(HealthDay News) – On-treatment related change in the bone scan index (BSI) is strongly associated with survival in patients receiving chemotherapy for metastatic prostate cancer, according to a study published online January 9 in the Journal of Clinical Oncology.

Elizabeth R. Dennis, of the Memorial Sloan-Kettering Cancer Center in New York City, and colleagues retrospectively examined serial bone scans from 88 patients with castration-resistant metastatic prostate cancer who were enrolled in four clinical trials. BSI was calculated at baseline and at three and six months on treatment, and the change in BSI was evaluated with respect to survival and compared with prostate-specific antigen (PSA) as an outcome measure.

The researchers found that, in the univariate analysis, survival was predicted by the log percent change in BSI from baseline to three and six months on treatment (hazard ratio [HR], 2.44 and 2.54, respectively), with a doubling in BSI resulting in a 1.9-fold elevated risk of death. At six months of treatment, the log percent change in PSA was also associated with survival (HR, 1.298). In the bivariate analysis, when adjusting for PSA, a change in BSI was prognostic at three and six months on treatment (HR, 2.368 and 2.226, respectively), but PSA was not prognostic when adjusting for BSI.

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“These data furnish early evidence that on-treatment changes in BSI are a response indicator and support further exploration of bone scintigraphy as an imaging biomarker in castration-resistant metastatic prostate cancer,” the authors write.

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