PSA Shows Early Potential as an Independent Biochemical Marker for Breast Cancer Prognosis

NEW YORK--The identification of prostate-specific antigen immunoreactivity(IR-PSA) in some cases of breast cancer has raised the possibilitythat PSA could be used as a biochemical marker for prognosis ofbreast cancer.

Speaking at the International Conference on Human Tumor Markers,He Yu, a doctoral candidate in clinical biochemistry at the Universityof Toronto, reported that IR-PSA was detected in 30% of tumorcytosols taken from 1,200 women with primary breast cancer.

Although PSA was initially thought to be produced exclusivelyby the prostate, Mr. Yu said that it can be detected in low levelsin the periurethral, perianal, salivary, and sweat glands.

Using a time-resolved immunoflu-orometric assay to measure extremelylow levels of PSA, the Toronto team was surprised to find IR-PSAin breast cancer tissue, but repeated testing yielded the sameresults.

"The PSA found in the breast cancer tissue was identicalto that found in the prostate," he said. He added that normalbreast tissue is also capable of producing PSA under conditionsof steroid hormone stimulation, eg, with use of oral contraceptives.Fluid secreted from the breast, such as milk and cystic fluid,also contains IR-PSA.

Preliminary clinical studies indicate that PSA-positive breastcancer is associated with the presence of steroid hormone receptors,younger patient age, and earlier clinical stage.

Survival analysis suggests that patients with PSA-positive breastcancer may have longer relapse-free survival than do those withPSA-negative disease. Mr. Yu concluded that PSA may, therefore,have value as an independent prognostic marker for breast cancer.