Serum Alkaline Phosphatase in Newly Diagnosed Genito-Urinary Cancers-Do We Need to Review the Guidelines?

Objectives: To evaluate the role of alkaline phosphatase (ALP) as marker of bone metastases in patients of genitourinary cancers compared to bone scan, and to correlate with NCCN guidelines.

Methods: This retro-prospective, observational study included all newly diagnosed patients of renal, bladder (muscle invasive) and prostate cancers who presented from July 2014 to March 2017. For diagnosis of bone metastases, ALP groups (raised/normal) were compared with bone scan (positive/negative). Sub-group analysis was done on patients with normal ALP levels and positive bone scan.

Results: 150 patients were included and stratified depending on bone scan findings. Hemoglobin values were significantly different between two groups in renal and prostate cancers (p=0.015 and 0.002 respectively). AL values were significantly different between two groups in prostate cancers (p=0.0008), but not for others. Three out of seven patients with bone metastases for renal cancers (42.9%) and all three for bladder cancers had normal ALP values, no bone symptoms, and would have been missed. For prostate cancers, out of 23 who had bone metastases, ALP was normal in ten. All these ten had Gleason score of > 8 and all except one had S. PSA > 20ng/ml. All cases would have been detected irrespective of ALP values.

Conclusions: ALP has limited sensitivity but reasonable negative predictive value for bone metastases in genitourinary cancers. Current guidelines may miss significant number of cases with bone metastases for renal and bladder cancers. Current guidelines have good accuracy for prostate cancers, since PSA and Gleason score are independent predictors of bone metastases.