Long-term use of continuous-combined estrogen-progestin hormone therapy and risk of endometrial cancer.

The daily administered dose of progestin in continuous-combined estrogen-progestin therapy is provided to counteract the proliferative effect of estrogen on the postmenopausal endometrium. However, there remains some uncertainty as to whether use of such a combined regimen, over the long term, is associated with an altered risk of endometrial cancer. We pooled data from four population-based case-control studies of endometrial cancer in western Washington State. Cases, ages 45-74, were diagnosed between 1985 and 2005. Using logistic regression with the adjustment for confounding factors, women who had exclusively used continuous-combined estrogen-progestin therapy (90 endometrial cancer cases, 227 controls) were compared with women who had never used any type of hormone therapy (774 cases, 1,116 controls). Associations with duration and recency of use were evaluated overall and within strata defined by body mass index. Long-term use of continuous-combined estrogen-progestin therapy (≥10 years) was associated with a reduced risk of endometrial cancer (OR = 0.37, 95% CI: 0.21-0.66). This association was most pronounced in women with a body mass index ≥30 kg/m(2) (OR = 0.19, 95% CI: 0.05-0.68). Associations did not differ according to recency of use. These results suggest that long duration of use of continuous-combined estrogen-progestin therapy is associated with a reduced risk of endometrial cancer.

Pregnancy history and risk of endometrial cancer.

BACKGROUND: Epidemiologic studies are consistent in finding that women who have had at least one birth are less likely to develop endometrial cancer. Less clear is whether timing of pregnancies during reproductive life influences risk, and the degree to which incomplete pregnancies are associated with a reduced risk. METHODS: We evaluated pregnancy history in relation to endometrial cancer risk using data from a series of 4 population-based endometrial cancer case-control studies of women 45-74 years of age (1712 cases and 2134 controls) during 1985-2005 in western Washington State. Pregnancy history and information on other potential risk factors were collected by in-person interviews. RESULTS: Older age at first birth was associated with a reduced risk of endometrial cancer after adjustment for number of births and age at last birth (test for trend P = 0.004). The odds ratio comparing women at least 35 years of age at their first birth with those younger than 20 years was 0.34 (95% confidence interval = 0.14-0.84). Age at last birth was not associated with risk after adjustment for number of births and age at first birth (test for trend P = 0.830). Overall, a history of incomplete pregnancies was not associated with endometrial cancer risk to any appreciable degree. CONCLUSIONS: In this study, older age at first birth was more strongly associated with endometrial cancer risk than was older age at last birth. To date, there remains some uncertainty in the literature on this issue.

Feasibility of including cellular telephone numbers in random digit dialing for epidemiologic case-control studies.

The usefulness of landline random digit dialing (RDD) in epidemiologic studies is threatened by the rapid increase in households with only cellular telephone service. This study assessed the feasibility of including cellular telephone numbers in RDD and differences between young adults with landline telephones and those with only cellular telephones. Between 2008 and 2009, a total of 9,023 cellular telephone numbers were called and 43.8% were successfully screened; 248 men and 249 women who resided in 3 Washington State counties, were 20-44 years of age, and used only cellular telephones were interviewed. They were compared with 332 men and 526 women with landline telephones interviewed as controls for 2 case-control studies conducted in parallel with cellular telephone interviewing. Cellular-only users were more likely to be college educated and less likely to have fathered/birthed a child than were their landline counterparts. Male cellular-only users were less likely to be obese and more likely to exercise, to be Hispanic, and to have lower incomes, while female cellular-only users were more likely to be single than landline respondents. Including cellular telephone numbers in RDD is feasible and should be incorporated into epidemiologic studies that rely on this method to ascertain subjects, although low screening rates could hamper the representativeness of such a sample.

Complex hyperplasia with and without atypia: clinical outcomes and implications of progestin therapy.

