Family history and oral contraceptives: unique relationships in breast cancer patients

[Oral contraceptives and breast cancer: analysis of the statistical power of the association]

The power of the association between oral contraceptives and breast cancer was analysed in all the papers published up to date. Seventy-seven publications (from 44 studies) were collected and graded as to quality using meta-analytical methods. Power achieved a figure of greater than or equal to 0.8 in a 10.8% of the associations studied. It showed a significant relationship with the existence of a significant relative risk of the oral contraceptives for breast cancer. The relationship with the sample size of a study was not linear. Power did not show any significant relationship to other variables related to the design of a study (apart from matching, being the power higher in unmatched studies), or to the biases detected, although studies considered as unbiased yielded a higher power. Logistic regression analysis included as predictors of a power greater than or equal to 0.80 the existence of a significant relative risk and the lack of biases in a research.

The role of exogenous hormones in the epidemiology of breast, ovarian and endometrial cancer

This review focuses on the effects of oral contraceptives (OC) and estrogen replacement therapy (ERT) on the risk of breast, ovarian and endometrial cancer. The relationship between OC and cancer risk is first placed in a historical perspective. Since 1960, when OC were introduced, the hormonal composition of OC as well as the characteristics of the OC user have changed considerably. Studies conducted in the 1970s were generally reassuring, but it was not until the 1980s that studies could evaluate the effect of prolonged OC use after an extended follow-up period. Although the relationship between breast cancer and OC has been investigated in about 40 studies, the issue still remains essentially unresolved. Most studies report no association between ever use of OC and breast cancer risk. Several studies find increased risk for prolonged use and other studies report elevated risks for women who used OC very early in their reproductive years. The inconsistent results of recent studies are attributed to bias or to geographical variation in latency period elapsed, types of OC preparations, or prevalence of other risk factors. In contrast, the use of combined OC has consistently been shown to reduce the risk of ovarian and endometrial cancer. The risk further decreases with increasing duration of use and the protective effect seems to persist in ex-users for at least 5 years. Some evidence indicates that higher parity reduces the protective effect. Though studies relating ERT to breast cancer are far from consistent, overall, there is evidence for a moderately increased risk with high dose and/or long duration. The effect seems to be modified by mode of administration (injections vs. pills) and by type of ERT, but this needs confirmation. The number of adequate studies on the relationship between ERT and ovarian cancer is too small to draw firm conclusions. The positive relationship between ERT and endometrial cancer is now well established. The ERT effect is dose- and duration-dependent and is characterized by a short latency period. The cyclic addition of progesterone (greater than 10 days/cycle) may reduce the risk increase.

Oral contraceptives and breast cancer: results from an expanded case-control study

The relationship between oral contraceptives and breast cancer was evaluated among 2,022 cases and 2,183 controls participating in a multicentre breast cancer screening programme. Ever use of oral contraceptives was not related to breast cancer risk (RR = 1.0, 95% CI 0.9-1.2), and no overall patterns of increasing or decreasing risks were observed according to the duration of use, or time since first or most recent use. Although we had no women with extended periods of oral contraceptive use early in life, no evidence of adverse effects attributable to short-term use before age 25, before first live birth or during the perimenopausal period were observed. Further, oral contraceptives did not interact with other breast cancer risk factors, except among those with a history of two or more breast biopsies (RR = 2.0). Analyses by stage of disease revealed that risk was related to the duration of oral contraceptive use: greater than or equal to 5 years use was associated with reduced risk for in situ cancer (RR = 0.59) and increased risks for invasive cancers (RR = 1.5 and 1.4 respectively for small and large lesions). These data suggest that oral contraceptive effects may vary by stage of disease, but provide no overall evidence of an association between oral contraceptives and breast cancer.

