SAN FRANCISCO – Age, race, and body mass index (BMI) do not appear to be related to achieving pathologic complete response (pCR) in breast cancer patients, according to data presented at the ASCO Breast Cancer Symposium.
“We did see some suggestions that maybe age and race were associated, but in our modeling, once we accounted for tumor characteristics such as tumor size and lymph node involvement, that association was attenuated to nonsignificance,” said Dr. Erica T. Warner of the Harvard T.H. Chan School of Public Health, Boston.
She noted that some previous research has found a higher pCR among young women and a lower pCR among overweight and obese women.
Roxanne Nelson/Frontline Medical News
Dr. Erica T. Warner
“Overall we had pretty high pCR rates, much higher than observed in these other studies,” said Dr. Warner. “It is likely due to our definition of pCR, the tumor subtypes that were included in our study, and the studies we included had combination therapy in addition to neoadjuvant therapy.”
Pathologic complete response is an important prognostic indicator and surrogate endpoint, and this is particularly true for patients with hormone receptor–negative breast cancer. Prior research has suggested there may be a differential response to preoperative therapy by age and BMI, although no association has been observed by race.
“Our motivation for this trial was that we know that young age, black race, and obesity are associated with poorer survival, and we wanted to try to better understand the mechanisms behind that,” explained Dr. Warner.
In this study, Dr. Warner and her colleagues conducted an analysis of 1,146 women with breast cancer, who were enrolled in four clinical trials of neoadjuvant chemotherapy (CALGB 40601 and 40603; ACOSOG Z1031 and Z1041). They used logistic regression models to determine the association of race/ethnicity and age at diagnosis with pCR.
Within the cohort, 156 patients (13.6%) were black; 590 tumors (51.5%) were HER2+, 169 (14.7%) were ER+/HER2-, and 387 (33.8%) were triple negative.
In multivariate analyses that controlled for tumor characteristics and other factors, black race (OR, 1.07; 95% CI, 0.67-1.70), age (OR, 0.99; 95% CI, 0.97-1.00), and BMI (OR, 0.99; 95% CI, 0.96-1.01) were not significant predictors of pCR. The researchers found similar associations when they stratified the data by subtype, and found no interaction between age and black race (P = .06), black race and BMI (P = .54), or age and BMI (P = .73).
For the ER+ HER2- subtype, there was a suggestion of an inverse association; per 5-year increase the probability of pCR decreased 17%, but again it was not statistically significant.
There were higher rates of pCR among HER2+ and triple-negative tumors, but there was no difference in pCR according to race (white women, 43.5%; black women, 44.2%; and other/unknown, 46.1%), Dr. Warner pointed out.
There was a lower median age for achieving pCR, as the median age for women who did not achieve pCR was 53, compared with 49 for those who did (P <less than .0001). And for BMI, women who didn’t achieve pCR had an average BMI of 28.6, compared with 28 for those who did (P = .03).
“But there was no association of black race with pCR for any subtype, no association between BMI and pCR for any subtype, and no association for age,” she said.