OBJECTIVE: Limited data exist to inform clinicians and patients as to the likelihood of long-term endometrial hyperplasia response to progestin therapy, especially for atypical hyperplasia. We evaluated women with complex and atypical endometrial hyperplasia, comparing those prescribed progestin with those not prescribed progestin. METHODS: This retrospective cohort study was conducted in 1985-2005 among women aged 18-88 years at an integrated health plan in Washington State. Women were ineligible if they achieved an outcome (endometrial carcinoma, hysterectomy, or both) within 8 weeks of hyperplasia diagnosis. Exposure was progestin use for at least 14 days by duration and recency. Outcomes included rate of 1) endometrial carcinoma, 2) hysterectomy, or 3) both. Analyses performed included Kaplan-Meier, incident rate ratios, and Cox proportional hazard ratios. RESULTS: One thousand four hundred forty-three eligible women were identified. One thousand two hundred one had complex (n=164 no progestin) and 242 had atypical (n=62 no progestin) hyperplasia. During follow-up, a median of 5.3 years (range 8 weeks to 20.8 years), 71 women were diagnosed with endometrial carcinoma (35 complex, 36 atypia) and 323 underwent hysterectomy (216 complex, 107 atypia). Among women with complex and atypical hyperplasia, rates of endometrial carcinoma among progestin users were 3.6 and 20.5 per 1,000 woman-years, respectively (compared with women who did not use progestin, 10.8 and 101.4). Among women with complex and atypical hyperplasia, rates of hysterectomy among progestin users were 23.3 and 61.4 per 1,000 woman-years, respectively (compared with women who did not use progestin, 55.1 and 297.3). CONCLUSION: Endometrial carcinoma risk is diminished approximately threefold to fivefold in women diagnosed with complex or atypical endometrial hyperplasia and dispensed progestin; hysterectomy risk is also decreased. LEVEL OF EVIDENCE: II.

Infertility treatment use in relation to selected adverse birth outcomes.

OBJECTIVE: To determine whether maternal infertility treatment is associated with adverse outcomes. DESIGN: Population-based cohort study using linked birth certificate-hospital discharge data. SETTING: Washington State. PATIENT(S): Live-born singleton infants conceived with infertility treatment between 2003 and 2006 (n = 2,182) and a random sample of live-born singleton infants conceived spontaneously, frequency matched by birth year (n = 10,989). INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Mantel-Haenszel adjusted relative risks (RRs) and 95% confidence intervals (CIs) were computed for low birth weight, delivery at <37 weeks, small for gestational age infants, any malformation, placenta previa, and placenta abruptio. RESULT(S): Women with infertility treatment were at increased risk of placental abnormalities, including placenta abruptio (RR, 1.6; 95% CI, 1.1-2.5) and placenta previa (RR, 3.0; 95% CI, 2.0-4.7). Their infants were more likely to be delivered at <37 weeks (RR, 1.7; 95% CI, 1.4-1.9) or weigh <2500 g (RR, 1.4; 95% CI, 1.1-1.7); however, they were not at increased risk of being small for gestational age. An increased risk of malformations was observed in infants born to older women with infertility treatment, but not to younger women. CONCLUSION(S): Women using infertility treatment are at increased risk for delivering preterm, placenta previa, and placenta abruptio. Studies with measurement of specific infertility treatments will help identify the mechanisms.

Does pregnancy provide vaccine-like protection against rheumatoid arthritis?