Prospective study of exogenous hormone use and breast cancer in Seventh-day Adventists

Exogenous hormone use as either oral contraceptives (OC) or hormone replacement therapy (HRT) was evaluated in reference to subsequent breast cancer risk in a cohort study of 20,341 Seventh-day Adventist women, residing in California, who completed a detailed lifestyle questionnaire in 1976 and who were followed for 6 years. During the follow-up period, 215 histologically confirmed primary breast cancers were detected in the cohort. The mean age at diagnosis was 66 years, indicating a primarily postmenopausal case series. In this cohort, after taking into account potentially confounding variables, current use of HRT (in 1976) was associated with a 69% increase in breast cancer risk, which was statistically significant (RR = 1.69; CI = 1.12-2.55). However, there was no strong increase in risk with increasing duration of use of HRT. Subgroups of women who did experience HRT associated increases in breast cancer risk included those women who had ever used HRT (RR = 1.39; CI = 1.00-1.94) and those with no history of maternal breast cancer (RR = 1.45), those women with prior benign breast disease (RR = 2.80), and those women who experienced menopause at 44 years of age or later (RR = 1.56). There was no substantial increase in breast cancer risk associated with use of OC in this population, although among women with exposure to both OC and HRT there was a suggested increase in risk (RR = 1.42; CI = 0.71-2.85).

A nationwide study of breast disease

Records of histopathology from the 3734 Jewish women having breast biopsy and/or operations in all Israeli hospitals during the year from July 1979 to June 1980 were reviewed. Approximately 28.5% of these women were diagnosed as having breast cancer and 71.5% as having benign breast disease: 48.5% had benign proliferative mastopathy (BPM), 16.6% had fibroadenoma (FA) without coexistent BPM, and 6.4% had other benign breast conditions. The age-specific incidence rate was 66 in 100,000 for breast cancer and 165.2 in 100,000 for benign breast disease. Native European or American women and native Israeli women had significantly higher age standardized incidence rates of both breast cancer and BPM, but not of FA, as compared to African/Asian-born women (P less than 0.01). Age-related ratios between invasive to precursor breast lesions were similar in all ethnic groups. The data suggest that breast cancer and benign proliferative mastopathy may have a common etiologic component.

Canine mammary tumours: protective effect of late ovariectomy and stimulating effect of progestins

Ovariectomy, even when performed at an advanced age, was found to be to some extent protective against mammary tumour development in dogs. Bitches treated with progestins had a slightly higher risk for mammary tumours (all types, benign and malignant) than controls. Progestin treatment did not increase the risk of mammary cancer. Benign tumours in (treated and untreated) dogs appeared earlier than malignant ones. Progestin treatment resulted in earlier appearance of both benign and malignant tumours than in controls. The ratio solitary/multiple mammary tumours was not significantly different between treated and untreated dogs.

Risk factors as an indicator for breast cancer screening in asymptomatic patients

A review of breast carcinoma risk factors has established that age and sex are dominant variables. Additional epidemiological factors include family history, past medical history, menstrual status, age at birth of first child, demographic factors and reproductive history, which are of established importance as major or minor risk determinants for breast cancer. Taking into account the various epidemiological correlations and the multifactorial aetiology of this type of carcinoma, there is only a small probability that the identification of known risk factors will enable conclusive identification or prevention of the disease. Nevertheless the recognition of known risk factors may enhance screening efforts through surveillance, more selective biopsies and interval xeromammography. Total ductoglandular mastectomy may possibly be considered a beneficial approach to the management of the high-risk patient in whom preinvasive disease is detected. The identification of the high-risk patient is of paramount importance for prophylaxis. Prospective clinical trials using diagnostic approaches may include the study of genetic markers, hormones and steroid metabolites, mammographic parenchymal patterns and the analysis of genetic pedigree or other undetermined risk markers. While screening and detection programmes for breast carcinoma are not cost-effective, these intensive surveillance procedures do allow the early identification of high-risk individuals with the disease. The formulation of screening programmes which incorporate major and minor risk determinants may enhance the effectiveness of efforts to achieve diagnosis at a prognostically favourable stage of disease. Established diagnoses of stage 0 or stage I disease will translate as direct benefits to survival and reductions in economic morbidity.

