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It is well established that prenatal biologic processes are important for the development of some childhood cancers, whereas less is known regarding their influence on adult cancer risk. High birth weight has been associated with risk of breast cancer, whereas studies of other specific cancers and all cancers together have been less conclusive.The authors established a cohort of more than 200,000 men and women who were born between 1936 and 1975. Birth weights were obtained from school health records and information concerning cancer from the Danish Cancer Registry. Follow‐up was performed between April 1, 1968 and December 31, 2003. During 6,975,553 person‐years of follow‐up, a total of 12,540 primary invasive cancers were diagnosed.Analyses of site‐specific cancers revealed that the majority of cancers had a positive linear association with birth weight. Departures from a positive linear association were found to be statistically significant for cancers of the pancreas and bladder, which demonstrated a V‐shaped association, and testicular cancer, which demonstrated an inverse association with birth weight. Excluding these 3 exceptions, the trends for the individual cancer sites were not heterogeneous, and the overall trend was a relative risk of 1.07 (95% confidence interval, 1.03–1.11) per 1000‐g increase in birth weight. This trend was the same in men and women and in all age groups.A 7% increase in cancer risk was observed per 1000‐g increase in birth weight. Few cancers demonstrated a nonlinear association with birth weight, and testicular cancer was found to be negatively associated with birth weight. The authors hypothesized that the biologic explanation behind the association between birth weight and cancer at different sites should be sought in a common pathway. Cancer 2007. © 2007 American Cancer Society. [ABSTRACT FROM AUTHOR]

A differential effect of reproductive factors on the incidence of carcinoma in situ of the breast (CIS) and invasive cancer may indicate that hormonal factors related to reproductive history not only influence the initial steps towards breast cancer but also preinvasive malignant lesions. A comparison of reproductive factors was performed using a population-based cohort of 1.5 million Danish women born between 1935 and 1978. Between 1983 and 1998, 15,590 cases of invasive breast cancer and 871 cases of CIS were identified using a database with extensive clinical information. Number of births and age at first birth were similarly associated with the risk of being diagnosed with ductal carcinoma in situ (DCIS) compared to invasive breast cancer [RR(DCIS)per birth/RR(invasive)per birth = 1.03(0.93–1.14), RR(DCIS)per 5yr /RR(invasive)per 5yr = 1.06(0.96–1.17)]. Also, the short-term risk the first 10 years after birth was similar for DCIS and invasive cancer [RR(DCIS) /RR(invasive) = 0.90 (0.74–1.09)]. Additional analyses were performed according to characteristics of the DCIS lesion (size, malignancy grade, noncomedo or comedo type). In conclusion, our observations do not support the theory that reproductive history is associated with progression from noninvasive to invasive breast cancer. © 2003 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The possible association between prenatal factors and breast cancer has been discussed for more than a decade. Birth weight has been used commonly as a proxy measure for intrauterine growth. Whereas some previous studies have found support for an association between birth weight and breast cancer, others have been inconclusive or found no association. We investigated the relationship between birth weight and risk of female breast cancer in a cohort of 106,504 Danish women. Birth weights were obtained from school health records on girls born between 1930–1975. Information on breast cancer came from linking the cohort with the Danish Cancer Registry and the Danish Breast Cancer Cooperative Groups Registry. A total of 2,334 cases of primary breast cancer were diagnosed in the cohort during 3,255,549 person-years of follow-up among women with birth weight between 500–6,000 g. Of these, 922 (40%) were diagnosed with primary breast cancer at the age of 50 years or older. A significant association between birth weight and breast cancer was found equivalent to an increase in risk of 9% per 1,000 g increase in birth weight (95% CI 2–17). The increase was observed for all age groups, representing both pre- and post-menopausal women, and irrespective of tumor characteristics. Adjustment for age at first birth and parity did not influence the results. Birth weight is positively associated with risk of breast cancer, indicating that prenatal factors are important in the etiology of breast cancer. © 2003 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Our objective was to investigate the influence of primary tumor location on breast cancer prognosis. We used a population-based registry since 1977 that has collected detailed information regarding clinical and histopathological presentation, postoperative therapy and follow-up status on Danish women with breast cancer. Nodal status and relative risk of dying was estimated according to primary tumor localization in the breast. Overall, 35,319 patients with primary breast cancer were included in the study. After adjustment for prognostic factors, the risk of dying increased significantly (up to 21%) with increasing distance of tumor location from the axilla. This trend was seen both among women with and without spread to the axillary lymph nodes. In conclusion, survival is significantly better for women with a tumor in the upper lateral quadrant than tumors located elsewhere in the breast. Our finding of a similar trend according to distance from the axilla among women with positive axillary lymph nodes who all are allocated to systemic therapy suggests that a better lymph node staging procedure alone is unlikely to eliminate these survival differences. Other reasons for the observed differences should be sought to help improve survival for women with breast cancer. © 2003 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]