The risk of epithelial ovarian cancer in short-term users of oral contraceptives

Expression of membrane progesterone receptors (mPR/PAQR) in ovarian cancer cells: implications for progesterone-induced signaling events

The high mortality rates associated with ovarian cancer are largely due to a lack of highly effective treatment options for advanced stage disease; a time when initial diagnosis most commonly occurs. Recent evidence suggests that the steroid hormone, progesterone, may possess anti-tumorigenic properties. With the discovery of a new class of membrane-bound progesterone receptors (mPRs) belonging to the progestin and adipoQ receptor (PAQR) gene family in the ovary, there are undefined mechanisms by which progesterone may inhibit tumor progression. Therefore, our goal was to define potential mPR-dependent signaling mechanisms operative in ovarian cancer cells. We detected abundant mPRα (PAQR7), mPRβ (PAQR8), and mPRγ (PAQR5), but not classical nuclear PR (A or B isoforms) mRNA expression and mPRα protein expression in a panel of commonly used ovarian cancer cell lines. In contrast to mPR action in breast cancer cells, progesterone alone failed to induce changes in cyclic adenosine monophosphate (cAMP) levels in ovarian cancer cells. However, progesterone enhanced cAMP production by β(1,2)-adrenergic receptors and increased isoproterenol-induced transcription from a cAMP response element (CRE)-driven reporter gene. Independently of β-adrenergic signaling, we additionally observed activation of both JNK1/2 and p38 MAPK in response to progesterone alone. This finding was supported by the results of a screen for potential mPR gene targets. Progesterone induced a significant increase in transcription of the pro-apoptotic marker BAX, whose activity and expression has been linked to JNK1/2 and p38 signaling. Inhibitors of JNK, but not p38, blocked progesterone-induced BAX expression. Taken together, these observations implicate at least two distinct signaling pathways that may be utilized by mPRs in ovarian cancer cells that exhibit regulatory genomic changes. These studies on mPR signaling in ovarian cancer lay the foundation for future work aimed at understanding how progesterone exerts its anti-tumorigenic effects in the ovary and suggest that pharmacologic activation of mPRs, abundantly expressed in ovarian cancers, may provide a new treatment option for patients with advanced stage disease.

Risk of breast cancer associated with short-term use of oral contraceptives

OBJECTIVE

To estimate breast cancer risk associated with short-term (<6 months) oral contraceptive use, and explore variation in estimates by use characteristics and medical, menstrual, and reproductive history.

METHODS

We analyzed data from the Women's Contraceptive and Reproductive Experiences Study. Case subjects were white women and black women, 35-64 years old, diagnosed with invasive breast cancer in July 1994-April 1998. Control subjects identified by random-digit dialing were matched to case subjects by age, race, and study site. Conditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Overall, short-term oral contraceptive use was not associated with breast cancer risk (OR = 1.0; 95% CI = 0.8-1.1). However, significant interaction between short-term use and menopausal status led to an observed increased breast cancer risk in pre-menopausal women (OR = 1.3; 95% CI = 1.0-1.7) and a reduced risk in post-menopausal women (OR = 0.8; 95% CI = 0.6-1.0) associated with short-term use. The association was more pronounced in women with non-contraceptive reasons for use and underlying risk factors for breast cancer.

CONCLUSIONS

These associations may result from underlying characteristics of users or unmeasured factors influencing duration of use and breast cancer risk.

Endocrine signaling in ovarian surface epithelium and cancer

Ovarian cancer is the sixth most common cancer and the fifth leading cause of cancer-related death among women in developed countries. Greater than 85% of human ovarian cancer arises within the ovarian surface epithelium (OSE), with the remainder derived from granulosa cells or, rarely, stroma or germ cells. The pathophysiology of ovarian cancer is the least understood among all major human malignancies because of a poor understanding of the aetiological factors and mechanisms of ovarian cancer progression. There is increasing evidence suggesting that several key reproductive hormones, such as GnRH, gonadotrophins and sex steroids, regulate the growth of normal OSE and ovarian cancer cells. The objective of this review was to highlight the effects of these endocrine factors on ovarian cancer cell growth and to summarize the signalling mechanisms involved in normal human OSE and its neoplastic counterparts.

