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Keywords:

  • castration-resistant prostate cancer;
  • bone scan;
  • bone scan index;
  • computer-assisted diagnosis;
  • chemotherapy

Study Type – Prognosis (case series)

Level of Evidence 4

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.

OBJECTIVE

  • • 
    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.

PATIENTS AND METHODS

  • • 
    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.

RESULTS

  • • 
    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.

CONCLUSIONS

  • • 
    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.