Practice patterns and outcomes of equivocal bone scans for patients with castration-resistant prostate cancer: Results from SEARCH

Objective:To review follow-up imaging after equivocal bone scans in men with castration resistant prostate cancer(CRPC)and examine the characteristics of equivocal bone scans that are associated with positive follow-up imaging.Methods:We identified 639 men from five Veterans Affairs Hospitals with a technetium-99m bone scan after CRPC diagnosis,of whom 99(15%)had equivocal scans.Men with equivocal scans were segregated into“high-risk”and“low-risk”subcategories based upon wording in the bone scan report.All follow-up imaging(bone scans,computed tomography[CT],magnetic resonance imaging[MRI],and X-rays)in the 3 months after the equivocal scan were reviewed.Variables were compared between patients with a positive vs.negative follow-up imaging after an equivocal bone scan.Results:Of 99 men with an equivocal bone scan,43(43%)received at least one follow-up imaging test,including 32/82(39%)with low-risk scans and 11/17(65%)with high-risk scans(p=0.052).Of follow-up tests,67%were negative,14%were equivocal,and 19%were positive.Among those who underwent follow-up imaging,3/32(9%)low-risk men had metastases vs.5/11(45%)high-risk men(p=0.015).Conclusion:While 19%of all men who received follow-up imaging had positive follow-up imaging,only 9%of those with a low-risk equivocal bone scan had metastases versus 45%of those with high-risk.These preliminary findings,if confirmed in larger studies,suggest follow-up imaging tests for low-risk equivocal scans can be delayed while high-risk equivocal scans should receive follow-up imaging.