OBJECTIVE: Previous studies have evaluated the correlation between rheumatoid arthritis (RA) risk and pregnancy history, with conflicting results. Fetal cells acquired during pregnancy provide a potential explanation for modulation of RA risk by pregnancy. The present study was undertaken to examine the effect of parity on RA risk. METHODS: We examined parity and RA risk using results from a population-based prospective study in Seattle, Washington and the surrounding area and compared women who were recently diagnosed as having RA (n = 310) with controls (n = 1,418). We also evaluated the distribution of parity in cases according to HLA genotype. RESULTS: We found a significant reduction of RA risk associated with parity (relative risk [RR] 0.61 [95% confidence interval 0.43-0.86], P = 0.005). RA risk reduction in parous women was strongest among those who were younger. Most striking was that RA risk reduction correlated with the time that had elapsed since the last time a woman had given birth. RA risk was lowest among women whose last birth occurred 1-5 years previously (RR 0.29), with risk reduction lessening progressively as the time since the last birth increased (for those 5-15 years since last birth, RR 0.51; for those >15 years, RR 0.76), compared with nulliparous women (P for trend = 0.007). No correlation was observed between RA risk and either age at the time a woman first gave birth or a woman's total number of births. Among cases with the highest genetic risk of RA (i.e., those with 2 copies of RA-associated HLA alleles), a significant underrepresentation of parous women versus nulliparous women was observed (P = 0.02). CONCLUSION: In the present study, there was a significantly lower risk of RA in parous women that was strongly correlated with the time elapsed since a woman had last given birth. While the explanation for our findings is not known, HLA-disparate fetal microchimerism can persist many years after a birth and could confer temporary protection against RA.

Is the incidence of invasive vulvar cancer increasing in the United States?

OBJECTIVE: To document incidence rates of vulvar cancer, specifically invasive vulvar cancer, from 1973 to 2004 in the United States. METHODS: Nine US cancer registries from the Surveillance, Epidemiology, and End Results (SEER) databases were used to identify women aged 15-84 years, who were first diagnosed with vulvar cancer during 1973-2004. Age-adjusted incidence rates and annual percentage changes were calculated for different time periods, stage of the disease, age, race, and geographic area. RESULTS: During 1973-2004, the incidence of in situ vulvar tumors increased by an average of 3.5% per year (95% CI: 2.9%, 4.1%), while the incidence of invasive tumors increased 1.0% per year (95% CI: 0.6%, 1.4%). An increasing incidence was observed for localized and regional invasive tumors. To at least some degree, the rise of incidence rates of incidence tumors was evident in every age category, race, and geographic region. CONCLUSIONS: Incidence rates of invasive vulvar cancer have increased in the United States during the last three decades. The reasons for this increase are unknown.

Incidence of endometrial hyperplasia.

OBJECTIVE: The objective of the study was to estimate the age-specific incidence of endometrial hyperplasia: simple, complex, and atypical, in order of increasing likelihood of progression to carcinoma. STUDY DESIGN: Women aged 18-90 years with endometrial pathology specimens (1985-2003) at a large integrated health plan were identified using automated data. Incidence rates were obtained by dividing the number of cases by the estimated number of female health plan enrollees who retained a uterus. RESULTS: Endometrial hyperplasia peak incidence was: simple, 142 per 100,000 woman-years, complex, 213 per 100,000 woman-years, both in the early 50s; and atypical, 56 per 100,000 woman-years in the early 60s. Age-adjusted incidence decreased over the study period, especially for atypical hyperplasia. CONCLUSION: Endometrial hyperplasia incidence without and with atypia peaks in the early postmenopausal years and in the early 60s, respectively. Given that some cases of endometrial hyperplasia likely go undiagnosed, the figures provided should be viewed as minimum estimates of the true incidence.

Endometrial hyperplasia risk in relation to recent use of oral contraceptives and hormone therapy.

PURPOSE: We sought to examine the relationship between recent use of oral contraceptives and hormone therapy and endometrial hyperplasia (EH) risk. METHODS: Cases comprised women diagnosed with complex EH (n = 289) or atypical EH (n = 173) between 1985 and 2003. One age-matched control was selected for each case; excluded were women with a prior hysterectomy or diagnosis of EH or endometrial cancer. Hormone use in the 6 months prior to the date of the case's first symptoms was ascertained using a pharmacy database and medical records. Odds ratios (OR) and 95% confidence intervals (CI) were calculated. RESULTS: Three (1.1%) cases had used oral contraceptives, compared to 16 (6.0%) controls (OR = 0.2, 95% CI: 0.0-0.6). Fifty-one (16.8%) cases had taken estrogen-only hormone therapy, in contrast to two (0.7%) controls (OR = 37.6, 95% CI: 8.8-160.0). The risk of EH among estrogen plus progestin hormone users did not differ from that of non-users (OR = 0.7, 95% CI: 0.4-1.1). CONCLUSIONS: This study suggests that previous findings of the association of estrogen-only hormone therapy with increased risk of EH and the lack of an association between estrogen plus progestin hormone therapy and EH risk are likely to apply to both complex EH and atypical EH. Further examination of the association between oral contraceptives and EH, with greater numbers of OC users, is warranted.

