Researchers reviewed nationwide data on 3,504 white, 858 black and 468 Hispanic patients treated from 2007 to 2013.
The average time between multiple myeloma diagnosis and start of treatment was 2.7 months for whites; 4.6 months for Hispanics; and 5.2 months for blacks.
Drugs are usually the first course of treatment for this type of blood cancer. If treatment is delayed, patients can suffer organ damage, kidney problems, anemia, broken bones, infections and other serious health problems.
"We noted that minorities are not getting introduced to treatment early enough to derive adequate clinical gains," said lead author Dr. Sikander Ailawadhi, an oncologist at the Mayo Clinic in Jacksonville, Fla.
Over the study period, the odds of beginning treatment within six months of diagnosis increased for the three groups. However, the improvement was greater among whites and Hispanics than among blacks.
Autologous stem cell transplant is considered the standard of care for eligible patients. Transplant rates within a year of diagnosis increased among whites and blacks, but not among Hispanics.
Median overall survival was similar across all three groups. (Median means half survived longer, half for a shorter time.) But the authors said a comparison to previous research suggests the survival rate for blacks could have been better if they had equal and timely access to treatment.
"Since our analysis is based on Medicare patient data, these disparities cannot be attributed to differences in insurance coverage. Patients are not receiving treatment equally even in this ostensibly equal-access setting," Ailawadhi noted in an American Society of Hematology news release.
Researchers also found that medical costs were highest among Hispanics. Their average total monthly medical cost was $12,657, compared with $11,546 for blacks and $10,143 for whites.
The authors said the higher amount for Hispanics could be due in part to higher hospitalization costs, possibly because of complications resulting from delayed treatment.
Ailawadhi said further research is needed to investigate reasons underlying the racial disparities.
"We hope that understanding and addressing them will lead to more equitable health care access, cost, and outcome profiles for all multiple myeloma patients, regardless of race or ethnicity," he concluded.
The study was published Oct. 17 in the journal Blood Advances.