NULLIPARITY NAD BREAST CANCER AGGRESSIVENESS

NEW YORK (Reuters Health) Oct 28 - Nulliparity and late-life first childbirth are associated with more aggressive breast cancer, according to Swedish researchers.

"We found that nulliparous women had a statistically significant high risk of grade III and HER2 over-expressing tumors," Dr. Salma Butt, of Malmo University Hospital, Sweden, and colleagues write in the October 15th issue of the International Journal of Cancer.

"Further, our study showed that women with late first childbirth had a higher risk of developing tumors with lobular type, grade III, high expression of cyclin D1, (and) low expression of p27," the researchers add.

For their analysis, the authors used data on 17,035 women in the Malmo Diet and Cancer Study (1991 to 1996), a prospective population-based cohort with linkage to the Swedish Cancer Registry until December 31, 2004.

A total of 622 breast cancer cases were evaluated for invasiveness, tumor size, axillary lymph node status, grade, tumor proliferation (Ki67), HER 2, cyclin D1, and p27. The authors also examined the tumors for tumor type according to WHO classification and hormone receptor status.

Nulliparity was linked to an increased risk of breast cancer compared to uniparity (RR 1.39), but the association fell short of statistical significance.

Nulliparous women were more likely to have large tumors (>20 mm) (RR 1.89), high Ki67 levels (RR 1.95), high cyclin D1 levels (RR 2.15), grade III tumors (RR 2.93), and HER2 positive tumors (RR 3.24).

Compared to women who had a first child before age 20, women who were older than 30 at first childbirth had a slightly higher risk of breast cancer (RR 1.39). Women with a first childbirth after 30 also had an increased risk of grade III tumors (RR 2.67), high levels of cyclin D1 (RR 2.69), low levels of p27 (RR 2.23), and lobular breast cancer (RR 2.51).

There was no association between parity and any specific breast cancer subgroup defined by estrogen or progesterone receptor status and histological type. Similarly, breast cancer risk in relation to axillary node status was not linked with parity.

"It is possible to hypothesize that the mechanism behind the observation in nulliparous women and women with a late age at first childbirth are similar as both these categories have breast tissue that is not fully evolved," the researchers explain. "Their breast tissue could, hence, be more susceptible to initiating and promoting factors."

Int J Cancer 2009;125:1926-1934.