The identification and treatment of isolated tumor cells reflect disparities in the delivery of breast cancer care

Abstract 

Background

Disparities in the quality of health care delivered among different socioeconomic strata (SES), race/ethnic groups, and health care systems are well documented; however, relevant quality measures in breast cancer have been debated. The identification of isolated tumor cells (ITCs) in axillary lymph nodes of patients with breast cancer requires diagnosis of early stage disease, appropriate implementation of sentinel lymph node (SLN) dissection, and pathologic analysis of the SLN with serial sectioning and immunohistochemical staining. We hypothesized that ITCs could be interpreted as a quality indicator and sought to determine factors that are associated with the identification and treatment of ITCs.

Methods

We performed a retrospective cohort review of women with N0(i+) breast cancer diagnosed between 2004 and 2006 in the California Cancer Registry. The proportions of patients in SES quintiles (1 = lowest, 5 = highest), race/ethnicity groups, and hospital surgical volume tertiles (low, 1–241 cases/y; medium, 242–491 cases/y; high, ≥492 cases/y) were compared for use of SLN dissection, identification of ITCs, and treatment of ITCs with additional axillary surgery or chemotherapy.

Results

SLN dissections were performed less frequently in women of lower SES, of nonwhite race/ethnicity, and in hospitals with lower surgical volumes (P <.0001). A total of 369 patients had ITCs (.6%). With increasing SES, the proportion of patients with ITCs increased: 7.1% of patients with ITCs were from SES 1; 15.7% were from SES 2; 20.3% were from SES 3; 23.9% were from SES 4; and 33.1% were from SES 5. A total of 69.4% of patients with ITCs were non-Hispanic white, 12.8% were Asian, 11.9% were Hispanic, and 5.2% were non-Hispanic black. A total of 46.9% of ITCs were identified in high-volume hospitals, although high-volume hospitals represented only one third of all surgical cases. There were no differences in the use of additional axillary surgery among different groups with ITCs, but chemotherapy was given more frequently to Hispanic women (P = .002) and those in higher-volume hospitals (P = .01).

Conclusions

Although the identification and chemotherapy treatment of ITCs vary among SES categories, race/ethnic groups, and hospitals, the infrequent occurrence of ITCs precludes its use as a valid quality indicator. Because significant disparities exist in the use of SLN dissection, further research will be required to validate the use of SLN dissection as a quality measure.

Keywords: Breast cancer, Isolated tumor cells, Sentinel lymph node dissection, Disparities