Change in Serum Biomarker CA 15-3 as an Early Predictor of Response to Treatment and Survival in Hypersensitivity Pneumonitis

Background: Hypersensitivity pneumonitis (HP) is an interstitial lung disease with a heterogeneous course of disease and treatment response. Cancer antigen 15-3 (CA 15-3), part of mucin 1, is believed to reflect epithelial cell injury and lung permeability and could be a potential biomarker for treatment response in HP. Objective: To assess the value of CA 15-3 as a predictive biomarker in non-fibrotic and fibrotic HP during immunosuppressive therapy. Design: Serum levels of CA 15-3 and pulmonary function tests (PFTs) were retrospectively retrieved from 48 HP patients treated with prednisone or cyclophosphamide at initiation of therapy (baseline), after 3 and 6 months. Pearson's correlation coefficient was computed to assess correlations between change in serum levels and PFT. Survival was evaluated using Kaplan–Meier curves. Results: After 6 months of immunosuppressive therapy CA 15-3 levels decreased significantly compared to baseline (p = 0.001). Change in CA 15-3 after 6 months correlated with FVC change (r = − 0.469; p = 0.001). Correlations with FVC change were observed in prednisone-treated HP (r = − 0.514; p = 0.005) and fibrotic HP (r = − 0.417; p = 0.007). Three-month CA 15-3 change correlated with 6-month FVC change (r = − 0.599; p < 0.001). CA 15-3 declines of at least 7.9% after 6 months were associated with increased survival compared to minor CA 15-3 changes (HR 0.34; p = 0.020). Conclusion: Serum CA 15-3 correlates with PFT during 6 months of immunosuppressive therapy in HP. Interestingly, early CA 15-3 changes could predict future PFT. Furthermore, a decrease in CA 15-3 is related to longer survival. Therefore, serum CA 15-3 is a promising biomarker for implementation in HP care.