BACKGROUND.
Although axillary lymph node metastasis is one of the most important prognostic determinants of breast carcinoma prognoses, the reasons why tumors vary in their capability to produce for axillary metastases remain unclear.
METHODS.
The authors used data from the nationwide Patient Care Evaluation (PCE) survey of the American College of Surgeons to evaluate the correlations between patient/tumor characteristics and lymph node status, and to explore the use of these factors, which are all known prior to axillary dissection, in predicting lymph node status. The PCE data set contained 18,025 breast carcinoma cases diagnosed in 1990 after exclusion of women older than 79 years or with fewer than 6 lymph nodes examined.
RESULTS.
In a multivariate logistic regression model, larger tumor size, young age, African American or Hispanic race, outer half tumor location, poor or moderate differentiation, aneuploidy, and infiltrating ductal histology were independently associated with a higher likelihood of one or more positive lymph nodes. Contrary to expectation, cases negative for estrogen receptor (ER) and progesterone receptor (PR) had a lower risk of positive lymph nodes when adjusted for other factors (odds ratio ฯญ 0.82; 95% confidence interval: 0.74 -0.91) compared with cases positive for both receptors. This model accurately predicted lymph node status in 2 validation data sets (a 50% random sample of 1990 PCE data and 1992 data from the National Cancer Data Base), but was less accurate in a third, older data set (1983 PCE data).
However, the percentage of cases (1990 validation set) with predicted probabilities less than 0.05 or greater than 0.95 were only 4.6% and ฯฝ0.1%, respectively.
CONCLUSIONS.
The authors concluded that 1) most variation in axillary lymph node metastatic status can be explained by routinely available data, 2) ER and PR status may be involved in the mechanism of this behavior, and 3) the difficulty of using prediction models to avert axillary dissection should not be underestimated.