Overestimation of multiple myeloma survival from cancer registry data.

Surveillance, Epidemiology, and End Results (SEER) multiple myeloma (MM) survival statistics (https://seer.cancer.gov/statfacts/html/mulmy.html) that have been used to guide MM management and control have been systematically overestimated due to the inclusion of smoldering multiple myeloma (SMM), a premalignant condition of MM. Using the latest SEER release, we estimated the extent of such overestimation in the survival statistics. In 2016, 77.9% out of 5,495 patients reported as overall MM were symptomatic MM and 10.9% were SMM. Median survival was 65.8 months for overall MM versus 56.8 months for symptomatic MM (p < .001). Inclusion of SMM overestimated MM survival by 9 months. Five-year relative survival estimates from 2015-2021 were 61.6% for overall MM, 57.9% for symptomatic MM, and 88.3% for SMM, versus SEER's reported 62.4%. Survival statistics for symptomatic MM and SMM should be reported separately to guide MM management and prevention at the population level.