There are few meaningful differences between CRC and non-CRC cohort characteristics. Both African American and white patients with CRC were slightly older than their non-CRC counterparts. The white CRC group had a higher percentage of men (). There were no notable differences in geographic setting or neighborhood characteristics. African American patients in the non-CRC cohort had greater health care costs prior to diagnosis than whites. Among CRC patients, prior costs for African American patients were considerably below those of their non-CRC counterparts, a differential not true of white patients. Standardizing prior costs for covariates increased prior expenditure differences by race (not shown). For African American patients, the higher prior costs among non-CRC cases is consistent with a slightly higher hospitalization rate but not with the greater percent without Medicare claims.
Characteristics of CRC and Non-CRC Cohorts by African American-White Race
Among CRC patients, African American patients were more likely than white patients to be diagnosed with colon rather than rectal cancer. Among rectal cancer patients, African American patients had lower rates of sphincter sparing surgery (36.4%) than white patients (52.2%). A lower proportion of African American (50.8%) compared with white (60.3%) patients received some adjuvant therapy. Among those receiving therapy, African American recipients had slightly longer mean treatment durations, a finding with marginal statistical significance.
Average Costs Unstandardized for Covariates
Unstandardized total per case expenditures for the first 16 months after CRC diagnosis, including both cancer and noncancer care, totaled $38,820 in year 2000 prices (). Rectal cancer cases cost 9.4% more than colon cancer cases ($41,439 vs. $37,884, P ≤ 0.001). Of these expenditures, 62.7% ($24,328) occurred in the 3-month surgical phase for colorectal cancer overall (64.7% for colon cancer, 57.4% for rectal cancer). As expected, postsurgical expenditures for rectal cancer, which include adjuvant radiation therapy, were approximately $4000 greater than for colon cancer (P ≤ 0.001).
Total Unadjusted Expenditures per CRC Case by Cancer Site, Phase, and Race
Total unstandardized costs for African American patients were $5821 more than white patients—$44,199 versus $38,378, a statistically significant 15.2% difference. African American–white differentials were similarly significant in both phases—African American patients cost 13.9% more in the surgical phase and 17.3% more in the postsurgical phase.
presents regression-standardized estimates of costs for CRC and non-CRC patients. Surgical, postsurgical, and total treatment costs are estimated separately. The consistency of the estimating model is illustrated by the fact that the sum of the estimated mean CRC costs for the 2 phases, $38,278, was only $299 less than the total cost estimate of $38,577. Detailed results and coefficients from the adjusted GLM models that allow estimation of net costs of CRC treatment are shown in .
Regression-Standardized Estimates of Medicare Treatment Expenditures per Colorectal Cancer Case
Net CRC costs were calculated by subtracting estimates of non-CRC costs from total expenditures for CRC patients. Average total CRC expenditures were reduced by estimated non-CRC care costs of $5126. The correction is low for the 3-month surgical phase ($850) but is 30.4% ($4270) of postsurgery phase costs. Postsurgical net cost estimates for CRC patients with and without adjuvant therapy were $11,856 and $6367 respectively, a statistically significant difference of $5489 (not shown).
Standardizing for differences in patient and environmental characteristics changes estimated racial differences in care costs. This adjustment reduces the total cost of African American CRC patients from $44,199 (, column 4) to $40,491 (, column 1). As a result, the mean African American-white difference drops to a statistically insignificant $1735—less than 1/3 of the unadjusted difference ($5821). Further adjusting to net costs (, column 3) reduces the differential to only $974, an insignificant difference. African American patients on average cost $1525 more than whites in the surgical phase, and $594 less in the postsurgical phase, but neither of these findings is statistically significant.
examines whether net CRC treatment costs are associated with other patient characteristics, such as health care spending in the year before diagnosis. Prior spending per case of more than $9165 (top decile) represents poor health unrelated to CRC, contrasted with beneficiaries with no claims (lowest decile). These groups demonstrate a $6520 difference in the estimated total cost of care for CRC patients (column 1). However, this differential is due to higher non-CRC costs of $7023 (column 2). Subtracting these higher expected non-CRC expenditures results in slightly lower net cancer costs (−$504) for those in the highest compared with those in the lowest decile of prior spending.
Regression-Standardized Estimates of Medicare Treatment Expenditures per Colorectal Cancer Case by Patient Characteristics
documents that some covariates are numerically of far greater import than race. The net costs for older patients (ie, 76–80 years old) are $3701 less than the youngest Medicare cohort (ie, 66–70 years old). Beneficiaries living in neighborhoods in the lowest income decile cost $4177 more than those in the highest decile. However, none of these cost differences are statistically significant, except for variations by SEER registry. These geographic variations produce the largest cost differences ($9201), even though CRC resection is known as a low variation procedure.35