Does the Levonorgestrel IUD Increase Cancer Risk?
No, the levonorgestrel IUD does not increase overall cancer risk and actually provides significant protection against several gynecologic cancers, though recent evidence suggests a small increased risk of breast cancer that must be weighed against substantial benefits.
Breast Cancer Risk
The most recent and highest quality evidence shows a modest association with breast cancer:
- A 2024 Swedish national cohort study of over 500,000 women found LNG-IUD use was associated with a 13% increased risk of breast cancer (adjusted HR 1.13,95% CI 1.10-1.17) 1
- This risk was particularly notable in women with a family history of breast cancer, showing a 19% relative excess risk for interaction and 1.63 additional cases per 10,000 person-years 1
- However, earlier studies from 2018 and 2011 found no increased breast cancer risk, with relative risks approaching unity 2, 3
- The 2010 CDC guidelines classify current breast cancer as category 4 (unacceptable health risk) for LNG-IUD initiation, noting that breast cancer is a hormonally sensitive tumor, though concerns about progression may be less with LNG-IUDs than with combined oral contraceptives 4
Clinical caveat: The observed breast cancer effect is small, and the 2024 study is limited by its observational design 1. Close monitoring is advisable for women with family history of breast cancer 1.
Protective Effects Against Gynecologic Cancers
The LNG-IUD provides substantial protection against multiple gynecologic malignancies:
Endometrial Cancer
- The 2024 Swedish study found a 33% reduced risk of endometrial cancer (adjusted HR 0.67,95% CI 0.56-0.80) 1
- A 2018 Norwegian study showed an even stronger 78% risk reduction (RR 0.22,95% CI 0.13-0.40) 2
- The CDC guidelines classify LNG-IUD as category 1 (no restriction) for women with endometrial hyperplasia, with evidence showing disease regression in most women 4
Ovarian Cancer
- The 2024 Swedish study demonstrated a 14% reduced risk of ovarian cancer (adjusted HR 0.86,95% CI 0.75-0.99) 1
- The 2018 Norwegian study found a 47% risk reduction (RR 0.53,95% CI 0.32-0.88) 2
- A 2016 Finnish study showed decreased risk for multiple ovarian cancer subtypes including mucinous (SIR 0.49), endometrioid (SIR 0.55), and serous carcinomas (SIR 0.75) 5
- The CDC guidelines classify LNG-IUD as category 1 for women with benign ovarian tumors 4, 6
Cervical Cancer
- The 2024 Swedish study found a 9% reduced risk of cervical cancer (adjusted HR 0.91,95% CI 0.84-0.99) 1
- However, the CDC guidelines note a theoretical concern that LNG-IUDs might enhance progression of cervical intraepithelial neoplasia, classifying it as category 2 (advantages generally outweigh risks) 4
- For women with cervical cancer awaiting treatment, initiation is category 4 due to infection and bleeding risks 4
Clinical Recommendations for Cancer Contexts
Women with Active Cancer
- The Society of Family Planning recommends IUDs as preferred first-line contraception for women with history of breast cancer 4
- For women on tamoxifen, LNG-IUD may be preferable as it reduces tamoxifen-induced endometrial changes without increasing breast cancer recurrence risk 4
- Combined hormonal contraceptives should be avoided in women with active cancer or treated within the past 6 months due to VTE risk 4
Women with Cancer History
- LNG-IUD is classified as category 3 (risks usually outweigh benefits) for women with past breast cancer and no evidence of disease for 5 years 4
- For ovarian cancer survivors undergoing fertility-sparing treatment, IUDs are category 1 4
Risk-Benefit Algorithm
For women considering LNG-IUD:
Strong family history of breast cancer: Counsel about the small increased breast cancer risk (1.63 additional cases per 10,000 person-years) and consider enhanced surveillance 1
Risk factors for endometrial or ovarian cancer: LNG-IUD provides substantial protection and should be strongly considered 1, 2
Active breast cancer: Contraindicated for initiation (category 4) 4
Breast cancer history >5 years disease-free: Use with caution (category 3), weighing individual circumstances 4
Other gynecologic cancers: Generally acceptable with appropriate timing relative to treatment 4
The overall cancer profile favors LNG-IUD use for most women, with significant reductions in endometrial and ovarian cancer risk outweighing the small breast cancer association in the general population 1, 2.