Transient Increase In Risk Research Articles

Clinical Stage of Breast Cancer by Parity, Age at Birth, and Time Since Birth: A Progressive Effect of Pregnancy Hormones?

Breast cancer diagnosed during pregnancy or 1 to 2 years after birth often occurs at a late stage. Little is known about tumor characteristics in the high-risk period shortly after a childbirth. We here explore whether stage of disease differs according to timing of births. Results are based on 22,351 Norwegian breast cancer patients of parity 0 to 5, ages 20 to 74 years. The proportion of stage II to IV tumors was considerably higher among parous than nulliparous women at age <30 years (52.7% versus 36.8%, P=0.009), but similar or lower in other age groups (P(interaction)=0.029). In general, the largest proportion of stage II to IV tumors was found among women diagnosed during pregnancy or <2 years after birth. However, among women with late-age births (first or second birth >or=30 years, third birth >or=35 years), as well as women with an early second birth (<25 years), the proportion with advanced disease was rather similar or even higher among those diagnosed 2 to 6 years after birth (49.3-56.0%). The association between clinical stage and time since birth reached statistical significance among women with a late first or second birth and among all triparous women (P <or= 0.032). The subgroups with a high proportion of advanced disease 2 to 6 years after birth corresponded quite well to those previously found to have the most pronounced transient increase in risk after birth. Thus, pregnancy hormones may have a progressive effect on breast cancer tumors in addition to a possible promoting effect. A potential effect of prolactin is discussed.

Allaitement maternel et cancer du sein

The objective of this review is to summarize the current knowledge about the impact of pregnancy and lactation on the risk of breast cancer and possibility of breastfeeding after breast cancer treatment. A Pubmed search was carried out for publications in English or French from 1974 through 2004, related to breast cancer, pregnancy and breastfeeding. There is a transient increase in risk of breast cancer in the first three to four years after pregnancy, whereas during lifetime, the risk seems lower than in nulliparity. Lactation reduced the risk for breast cancer. This protective effect seems greater for women who had extended periods of breastfeeding during their lifetime, particularly in case of BRCA1 mutation. Various physiopathological mechanisms are involved in the protective effect of breastfeeding: anovulation, cellular differentiation of the mammary cells and excretion in the milk of breast carcinogens. After breast cancer treatment, there is no evidence that breastfeeding increases the risk of breast cancer recurrence, nor that it carries any health risk to the newborn. Women previously treated for breast cancer and free of recurrence are allowed to breastfeed their children. Beneficial effects of breastfeeding for the mother and the newborn should lead physicians and midwives to encourage prolonged breastfeeding in their medical practice.

Breast cancer risk by age at birth, time since birth and time intervals between births: exploring interaction effects

In a Norwegian, prospective study we investigated breast cancer risk in relation to age at, and time since, childbirth, and whether the timing of births modified the risk pattern after delivery. A total of 23 890 women of parity 5 or less were diagnosed with breast cancer during follow-up of 1.7 million women at ages 20–74 years. Results, based on Poisson regression analyses of person-years at risk, showed long-term protective effects of the first, as well as subsequent, pregnancies and that these were preceded by a short-term increase in risk. The magnitude and timing of this adverse effect differed somewhat by birth order, maternal age at delivery and birth spacing. No transient increase in risk was seen shortly after a first birth below age 25 years, but an early first birth did not prevent a transient increase in risk after subsequent births. In general, the magnitude of the adverse effect was strongest after pregnancies at age 30 years or older. A wide birth interval was also related to a more pronounced adverse effect. Increasing maternal age at the first and second childbirth was associated with an increase in risk in the long run, whereas no such long-term effect was seen with age at higher order births.

Transient increase in breast cancer risk after giving birth: postpartum period with the highest risk (Sweden).

Identify time-points when the elevated postpartum maternal breast cancer risk peaks. A case-control study nested within the Swedish Fertility Register included 34,018 breast cancer cases from the Swedish Cancer Register between 1961 and 1995. From the Fertility Register, 170,001 eligible subjects matched to the cases by age were selected as controls. Analysis contrasted risk between uniparous (7084 cases and 31,703 controls) and nulliparous (5411 cases and 22,580 controls) women and between biparous (13,239 cases and 65,858 controls) and uniparous women. Logistic regression analysis included indicator variables representing each year of age, ages at delivery, and time since delivery. Comparing uniparous with nulliparous women the transient increase in maternal breast cancer risk peaked 5 years following delivery (odds ratio= 1.49, 95% confidence interval 1.01-2.20) and leveled off 15 years postpartum. Biparous women had a transient increase in risk that was lower at its peak than that of uniparous women, occurring about 3 years following second delivery. A time window of 5 years postpartum when maternal breast cancer risk is highest was observed. Establishing timing of peak transient increase in postpartum breast cancer risk may define the latent period required for pregnancy hormones in promoting progression of breast cells that have undergone early stages of malignant transformation.

Breast cancer risk after childbirth in young women with family history (Denmark).

