The current study further supports what many oncologists observe anecdotally in clinical practice in patients with multiple myeloma.
Study authors identified patients who received a diagnosis of multiple myeloma between 1971 and 2016 at the Mayo Clinic and had CPCs detected on a peripheral blood smear within 30 days of diagnosis. Patients were categorized into 1 of 3 groups based on CPC count: less than 5%, between 5% and 19%, and 20% or greater.
The study cohort included 176 patients, for which the median age was 62 years and the majority of which were men (56%). Similar numbers of patients were in each group: 54 patients (31%) had less than 5% CPCs, 63 patients (36%) had between 5% and 19% CPCs, and 59 patients (34%) had 20% or greater CPCs.
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The median overall survival (OS) was 1.4 years for less than 5% CPCs, 1.1 years for between 5% and 19% CPCs, and 1.1 years for 20% or greater CPCs. Due to the similarity in the latter 2 groups, the study authors re-stratified patients as having either less than 5% or at least 5% CPCs. The median OS for patients with less than 5% CPCs (54 individuals) was 1.4 years and 1.1 years for patients with at least 5% CPCs (122 individuals; P = .154).
To further explore the relationship between CPC count and survival, the study authors compared these 122 patients with 5% or greater CPCs to a cohort of patients who received a diagnosis of multiple myeloma between 1971 and 2016 but did not have detectable CPCs (9724 individuals). Patients with 5% or greater CPCs lived a median of 3 years less than patients with no detectable CPCs (1.1 vs 4.4 years; P < .001).
When the time period of diagnosis was restricted to 2001 or later, the survival difference became even more pronounced. Patients with 5% or greater CPCs lived a median of 6 years fewer than patients with standard-risk multiple myeloma (1.4 years vs 7.5 years, respectively).