Prediction of survival benefit using an automated bone scan index in patients with castration‐resistant prostate cancer

Abstract

What's known on the subject? and What does the study add? A bone scan index (BSI) can quantify the extent of bone involvement and response to treatment, but it has not been widely accepted, because of its time-consuming nature. The study is the first to demonstrate that automated BSI calculated with a computer-assisted diagnosis system is effective in judging the chemotherapeutic response of bone metastatic lesions in patients with castration-resistant prostate cancer. • To evaluate the value of an automated bone scan index (aBSI), calculated using a computer-assisted diagnosis system, to indicate chemotherapy response and to predict prognosis in patients with castration-resistant prostate cancer (CRPC) with bone metastasis. • Forty-two consecutive CRPC patients underwent taxane-based chemotherapy between November 2004 and March 2011 at our institution. • The aBSIs were retrospectively calculated at the diagnosis of CRPC and 16 weeks after starting chemotherapy. • Cox proportional hazards regression models were applied to multivariate analyses with and without aBSI response in addition to the basic model. • Based on the difference in the concordance index (c-index) between each model, the prognostic relevance of adding the aBSI response was determined. • A decrease in aBSI was found in 28 patients (66.7%), whereas a response was shown by bone scan in only 23.8% of patients. • Patients with a reduction in aBSI had longer overall survival (OS) in comparison with the other patients (P= 0.0157). • Multivariate analysis without aBSI response showed that performance status (P= 0.0182) and PSA response (P= 0.0375) were significant prognosticators. • By adding the aBSI response to this basic model, the prognostic relevance of the model was improved with an increase in the c-index from 0.621 to 0.660. • The aBSI reflected the chemotherapy response in bone metastasis. • The index detected small changes of bone metastasis response as quantified values and was a strong prognostic indicator for patients with CRPC.