An Evaluation Of The Role Of Bone Marrow Biopsy In Patients With Multiple Myeloma Who Achieve An Unconfirmed Stringent Complete Remission

8144 Background: The latest guidelines for response published by the International Myeloma Working Group introduce sCR (stringent Complete Response) as a response criterion for patients who have normal free light chain ratio and absence of clonal cells in the bone marrow, in addition to satisfying all the criteria for complete response (CR). The clinical significance of sCR vs. those patients who are in sCR unconfirmed by bone marrow biopsy (uSCR) in terms of progression free survival (PFS) and overall survival (OS) is unknown. Methods: A retrospective cohort study of patients undergoing treatment for symptomatic multiple myeloma was performed using a institutional database for category of response and clinical outcomes. All subjects had serial disease evaluation with serum and urine protein electrophoresis, serum free light chain assay by nephelometry, and radiologic imaging when appropriate. The results of patients who achieved sCR and usCR (patients believed to have sCR but not confirmed by immunohistochemistry or immunofluorescence for absence of clonal cells on bone marrow biopsy) are reported. Results: A total of 56 patients had achieved either sCR (n = 38) or usCR (n = 18). The median time of follow-up was 3 years (range .04 – 6.67 years). The median PFS for sCR of 210 weeks was not significantly different than for usCR 142 weeks, (P = 0.12 by log-rank). The median overall survival was not reached for both groups, with a statistically equivalent OS at 4.5 years of 100% for patients achieving usCR versus 89% for sCR (P = 0.134 by log- rank). Conclusions: Persons with myeloma who achieve either a sCR or usCR have similar rates of progression and survival at 3 years of follow-up. Although more follow-up time may bear out a statistically valid difference in the clinical endpoints of PFS and OS, a normal free light chain assay for a patient may serve as less invasive alternative to bone marrow biopsy in conventional myeloma disease response assessment. No significant financial relationships to disclose.