Integration of Bone and Computed Tomography Scans to Assess Bone Metastasis in Metastatic Castration-Resistant Prostate Cancer
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BACKGROUND: Progression of bone metastasis in metastatic castrate-resistant prostate cancer (mCRPC) is assessed using bone scan (BS) and correlates modestly with overall survival (OS). Because of the poor reliability of BS and routinely performed computed tomography (CT) scans, we assessed bone progression by integrating BS and CT. PATIENTS AND METHODS: Data were obtained from patients receiving docetaxel chemotherapy or postdocetaxel orteronel with baseline and on-therapy CT and BS within 90 days. Imaging underwent central radiology review by a single dedicated radiologist. Progressive disease (PD) was defined as ≥ 1 new lesion on either BS or CT. Cox proportional hazards regression was used to explore potential prognosticators of OS. RESULTS: Twenty-eight patients were evaluable. The mean age was 71.4 years and median OS was 18.4 (range, 9.7-35.4) months. Four patients (14.3%) had PD on BS and CT scan, and 2 (7.1%) had PD on CT scan but not on BS, and 3 (10.7%) had PD on BS but not CT scan. Patients with PD on BS or CT scan had worse OS (hazard ratio [HR], 2.68; 95% confidence interval [CI], 1.04-6.90; P = .041) than those with no PD on either CT or BS. When examining individual lesions, 4 patients had ≥ 1 new lesion identified on CT but not BS, and they were associated with worse OS (HR, 3.72; 95% CI, 1.01-13.66; P = .048). No significant difference in OS was observed for 4 patients with new lesions on BS but not CT scan. CONCLUSION: Results of this hypothesis-generating study suggest that the integration of ≥ 1 new lesion on CT and/or BS within 90 days in mCRPC might better capture bone progression and predict OS. This composite metric needs to be compared with current criteria.
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