The A metanalysis of cohort study involving 11722 cases

Thestudy “Contemporary hormonal contraception and the risk of breast cancer” is anationwide large prospective study conducted in Denmark involving all women between15 to 49 years to find the association of modern day hormonal contraceptives andrisk of breast cancer. In this study 1.

8 million women were followed for 10.9 years.Denmark nationwide registries provided individually updated informationof hormonal contraception, breast-cancer diagnoses, and potential confounders. The study documented 11517 casesof breast cancer in this population during the study period.   Thefindings of the study are  – 20 %higher risk of breast cancer in women who are current or recent users ofhormonal contraception.-Riskincreased with duration of use of hormonal contraception from 9% in females whoused for 1 year to 38 % in women who used for more than 10 years.

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– Allhormonal contraception methods including progesterone only IUD showed increasedrisk when compared with never users. – Therisk persisted even after stopping hormonal contraception in patients who havetaken it for more than 5 years.-Theabsolute increase in breast cancer among current and recent hormonalcontraceptive user was 13 /100000 person’s years or one extra breast cancer forevery 7690 hormonal contraceptive users in 1 year.

Theauthors concluded that hormonal contraceptives are associated with increasedrisk of breast cancer but the absolute increase in risk is small. Comment:Why thestudy is important?Hormonalcontraception (pills, hormonal IUD, injections) is reliable form ofcontraception with less failure rates.  Cancerrisk remains a concern with long term use of hormonal contraception.  To answer this, a large cohort study reporteda significant lower rates of large bowel, uterine body and ovarian cancers, andincreasing risk trends towards cervical and CNS tumors with long term hormonalcontraceptive users. Incidence ofbreast cancer was similar in pill users and never users in that study. (2) A metanalysis of cohort study involving 11722 cases and over850000 women reported non-significant increase in breast cancer in ever usersof oral contraceptives compared with non users (RR1.08 CI 0.99-1.

17) .(3) A recent study fromThailand showed that oral contraceptives might increase risk ofbreast cancer.(4) There is no data onmodern day hormonal contraception which were considered safer options inregards to cancer risk.

The study was conducted to answer if current hormonalformulations increased risk of breast cancer.What are the messages from the study?The present study gains importance by addingsignificant data on current hormonal contraceptives including low estrogenpills, progesterone only pills and their breast cancer risk for which evidencewas lacking and one can conclude that no present day formulation of hormonalcontraception is free of breast cancer risk . Secondly the persistent risk in woman who usedhormonal contraception for more than 5 years is also an additional input toexisting data.  Lastly the study showed how a large informativeresearch is possible in relatively low cost to address common but importantquestions when nationwide registries for medicines, cancer are maintained andare linked with each other.Critical review:            Limitations of study include factorslike age at menarche, breast feeding, alcohol consumption or physical activity,environmental and dietary factors was not adjusted.

The absolute risk of breast cancer will be determined by thewoman’s individual baseline risk which includes above factors. Authorsexplained decrease in incidence of breast cancer in patients who stoppedhormonal contraception within 5 years is not expected if these risk factorsacted as confounders. Weather these factors influence risk in long term usersis unknown.

Marsden  reported that excess risk  associated with hormonal contraceptive issmall and comparable with risk by other modifiable risk factors like smoking,alcohol consumption , age at first birth etc. for hormone sensitive breastcancer in premenopausal women.(5)     Though thereis increased risk in breast cancer, there is no evidence till date thatcontraceptive use leads to increased breast cancer specific mortality whencompared with never users.   Contraceptiveusers tend to be more health conscious and likely to seek medical attention earlywhen they have breast symptoms can lead to many early breast cancer diagnosisin this group theoretically.

  Weather this increased risk is associated withadvanced disease stage or increased disease specific mortality in contraceptiveusers’ needs to be answered. Implications in Indian scenario:InIndia the incidence of breast cancer is 25.8 per 100000. The data of NationalFamily Health Survey 4 have shown only 53.

5 % of population use some of contraception.  Unlike Denmark where 39% woman inreproductive age group uses hormonal contraception, only 4.1% in India usehormonal pills.  (6).

The population at risk of breastcancer due to oral contraception in our country is smaller when compared to westernworld. The  advantages ofcontraception  such as good efficacy inavoiding unwanted pregnancy , reduced risk of certain malignancy likecolorectal , endometrial should also be considered before counseling thepatient regarding contraception . UK Medical Eligibility criteria (UKMEC) recommendations are based onevidence and consensus opinion, which assists clinicians in prescribing safeand suitable contraception .It recommends considering the individual absoluterisk in women with high risk before advising contraception.               In conclusion clinicians should use the data of the study to discussthe advantages and disadvantages of hormonal and nonhormonal contraceptivemethods (condom, diaphragm, copper IUD) and help women to take informeddecision on contraceptive method most consistent with her lifestyle withminimal side effects.