Oral contraceptives and breast cancer. In vitro effect of contraceptive steroids on human mammary cell growth

The proliferative response of human mammary epithelial cells cultured in medium containing oral contraceptive steroids, singly and in combination, was measured. Cells came from 59 normal, nonmalignant atypical, and malignant breast tissue specimens. Growth of most cultures was stimulated by the estrogens 17 beta-estradiol and ethinyl estradiol, and any combination containing ethinyl estradiol. Most (75%) malignant specimens were stimulated by one or more of the progestins, whereas none of the nonmalignant cells were. For two of the estrogen/progestin combinations found in many birth control pills, malignant cells were stimulated to grow faster than nonmalignant cells. It was concluded that oral contraceptive steroids can stimulate the growth of mammary epithelia in cell culture and might do the same in vivo. These data corroborate epidemiologic data which suggest oral contraceptives might act as tumor promoters, especially in the older user, who is more likely to have malignant cells already present in the breast.

Oral-contraceptive use and the risk of breast cancer

To investigate the effect of individual formulations of oral contraceptives on the risk of breast cancer in women, we analyzed case-control data from the Cancer and Steroid Hormone Study of the Centers for Disease Control. The cases were 4711 women 20 to 54 years old with newly diagnosed breast cancer who were selected from eight population-based cancer registries. The controls were 4676 women selected by random-digit dialing of the population of each area covered by a registry. As compared with women who had never used oral contraceptives, women who had used them had a relative risk of breast cancer of 1.0. Among women who used only one oral-contraceptive formulation, this estimate of relative risk did not change appreciably according to the formulation used. Neither the type of estrogen nor the type of progestin contained in oral contraceptives used was associated with an increased risk of breast cancer. The duration of oral-contraceptive use and the time since last use did not influence the risk. These findings provide further support for the contention that oral-contraceptive use does not increase the risk of breast cancer in women.

Oral contraceptive use has no adverse effect on the prognosis of breast cancer

This study evaluates the possible effect of OC use on the prognosis of established breast cancer. Three hundred forty-seven patients with primary invasive breast carcinoma age 50 and under treated from 1971 to 1981 are included in this study. There were 112 OC Users (U) and 235 Non-Users (NU). Separate retrospective analysis were done for a group of 154 patients (59 U and 95 NU) under age 35 (Group A) and for 193 patients (53 U and 140 NU) age 35 to 50 (Group B), in order to pay particular attention to relationship of duration, recency and latency of OC usage. Both subsets of U and NU presented similar clinical characteristics regarding menstrual, reproductive, family history, histology, receptor status. Users presented with a similar extent of disease as Non-Users. No significant differences were found between U and NU in disease-free interval (Gr A p = .41; Gr B p = .81), metastatic period (Gr A p = .66; Gr B p = .41) or survival (Gr A p = .54; Gr B p = .79), either alone or when adjusted for extent of node involvement. Users of less than two years (78 patients) had a similar survival (Gr A = .54; Gr B p = .36) as those of longer duration (33 patients). Recent OC users within a year of diagnosis had a similar survival as other users who stopped the pills more than one year (Gr A p = .86; Gr B p = .14). No significant differences were noticed in survival between the patients who began the use 10 years or more before diagnosis from those beginning more recently (Gr A p = .82; Gr B p = .69). Our data suggests no adverse effect of OC on the outcome of breast cancer, regardless the duration of use, latency or recency period.

Oral contraceptives and prognosis of breast cancer in women aged 35 to 50

Among 193 breast cancer patients aged 35-50 years, there was no appreciable difference in the extent of disease at diagnosis between 53 oral contraceptive (OC) users and 140 OC non-users. There was no overall significant difference between OC users and non-users for either the disease-free interval (P = .81), metastatic period (P = .41), or survival (P = .79), either alone or when adjusted for stage or family history. The survival rate of OC users of more than 2 years was similar to the survival rate of those of shorter duration (P = .36). Patients who began the use of OC 10 years or more before diagnosis showed no statistical difference from those beginning more recently (P = .69). Recent OC users within a year of diagnosis had a survival rate similar to that of other users who stopped the pills at least 1 year prior to diagnosis (P = .14). Our data suggest no adverse effects of OC use on the prognosis of breast cancer, regardless of duration of use, latency or recency period.

