Is Mirena (levonorgestrel) safe for patients with breast cancer?

Safety of Mirena (Levonorgestrel IUD) in Breast Cancer Patients

The levonorgestrel-releasing intrauterine system (Mirena) is generally not recommended for patients with breast cancer due to concerns about hormonal effects and potential increased risk of breast cancer recurrence.

Current Guidelines on Contraception in Breast Cancer Patients

• The European School of Oncology-European Society for Medical Oncology (ESO-ESMO) guidelines explicitly state that hormonal contraception is generally contraindicated in breast cancer survivors 1
• Alternative non-hormonal contraceptive methods should be considered first-line, including:
  • Barrier methods (condoms, cervical diaphragm) 1
  • Copper IUDs (non-hormonal) 1
  • Male contraception options 1

Evidence on Levonorgestrel IUD (Mirena) in Breast Cancer Patients

• The safety of levonorgestrel-releasing IUD in breast cancer patients remains controversial 1
• A meta-analysis of three randomized clinical trials assessing Mirena's efficacy in preventing tamoxifen-induced endometrial lesions did not show an increased incidence of breast cancer recurrence 1
• However, a large epidemiological study suggested that Mirena use may increase the risk of developing breast cancer 1
• A 2020 systematic review and meta-analysis found increased breast cancer risk in LNG-IUS users regardless of age and indication (OR = 1.16,95% CI 1.06-1.28) 2
• A recent 2024 Swedish national cohort study found Mirena was associated with a 13% higher risk of breast cancer (adjusted HR, 1.13; 95% CI, 1.10-1.17) 3

Hormonal Considerations in Breast Cancer Patients

• For patients with hormone receptor-positive breast cancer, endocrine therapy is the preferred treatment option 1
• Adding hormonal contraception could potentially interfere with endocrine therapy or increase recurrence risk 1
• The American Society of Clinical Oncology (ASCO) guidelines emphasize that hormone receptor-positive breast cancers represent the majority of breast cancers worldwide and are treated with endocrine therapy 1

Alternative Contraceptive Options for Breast Cancer Patients

• Non-hormonal contraception methods are strongly preferred 1:
  • Copper IUD (non-hormonal) provides effective long-term contraception without hormonal effects
  • Barrier methods such as condoms and diaphragms with spermicide
  • Permanent methods like tubal ligation or vasectomy for those with no future pregnancy plans

Special Considerations for Sexual Health in Breast Cancer Patients

• Sexual dysfunction is a major issue for breast cancer patients, especially those on endocrine therapy 1
• First-choice treatments for vaginal symptoms include non-hormonal therapies:
  • Vaginal moisturizers 1
  • Lubricants and gels 1
  • Vaginal dilators for pain or stenosis 1
  • Pelvic floor physical therapy 1

Clinical Decision Algorithm

1. Assess hormone receptor status of the breast cancer:

   • For hormone receptor-positive breast cancer: Avoid Mirena due to potential hormonal effects 1
   • For hormone receptor-negative breast cancer: Still exercise caution, as recent evidence shows increased breast cancer risk with Mirena 2, 3

2. Consider patient-specific factors:

   • Time since diagnosis (risk may be higher with active disease) 4
   • Current endocrine therapy (potential interactions) 1
   • Family history of breast cancer (significant additive interaction observed) 3

3. Recommend contraceptive options in order of preference:

   • Copper IUD (non-hormonal) 1
   • Barrier methods 1
   • Permanent sterilization if appropriate 4
   • Mirena only as a last resort after thorough discussion of risks

Conclusion

Based on the most recent evidence from the 2024 Swedish national cohort study, Mirena is associated with a small but significant increased risk of breast cancer 3. While it may offer benefits for preventing endometrial issues, the potential breast cancer risk outweighs these benefits for breast cancer patients. Non-hormonal contraceptive methods should be strongly preferred in this population.