Five-Year Relative Survival
The SEER data further state that five-year relative survival (eliminating other causes of death) for the nine cancer registries including San Francisco-Oakland followed to the year 2000 is as follows: all stages is 86.6 percent, 97.7 percent for localized, 78.7 percent for regional, 23.3 percent for distant, and 56 percent for unstaged. The low fiveyear relative survival rate for the unstaged cases may suggest that unstaged cases include many of those that are diagnosed late, are poorly compliant with treatment, or receive inferior care, of which lack of staging information may be a component. Further research on this group would be of interest.
Five-year relative survival as a meaningful surrogate or proxy for survival has been widely questioned by breast cancer advocates and others. This is in part because of the slow-growing nature of the disease in general, as well as the delays in recurrences that have become more common now than in the era before widespread adjuvant treatment. For women with regional and distant metastatic disease, however, because they are at higher risk for recurrence and have more aggressive disease, five-year survival is worth discussing.
The five-year relative survival figures vary significantly when broken down by race and age. According to the SEER data, in the United States as a whole, white female breast cancer patients have better five-year survival from breast cancer than black patients.
Five-year survival from breast cancer is lowest for black women under the age of fifty, and highest for white women over the age of fifty. The higher rate of mortality in black women is often ascribed to diagnosis at a later stage, but this table demonstrates that even when women are classified by stage and age alone, a broad disparity exists in survival between white women and black women.
Expressed in graphic terms on the bar chart in Figure 3, below, the disparities between younger black and white women become immediately apparent.
|Figure 3. Five-year Relative Survival by Stage and Race, Women less than 50 (US SEER data)|
The meaningfulness of the five-year relative survival statistic as a predictor of ultimate survival is directly related to the stage of the disease at diagnosis. As mentioned above, for early-stage disease, you would not expect disparities in treatment or inherent differences between groups to be fully evident at five years, because women in this group are less likely to recur. The early stage of their cancers may reflect inherently indolent disease that would never spread or spread only very slowly, regardless of early detection or treatment. Some women in this five-year relative survival group may be living with recurrence. Others, perhaps as many as 10–30 percent, will eventually have recurrences that have not yet manifested themselves.
So, it is important to note in the bar graph above that the point spread in five-year survival in early-stage localized disease is a minimal 3.1 percent between black and white breast cancer patients under 50. In regional disease, however, the disparity expands to 14.5 percent, and in distant disease it is an even greater 19.6 percent. This clearly reflects the more aggressive nature of the disease, and may be more likely to point to treatment related issues, like access to standard of care, compliance with treatment and follow-up. These differences persist for older women, as is evident in Figure 4 below, but are somewhat less pronounced, perhaps reflecting the less aggressive, more hormonally- dependent nature of breast cancer in older women, as well as access to treatment under Medicare, which has been suggested as a potential modifying factor of racial disparities in outcome.
|Figure 4. Five-year Relative Survival by Stage and Race, Women over 50 (US SEER data)|