Short-term oral contraceptive use and the risk of epithelial ovarian cancer

Oral contraceptive (OC) use has been consistently linked to a reduction in ovarian cancer in a dose-dependent fashion. Whether short-term OC use is protective remains controversial. In 1994-1998 in the Delaware Valley of Pennsylvania, the authors examined the association between short-term OC use and ovarian cancer in a population-based case-control study comparing 608 incident epithelial ovarian cancer cases with 926 community controls. Using unconditional logistic regression and adjusting for known confounders, they found a significant reduction in ovarian cancer risk for women who had used OCs for < or =6 months (odds ratio = 0.73, 95% confidence interval: 0.54, 0.99). This protective effect was observed in only that group who had used OCs for < or =6 months and stopped because of side effects (odds ratio = 0.59, 95% confidence interval: 0.40, 0.87 for side effects and odds ratio = 0.91, 95% confidence interval: 0.60, 1.37 for non-side-effects). Women who used OCs for >6 months were at a reduced risk independent of their reason for stopping. Results were similar when stratifying by parity and hormone therapy use. Thus, OC use for as little as 6 months provides significant protection against ovarian cancer risk, protection that appears limited to those women who stop using OCs because of side effects. Mediating factors may reflect endogenous hormone levels, OC metabolism, or OC bioactivity.

Family history of cancer, oral contraceptive use, and ovarian cancer risk

OBJECTIVE

The purpose of this study was to determine whether women with a family history of ovarian cancer are at reduced risk of ovarian cancer from the use of oral contraceptives and to compare their risk with that of women with no family history of ovarian cancer.

STUDY DESIGN

A population-based case-controlled study was conducted from May 1994 through July 1998 in which 767 women aged 20 to 69 years with a diagnosis of epithelial ovarian cancer were ascertained from 39 hospitals in 3 northeastern states. Personal interviews with the women and 1367 control subjects provided data that allowed us to estimate the relative risk of ovarian cancer in relation to a family history of cancer and total duration of oral contraception.

RESULTS

Among the 33 case patients and 24 control subjects with a first-degree family history of ovarian cancer, risk of ovarian cancer declined with increasing duration of oral contraception (P =.01). Risk reduction from short-term use of oral contraceptives (< or = 48 months) did not differ significantly by family history (combined estimate of odds ratio, 0.72; 90% CI, 0.59%-0.87%). Risk reduction from long-term use of oral contraceptives (>48 months) was greater in women with a positive family history of ovarian cancer (odds ratio, 0.12) than in women with a negative family history of ovarian cancer (odds ratio, 0.51; test of interaction, P =.04; 692 case patients, 1279 control subjects).

CONCLUSION

Four to 8 years of oral contraception may substantially reduce the risk of ovarian cancer by age 70 years in women with a family history of the disease, from approximately 4 women per 100 women who did not use oral contraceptives to only 2 women per 100 women who did use oral contraceptives.

Low-dose oral contraceptives: protective effect on ovarian cancer risk

Low-dose oral contraceptive (OC) formulations containing 35 microg or less ethinyl estradiol have preferably been prescribed in the last decade, however, few data exist on its relation to ovarian cancer risk. We determined the effects of low-dose OC on the risk of ovarian cancer in a population-based case-control study, including 282 patients ages 20-75 years at diagnosis of incident primary invasive ovarian cancer or borderline tumour between 1993-1996 and 533 control subjects individually matched by age and study area to each case. Analysis excluded women who had undergone a bilateral ovariectomy or had a previous diagnosis of either ovarian cancer or borderline tumour. The association of OC use by ethinyl estradiol dose and ovarian cancer risk was assessed by odds ratios (OR), adjusting simultaneously for the other OC types and determinants of ovarian cancer risk. Ovarian cancer risk was significantly reduced by 52% for ever use of any type of OC. The reduction in risk was 7% per year of use (OR = 0.93, 95% confidence interval [CI] = 0.90-0.96) and was more evident in first-use subjects younger than 25 years. Risk reduction for ovarian cancer was substantial for use of low-dose OC, the odds ratios being 0.86 (95% CI = 0.77-0.94), 0.91 (95% CI = 0.83-1.00), and 0.95 (95% CI = 0.91-0.99) per year of using OC containing <35 microg, 35-<50 microg, and >or=50 microg ethinyl estradiol, respectively. Our study provides evidence that low-dose oral contraceptives confer substantial protection against the development of ovarian cancer.

