Nomograms for determining the probability of axillary node involvement in women with breast cancer.

We have previously reported that a history of pregnancy is independently associated with axillary node involvement in breast cancer patients. We have now studied additional women with breast cancer and have used our data and the logistic model to produce nomograms for determining the risk of axillary node involvement, based on tumor size, age, and number of pregnancies. There was an increase in the incidence of axillary node involvement in women with a history of pregnancy. To exclude the confounding effect that tumor size or age might have on node involvement, logistic regression was performed. Pregnancy, tumor size, and age were the three independent variables. History of pregnancy had a significant effect on node involvement (P = 0.036) that was independent of tumor size and age. Nomograms were constructed from these data. Surgeons do not perform an axillary dissection in every breast cancer patient. If the axilla is clinically negative and the tumor small, the surgeon, medical oncologist, and radiation oncologist may decide that a dissection need not be done. The nomograms in this article may allow for a more methodical choice of patients for axillary dissection. Moreover, a radiation oncologist might use the nomograms to help decide whether to irradiate an undissected axilla.