Elevated levels of acid phosphatase, particularly the prostatic isoenzyme, are most commonly associated with prostate cancer. This enzyme is released into the bloodstream when prostate cancer invades the bone or metastasizes, making it a useful marker for assessing disease progression. Historically, acid phosphatase was used before PSA became standard. Its elevation indicates advanced or metastatic disease, especially to the bone, guiding clinical management and surgical decisions related to tumor burden and spread.

Reference: Campbell-Walsh Urology, Wein et al., 12th Edition.