Factors Affecting Msa Levels in Normal Women and Women With Breast Cancer

Abstract

Blood from 1497 women who were either non‐pregnant, pregnant at all stages of gestation, lactating after parturition, postmenopausal, or who had benign breast lumps, primary breast cancer or advanced breast cancer were tested for their peripheral blood mammary serum antigen (MSA), using the 3E1.2 monoclonal antibody (MoAb) in an inhibition enzyme linked immunosorbent assay test system. The study aimed to establish normal ranges for comparison with MSA levels in breast cancer and benign breast disease. Compared with normal premenopausal women, which included women measured 8–10 times throughout their menstrual cycle, circulating MSA levels were significantly elevated throughout pregnancy (P > 0.0001), in postmenopausal women (P > 0.05), in women with primary breast cancer (P > 0.05) and women with advanced (metastatic) breast cancer (P > 0.0001). As a group, the 30 women with benign breast disease did not demonstrate significantly different MSA level from normal. However, 3% of the group did have levels above the cut off for normal (400 IU/mL). Analysis of the normal premenopausal women according to age, parity and stage of the menstrual cycle and during lactation showed that these parameters did not affect MSA levels. It is concluded that the test is potentially valuable in the detection of metastatic but not primary breast cancer, and the effects of pregnancy and postmenopausal status on the circulating MSA levels need to be considered in the interpretation of MSA measurements.

Mammary serum antigen (MSA) in advanced breast cancer

“…This represents a significantly smaller percentage of advanced breast cancer patients who have raised circulating MSA levels compared to the published data [3]. We have discussed this discrepancy in a previous report, which concluded that measurement of serum MSA levels would be of no use in the detection of early (Stage I and Stage II) breast cancer [6]. In that report we suggested that serial measurements of serum MSA might be useful in the management of advanced breast cancer, and this paper reports the results of a study to explore this possibility.…”

“…A modification of the Stacker ELISA assay [8] was used as previously described [6]. In our laboratory an arbitrary value of > 400 inhibition unit/ml (IU/ ml) is taken to indicate the presence of an abnormal MSA level in the serum.…”

“…In this paper, we report further results on the 123 advanced breast cancer patients whose circulating MSA levels at presentation to the oncologist have been reported [6]. In this study, we determined the usefulness of circulating MSA measurements in the management of advanced breast cancer patients by correlation of serial measurements of circulating MSA levels with treatment, number of secondary sites, and status of the disease (progressive disease, stable disease, and partial response to treatment).…”

“…Using MoAb 3E1.2, we have established the MSA serum test in our laboratory and have shown that pregnancy has a profound effect on circulating MSA levels; that circulating MSA is very significantly raised in 53% of advanced breast cancer patients on palliative therapy; that although early breast cancer patients have significantly different circulating MSA levels from normal, only 7% of these patients have abnormal circulating MSA levels; and that post-partum lactation, benign breast lumps, age, parity, and menstrual status do not affect circulating MSA levels [6].…”