Clinical course and prognosis of non-secretory multiple myeloma.

Objective: To determine the prognosis of patients with non-secretory myeloma.

Methods: We studied 124 patients diagnosed with multiple myeloma who had no monoclonal protein detected on serum and urine immunofixation at diagnosis and on all subsequent follow-up testing (non-secretory myeloma). The overall survival (OS) of patients with non-secretory myeloma was compared with 6953 patients with typical myeloma seen during the same time period in whom a monoclonal protein was detected at the time of diagnosis.

Results: One hundred and twenty-four patients met criteria for non-secretory multiple myeloma. The median follow-up was 102 months (range, 1-204 months). The median progression-free survival with initial therapy was 28.6 months, and the median OS was 49.3 months. There was a significant improvement in OS since 2001; median survival 43.8 months (prior to 2001) vs. 99.2 months (2001-2012), P < 0.001. OS was superior in patients with a normal baseline FLC ratio (n = 10) compared to patients with an abnormal ratio (n = 19), medians not reached in both groups. Prior to 2001, OS was similar in non-secretory myeloma (n = 86) and secretory myeloma (n = 4011), median 3.6 vs. 3.5 yr, respectively, P = 0.63. However, among patients diagnosed between 2001 and 2012, OS was superior in non-secretory myeloma (n = 36) compared to secretory myeloma (n = 2942), median 8.3 vs. 5.4 yr, respectively, P = 0.03.

Conclusions: Non-secretory myeloma is an uncommon subtype of multiple myeloma. In the last decade, there has been an improvement in the survival of non-secretory myeloma and appears superior to secretory myeloma.