Risk of complex and atypical endometrial hyperplasia in relation to anthropometric measures and reproductive history.

The authors sought to test the hypothesis that characteristics and exposures which influence the balance of estrogen and progesterone bear on the incidence of endometrial hyperplasia (EH), a noninvasive proliferation of the lining of the uterus. Cases included all female members of Group Health (Washington State) who were diagnosed with complex EH or EH with atypia during the period 1985-2003 and whose diagnoses were confirmed in a pathology review (n = 446). Controls were selected randomly from Group Health membership files and were matched to the cases by age and enrollment status at the reference date. An increased risk of EH was associated with increasing body mass index and nulliparity. There was a suggestion of a decreased risk of EH with atypia among current smokers. No association with diabetes or hypertension was found. The risk factors observed to be associated with EH in this study are similar to those associated with endometrial cancer. Whether these risk factors predispose women to cancer simply by increasing EH incidence or continue to augment cancer risk even after EH is present is currently unknown.

Diagnosing endometrial hyperplasia: why is it so difficult to agree?

Current World Health Organization classification of endometrial hyperplasia is problematic because of poor diagnostic reproducibility. We sought to determine factors that cause diagnostic disagreement in a review of 2601 endometrial specimens. Blinded random specimens of normal endometrium, hyperplasias, and carcinoma were reviewed by 2 pathologists, with review by a third pathologist in cases with disagreement. All cases of endometrial hyperplasia or carcinoma were scored for degree of glandular crowding, architectural complexity, and cytologic atypia. Sample adequacy, hyperplasia volume, presence of metaplasia, or endometrial polyp were also scored. The overall kappa for agreement was 0.71, with a lower kappa of 0.36 when cases called "no hyperplasia" were excluded. The percent specific agreement was 90.3% for no hyperplasia, 31.1% for simple hyperplasia, 51.1% for complex hyperplasia, 49.8% for atypical hyperplasia, and 57.5% for adenocarcinoma. Cases categorized as "low volume hyperplasia" had more diagnostic disagreement than "high volume," (62% vs. 39%, P=0.003). Similarly, cases called "scant" had more diagnostic disagreement than "not scant" (65% vs. 57%, P=0.013). The histologic feature associated with the most diagnostic disagreement was cytologic atypia (P<0.0001). Architectural crowding, architectural complexity, or the presence of a polyp were all associated with diagnostic disagreement (P<0.0001). High diagnostic disagreement in endometrial hyperplasia is related to both sample adequacy and interpretation of histologic features present. Although obtaining additional tissue may increase diagnostic reproducibility, differences in interpretation of key histologic features like cytologic atypia remain major factors contributing to diagnostic disagreement.

Relationship between menopausal hormone therapy and risk of ductal, lobular, and ductal-lobular breast carcinomas.

