Parity and prognosis in breast cancer.

Analysis of five-year disease-free survival rates in 608 women with operable breast cancer revealed that the reproductive history is a significant prognostic determinant. Overall parous women had a significantly higher cumulative five-year disease-free survival rate (60%), compared to the nulliparous (46%) (z = 2.5, p = 0.012). Significant differences were also noted when gravidity in addition to parity was taken as the determinant. The corresponding disease-free survival rates were 61% and 50%, respectively (z = 1.98, p = 0.048). Five-year survival rates were influenced in a similar manner by these variables but the observed differences were less significant. The trend toward higher survival rates in parous and gravidae women were noted in all tumor stages but achieved statistical significance only in stage III. The findings indicate that parity and gravidity affect not only the risk of breast cancer development but also the subsequent course of the disease. Parity seems to be a strong risk and prognostic factor than gravidity.