statistics resulted in an overestimation of MM survival by 
nine months.1
“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%,” 
the researchers reported. “Survival statistics for symp-
tomatic MM and SMM should be reported separately to 
guide MM management and prevention at the popula-
tion level.”
With SEER data widely quoted in clinical and 
epidemiological studies, getting the number right could 
have broad implications for treatment recommendations 
and care decisions. The lack of a specific ICD or 
ICDO code for SMM separate from MM makes such a 
breakdown challenging. 
Nearly 78% (4,282) patients recorded with MM 
in 2016 had symptomatic MM, 10.9% had SMM, and 
the balance were missing or other/unknown. Median 
survival for those with overall MM was 65.8 months 
vs. 56.8 months for those with symptomatic MM and 
median survival not reached for those with SMM, as of 
Dec. 31, 2022.
“By differentiating symptomatic MM from SMM 
using the newly released SEER17 site-specific variable, 
we demonstrated that the median observed MM survival 
was overestimated by nine months in 2016 due to the 
inclusion of SMM patients,” the team concluded. “This 
overestimation may lead to an overly optimistic attribu-
tion of changes in MM survival to evolving management 
strategies in recent years.” 
Refining SMM Definition
Separating SMM from MM might still overstate the risk 
for individuals with SMM, a team from Memorial Sloan 
Kettering Cancer Center and Weill Cornell Medicine in 
New York argued in a letter in Blood Advances late last 
year. While the rate of progression for SMM has been 
assumed to be 10% per year for the first 5 years post-
diagnosis, 3% per year for the next five years and 1% 
per year after 10 years, the New York team and Greek 
researchers from the University of Athens both found 
that current diagnostic criteria and advanced imaging 
have dramatically reduced this risk.
The 2014 definition of MM included three biomarkers 
(SLiM) to the classic CRAB symptoms (calcium, renal, 
anemia, bone), and advanced imaging allow earlier 
identification of symptomatic MM, removing early-stage 
patients who would previously have been considered to 
have SMM at diagnosis. 
Using the 20/2/20 model, the Greek team classified 
427 SMM patients into low (52%), intermediate (31%) 
and high risk (17%). At three years of follow-up, they 
found that progression varied notably between risk 
groups. Low-risk patients had 1-, 2- and 3-year progres-
sion rates of 0%, 1% and 1%, while at the same inter-
vals, 1%, 8% and 13% of intermediate-risk patients had 
progressed. Among high-risk patients, however, the rates 
were 13%, 26% and 43%.2
Observed and 5-year relative survival from SEER 17
Source: Overestimation of multiple myeloma survival from cancer registry data. J Natl Cancer Inst. 2026 Feb 6:djag028. doi: 10.1093/jnci/djag028. Epub ahead of 
print. PMID: 41652897; PMCID: PMC12967285.
	
	
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