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

Authors


Yozo Mitsui, Department of Urology, Shimane University School of Medicine, 89 1 Enya cho 693-8501, Izumo, Japan. e-mail: mitsui@med.shimane-u.ac.jp

Abstract

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.

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