The increased risk of breast cancer in women with family history of breast cancer (FHBC) might be reduced by early childbirths. However, childbirth induces a transient increase in risk in the first 5-10 years, which coincides with the relatively increased risk of family cases at a young age. The objective was to investigate this short-term change in risk according to FHBC. We used a population-based cohort of 1.5 million Danish women. Between 1968 and 1990, 2770 incident cases of breast cancer below 40 years of age were identified in the Danish Cancer Register, of whom 276 (10%) had a FHBC. The first 5 years after a birth the short-term increase in risk was 30% (3-64%) larger in women with FHBC than without FHBC. After the first 5 years we observed no difference in the effect of a birth between women with and without FHBC. The adverse short-term effect of childbirthis stronger in women with FHBC.

Reproductive factors and risk of papillary thyroid cancer in women.

The authors conducted a population-based case-control study of 410 women residing in three counties in western Washington State who were aged 18-64 years when diagnosed with papillary thyroid cancer in 1988-1994 and 574 controls to assess the effects of pregnancy history and other aspects of reproductive life on risk of this disease. Among women aged 45-64, the authors observed no associations with number of live births, age at first live birth, or age at last live birth. Risk was somewhat increased in women <45 years who had given birth within the previous 5 years; this association was most evident among women who reported that cancer symptoms had led to diagnosis. Among women who had given birth within the last 5 years, risk was greatest among those with two or more births during that time period (relative risk (RR) = 4.2, 95% confidence interval (CI): 2.0, 8.9, relative to parous women whose last birth was >5 years before the reference date). Risk of thyroid cancer was also associated with lactation during the previous 5 years (e.g., RR = 2.9, 95% CI: 1.5, 5.5, among parous women who had breastfed > or =12 months, vs. 0-1 months, during that interval). Our results suggest that thyroid stimulation during both pregnancy and lactation may result in a transient increase in risk of papillary thyroid cancer.

Epidemiology, prevention, and early detection of breast cancer.

Breast cancer is a leading women's health issue. Continued advances in understanding the temporal sequencing of relevant exposures promises to shed light on the continuum of breast carcinogenesis. Oral contraceptive use and the transient increase in risk following childbirth are exposures that affect the near-term risk of breast cancer. The availability of commercial testing for inherited susceptibility to breast cancer has accelerated the need for data to develop sound policy for implementing gene testing. The risks associated with BRCA1 and BRCA2 mutations may be less than previously estimated. Antiestrogens with lesser risks than tamoxifen hold promise for chemoprevention, but await testing. Not enough is known to formulate primary prevention strategies based on lifestyle interventions. Further understanding lifestyle factors that may be involved in the etiology of breast cancer and are amenable to preventive intervention thus remains a top priority, with diet and physical activity of greatest interest.

EXERCISE AND ITS ROLE IN SUDDEN CARDIAC DEATH

This article summarizes available population-based data related to the risk of sudden cardiac death during exercise and the factors that influence the risk among apparently healthy adults in the community. Recent evidence puts into perspective the cardiac risks and benefits of exercise. The data suggest that although the occurrence of sudden cardiac death during acute bouts of exercise is not a chance occurrence, the transient increase in risk is outweighed by the cardiac benefits of habitual exercise. The implications of these findings for both clinical practice and public health are reviewed.

Breast cancer in Swedish women before age 50: evidence of a dual effect of completed pregnancy

We set out to detect a transient increase in risk of breast cancer following childbirth, the existence of which has been postulated, but for which empirical evidence is contradictory. Breast cancers and births occurring among the cohort of Swedish women born after 1939 were linked, yielding 3,439 cases and 25,140 age-matched controls with at least two children. Within three years of their last childbirth, women had an estimated rate of breast cancer of 1.21 (95 percent confidence interval [CI] = 1.02-1.44) times that of women whose last birth was 10 or more years earlier, after adjustment for parity and age at first birth. Further analyses suggested that this effect reflected, in part, a small transient increase in breast cancer risk that lasts for about three years following completed pregnancy. The effect of age at first birth on breast cancer risk appears to be confounded by time since last birth; the parity-adjusted rate ratio for having a first birth at age 35 years or more compared with under 20 years is reduced from 1.72 (CI = 1.14-2.58) to 1.36 (CI = 0.88-2.09) on additional adjustment for time since last birth. A transient increase in breast cancer risk after childbirth appears thus appears to account for part of the effect of age at first birth on breast cancer risk.

Pregnancy-related factors and risk of breast cancer in a prospective study of 29 981 Norwegian women

It has been suggested that pregnancy is associated with a short-term increased risk of breast cancer followed by a life-long protection. We studied 340 incident cases of breast cancer in relation to parity, age at first full term birth, and time since last child birth during 14 years follow-up in a prospective cohort of 29981 Norwegian women. We found no evidence for a transient increase in risk of breast cancer subsequent to pregnancy followed by a reduction in risk of long lasting duration. However, our results indicate that up to an approximate age of 45 years, the nulliparous have a lower breast cancer risk than everparous women. Among parous women, there was an increasingly protective effect on breast cancer risk at a young age (<50 years) with increasing number of child births, independent of age at first birth, whereas the protection associated with an early age at first full term pregnancy may increase in importance with increasing age. This finding may reconcile conflicting reports related to these two factors. This study confirms the results of previous investigations suggesting that a “cross-over” in breast cancer incidence between nulliparous and ever-parous women appears to take place some time during the fifth decade of life.