Influence of oral contraceptives on the prognosis of breast cancer in young women

The possible effect of oral contraceptive (OC) use on the prognosis of established breast cancer was investigated in 154 young women aged 35 and younger. No significant differences were found between the study group of 59 OC users, and the control group of 95 nonusers in age, parity and gravidity, family history of breast cancer, benign breast disease, morphology, or surgical therapy. No appreciable differences were found between OC users and nonusers in extent of disease at presentation (P = 0.78), histologic features of tumor (P = 0.83), or axillary node involvement (P = 0.88). No significant or even suggestive differences were found between users and nonusers in disease-free interval (P = 0.41), metastatic period (P = 0.66), or survival (P = 0.54), respectively, either alone or when adjusted for extent of node involvement, duration of OC use, or other risk factors. In this study no evidence was found that the use of OC has any harmful or beneficial effect on evolution and survival of breast cancer.

Family history, oral contraceptive usage, and breast cancer

When breast cancer patients were grouped according to their family history of breast cancer striking differences were found in age distribution. Thus, the proportion of cases less than 45 years of age was grandmother greater than aunt greater than mother greater than FH-negative greater than sister. A similar FH-related sequence was observed in regard to current OC usage among breast cancer patients less than 45 years of age. It also appeared that current oral contraceptive (OC) usage increased the risk of invasive breast cancer among grandmother- or aunt-positive women while decreasing the risk among FH-negative women. There are important practical and conceptual reasons for further studies of the influence of interactions between age, OC usage and family history on the stepwise development of breast cancer.

The relationship between family history, exposure to exogenous hormones, and estrogen receptor protein in breast cancer

Eight-hundred and thirteen patients were prospectively studied to examine the influence of family history and the prior use of exogenous hormones as covariables in the subsequent expression of estrogen receptor protein (ERP) in the primary tumor of patients with breast cancer. Cases were divided by menstrual status; there were 385 pre- and perimenopausal and 428 postmenopausal patients. The influence of prior exposure to estrogen replacement therapy (ERT) in postmenopausal patients or oral contraceptives (OC) in pre- and perimenopausal patients on tumor ERP was analyzed controlling for family history: none, first degree (1 degree, mother or sister), second degree (2 degrees, grandmother or aunt), or both 1 degree and 2 degrees relatives. The results showed no influence of the prior use of ERT in postmenopausal women on subsequent tumor ERP. Among pre- and perimenopausal women, those with a family history of breast cancer in only a 1 degree relative, showed a borderline significant association between prior OC usage and subsequent tumor ERP. The use of OC was consistently associated with ERP negative tumors (9/9) whereas of 29 patients who had no prior OC exposure 17 had ERP negative tumors (P = 0.04, Fisher's Exact Test). Analysis of the prior exposure to OC, verified with the primary care physician or pharmacist, showed that these patients first used OC at the mean age of 32.2 years, had used OC for a mean duration of 41.9 months and stopped OC use a mean of 79.5 months before being diagnosed as having breast cancer. These results suggest that in a subset of patients with breast cancer, and a first degree relative only who had breast cancer, prior exposure to OC may influence the subsequent ERP status of the tumor. This is not due to exogenous estrogen saturation of receptors as there was a long latent period between exposure and diagnosis. Alternative hypotheses as to the mechanism of selection of subsequent tumor ERP may be either inhibition of ERP positive preneoplastic or tumor cell clones early in the evolution of the tumor or early selection of a tumor capable of endogenous estrogen synthesis with receptor saturation.