Parity is associated with axillary nodal involvement in operable breast cancer

Although multiparous women have a decreased incidence of breast cancer, several series have observed that multiparous women have a higher risk of axillary nodal metastases and diminished survival.

To study this hypothesis in greater detail, this study analyzed data from 223 consecutive women with clinically operable (T1-3, N0-1, M0) breast cancer, all of whom had undergone axillary node dissection (AND) by one surgeon (83 mastectomy/AND, 140 lumpectomy/AND). The number of pregnancies and other hormonally related factors were recorded. Results were compared to pathologic data (node status, tumor size, estrogen and progesterone receptors).

Seventy-eight patients (35.0%) had positive axillary nodes. Increasing parity was associated with an increased likelihood of positive nodes (Odds ratio 1.22 (95% CI: 1.04-1.42), p = 0.012) as was increasing tumor size (Odds ratio 1.31 (1.07-1.59), p = 0.007). The effect of parity was independent of tumor size, age, or hormone receptors.

In this series, which includes only operatively staged patients, increasing parity is associated with nodal positivity. This effect is of a magnitude similar to that of increasing tumor size, and confirms observations from other studies. Information regarding parity may be useful for prognostic purposes, as well as providing insights into basic breast cancer biology.