Using Serum Parathyroid Hormones and Calcium to Improve Prostate Cancer Diagnosis

This is a cross sectional study to examine the relationship between serum calcium and PTHrP and serum PSA in men referred for prostate biopsy at Wake Forest University. Men scheduled for biopsy will be approached by the study nurse who will explain the study and invite the men to participate. After the patients provide written consent, she/he will obtain the following information from the patient chart: age, race (self-report, white, black, other), height, weight (for determination of Body Mass Index, a variable reported to influence PSA). Blood draw for study analytes will be coordinated with routine blood draw for PSA testing to minimize the need for an additional needle stick. A copy of the informed consent is given to the patient and the original is placed in a file for the P.I.

The biopsy status of men at the time they are invited to participate is unknown. Men are "sorted" into cancer and non-cancer groups only after their biopsies are read. Serum samples are sent to the Department of Laboratory Medicine at Wake Forest. All assays are performed "in house". Based on consultation with our urologists, we anticipate that approximately 30% of the biopsies will be positive (i.e., prostate cancer). The majority (approximately 70%) will be negative (benign). Approximately 1-2% of the biopsies may be classified as "indeterminate". Because there will not be a sufficient number of "indeterminate" pathologies to be treated as a separate category, this group will not be analyzed further. However, men with "indeterminate" biopsies are eligible for the study if they are re-biopsied.

Inclusion criteria

• Men age > 40 years
• Men referred for biopsy because of an abnormal or suspicious PSA digital rectal exam, or both.
• Ability and willingness to sign a written, IRB-approved informed consent document

Exclusion criteria

• Men using drugs known to interfere with serum PSA or with serum PTHrP and calcium. Drugs known to interfere with PSA include 5-alpha-reductase inhibitors (Proscar). Drugs known to interfere with calcium and/or PTH include lithium and thiazide diuretics.
• Patients with prior transurethral resection of the prostate (TURP) or equivalent procedure (laser incision). In these men the reduction in prostatic volume may give a biased estimate of the relationship between PSA, calcium and PTHrP.
• Patients on dialysis. These are excluded because dialysis increases the percentage of free PSA in serum.