A study has observed a rise in the number of new cases of myeloma in both men and women in the U.S. since the turn of the century, with the steepest increases seen among young Hispanic women.

The incidence, or number of new cases diagnosed each year, of myeloma dropped in 2020 with the COVID-19 pandemic, which could “be attributed to impaired screening and utilization of diagnostic measures during the pandemic,” the study’s researchers said.

Understanding these trends may aid public health strategies toward preventing and treating the disease, the researchers noted in “A population-based study on incidence trends of myeloma in the United States over 2000–2020,” which was published in Scientific Reports.

Myeloma is a cancer that arises in plasma cells, a type of white blood cell that produces large amounts of antibodies. The second most common blood cancer, it makes up 1% of all cancers. Over time, the early, slow-growing cancer can develop into active forms of the disease. Multiple myeloma, also known as plasma cell myeloma, is its most advanced and aggressive form.

In rare cases, myeloma may grow as a single tumor in bones, called solitary plasmacytoma of bone, or in soft tissues outside bones, called extraosseous plasmacytoma.

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Increases in myeloma incidence

A team led by researchers in Iran drew on the U.S. National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) database, which includes cancer data associated by age, sex, race, and year of diagnosis, to describe the trends of incidence of myeloma over two decades.

“To the best of our knowledge, this is the first U.S. population-based study that utilized a large data integrated in the SEER program, focusing on different subtypes of myeloma to perform a comprehensive analysis of the epidemiological trends of myeloma within 2000-2020,” the researchers wrote.

In those years, 217,049 new cases were reported in the U.S., with most occurring in people ages 55 and older (88.45%), non-Hispanic whites (63.22%) and males (54.85%). The researchers analyzed 2000-2019 and 2019-2020 separately to study the potential effects of the COVID-19 pandemic on myeloma incidence.

Similar to the overall findings, the 204,872 new cases of myeloma reported from 2000-2019 were most commonly older people, non-Hispanic whites, and males. The incidence of myeloma showed an average annual percent change (AAPC) increase of 1.19% for men and 1.11% for women over that period, with higher gains among both sexes of non-Hispanic Black people, by 1.55-1.64%.

The AAPC increase surpassed 2% in women younger than 55 across all races/ethnicities, the highest being among Hispanic women (2.27%), closely followed by Black women (2.22%), and then white women (2.18%). Black men showed the highest incidence increase among younger men (by 1.55%). Among people 55 and older, Black people also had the highest incidence rise in both men (by 1.99%) and women (by 1.5%).

“The concerning rise in the incidence rate of myeloma among younger women, specifically among young women of Hispanic ethnicity, should be carefully acknowledged when formulating public health strategies to address these worrisome patterns,” the researchers wrote.

The most common myeloma type was multiple myeloma, with 193,530 (94.46%) cases, followed by 8,478 cases of solitary plasmacytoma of the bone and 2,864 cases of extraosseous plasmacytoma. “A male predominance was observed in all three … subtypes,” the researchers wrote.

Trends of multiple myeloma incidence were generally similar to those of overall myeloma, with a notable exception in the younger age group, where Black women showed the highest rate of increase (2.11%).

“Extraosseous plasmacytoma was the only subtype with decreasing AAPC in both men and women,” the researchers wrote. Black people had “the highest rate of decrease” in women, by 7.67%, and men, by 4.97%. In the older group, white people showed “the highest rate of decline in incidence rate,” by about 3.7%.

The incidence rate of solitary plasmacytoma of bone remained generally the same throughout the study period, “except for [white] women who exhibited significant AAPC increase, which was pronounced in the older age women,” the researchers wrote.

Decline with COVID-19 pandemic

From 2019 to November 2020, during the first year of the COVID-19 pandemic, the AAPC of myeloma incidence showed a significant drop, by 8.28% in women and 7.66% in men. This reduction was most pronounced in the older age group, and the steepest decrease, by 15.94%, was seen in older Hispanic women.

“Notably, male Hispanics were the only group who were not affected by the pandemic in any of the age groups,” the researchers wrote. “Supporting these observations, a recent umbrella review identified a substantial decrease in screening and diagnosis of several cancers during the pandemic, which was more remarkable in regions that implemented a lockdown strategy.”

The researchers said “the delay in treatment and changes in treatment pattern, may also cause the pandemic to leave a mark on the survival of myeloma patients in the subsequent years.”