OBJECTIVES:

The objective of this study was to determine whether, in patients with prostate cancer (PCa) bone metastases receiving chemotherapy, early post-treatment changes on CT are reproducible and associated with clinical outcomes.

METHODS:

Blinded to outcomes, two radiologists with 1 year and 5 years of experience independently reviewed CTs obtained before and 3 months after chemotherapy initiation in 38 patients with bone metastases from castration-resistant PCa, recording the size, matrix and attenuation of ≤5 lesions; presence of new lesions, extraosseous components, periosteal reactions and cortical thickening; and overall CT assessment (improved, no change or worse). Kappa statistics were used to assess inter-reader agreement; the Kruskal-Wallis test and Cox regression model were used to evaluate associations.

RESULTS:

Inter-reader agreement was low/fair for size change (concordance correlation coefficient=0.013), overall assessment and extraosseous involvement (κ=0.3), moderate for periosteal reaction and cortical thickening (κ=0.4-0.5), and substantial for CT attenuation (κ=0.7). Most metastases were blastic (Reader 1, 58%; Reader 2, 67%) or mixed lytic-blastic (Reader 1, 42%; Reader 2, 34%). No individual CT features correlated with survival. Readers 1 and 2 called the disease improved in 26% and 5% of patients, unchanged in 11% and 21%, and worse in 63% and 74%, respectively, with 64% interreader agreement. Overall CT assessment did not correlate with percentage change in prostate-specific antigen level. For the more experienced reader (Reader 2), patients with improved or unchanged disease had significantly longer median survival (p=0.036).

CONCLUSIONS:

In PCa bone metastases, interreader agreement is low in overall CT post-treatment assessment and varies widely for individual CT features. Improved or stable disease identified by an experienced reader is statistically associated with longer survival.