Venous thromboembolism risk in relation to use of different types of postmenopausal hormone therapy in a large prospective study

BACKGROUND

Current use of menopausal hormone therapy (HT) increases the risk of venous thromboembolism (VTE) and the formulations used may affect risk.

METHODS

A total of 1,058,259 postmenopausal UK women were followed by record linkage to routinely collected National Health Service hospital admission and death records. HT use and risk of VTE was examined using Cox regression to estimate relative risks (RRs) and 95% confidence intervals (CIs).

RESULTS

During 3.3 million years of follow-up, 2200 women had an incident VTE, diagnosed, on average, 1.5 years after last reporting HT use. RRs in current vs. never users at last reporting varied by HT formulation: the risk was significantly greater for oral estrogen-progestin than oral estrogen-only therapy (RR = 2.07 [95%CI, 1.86-2.31] vs. 1.42 [1.21-1.66]), with no increased risk with transdermal estrogen-only therapy (0.82 [0.64-1.06]). Among users of oral estrogen-progestin, the risk from HT varied by progestin type, with significantly greater risks for preparations containing medroxyprogesterone acetate than other progestins (2.67 [2.25-3.17] vs. 1.91 [1.69-2.17]; Pheterogeneity = 0.0007). Current users of oral HT at last reporting had twice the risk of VTE in the first 2 years after starting HT than later (Pheterogeneity = 0.0006). Associations were similar for deep vein thrombosis with and without pulmonary embolism. Over 5 years, 1 in 660 who had never used HT were admitted to hospital for (or died from) pulmonary embolism, compared with 1 in 475 current users of oral estrogen-only HT,1 in 390 users of estrogen-progestin HT containing norethisterone/norgestrel, and 1 in 250 users of estrogen-progestin HT containing medroxyprogesterone acetate.

CONCLUSIONS

The risk of VTE varied considerably by HT formulation, being greatest in users of oral estrogen-progestin HT, especially formulations containing medroxyprogesterone acetate.

Carcinoma of the cervix and tobacco smoking: collaborative reanalysis of individual data on 13,541 women with carcinoma of the cervix and 23,017 women without carcinoma of the cervix from 23 epidemiological studies

Tobacco smoking has been classified as a cause of cervical cancer, but the effect of different patterns of smoking on risk is unclear. The International Collaboration of Epidemiological Studies of Cervical Cancer has brought together and combined individual data on 13,541 women with and 23,017 women without cervical carcinoma, from 23 epidemiological studies. Relative risks (RRs) and 95% confidence intervals (CIs) of carcinoma of the cervix in relation to tobacco smoking were calculated with stratification by study, age, sexual partners, age at first intercourse, oral contraceptive use and parity. Current smokers had a significantly increased risk of squamous cell carcinoma of the cervix compared to never smokers (RR = 1.60 (95% CI: 1.48-1.73), p<0.001). There was increased risk for past smokers also, though to a lesser extent (RR = 1.12 (1.01-1.25)), and there was no clear trend with time since stopping smoking (p-trend = 0.6). There was no association between smoking and adenocarcinoma of the cervix (RR = 0.89 (0.74-1.06) and 0.89 (0.72-1.10) for current and past smokers respectively), and the differences between the RRs for smoking and squamous cell and adenocarcinoma were statistically significant (current smoking p<0.001 and past smoking p = 0.01). In current smokers, the RR of squamous cell carcinoma increased with increasing number of cigarettes smoked per day and also with younger age at starting smoking (p<0.001 for each trend), but not with duration of smoking (p-trend = 0.3). Eight of the studies had tested women for cervical HPV-DNA, and in analyses restricted to women who tested positive, there was a significantly increased risk in current compared to never smokers for squamous cell carcinoma (RR = 1.95 (1.43-2.65)), but not for adenocarcinoma (RR = 1.06 (0.14-7.96)). In summary, smokers are at an increased risk of squamous cell but not of adenocarcinoma of the cervix. The risk of squamous cell carcinoma increases in current smokers with the number of cigarettes smoked per day and with younger age at starting smoking.

Comparison of risk factors for squamous cell and adenocarcinomas of the cervix: a meta-analysis

While most cancers of the uterine cervix are squamous cell carcinomas, the relative and absolute incidence of adenocarcinoma of the uterine cervix has risen in recent years. It is not clear to what extent risk factors identified for squamous cell carcinoma of the cervix are shared by cervical adenocarcinomas. We used data from six case–control studies to compare directly risk factors for cervical adenocarcinoma (910 cases) and squamous cell carcinoma (5649 cases) in a published data meta-analysis. The summary odds ratios and tests for differences between these summaries for the two histological types were estimated using empirically weighted least squares. A higher lifetime number of sexual partners, earlier age at first intercourse, higher parity and long duration of oral contraceptive use were risk factors for both histological types. Current smoking was associated with a significantly increased risk of squamous cell carcinoma, with a summary odds ratio of 1.47 (95% confidence interval: 1.15–1.88), but not of adenocarcinoma (summary odds ratio=0.82 (0.60–1.11); test for heterogeneity between squamous cell and adenocarcinoma for current smoking: P=0.001). The results of this meta-analysis of published data suggest that squamous cell and adenocarcinomas of the uterine cervix, while sharing many risk factors, may differ in relation to smoking. Further evidence is needed to confirm this in view of the limited data available.

Risk factors for adenocarcinoma and squamous cell carcinoma of the cervix in women aged 20-44 years: the UK National Case-Control Study of Cervical Cancer

We report results on risk factors for invasive squamous cell and adenocarcinomas of the cervix in women aged 20–44 years from the UK National Case–Control Study of Cervical Cancer, including 180 women with adenocarcinoma, 391 women with squamous cell carcinoma and 923 population controls. The risk of both squamous cell and adenocarcinoma was strongly related to the lifetime number of sexual partners, and, independently, to age at first intercourse. The risk of both types of cervical cancer increased with increasing duration of use of oral contraceptives, and this effect was most marked in current and recent users of oral contraceptives. The risk of squamous cell carcinoma was associated with high parity and the risk of both squamous cell and adenocarcinoma increased with early age at first birth. Long duration smoking (20 or more years) was associated with a two-fold increase in the risk of squamous cell carcinoma, but smoking was not associated with the risk of adenocarcinoma. Further studies are needed to confirm the suggestion from this and other studies of differences in risk related to smoking between squamous cell and adenocarcinomas of the cervix.

A meta-analysis of obesity and the risk of pancreatic cancer

Smoking and diabetes are the only established risk factors for pancreatic cancer. Findings from recent studies suggest that obesity may also be associated with an increased risk of pancreatic cancer, but several earlier studies were less conclusive. We examined this relationship in a meta-analysis of published data. Six case-control and eight cohort studies involving 6391 cases of pancreatic cancer were identified from a computer-based literature search from 1966 to 2003. The relative risk per unit increase in body mass index was estimated for each of the studies from the published data. In a random effects model, the summary relative risk per unit increase in body mass index was 1.02 (95% CI: 1.01-1.03). There was some evidence of heterogeneity between the studies' results (P=0.1). The summary relative risk estimates were slightly higher for studies that had adjusted for smoking and for case-control studies that had not used proxy respondents. The estimated per unit increase in body mass index would translate into a relative risk of 1.19 (95% CI: 1.10-1.29) for obese people (30 kg m(-2)) compared to people with a normal body weight (22 kg m(-2)). These results provide evidence that the risk of pancreatic cancer may be weakly associated with obesity. However, the small magnitude of the summary risk means the possibility of confounding cannot be excluded.