Rate of pCR and Race Unrelated After Neoadjuvant Chemotherapy for Breast Cancer
OCTOBER 10, 2009
Breast cancer survival outcomes vary significantly according to race in the United States, but a University of Texas MD Anderson Cancer Center found that race/ethnicity did not significantly affect the rate of pathologically complete response (pCR) in women with locally advanced breast cancer treated with neoadjuvant chemotherapy.
The retrospective study looked at data for 2074 women who received a diagnosis of stage II/III breast cancer in 1994-2008 and had treatment with an anthracycline- and taxane-based chemotherapy regimen prior to surgery. Approximately 64% of patients were white (n = 1334), 15% were black (n = 302), 15% were Hispanic (n = 316), and 6% (n = 122) belonged to other ethnic groups.
Mariana Chavez-Mac Gregor, MD, who led the study, said it was the first to look at whether pCR (defined as no residual invasive cancer in the breast and ipsilateral axilla) had any relationship to race. “If a specific ethnic group had a better or worse response rate, maybe we could then determine which groups may be in need of additional and/or improved therapies,” she said. Instead, the researchers found no significant difference in pCR rates between the different groups at the time of surgery. The rates of pCR were 12.5% in black women, 14.24% in Hispanics, 12.3% in whites, and 11.5% in the remaining group of patients (P = .788).
More variance was noted in estimated rates of 5-year recurrence-free survival (RFS) between the groups, which was 60% for blacks, 76% for Hispanics, 71% for whites, and 75% for others (P <.0001). When patients were stratified according to breast cancer subtype, however, differences in RFS remained only for patients with hormone receptor-positive disease. Estimates of 5-year overall survival (OS) were 57% for blacks, 79% for Hispanics, 79% for whites, and 84% for others (P <.0001).
While blacks had statistically significant lower estimates of RFS and OS compared with the other groups, Dr Chavez-Mac Gregor advised caution when attaching meaning to this finding. “Black patients tended to have tumor characteristics associated with worse outcome (more advanced stages, higher tumor grade).” She noted that, in the final multivariate analysis, investigators adjusted for “age, tumor subtype, stage, and nuclear grade.” They observed that, compared with whites, Hispanics had a statistically significant improvement in survival outcomes. “We observed a trend for worse outcomes in black patients compared to whites,” she said, but added that the difference did not reach statistical significance.
The researchers identified several independent predictors of poor RFS and OS, including failure to achieve pCR, HER2-positive and triple-negative disease, nuclear grade 3, and lymphovascular invasion. Race/ethnicity alone was not a predictor of survival outcome. Asked about the importance of these findings, Dr Chavez-Mac Gregor said, “Showing that irrespective of race, pCR is a very important surrogate for improved long-term outcome, should make us continue to look for better treatment strategies to improve the rates of pCR in all our patients.”
Her team is planning additional studies using the same cohort of patients Dr Chavez-Mac Gregor told Oncology & Biotech News. “We are planning to explore the outcome of the patients that did not achieve pCR. Maybe the outcomes according to race are different according to the amount of residual disease.” She said they are also planning to look at variations in molecular markers between additional ethnic subgroups, including Mexicans and Mexican-Americans compared with whites.
In April 2009, ASCO issued its “Disparities in Cancer Care” policy statement, emphasizing the need to find ways to address an expected 99% increase in the incidence of cancer among minorities by 2030. This is more than triple the expected increase in the incidence of cancer for non-Hispanic whites over the same period. Disparity was also a central topic of several presentations at the recent ECCO/ESMO Congress in Berlin, Germany, which Oncology & Biotech News attended.
Dr Chavez-Mac Gregor agrees that more needs to be done to reduce racial disparities in survival outcomes. “There are still many questions that remain unanswered regarding outcomes among Hispanic and black patients,” she said. “Further epidemiological and molecular characterization of the tumors is needed to explore the potential differences in biology and outcome.” Abstract No. 229.