Among men, the overall cancer death rate was 47% higher for blacks than for whites in 1990, but that difference dropped to 19% in 2016, and the disparity has been nearly eliminated in men younger than 50, according to the study published in CA: A Cancer Journal for Clinicians on Thursday.
Among women, the disparity decreased from 19% in 1990 to 13% in 2016 and was nearly eliminated for women 70 and older.
The four most common cancer types among black Americans, accounting for 54% of all cases, are breast, prostate, colorectal and lung, according to the study.
The study found that racial disparities in cancer deaths are declining among the latter three.
"We have seen the most progress for lung cancer, followed by prostate and colorectal cancer. For breast cancer, the racial disparity continued to widen until 2010 and has since held steady," said Carol DeSantis, principal scientist of surveillance research at the American Cancer Society and first author of the new study.
"I was surprised and encouraged to see that the racial disparity in cancer mortality is narrowing," she said. "This is also the first time that we looked at black-white disparities in cancer mortality by age groups, and it was very exciting to see the great progress in eliminating racial disparities in several age groups, including younger men and older women."
Cancer is the second leading cause of death, both in the United States and worldwide.
The study included data on cancer incidence, mortality, survival, screening and risk factors in the United States from the National Cancer Institute's Surveillance, Epidemiology, and End Results database, the North American Association of Central Cancer Registries and the National Center for Health Statistics.
Some of the data dated to 1975, and the most recent data came from 2016.
The researchers also used the most recent incidence and mortality data to project the numbers of new cancer cases and deaths among black Americans in 2019.
Prostate cancer was found to be the most commonly diagnosed cancer in black men, and breast cancer was the most commonly diagnosed cancer in black women, each accounting for nearly one-third of cancers diagnosed in each group.
The researchers projected that about 98,020 overall cancer cases in black men and 104,240 cases in black women are estimated to be newly diagnosed in 2019.
Between 2006 and 2015, overall cancer incidence rates decreased faster in black men, at 2.4% per year, compared with white men, at 1.7% per year, according to the study. The study also found that the overall cancer incidence rate has been relatively stable among black women since 2009, but has increased slowly, at 0.2% per year, among white women.
Historically, US cancer death rates were lower in blacks than in whites in the early 1950s. Then, rates sharply climbed in blacks from the 1950s through 1990, according to the study.
Those rates have remained higher compared with those of white Americans ever since the 1960s, and they peaked among black men and women in the early 1990s before declining, the study found.
Racial disparities now could be narrowing due to a smoking rates going down among black men and greater access to cancer screening and cancer treatment across the black community, DeSantis said.
"Improvements in cancer therapies and early detection first benefited those with higher socioeconomic status, who are more likely to be white," DeSantis said, but that slowly seems to be changing.
"For several cancers -- including colorectal and breast -- cancer death rates in blacks were similar, or even higher, compared to whites in the 1970s and '80s. The disparity emerged when cancer death rates began to fall, with medical advances that benefited one group more than the other," she said. "In the US, blacks are unduly burdened by cancer in large part due to socioeconomic barriers to high-quality cancer treatment, screening, as well as prevention."
The new study has some limitations, including that the projections for 2019 are based only on models and should be interpreted with caution. Also, the data in the study is only for non-Hispanic blacks and whites.
"It is essential to monitor progress in reducing these disparities if we want to continue to see improvement and eventually eliminate racial disparities in cancer outcomes," DeSantis said.
While disparities remain in cancer death rates among black and white patients in the United States, several factors have been important in closing those gaps, said Dr. Samuel Cykert, professor of medicine at the University of North Carolina School of Medicine in Chapel Hill.
"Two of the most important things right now are that the smoking rate among black men has fallen fairly dramatically over the last 10 years," said Cykert, who was not involved in the new study but who has conducted research on racial disparities in cancer treatment.
"Then, the second big factor is the Affordable Care Act. With insurance expansion, access to care is greater both in terms of prevention and treatment," he said.
Also, "some lesser factors include that the medical school curricula have changed over the last decade, so doctors are trained to think about disparities a little bit more, and another important thing is cancer centers themselves are more aware of disparities," he said.
To eliminate racial disparities among cancer patients entirely, Cykert said, giving additional attention to the progression of a patient's care in real time as well as prevention efforts -- including screenings and reducing obesity risk -- are both key.
"As far as what causes disparities, the classic and most superficial cause is that if people are poorer and they don't have health insurance and they don't have access to care. But some of the more subtle factors are, for instance, that in neighborhoods where you have heavy concentrations of black cancer patients, oftentimes, either the advanced evidence of care or the technology doesn't diffuse out as quickly," Cykert said.
"Another thing that's really important is the historical barrier of trust and communication," he said, referring to a deep-rooted distrust of the medical community in some patients, as well as the geographic and cultural barriers that some patients face when trying to access adequate health care.
Among physicians, "there seems to be less awareness and effort" to rebuild that trust and improve communication, he said, but he remains hopeful that improvements can be made.
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