Background: Prostate cancer metastasize to bone in about 80% of the patients. The present knowledge of quantifying metastatic bone disease is not sufficient. A lot of work has been done to quantify the bone metastasis using bone scans.
Aim:This study explored the prognostic value of bone scan quantitative parameters in prostate cancer patients. In addition utility of four different bone scan quantitative parameters as disease predictor was also compared.
Methods:This was a retrospective study based on 141 consecutive prostate cancer patients at high risk, based on clinical stage, Gleason score and prostate-specific antigen, who had undergone baseline whole-body bone scans. Four different bone scan quantitative parameters namely; Bone scan index (BSI), Extent of disease (EOD), percentage uptake (%PAB) and bone lesions scoring (BLS) were calculated. Utility of these parameters in stratifying disease prognosis was evaluated. Cox proportional-hazards regression models were used to investigate the association between clinical stage, Gleason score, PSA, bone scan quantitative parameters and survival.
Results: The % PAB and % BSI quantitative method was found to be the best ones (with R2 of 0.9 and 0.8 respectively) whereas BLS and EOD showed moderate correlation with tumour burden in 141 patients. Kaplan Meir curve analysis showed that % PAB and EOD were best in predicting survival followed by BLS and BSI. In a multivariate analysis, Gleason score (p = 0.01) and BSI (p < 0.001), % PAB (p<0.001), EOD (p<0.01) were associated with survival, but clinical stage and PSA were not prognostic.
Conclusions: All four bone scan quantitative parameters were found to be good prognostic indicator, risk stratification calculators and tumour burden evaluators. These imaging biomarker, reflecting the extent of metastatic disease, can be of value both in clinical trials and in patient management when deciding on treatment