Risk factors and 10-year breast cancer survival in Northern Alberta

Abstract

1,121 women in northern Alberta diagnosed as having breast cancer between 1971-74 were followed for 10 years. Risk factors for breast cancer were studied with respect to their possible influence on survival by comparing survival curves, using both Logrank and Cox's regression model, and controlling for intercurrent death, stage and axillary node status. A complex interaction was found between age and menopausal status and survival rates. Premenopausal women aged 45-55 had a better survival rate than postmenopausal women of the same age. However, one subgroup of premenopausal women aged 35-39 had a significantly worse prognosis than those aged 40-44 as did a group of post menopausal women aged 70-74. No cause was found other than the effect of age. There was a significant trend to worsening survival with heavier weight at time of diagnosis and with breast feeding. Parity of five or more and family history of breast cancer were less consistently associated with worse survival. Oral contraceptive use was only associated with worsened prognosis significantly when stage was controlled for; there was no overall effect. Age at menarche and age at first birth did not influence prognosis. Theories to explain the findings are discussed.

Parity, age at first childbirth and the prognosis of primary breast cancer

“…We have previously found that pregnancy within 2 years before a diagnosis of breast cancer was associated with reduced survival (Kroman et al, 1997). This, combined with the present observation of early first childbirth being a negative prognostic factor, could explain the finding reported by some researchers of an association between high parity and poor prognoses (Wang et al, 1985;Lees et al, 1989;Korzeniowski and Dyba, 1994). Women with high parity would be expected to have their first child early and have their last child late.…”

“…Although some studies have not supported this observation (Mohle Boetani et al, 1988;Lees et al, 1989;Ewertz et al, 1991), there is accumulating evidence that does support it (Greenberg et al, 1985;Kogevinas, 1990;Schouten et al, 1997 (MacMahon et al, 1970;Ewertz et al, 1990 (Ewertz et al, 1990).…”

“…Our study suggests that the postponement of motherhood might have a beneficial effect on overall breast cancer prognosis. Studies on overall parity as a prognostic factor have been contradictory (von Papatestas et al, 1980;Palmer et al, 1982;Black et al, 1983;Wang et al, 1985;Mohle-Boetani et al, 1988; Lees et al, 1989;Mason et al, 1990;Lehrer et al, 1992;Guinee et al, 1994;Korzeniowski and Dyba, 1994;Orr and Fraher, 1995;Schoultz et al, 1995). We have previously found that pregnancy within 2 years before a diagnosis of breast cancer was associated with reduced survival (Kroman et al, 1997).…”

“…Factors influencing the development of breast cancer might also affect its course, but studies of the prognostic influence of reproductive factors have been contradictory (Papatestas et al, 1980;Palmer et al, 1982;Black et al, 1983;Wang et al, 1985;Mohle Boetani et al, 1988;Lees et al, 1989;Mason et al, 1990;Lehrer et al, 1992;Guinee et al, 1994;Korzeniowski and Dyba, 1994;Off and Fraher, 1995;von Schoultz et al, 1995;Schouten et al, 1997). We took advantage of the population-based registration of breast cancer patients established by the Danish Breast Cancer Cooperative Group (DBCG) and a database containing complete information on parity to evaluate the possible importance of childbirth history and age at first birth as prognostic factors in primary breast cancer.…”

Oral Contraceptives and Survival in Breast Cancer Patients Aged 20 to 54 Years

“…Among younger women, current or recent OC use and use of higher dose and potency pills have been associated with modestly higher breast cancer incidence (3,4), but effects on survival are unclear (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). To date, no studies have examined pill characteristics and survival.…”