About BSI

About BSI

The Bone Scan Index

  • represents the percentage of total skeletal mass taken up by the tumors [1]
  • is a valuable metric for estimating metastatic burden in patients with advanced prostate cancer [1]
  • is a reproducible, quantitative expression of tumor burden seen on bone [2]
  • is suggested as a tool in advanced prostate cancer; for prostate cancer patients entering treatment protocols for the extent of the tumor involvement of bone; and for the development of a or  biomarker in prostate cancer


  • Whole-body bone scintigraphy is the most widely available and least expensive technique for the detection of bone metastases in patients with prostate cancer
  • There is no standard established for evaluating and interpreting whole-body bone scintigraphy

Estimating BSI

  • The estimation of BSI is based on the known proportional weights of each of the 158 bones that were derived from the reference man, a standardized skeleton in which autopsy-based individual bone weights were reported for the average adult [3]
  • BSI is calculated by summing the fractional contribution of each bone expressed as a percentage of the entire skeleton (see Figure 1) [4]
  • A BSI value of 1.0 indicates the tumor(s) to be present in 1% of the entire skeleton (arms and legs included) 
  • Automated quantification of BSI based on the original method developed by Memorial Sloan-Kettering Cancer Center, New York, USA, is available.

Figure 1 - Schematic picture of the method used to estimate BSI

Ulmert D, Kaboteh R, Fox JJ, et al. A novel automated platform for quantifying the extent of skeletal tumor involvement in prostate cancer patients using the Bone Scan Index. Eur Urol 2012 Jan; 78-84. doi: 10.1016/j.eururo.2012.01.037


Dennis ER, Jia X, Mezheritskiy IS, et al. Bone Scan Index: A quantitative treatment response biomarker for castration-resistant metastatic prostate cancer. J Clin Oncol 2012; 30(5): 519-524. doi: 10.1200/JCO.2011.36.5791


Sabbatini P, Larson SM, Kremer A, et al. Prognostic significance of extent of disease in bone in patients with androgen-independent prostate cancer. J Clin Oncol 1999; 17: 948-957


Erdi YE, Humm JL, Imbriaco M, Yeung H, Larson SM. Quantitative bone metastases analysis based on image segmentation. J Nucl Med 1997; 38(9): 1401-1406