Increased risk for familial ovarian cancer among Jewish women: a population-based case-control study

Jewish women have been reported to have a higher risk for familial breast cancer than non-Jewish women and to be more likely to carry mutations in breast cancer genes such as BRCA1. Because BRCA1 mutations also increase women's risk for ovarian cancer, we asked whether Jewish women are at higher risk for familial ovarian cancer than non-Jewish women. To determine the effects of 1) Jewish religion and 2) ovarian cancer in a first-degree relative on women's risk for epithelial ovarian cancer, we used data from a population-based, case-control study conducted in 8 geographic regions in the United States from 1980 through 1982. The study group included 471 cases and 4,025 controls. Jewish women were more likely to have familial ovarian cancer than non-Jewish women [odds ratio (OR) = 8.4, 95% confidence interval (CI) = 2.6-28]. The risk of having ovarian cancer appeared to be greater in Jewish women having a first-degree relative with ovarian cancer (OR = 8.81, 95% CI = 2.02-38.23) than in non-Jewish women having a first-degree relative with ovarian cancer (OR = 3.01, 95% CI = 1.61-5.64), but differences between Jewish and non-Jewish women were not statistically significant. Jewish women with no first-degree relative with ovarian cancer had no increased risk for ovarian cancer (OR = 1.27, 95% CI = 0.74-2.91) compared to non-Jewish women. These results suggest that Jewish women may have a higher rate of familial ovarian cancer than non-Jewish women, but because the results are based on a small number of Jewish women with familial ovarian cancer, the results need to be confirmed in larger studies.

Beyond ovulation: oral contraceptives and epithelial ovarian cancer

In a case-control study in three Australian states that included 794 women with epithelial ovarian cancer and 853 community controls for whom we had adequate contraceptive and reproductive histories, we examined the effects of oral contraceptive use after controlling for estimated number of ovulatory cycles. Other covariates included in the multiple logistic regression analysis were parity, smoking, and history of pelvic surgery. The protective effect of duration of oral contraceptive use appeared to be multiplicative, with a 7% decrease in relative risk per year [95% confidence interval (CI) = 4-9%], persisting beyond 15 years of exposure. Use for up to 1 year may have a greater effect than predicted (odds ratio = 0.57; 95% CI = 0.40-0.82), whereas use before the first pregnancy may be additionally beneficial (odds ratio = 0.95; 95% CI = 0.87-1.03, adjusted for overall duration of use). Better control for ovulatory life might attenuate these estimates somewhat. There was little evidence of waning protection with time since last exposure or of extra benefit with early commencement of oral contraceptive use. We found no convincing evidence of effect modification in any factor examined or differences in effect among the three main histologic cancer types or between borderline and malignant tumors. Oral contraceptives may act by both suppressing ovulation and altering the tumor-promoting milieu.

Safety implications of transferring the oral contraceptive from prescription-only to over-the-counter status

The idea of making oral contraceptives available without prescription has a long history, and has been recently revived in the US and the UK. High dose oral contraceptives have generally been replaced by low dose formulations and, subsequently, most cardiovascular risks have been reduced and a protection against ovarian and uterine cancers has been consistently demonstrated. Oral contraceptive compliance, however, continues to be a problem, but there is no reason to assume that wise practice would be any more or less if oral contraceptives were available over-the-counter (OTC). Some countries have introduced alternatives to prescription-only oral contraceptives, whereby nurses, midwives, social workers and/or pharmacists are incorporated into the distribution process. This article concludes that the balance of risks and benefits is in favour of OTC access for oral contraceptives.