SAN ANTONIO — Reduced pretreatment serum B-cell maturation antigen appeared associated with shorter time to progression among patients with hormone receptor–positive metastatic breast cancer, according to results of a randomized phase 3 trial of second-line hormone therapy presented at San Antonio Breast Cancer Symposium.
The correlation may be explained by the link between reduced serum B-cell maturation antigen (BCMA) with immune deficiency, Suhail M. Ali, MD, associate professor at Penn State Hershey Medical Center in Hershey, Pennsylvania, and colleagues concluded.
“Evaluation of serum BCMA as a new biomarker to predict outcomes for breast cancer and other [patients with solid tumors] deserves further study,” Ali and colleagues wrote.
BCMA, a member of the tumor necrosis factor receptor family, has two ligands — B-cell activating factor and a proliferation-inducing ligand. These ligands inhibit apoptosis of normal and malignant B cells and also activate cell proliferation, according to study background.
Prior research suggested circulating BCMA levels may be elevated in B-cell malignancies and may predict PFS and OS for patients with multiple myeloma, Waldenstrom’s macroglobulinemia and chronic lymphocytic leukemia.
However, other research showed serum BCMA levels are quite low among patients with myeloma who are in complete remission and have low antibody levels, as well as among those with primary immune deficiencies.
The possible importance of serum BCMA for patients with solid tumors had not been established.
Ali and colleagues used an enzyme-linked immunosorbent assay for BCMA to evaluate pretreatment serum from 139 patients with hormone receptor–positive metastatic breast cancer who were enrolled in a randomized phase 3 clinical trial of second-line hormone therapy.
The median BCMA level was 55.61 ng/mL (range, 34.2-78.7).
Univariate analysis showed reduced serum BCMA was significantly associated with shorter time to progression for patients below the following dichotomous serum BCMA cutpoints:
- 20 ng/mL (n = 10) — HR = 2.88; P = .005;
- 25 ng/mL (n = 13) — HR = 2.16; P = .023; and
- 30 ng/mL (n = 27) — HR = 1.77; P = .016.
Researchers analyzed patient response according to serum BCMA using a 30 ng/mL cutpoint. Considerably more patients above the cutpoint than below the cutpoint achieved complete response, partial response or no change (47.3% vs. 22.2%), whereas patients below the cutpoint were more likely to experience progressive disease (70.3% vs. 41.9%).
Researchers determined significant associations between time to progression and BCMA levels below 30 ng/mL vs. above 30 ng/mL (P = .016), below 25 ng/mL vs. above 25 ng/mL (P = .023), and below 20 ng/mL vs. above 20 ng/mL (P = .005). – by Jennifer Southall
Ali, SM. Abstract P1-02-10. Presented at: San Antonio Breast Cancer Symposium; Dec. 6-10, 2016; San Antonio, Texas.
Disclosure: Ali reports no relevant financial disclosures. Please see the abstract for a list of all other researchers’ relevant financial disclosures.