Luc, Brussels, Belgium
    • 8Medical Oncology, Englander Institute for Precision Medicine, Weill Cornell Medicine, New York, New York
    • 9Division of Clinical Studies, The Institute of Cancer Research, The Royal Marsden National Health Service Foundation Trust, London, United Kingdom
    • 10Genitourinary Oncology Service, Memorial Sloan Kettering Cancer Center, Weill Cornell Medical College, New York, New York
    • 11Division of Hematology/Medical Oncology, OHSU Knight Cancer Institute, Oregon Health & Science University, Portland
    JAMA Oncol. 2020;6(2):217-225. doi:10.1001/jamaoncol.2019.4636
    Key Points

    Question  What is the association between new lesions detected on a first follow-up bone scan and outcomes in enzalutamide-treated men with metastatic castration-resistant prostate cancer with a stable or decreasing prostate-specific antigen level and regressing soft-tissue disease?

    Findings  This secondary analysis of the PREVAIL and AFFIRM randomized clinical trials found that chemotherapy-naive men with new early bone lesions whose condition was stable or responding to enzalutamide had similar progression-free and overall survival times and a quality of life similar to that of men without new lesions whose condition was responding to enzalutamide; however, overall survival after chemotherapy may have a negative association with new bone lesions.

    Meaning  These findings reinforce the importance of avoiding premature discontinuation of treatment based on new unconfirmed lesions detected on a follow-up bone scan in men with metastatic castration-resistant prostate cancer whose condition is stable or responding to enzalutamide, and the importance of functional imaging for diagnosing bone metastases.

    Abstract

    Importance  For men with metastatic castration-resistant prostate cancer (mCRPC) whose condition is responding to enzalutamide, new unconfirmed bone lesions detected at posttreatment scinitigraphy may reflect an osteoblastic reaction that represents healing, known as pseudoprogression, which can lead to premature discontinuation of therapy.

    Objective  To determine the association between new unconfirmed lesions detected on a follow-up bone scintigram (bone scan) and outcomes in enzalutamide-treated men with mCRPC.

    Design, Setting, and Participants  This post hoc, retrospective secondary analysis of 1672 enzalutamide-treated men from 2 phase 3, randomized mCRPC studies (PREVAIL and AFFIRM) before or after treatment with docetaxel was conducted from April 12, 2018, to July 25, 2019. Participants were men from the enzalutamide groups of the 2 studies with a decrease in prostate-specific antigen level at any time or with stable disease or soft-tissue disease responding to treatment based onradiologic findings.

    Intervention  Enzalutamide, 160 mg once daily.

    Main Outcomes and Measures  The clinical significance of new lesions detected on the first (early) or second (late) posttreatment bone scan, without an unfavorable change in prostate-specific antigen level or soft-tissue progression, was investigated. Associations of new unconfirmed lesions with radiographic progression-free survival, overall survival, decrease in prostate-specific antigen level, objective response in soft tissue, and quality of life were evaluated.

    Results  Among the 643 men (median age, 72 years [range, 43-93 years]) in PREVAIL, early and late unconfirmed lesions were observed in 177 men (27.5%) with stable disease or disease responding to enzalutamide. Among the 404 men (median age, 70 years [range, 41-88 years]) in AFFIRM, early and late unconfirmed lesions were observed in 73 men (18.1%) with stable disease or disease responding to enzalutamide. In PREVAIL, men with new unconfirmed lesions had median radiographic progression-free survival (hazard ratio [HR], 1.37 [95% CI, 0.81-2.30]; P = .23) and median overall survival (HR, 1.25 [95% CI, 0.85-1.83]) in the chemotherapy-naive setting similar to men those of men without such new lesions. In AFFIRM, the median overall survival (HR, 1.94 [95% CI, 1.10-3.44]) was reduced among men with unconfirmed bone lesions, but the median radiographic progression-free survival was not reduced (HR, 1.21 [95% CI, 0.83-1.75]; P = .32). Quality of life over time was similar regardless of the presence of new unconfirmed lesions detected on a follow-up bone scan in either setting.

    Conclusions and Relevance  These results suggest that new unconfirmed lesions detected on follow-up bone scans may represent pseudoprogression in men with mCRPC and are indicative of a favorable treatment response to enzalutamide. The detection of new unconfirmed bone lesions in men with mCRPC that responded to treatment with enzalutamide after docetaxel appears to be associated with worse overall survival and may represent true progression, thus highlighting the need for improved functional bone metastasis imaging.

    Trial Registration  ClinicalTrials.gov Identifiers: NCT01212991 and NCT00974311

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