Prognostic Impact of Immunoglobulin Kappa C in Breast Cancer Patients Treated with Adjuvant Chemotherapy

Introduction: Immunoglobulin kappa C (IGKC)-positive tumor-infiltrating plasma cells are associated with better prognosis in node-negative breast cancer patients without adjuvant systemic therapy. In the present study we evaluated the prognostic significance of IGKC in breast cancer patients treated with adjuvant chemotherapy +/- tamoxifen. Methods: IGKC expression was immunohistochemically analyzed in 193 breast cancer patients who were treated with adjuvant chemotherapy, either with cyclophosphamide, methotrexate, and 5-fluorouracil (CMF) or 5-fluorouracil, epirubicin, and cyclophosphamide (FEC) between 1993 and 2001 with a median follow-up of 11 years. The prognostic impact of IGKC expression was evaluated by Kaplan-Meier survival analyses as well as uni- and multivariate Cox regression. An interaction term was used to investigate a possible association between tamoxifen treatment and prognostic effect of IGKC expression. Results: Kaplan-Meier analyses identified IGKC as a prognostic marker for metastasis-free survival (MFS): higher IGKC expression was associated with a better outcome (p = 0.02, log rank). Results of univariate Cox regression confirmed the prognostic impact of IGKC expression: patients with a strong IGKC expression had a longer MFS (hazard ratio [HR] 1.931; 95% confidence interval [CI] 1.087-3.431; p = 0.025). Multivariate Cox regression analysis showed the independent prognostic significance of IGKC expression (HR 2.070; 95% CI 1.088-3.938; p = 0.027). The interaction term confirmed a significant interaction between tamoxifen treatment and the prognostic impact of IGKC expression (p(interaction) = 0.04). Conclusion: IGKC expression had an independent prognostic impact in early breast cancer patients who received adjuvant chemotherapy. There was a significant interaction with the use of tamoxifen.