This study investigates the safety and side effects of combining an investigational medication with radiation for treating women with breast cancer. Specifically, it focuses on women who still have cancer in their breast or underarm lymph nodes after receiving chemotherapy before surgery. The study aims to find out how many participants can handle the treatment safely and to determine the maximum dose that can be tolerated.

Participants in the study will undergo procedures that include receiving a combination of the investigational medication and radiation therapy. The study will monitor participants for any side effects and their intensity at different dosing levels to ensure safety.

• Who can participate: Women with confirmed adenocarcinoma of the breast and nodal metastasis who have not received prior radiation therapy to the affected breast are eligible. Participants must have a performance status of 0 or 1 by ECOG criteria and should not have any serious medical or psychiatric illness that prevents informed consent. Additionally, participants need a Medical Oncology consult and a recommendation for neoadjuvant chemotherapy to meet eligibility criteria.
• Study details: Participants will receive a combination of the investigational medication and radiation therapy. The study will assess the safety of this combination and monitor for side effects. A placebo is not used in this study.