Combined estrogen and progestin hormone therapy (CHT) increases breast cancer risk, but this risk varies by breast cancer type. Several studies indicate that CHT is more strongly related to lobular carcinoma risk than to ductal carcinoma risk, but these studies have been limited in their assessments of recency and duration of use, and none included a centralized pathology review. We conducted a population-based case-control study consisting of 324 lobular, 196 ductal-lobular, and 524 ductal cases diagnosed from 2000 to 2004 and 469 controls ages 55 to 74 years old. Tissue specimens were centrally reviewed for 83% of cases. Associations between hormone use and breast cancer risk were evaluated using polytomous logistic regression. Current CHT users had 2.7-fold [95% confidence interval (95% CI), 1.7-4.2] and 3.3-fold (95% CI, 2.0-5.7) elevated risks of lobular and ductal-lobular carcinomas, respectively, regardless of tumor stage, size, or nodal status. Elevations in risk were observed only among users of CHT for > or =3 years. Among ductal-lobular cases, CHT increased risk of tumors that were > or =50% lobular (odds ratio, 4.8; 95% CI, 2.1-11.1) but not tumors that were <50% lobular (odds ratio, 1.9; 95% CI, 0.9-4.1). Current CHT users for > or =3 years have a substantially increased risk of lobular carcinomas. Although lobular carcinomas are less common than ductal carcinomas ( approximately 16% versus 70% of all invasive breast cancers in the United States), this duration is shorter than the 5 years of use widely cited to be needed to confer an increased risk of breast cancer overall. Further studies focusing on the etiology of lobular carcinomas are needed.

Diabetes and endometrial cancer: an evaluation of the modifying effects of other known risk factors.

To determine whether risk of endometrial cancer among women with type 2 diabetes differs with respect to other endometrial cancer risk factors, the authors used data from a population-based case-control study (1,303 cases and 1,779 controls) conducted in western Washington State during 1985-1999. History of type 2 diabetes was associated with endometrial cancer (odds ratio (OR) = 1.7, 95% confidence interval (CI): 1.2, 2.3), more strongly among women with a recent diabetes diagnosis (<5 years) (OR = 2.6, CI: 1.5, 4.7) than among those with a more distant diagnosis (> or =5 years) (OR = 1.3, CI: 0.8, 1.9). Type 2 diabetes was associated with endometrial cancer among women with a body mass index (BMI) (weight (kg)/height (m)(2)) less than 35 but not among women with a BMI of 35 or more. The observed associations persisted after finer adjustment for BMI to control for residual confounding. History of diabetes was associated with a twofold increased risk of endometrial cancer among hypertensive women, but no association was observed among nonhypertensive women. The risk associated with type 2 diabetes appeared not to vary greatly with respect to other endometrial cancer risk factors. These results support the hypothesis that type 2 diabetes is associated with endometrial cancer irrespective of the presence of other risk factors for this disease, except possibly hypertension and extreme obesity.

Ovarian cysts and breast cancer: results from the Women's Contraceptive and Reproductive Experiences Study.

A diagnosis of ovarian cysts is likely an indicator of hormonal milieu and thus may be related to breast cancer risk. Recent studies have reported an inverse relationship between prior ovarian cyst diagnosis and breast cancer risk. We evaluated this relationship in the Women's Contraceptive and Reproductive Experiences (CARE) Study, a population-based case-control study conducted in Atlanta, Detroit, Philadelphia, Los Angeles, and Seattle. Cases had first primary invasive breast cancer diagnosed between 1994 and 1998 at ages 35-64 years. African American women were over-sampled. Controls were identified through random digit dialling and were frequency matched to cases on centre, race, and five-year age group. A total of 4575 cases and 4682 controls were interviewed. We used unconditional logistic regression adjusted for age and study centre within racial groups to estimate the odds ratio (OR) and 95% confidence interval (CI) for the relationship between prior ovarian cysts and breast cancer. Ovarian cyst diagnosis was associated with a significantly reduced risk among Caucasians (OR=0.85, 95% CI 0.76-0.96) and among African Americans (OR=0.68, 95% CI 0.57-0.81). The association in Caucasians was not significant within subgroups defined by menopausal status, hormone use, or gynecological surgery while the OR estimates in African Americans were consistently lower and frequently significant. These data are consistent with the previously reported inverse association between ovarian cysts and breast cancer, but the evidence for a relationship was stronger in African Americans than Caucasians. Additional studies are required to determine the specific cyst type(s) responsible for the observed relationship.

