Comparing Hormone Therapy With and Without Chemotherapy for Premenopausal Breast Cancer (OFSET)

About the Study

This phase 3 study is for premenopausal people with early-stage ER-positive/HER2-negative breast cancer. The study is testing whether adding chemotherapy after surgery to standard ovarian function suppression (aromatase inhibitor) and endocrine (hormone) therapy can help prevent breast cancer from coming back in younger women with early-stage disease. All participants will receive an aromatase inhibitor plus hormone therapy, and some will also receive chemotherapy. Researchers will also collect health information and medical records to see how the different treatments affect long-term results. The goal is to help doctors choose the safest and most effective treatment for younger women with breast cancer.

What the Study Involves

If you join this study, you will receive an aromatase inhibitor and endocrine (hormone) therapy to lower estrogen levels. You will be assigned to one of two groups:

• Group 1: Aromatase inhibitor plus hormone therapy alone
• Group 2: Chemotherapy plus an aromatase inhibitor and hormone therapy

Both groups will attend regular follow-up visits, tests, and monitoring to check their health.

You may be able to take part in this study if ALL of the following apply to you:

• You can understand and sign the consent form (or have someone who can)
  • If you are in the U.S., you will need to allow the study team to review your medical records
• Are 18 to 60, female, and premenopausal
• You are well enough to do most daily activities
• You have early-stage breast cancer that:
  • Has been treated with surgery (lumpectomy or mastectomy)
  • Has had lymph nodes checked
  • Is hormone receptor-positive and HER2-negative
  • Has an Oncotype DX 21-gene Recurrence Score within the study range (16–25 if no lymph nodes are involved, or 0–25 if 1 lymph node is involved
• It has been 16 weeks or less since your last surgery
  • You have had little or no hormone therapy before joining

You would NOT be able to join this study if you:

• Have metastatic breast cancer that has spread  to other parts of the body
• Had invasive breast cancer in the past
• Have serious health conditions (including heart problems) or abnormal lab results that could affect your safety
• Have already received treatment for this cancer (such as chemotherapy or radiation)
• Are using hormonal birth control
• Have active hepatitis B or C that is not well controlled
• Are pregnant or breastfeeding
• Have any other condition that, in your doctor’s opinion, would make it unsafe to participate