Plain-English translation of NCT03804944 on ClinicalTrials.gov ↗ · Source last updated · Translation generated · How we translate trials
Read our Breast Cancer research guide →Phase 2 — Testing in a bigger group (up to a few hundred people) to see if the treatment actually works and is still safe.
This clinical trial is testing whether combining focused radiation therapy with one or more new immune-boosting treatments can help prepare hormone-receptor-positive breast cancer for surgery. Researchers are evaluating four different treatment combinations, some using a medication called pembrolizumab (an immune checkpoint inhibitor), others using an experimental immune-boosting injection called FLT3L, and some combining both. All participants will also receive a hormone therapy medication called letrozole and radiation therapy to the breast tumor.
Current treatments for hormone-receptor-positive breast cancer don't work equally well for all patients. This trial is exploring whether combining radiation therapy with new immune-based treatments can make the cancer more responsive to surgery and potentially improve long-term outcomes.
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You will be randomly assigned to one of four treatment groups. All participants receive radiation therapy to the breast tumor over three days in week two, plus a daily hormone pill (letrozole) for four months. Depending on your group, you may also receive a series of self-injected immune-boosting treatments in week one and/or an intravenous immune medication every three weeks. After four months of treatment, you will have breast surgery. The entire study lasts five months, including one month of follow-up visits after your surgery.
AI-generated summary from trial data · Jun 9, 2026 · Not medical advice
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