Long-term use of postmenopausal estrogen and progestin hormone therapies and the risk of endometrial cancer.

OBJECTIVE: The purpose of this study was to assess whether endometrial cancer risk among long-term users of (1) sequential estrogen plus progestin 10-24 days per month exceeds that of nonusers and (2) daily estrogen plus progestin (continuous combined hormone therapy) is below that of nonusers. STUDY DESIGN: In this population-based case-control study with 1038 endometrial cancer cases diagnosed in 1985-1999 and 1453 control subjects, exclusive users of a single form of hormone therapy were compared with never users of hormone therapy. RESULTS: For sequential therapy, only long-term use (> or = 6 years) was associated with increased risk (odds ratio, 2.0; 95% CI, 1.2-3.5). Continuous combined therapy was associated with decreased risk (odds ratio, 0.59; 95% CI, 0.40-0.88), with no increased risk among long-term users (odds ratio, 0.77; 95% CI, 0.45-1.3). CONCLUSION: These results support the hypotheses that continuous combined therapy does not increase (and may decrease) endometrial cancer risk and that long-term sequential therapy can lead to a modest increased risk. However, the collective results of all studies of these questions and their clinical implications remain unclear.

Endometrial cancer risk in estrogen users after switching to estrogen-progestin therapy.

OBJECTIVE: It is unknown whether postmenopausal unopposed estrogen users are better off, in terms of endometrial cancer risk, switching to a combined estrogen-progestin regimen or stopping hormone use altogether. METHODS: We analyzed data from a series of three population-based case-control studies in western Washington state during 1985-1999, comparing proportions of "switchers" and "stoppers" in cases and controls. We also assessed whether the risk of endometrial cancer in either group of former unopposed estrogen users returned to that of never users. RESULTS: After multivariate adjustment using unconditional logistic regression, women who switched to a combined regimen with a progestin added for at least ten days/month (37 cases, 47 controls) had half the risk of endometrial cancer of women who stopped hormone use altogether (86 cases, 78 controls) (adjusted odds ratio = 0.5, 95% confidence interval: 0.3-1.1). Most subgroups of former users, whether they switched or stopped, had some increased risk of endometrial cancer compared to never users. CONCLUSIONS: Results from this study suggest that unopposed estrogen users may reduce their risk of endometrial cancer more by switching to a combined regimen with progestin added for at least ten days/month than by stopping hormone use altogether.

Prostate cancer risk in relation to selected genetic polymorphisms in insulin-like growth factor-I, insulin-like growth factor binding protein-3, and insulin-like growth factor-I receptor.

We conducted a nested case-control study within a cohort of elderly Americans to examine the role of the insulin-like growth factor (IGF) signaling pathway in prostate cancer etiology. The distribution of genotypes of IGF-I (CA)n, IGF binding protein-3 (IGFBP-3) A-202C, and of the 2-bp deletion and (AGG)n polymorphisms in IGF-I receptor (IGF-IR) was compared between men with prostate cancer (n = 213) and equal number of controls matched on year of blood draw, survival until the date of diagnosis, race, and age. Among controls, the number of CA repeats in IGF-I was not correlated to any appreciable degree with plasma IGF-I concentration, whereas the IGFBP-3 CC genotype was associated with a relatively low level of plasma IGFBP-3. There was no association between prostate cancer risk and the number of CA repeats in IGF-I, IGFBP-3 genotype, or the presence of the 2-bp deletion in IGF-IR. There was a small increased risk among men who did not carry two copies of the (AGG)7 allele of IGF-IR. These results add to the evidence that the number of IGF-I CA repeats is not associated with prostate cancer risk. Our observation that men who do not carry two copies of the IGF-IR (AGG)7 allele are at increased risk of prostate cancer merits further investigation.

Risk factors for the incidence of endometrial cancer according to the aggressiveness of disease.

