Breast Cancer After Use of Estrogen Plus Progestin and Estrogen Alone: Analyses of Data From 2 WHI Randomized Clinical Trials

JAMA - open access

At a Glance

• We examined influences of menopausal hormone therapy on breast cancer incidence during intervention and early and late postintervention phases in the Women’s Health Initiative trials (13 years of follow-up)
  
  
• Estrogen plus progestin use significantly increased breast cancer incidence while patients were receiving the agents, but the hazard ratio (HR) decreased when the therapy was discontinued.
  
  
• An elevated HR persisted (HR, 1.37; 95% CI, 1.06-1.77) years after stopping combined hormone therapy.
  
  
• Use of estrogen alone significantly reduced breast cancer incidence.
  
  
• For estrogen alone, the reduction of breast cancer incidence persisted throughout the early postintervention phase but was lost during the late postintervention phase (HR, 1.17; 95% CI, 0.73-1.87) (P = .03).
  
   
  

  CONCLUSIONS

  ABSTRACT | INTRODUCTION | METHODS | RESULTS | DISCUSSION | CONCLUSIONS | ARTICLE INFORMATION | REFERENCES

   

  With longer follow-up of the 2 WHI hormone therapy trials, a complex pattern of changing year-to-year influences on breast cancer was observed. The ongoing influences on breast cancer after stopping hormone therapy in the WHI trials require recalibration of breast cancer risk and benefit calculation for both regimens, with greater adverse influence for estrogen and progestin use and somewhat greater benefit for use of estrogen alone.