Minorities most likely to have aggressive tumors, less likely to get radiation

October 28, 2012

SAN DIEGO -- Women with aggressive breast cancer were more likely to receive adjuvant chemotherapy, but at the expense of completing locoregional radiation therapy, according to recently presented data. This was especially true in minorities, who were the most likely to present with moderate- to high-grade and symptomatically detected tumors.

"Radiation treatment decreases the risk for breast cancer recurring and improves survival from the disease," said Abigail Silva, M.P.H., Susan G. Komen Cancer Disparities Research trainee at the University of Illinois in Chicago, who presented the results at the Fifth AACR Conference on The Science of Cancer Health Disparities, held here Oct. 27-30, 2012.

Prior studies have shown that black and Hispanic women are less likely than white women to obtain radiation treatment when eligible, and this may partly explain racial/ethnic disparities in breast cancer outcomes, according to Silva.

To further examine factors in disparities in guideline-concordant radiation treatment, Silva and colleagues gathered interview and medical record data from a population-based study of patients with single invasive primary tumors, including 397 non-Hispanic whites, 411 non-Hispanic blacks and 181 Hispanics.

Of the patients who consented to medical record abstraction and were eligible for radiation treatment, 88 percent received a recommendation for radiation treatment and 93 percent of those patients accepted treatment. However, only 97 percent of patients who accepted treatment actually received radiation. Therefore, initiation occurred in only 79 percent of the initial population of women who were eligible for radiation treatment.

Data indicated that minority women were less likely to initiate radiation treatment compared with non-Hispanic white women. In addition, minority women were more likely to have moderate- to high-grade tumors and symptomatically detected tumors.

"We also found that patients who got chemotherapy were less likely to get radiation when they needed it," Silva said. "Because minorities tended to have more aggressive breast cancer that more often required chemotherapy, this disproportionately affected them."

Given these results, Silva and colleagues said clinicians may not be recommending guideline-concordant radiation treatment to all eligible patients.

"Indeed, we found that once a treatment recommendation was made, the vast majority of patients received treatment," Silva said. "In addition, greater diffusion of gene expression profiling may improve cancer care, not only by reducing overuse of chemotherapy but by eliminating chemotherapy as a potential barrier to receipt of radiation."

In the next phase of their research, Silva and colleagues plan to examine the role of mutable patient factors such as social support, cultural beliefs and provider mistrust, which may help explain the disparity in initiation of radiation treatment.
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Mediators of Racial/Ethnic Disparities in Radiation Treatment among Breast Cancer Patients. Abigail Silva1, Garth H. Rauscher1, Rao D. Ruta2, Kent Hoskins3. 1University of Illinois School of Public Health, Division of Epidemiology and Biostatistics, Chicago, IL, 2Rush University Medical Center, Chicago, IL, 3University of Illinois College of Medicine, Chicago, IL.

BACKGROUND: Radiation after surgery can reduce recurrence and breast cancer mortality yet there is some evidence that not all women receive guideline-concordant radiation treatment. Indeed, studies that have examined the receipt of radiation among women who underwent breast-conserving surgery have found that Black and Hispanic women were less likely than White women to complete their locoregional treatment. However, little is known about the factors that may facilitate or impede treatment. In order to better understand the causes of disparities in radiation treatment, this study seeks to: 1) determine the extent to which there is a racial/ethnic disparity in radiation treatment initiation, and 2) examine patient factors and hospital characteristics that may help explain the variation.

METHODS: Interview and medical record data came from a population-based study of 989 breast cancer patients (397 non-Hispanic White, 411 non-Hispanic Black, 181 Hispanic) diagnosed between 2005-2008. Of these, 87% (N=849) consented to medical record abstraction, including a linkage with the Illinois State Cancer Registry (ISCR). Patients who consented to the medical record abstraction and had single invasive primary tumors were considered for this study. Radiation treatment eligibility was defined according to the 2005-2007 National Comprehensive Cancer Network (NCCN) guidelines. The outcome variables included treatment recommendation, acceptance, and initiation which were derived from the interview, medical record, and ISCR data. Risk differences (RDs) were estimated using logistic regression (with marginal standardization). Potential mediators related to radiation initiation were identified, and then assessed by rescaling model coefficients using the method of Karlson, Holm, and Breen. All models were adjusted for age and time from diagnosis to interview.

RESULTS: Among patients with single invasive primary tumors (n=614), 443 patients (72%) were eligible for radiation treatment (RT) per the NCCN guidelines. Radiation treatment was recommended to 88% of eligible patients of which 93% accepted it. Among those who accepted treatment, 97% received radiation. This translated into an overall treatment initiation of 79%. Minority patients were less likely than non-Hispanic (nH) White patients to initiate radiation (0.75 vs. 0.85, RD=10%p=0.000). Minorities were more likely to have moderate-high grade tumors and symptomatically detected tumors which in turn were less likely to receive radiation (all p-values <0.01). Minority women were also more likely than nH White women (p<0.0001) to receive chemotherapy, which in turn was associated with lower receipt of RT (p<0.05). Together these factors explained 46% of the disparity (p=0.002).

CONCLUSIONS: Patients who are eligible for radiation and have more aggressive appearing tumors at diagnosis are more likely to receive chemotherapy but at the expense of completing their locoregional (radiation) therapy. This disproportionately affects minority patients and results in underuse of radiation in these women. Greater diffusion of gene expression profiling (e.g. Oncotype) may improve cancer care not only by reducing overuse of chemotherapy but by eliminating chemotherapy as a potential barrier to receipt of RT.

American Association for Cancer Research

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