| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | COVER ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
||||||||
|
||||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
NEWS & VIEWS |
|
Ovarian cancer ranks fifth as a cause of cancer death among women in the United States. Only 19% of cases are diagnosed at a localized stage, and no screening tests have been proven specific enough for routine use. Risk reduction is, therefore, an important area of research, and 2 recent studies of several potential factors for ovarian cancer offer valuable information.
A meta-analysis conducted by Oxford University Professor Valerie Beral, MD, Director of the Cancer Research UK Epidemiology Unit, along with researchers from the Collaborative Group on Epidemiological Studies of Ovarian Cancer, which includes epidemiologists from the American Cancer Society (ACS), investigates the link between ovarian cancer and oral contraceptive use. Many individual studies have reported that oral contraceptive use is associated with a lower incidence of ovarian cancer, but this meta-analysis offers a more detailed picture of how large the protective effect is and how long it lasts. The results were published in The Lancet (2008;371:303–314).
Researchers pooled data from 45 epidemiological studies, which included 23,257 women who had ovarian cancer and 87,303 who did not, conducted in the 1960s, 1970s, and 1980s. Thirteen among the 45 studies were prospective studies, 19 were case-control studies with population controls, and 13 were case-control studies with hospital controls. Researchers adjusted for 15 factors that might play a role in whether a woman developed ovarian cancer, including age, parity, ethnicity, family history, menopausal status, use of hormone replacement therapy, body mass index, and alcohol and tobacco use.
This comprehensive review found a reduction in overall ovarian cancer risk (relative risk [RR] 0.73, P <.0001) in ever-users of oral contraceptives compared with never-users.
The protection conferred by oral contraceptives seemed to start within a year of taking the pills and increase over time. Longer duration of use reduced risk to a greater extent (P for trend <.00001). Use for 15 years or more lowered a woman's risk of ovarian cancer by 58% (RR 0.42); use for 10 to 14 years cut risk by 44% (RR 0.56); 5 to 9 years of use cut risk by 36% (RR 0.64); and even use for only 1 to 4 years reduced risk by 22% (RR 0.78).
Oral contraceptives reduced incidence of serous, clear cell, and endometrioid cancers to a similar degree but had no significant effect on mucinous ovarian cancers.
The degree of protection offered by the pill appeared to lessen the longer it had been since a woman last took it. Nevertheless, the protective effect of oral contraception was significant even 30 or more years after use stopped (RR 0.86).
The study also examined the role of estrogen levels in oral contraceptives. Even though the amount of estrogen used in birth control pills lessened between 1960 and 1980, the researchers did not see a different level of risk reduction.
Based on these data, the researchers estimated that 200,000 ovarian cancer cases and 100,000 deaths worldwide have been prevented by oral contraceptive use during the past 50 years and that if use remains at the current level, as many as 30,000 ovarian cancers a year could be prevented.
However, while oral contraceptive use could reduce a woman's risk of ovarian cancer by almost 50%, it is not recommended for all women.
"Ovarian cancer prevention is only one consideration to take into account when balancing the risks and benefits of oral contraceptives," says Carmen Rodriguez, MD, MPH, Strategic Director, Biospecimen Repository, ACS, and one of the study coinvestigators. "There are cardiovascular disease contraindications that should be discussed between women and their doctors. Pill use would certainly be contradicted among smokers or women with hypertension."
Oral contraceptives also have been shown to slightly and temporarily increase the risk for both breast and cervical cancers.
"However, oral contraceptive use is the strongest modifiable risk factor that can reduce the likelihood of being diagnosed with ovarian cancer, and it should be at least mentioned to women if they are considering their use for birth control," Rodriguez says.
A second study by Harvard University researchers suggests caffeine intake might affect ovarian cancer risk, particularly in women who have never used oral contraceptives. Although the finding is preliminary, it merits further study, they say.
The researchers analyzed data from the Nurses' Health Study to look for associations among cigarette smoking, alcohol use, and caffeine intake (measured by the cups of coffee, tea, or cola consumed in a week) and the likelihood a woman might develop ovarian cancer. They assessed the relationship between smoking status and ovarian cancer among 110,454 women and examined the records of 80,253 women for links between alcohol and caffeine use.
The results, published in Cancer (2008;112:1–9) showed that cigarette smoking had no significant effect on ovarian cancer incidence overall, although there was a higher risk for mucinous ovarian cancers. Researchers did not detect any association with alcohol use.
On the other hand, caffeine intake was significantly associated with lower incidence, but only in women who had never used oral contraceptives or postmenopausal hormone therapy. RR for the top quintile of caffeine intake versus the bottom quintile was 0.65 among women who never used oral contraceptives and 0.57 among postmenopausal women who never used hormone therapy.
Although tantalizing, the researchers say their finding of a lower risk associated with caffeine should be interpreted with caution, and other experts agree.
"The findings regarding caffeine are interesting as a biological hypothesis, but women should not increase caffeine intake until we know more about its role. So far, the strongest modifiable factor for preventing ovarian cancer is oral contraceptive use," says Rodriguez.
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | COVER ARCHIVE | SEARCH | TABLE OF CONTENTS |
