Since the introduction of hormonal contraceptives (birth control pills) in the 1960s, the risk of carcinoma (cancer risk) has also been a recurring topic of discussion, as estrogens and progestins are involved in the regulation and function of many organs that could form malignant tumors over a lifetime. The focus, as with postmenopausal hormone use* , is particularly on mammary carcinoma (breast cancer).
- For oral contraceptive use, except for breast carcinoma, there are sufficient analyses to provide a clear statement of risk [1, 2, LL1].
- For the use of progestogen monopreparations (oral, implant (hormonal implant; contraceptive sticks), intramuscular, intrauterine) appropriate studies are mostly missing, so that the effect is currently not clearly definable [2, LL1].
* Postmenopause is the last stage of menopause; begins twelve months after the last menstrual period (menopause).
Hormonal contraceptives and breast cancer risks
Based on current (2019) research, the risk of breast cancer appears (not unchallenged) to be increased by about 20% when combined oral contraceptives (COCs) are used while taking them until about five years afterward. 5-10 years after discontinuation, the risk has normalized, i.e., the incidence is equivalent to that of women who never took hormonal contraceptives. The most recent research on this comes from a Danish prospective cohort study of 1.8 million women aged 15-49 years published in 2018. There are no conclusive studies on the risk of progestins contained in contraceptives, in contrast to hormone therapy in postmenopause (see above ). The same applies to progestin monotherapy, see above. When using an intrauterine device (“IUD”) with levonorgestrel, the risk was increased to 1.2 OR (odds ratio) in the Danish study. At the moment, no definitive conclusion can be drawn from this. The current position is that further studies in larger cohorts are needed to draw a clear conclusion [2, 3, 4, LL1]; however, a risk cannot be ruled out for progestin monopreparations either. Hormonal contraceptives and breast cancer recurrence risk.
In breast cancer patients undergoing therapy (chemotherapy, radiotherapy, postoperative), safe contraception is absolutely essential. However, there are no conclusive studies on whether combined oral contraceptives (COCs) or progestin monopreparations increase the risk of recurrence (recurrence of the disease) in post-mammary carcinoma condition. Current recommendations are as follows.
- Guideline 2019 [LL1]: method of choice: copper IUD.
- Centers for Disease Control and Prevention: method of choice: copper IUD even after five years with no evidence of recurrence (reoccurrence of disease)
- WHO: category → 4: contraindication (contraindications) for
- Hormonal combination preparations (oral, transdermal, vaginal).
- Progestogen monopreparations (oral, implant, intramuscular, intrauterine).
WHO categories: 1 = fully recommended; 2 = benefit > risk; 3 = risk ≥ benefit (relative contraindications); 4 = unacceptable risk (absolute contraindication).
Hormonal contraceptives and ovarian cancer
Unanimous are the results of many studies that oral contraceptives lead to a risk reduction of 30-50% for the development of ovarian cancer (ovarian cancer). This effect depends on the duration of use and is detectable for up to 30 years after discontinuation of hormonal contraceptives, but gradually decreases after about ten years [1, 5, LL1].The risk-reducing effect also applies to women with a mutation of the BRCA1 or BRCA2 gene (components of a repair system for DNA double-strand breaks whose task is to prevent cancer). Whether the protective effect (protective effect) is also detectable with the levonorgestrel-containing IUD is currently assessed differently.Other progestin monotherapy types do not appear to have a protective effect, but neither do they have a negative effect.
Hormonal contraceptives and cervical cancer
Studies have been inconsistent. Most cohort and case-control studies, however, conclude that there is a substantial risk of cervical cancer.This risk increases with time and persists for up to 20 years after discontinuation [Review: 1, LL 1].
Hormonal contraception and endometrial cancer
The available studies uniformly show a reduction of at least 30% in the risk of corpus carcinoma (cancer of the uterine corpus; cancer of the endometrium) with the use of hormonal contraceptives, in contrast to women who have never used oral contraceptives. The risk-reducing effect is associated with duration of use and persists for many years after hormones are discontinued [review: 1, LL1].
Hormonal contraceptives and colon cancer
Available cohort and case-control studies, as well as meta-analyses, uniformly show a significant 15-20% risk reduction for colon cancer (colorectal cancer) with hormonal contraceptive use [Review: 1, LL 1].
