SURVIVAL OF U.S. BLACK AND WHITE PATIENTS: DISCUSSION

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Because the black-white disparity in survival was largely confined to patients coded as having localized-stage cancer at diagnosis, as also reported for colon cancer, the potential for more understag-ing in blacks than whites should be considered. The small number of patients with localized-stage cancer who had pathologic review of regional lymph nodes indicates that most staging was based on the results of cancer-directed surgery and clinical examinations. Cancer-directed surgery was less frequent in blacks than whites, as also reported for certain other cancer sites, and this variable was included in the analyses. However, imprecise preoperative staging is a major difficulty in studies of esophageal cancer treatments and outcomes. If clinical staging were less aggressively pursued in black versus white patients, then more frequent understaging in blacks would affect black-white comparisons of RSRs by stage and also Cox proportional hazards regression models attempting to control for stage.

Understaging is difficult to evaluate directly due to the absence of information on clinical-diagnostic procedures in cancer registries. Indirect evidence for an overall effect of understaging on survival of all patients coded as localized stage is suggested by lower RSRs (Table 2) and lower relative risk of death (Table 3) for patients without versus with pathologic review of regional lymph nodes. Before considering the hypothesis of inherent biological differences (by race) in tumor aggressiveness of localized-stage cancers, future studies should evaluate potential racial differences in understaging. Information should be obtained on the specific clinical-diagnostic procedures involved in staging—including radiographic and endoscopic evaluations, such as computed tomography, endoscopic ultrasound, and positron emission tomography, as well as minimally invasive surgery (thoracoscopy and laparoscopy). Control for comorbidity (which influences both surgical decisions and survival) and socioeconomic status (SES) indicators also should be included, although the effect of SES on black-white survival differences may be mediated through stage. Although interpretation of RSRs in terms of progress in cancer control is problematic, five-year RSRs for squamous cell carcinoma are low in both blacks and whites (Table 2), despite recent increases in RSRs. Further improvement in survival rates through surgical advances appears uncertain, and more clinical trials of chemothera-peutic agents are needed. Expanded primary prevention efforts addressing tobacco and heavy alcohol use are also needed to enhance the slow decline in incidence rates for squamous cell carcinoma of the esophagus in the U.S. population.
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