SAN DIEGO — Two proposed new multiple myeloma staging systems offer similar prognostic accuracy compared with the standard staging system, but the new systems provide more refined risk classifications across different disease stages.
The findings should encourage greater use of these newer staging systems in routine clinical practice, first author Manni Mohyuddin, MD, said during a presentation at the American Society of Hematology (ASH) annual meeting.
Mohyuddin and his colleagues retrospectively compared the standard Revised International Staging System (R-ISS) with two newer systems, the Second Revision of the R-ISS (R2-ISS) and the Mayo Additive Staging System (MASS), using real-world data from nearly 500 patients with newly diagnosed multiple myeloma.
The R-ISS, the most common multiple myeloma staging system, incorporates a range of prognostic features, including high-risk genetic markers assessed using fluorescence in situ hybridization as well as levels of lactate dehydrogenase, albumin, and beta-2 microglobulin, explained Mohyuddin, assistant professor at the Huntsman Cancer Institute, University of Utah, Salt Lake City.
R2-ISS and MASS include additional factors that reflect experts' growing understanding of multiple myeloma. Specifically, the systems also evaluate a gain of chromosome 1q, in which patients have an extra copy of chromosome 1q, as well as the additive effects of multiple high-risk cytogenetic abnormalities, both of which indicate worse prognosis in multiple myeloma , Mohyuddin told Medscape Medical News.
To compare the three staging systems, the investigators used information on newly diagnosed patients in the Flatiron Health EHR–derived deidentified database, which includes data from cancer clinics across the United States. Patients were followed from first-line treatment initiation until death, the end of the study period, or last recorded activity.
The patients from the database had a median age of 70 years, and most had not received a transplant. The most common cytogenetic abnormality was gain 1q, present in about one third of patients.
Given that the R2-ISS originated from patients in clinical trials, Mohyuddin noted the importance of assessing how the system would perform in a real-world setting.
Of the 497 patients in the analysis, the R-ISS staging system classified 24% as stage I, 63% as stage II, and 13% as stage III. Overall survival differed across these R-ISS stages, indicating the system was prognostic for survival. Median overall survival was not reached for those with stage I disease, was 62.9 months for those with stage II disease, and 37.6 months for those with stage III disease.
Because the R-ISS doesn't consider the additive effect of multiple cytogenetic abnormalities, many patients end up in the R-ISS stage II category but ultimately may have vastly different outcomes, Mohyuddin said.
The R2-ISS includes four risk categories, which provide more granularity to the stage II classification: Stage I is low risk, stage II is low-intermediate, stage III is intermediate, and stage IV is high risk. Using this staging system, 20% of patients were stage I, 25% were stage II, 46% were stage III, and 9% were stage IV.
The R2-ISS was also prognostic for survival, which generally worsened from stage I to stage IV: Median overall survival was not reached in stage I patients, was 69.3 months for stage II, 50.0 months for stage III, and 50.6 months for stage IV patients. However, Mohyuddin noted that there was some overlap in the survival curves for stages I and II and for stages III and IV.
When applying MASS, 34% of patients were categorized as stage I, 35% as stage II, and 31% as stage III disease. This system was prognostic for survival as well, with median overall survival of 76.9 months for stage I, 61.2 months for stage II, and 45.0 months for stage III.
With R2-ISS, many of those in R-ISS stage II are moved into stage I and III. With MASS, the R-ISS stage II patients are more evenly distributed across stages I, II, and III.
In other words, "we show that both these newer staging systems basically recategorize patients into different stages," essentially "decreasing the number of people in the large, ambiguous (R-ISS) stage II category," said Mohyuddin.
Mohyuddin and colleagues also evaluated the staging systems in fully adjusted analyses that controlled for age, race/ethnicity, sex, practice type, and diagnosis year.
Using R2-ISS, stage I patients had a similar risk for death compared with stage II patients (hazard ratio [HR], 1.2). Compared with stage I patients, stage III and IV patients had comparable risks for death, both about 2.5-fold higher than in those with stage I disease (HR, 2.4 and 2.6, respectively).
Compared with stage I MASS patients, those with stage II had a twofold higher risk for death (HR, 2.0), and those with stage III had an almost threefold higher risk (HR, 2.7).
Although no system considers all factors associated with myeloma outcomes, R2-ISS and MASS do offer a benefit over R-ISS, Mohyuddin said.
Mohyuddin added that the R2-ISS and MASS are similar from a statistical standpoint, but he gave MASS a slight edge for use in clinical practice.
MASS "more cleanly demarcated [patients] into prognostic subsets," plus it is "a little easier to remember by heart," he explained. MASS also puts more emphasis on the presence of multiple high-risk cytogenetic abnormalities, which is a worse prognostic in this era of quadruplet therapy for multiple myeloma, he added.
Because the study largely took place in an era when triplet therapy dominated, "we would be curious to see, with longer follow-up and more use of quadruplets, how these staging systems would perform," he said.
Despite the benefits of these newer staging systems, many factors play a role in multiple myeloma outcomes, Mohyuddin explained. Staging systems are "only a piece of the puzzle."
Mohyuddin reported having no financial interests to disclose.
Sharon Worcester, MA, is an award-winning medical journalist based in Birmingham, Alabama, writing for Medscape, MDedge and other affiliate sites. She currently covers oncology, but she has also written on a variety of other medical specialties and healthcare topics. She can be reached at sworcester@mdedge.com or on Twitter: @SW_MedReporter.
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