Ovarain Cancer and the Low-Dose Pill

Researchers looking at the risk of ovarian cancer in Pill users find an 81 percent risk reduction for women taking low-dose Pill brands (low levels of both estrogen and progestin):

NEW YORK (Reuters Health) - Oral contraceptives with low levels of estrogen and progestin reduce the risk of ovarian cancer even more than older versions of the "Pill," according to investigators at the University of Hawaii in Honolulu.

The benefits of oral contraceptive pills in protecting against ovarian cancer have long been recognized, Dr. Galina Lurie and her colleagues note in their report in the medical journal Obstetrics & Gynecology. However, over the last 30 years the doses of hormones in the pills have been decreased, to reduce side effects.

To see how this might have affected ovarian cancer risk, Lurie's group conducted a population-based study in Hawaii and Los Angeles involving 745 women diagnosed with ovarian cancer and a comparison group of 943 women matched by age and ethnicity and who were free of cancer.

Health information was collected by standard questionnaires, and interviewers used photo albums to help participants identify the specific oral contraceptive pills they had used.

Overall, women who had used any oral contraceptive had a 50 percent reduction in the risk of developing ovarian cancer than women who had never taken the Pill, the investigators report.

However, the risk was reduced by 38 percent for women who took high estrogen and high progestin pills, while the risk reduction was 81 percent for those taking pills with low levels of both hormones.

"Up to 42 percent of ovarian cancers might have been avoided if all women used some form of combined oral contraceptive pills," Lurie and her associates calculate.

Furthermore, they say, "An estimated 73 percent of ovarian cancers might have been avoided if all women used oral contraceptive pill formulation of low estrogen and low progestin."

One thing I'd like you to note is the methodology used:

Health information was collected by standard questionnaires, and interviewers used photo albums to help participants identify the specific oral contraceptive pills they had used.

There's nothing wrong with this method, but I want you to take a moment and think about its limitations [you should do that every time you read a study. It will help you better understand the conclusion.], and realize that this is not a definitive study.

For example, health info was collected via a questionnaire. What would've been a more accurate method? And what about showing the participants a photo album to identify Pill brands? What type of bias could this introduce?