Prior studies have demonstrated differences between black and white patients in the use of chemotherapy for stage III colon cancer but have not determined which factors might explain the disparity. This study, which evaluated patient, environmental, physician, and hospital factors, showed no single or simple explanation.
We observed that black patients did not see medical oncologists at different rates than whites, suggesting that physicians were referring black and white patients to medical oncologists in a comparable manner and that both black and white patients adhered to these recommendations and/or considered chemotherapy. Black patients, however, were less likely than white patients to initiate chemotherapy after this consultation.
Patient age was one of the most powerful factors associated with the black – white disparity in chemotherapy use. The youngest black Medicare beneficiaries experienced the greatest dis parity in chemotherapy receipt. This is worrisome, because the “ young ” elderly are the most likely to derive a survival benefit from chemotherapy ( 32
) . Older black patients had more similar care to older whites, in large part because of decreasing chemotherapy receipt with increasing age among both groups.
About half of the black – white disparity in chemotherapy use among patients aged 66 – 70 years could be explained by our study variables. The factors with the greatest explanatory power were not related to treating physicians or hospitals but rather to the patients’ severity of illness, social support, and environment. Surgical resection length of stay accounted for a substantial proportion of the black – white disparity. Black patients had longer lengths of stay than white patients. Length of stay could indicate underlying health status and/or the level of postoperative complication and thus provide a functional measure of health status at the time chemotherapy was being considered. Length of stay may also represent the level of home care support, because individuals with less support in their homes may require more care in the hospital before discharge. Poorer health status and less home care support could affect an oncologist’s likelihood of recommending chemotherapy or a patient’s perception of the ability to tolerate chemotherapy, although neither of these factors represents an absolute contraindication to receipt of chemotherapy.
Among the socioeconomic factors explored in the study, educational status in a patient’s residence census tract explained a substantial proportion of the black – white disparity in chemotherapy use. A higher proportion of black patients lived in census tracts with lower high school graduate rates; these areas had lower chemotherapy rates. Several studies have found an association between education level and use of recommended medical care, such as cancer screening ( 33
) and disease treatments ( 41
) . Lower educational attainment is associated with lower income. For persons under age 65 years, lower income is associated with less insurance coverage ( 44
) , which is highly correlated with receipt of less medical care, including cancer screening and treatment ( 34
) . In this study of Medicare-insured individuals, it is Medicare-required cost sharing rather than a lack of insurance coverage that would have an impact on receiving medical care. Although most Medicare beneficiaries have supplemental private insurance to cover deductibles and copayments, the rate of private insurance coverage differs substantially by race. Only 11% of white patients have no supplemental coverage compared with 25% of black patients ( 49
) . Chemotherapy for colon cancer would include copayments for at least 6 months of outpatient treatment, which could affect acceptance rates among those without supplemental insurance. Supplemental insurance status was unavailable in the SEER – Medicare database, however, and thus could not be included as a variable in our analysis.
We were unable to account for about half of the black – white disparity in chemotherapy receipt. What might explain this remaining disparity? Chemotherapy is a treatment with high morbidity and no guaranteed outcome. The literature suggests that black individuals are more likely than white individuals to have a fatalistic attitude toward medical illness ( 50
) ; to experience stigma, fear, and denial related to a cancer diagnosis ( 54
) ; to have an aversion to health care treatments such as surgery ( 56
) ; to mistrust the health care system ( 51
) ; and to have misperceptions about cancer that interfere with treatment ( 50
) . Black patients may place values on the projected benefits of chemotherapy that differ from those of white patients. It is also possible that black patients are more likely than white patients to misperceive chemotherapy for stage III colon cancer as palliative rather than adjunctive treatment. Oncologists may have difficulty communicating the benefits of chemotherapy alongside its risks in the context of these beliefs, perceptions, and experiences. Alternately, medical oncologists caring for black patients may provide a lower quality of care than those caring for white patients. Primary care physicians treating black patients have reported greater difficulty obtaining access for their patients to high-quality subspecialists than physicians treating white patients ( 61
) . Oncologists may also view their black patients as less favorable chemotherapy candidates or may present chemotherapy less enthusiastically to black patients than to white patients. Several studies have shown that physicians are less likely to suggest ( 62
) or to provide ( 12
) recommended treatments to black patients than to white patients. Indeed, black patients perceive greater levels of racism or unfair treatment because of race in the health care system than white patients ( 59
) . They have also rated their medical visits as less participatory than have white patients ( 67
Our study has several limitations. Study variables were limited to those available in the research database. No variables measuring patient attitudes toward cancer treatment or directly measuring social or home support were available. Our indicators of socioeconomic status, social class, and education were measured at the ecologic level. Although these measures may serve as proxies for individual-level indicators, they mix in neighborhood-based relationships and may only partially account for the individual-level effects ( 68
) . Some colon cancer patients who receive chemotherapy are not identified by the Medicare claims data, although Warren et al. ( 70
) reported the overall sensitivity of Medicare claims for identifying adjuvant chemotherapy use among colon cancer patients as 90%. There is no information on whether the sensitivity of Medicare claims for identifying chemotherapy varies by patient race. Our medical oncologist practice volume variables measured care related to colorectal cancer among individuals with SEER – Medicare data only, so they may not reflect medical oncologists’ overall practice volumes. Patients cared for in teaching hospitals may have received care primarily from oncology fellows rather than the attending medical oncologists, although medical oncologist characteristics linked to the database via Unique Physician Identification Numbers (UPINs) were those of the attending physicians rather than those of the fellows. Last, none of our medical oncologist variables measure the quality of care that they delivered. Although black patients in our study were less likely than white patients to consult with board-certified physicians, this difference explained little of the black – white disparity in chemotherapy use.
Another limitation is the relatively small number of black patients in the SEER – Medicare database, although the proportion of black colon cancer patients reported to the SEER program in 1992 – 1996 (7.5%) was comparable to the proportion of black individuals aged 65 years and older in the United States population at the time of the study (7.8%) ( 71
) . This small number of black patients precluded more detailed investigation into the intriguing finding of equivalent unadjusted rates of adjuvant chemotherapy among black and white patients in Atlanta/rural Georgia. Further study with additional data is needed to examine potential regional variation in black – white disparity in chemotherapy receipt.
This study found that black and white patients begin their colon cancer therapy with an equal opportunity to learn about chemotherapy from a medical oncologist but do not receive this therapy at equal rates. We expected to identify specific health systems factors that explained the black-white disparity in chemotherapy receipt and that could be modified to improve care. Instead, we found that among the factors that could be analyzed in this study, patients’ age, surgical hospitalization length of stay, and neighborhood educational level were the most important. Although length of stay in the hospital after resection may be more difficult to affect, developing strategies to effectively educate and communicate the risks and benefits of chemotherapy may diminish some of the black – white treatment disparity. Further qualitative and quantitative research is needed to understand the mechanisms through which these and other factors, such as out-of-pocket costs, influence chemotherapy receipt. This research might begin with exploration of the interactions at colon cancer patients’ visits with their medical oncologists and other physicians and then trace the complex decision-making process that follows those visits.