There is a wide range of aggressiveness of endometrial tumors, some being indolent and easily treated while others metastasize and prove fatal. The authors used data from three population-based, case-control studies to determine if etiologic factors differ for aggressive disease. Interview data were obtained from 1,304 female residents of western Washington State who were 45-74 years of age and diagnosed with endometrial cancer during 1985-1991, 1994-1995, and 1997-1999 and from 1,779 controls who were of similar ages and selected primarily by random digit dialing. As a means of gauging aggressiveness, tumor characteristics were abstracted from the population-based cancer registry that serves western Washington State. The risk of endometrial cancer among long-term users (> or = 8 years) of unopposed estrogens was particularly high for the least aggressive tumors (odds ratio = 18.6, 95% confidence interval: 12.2, 28.6) but was elevated for moderate and highly aggressive tumors as well (odds ratios = 6.6 and 7.1, respectively). Women who were obese, had a history of diabetes, and had fewer than two children were also at increased risk, regardless of tumor aggressiveness, while oral contraceptive users were at decreased risk of only relatively more aggressive disease. In general, a woman's risk of endometrial cancer appears to be influenced by similar risk factors regardless of disease severity.

Do cases and controls matched on the first eight digits of their telephone number share geographic proximity and socioeconomic characteristics?

PURPOSE: The aim of this study is to assess the geographic proximity of cases and controls who share the same "stem" of their telephone number (area code, prefix, and next two digits) and compare their socioeconomic characteristics. METHODS: We compared residential proximity and characteristics of case-control sets selected in this way with sets consisting of the same cases matched to different controls on all variables except telephone number stem. RESULTS: Mean distance between telephone stem-matched pairs was much less than that between pairs not matched by telephone number stem (3.53 and 20.14 km, respectively). There was slight agreement between cases and controls for some measures of socioeconomic status in both sets. We also compared distances between residences of control respondents who shared the same telephone number stem with those between residences of respondents who shared only the same telephone area code and prefix. Mean distances for the two groups were similar. CONCLUSIONS: Geographic proximity between cases and controls can be achieved by matching on either telephone number stem or only telephone area code and prefix. Adjustment for socioeconomic factors may be needed even if cases and controls live close to each other.

Interindividual variation in nucleotide excision repair genes and risk of endometrial cancer.

Exposure to estrogens is a likely cause of endometrial cancer, but the means by which estrogens exert this effect are not entirely clear. One hypothesis is that certain estrogen metabolites bind to the DNA, forming bulky adducts that damage the DNA and initiate carcinogenesis. A woman's reduced capacity to repair such damage may increase her risk of endometrial cancer. We conducted a population-based case-control study in western Washington State to address the role of variation in nucleotide excision repair genes on the risk of endometrial cancer. Case women (n = 371), ages 50 to 69 years, were diagnosed with invasive endometrial cancer between 1994 and 1999. Control women (n = 420) were selected using random-digit dialing (ages 50-65 years) and by random selection from Health Care Financing Administration data files (ages 66-69 years). Genotyping assays were done for ERCC1, ERCC2 (XPD), ERCC4 (XPF), ERCC5 (XPG), XPA, and XPC. No appreciable differences between cases and controls were observed in the genotype distributions of ERCC1 (c8092a and c19007t), ERCC2 (D312N, K751Q, and c22541a), ERCC4 (R415Q and t30028c), or ERCC5 (D1104H). Carriage of at least one variant allele for XPA G23A was associated with decreased risk of endometrial cancer [odds ratio (OR), 0.70; 95% confidence interval (95% CI), 0.53-0.93]. Carriage of at least one XPC A499V variant allele was associated with a modest decrease in risk (OR, 0.79; 95% CI, 0.59-1.05). Women with variant alleles at both XPC A499V and K939Q had 58% of the risk of women with no XPC variant alleles (OR, 0.58; 95% CI, 0.35-0.96). Our data suggest that interindividual variation in XPA and XPC influences a woman's risk of endometrial cancer.