Capecitabine and Radiotherapy in the Adjuvant Treatment of Resistant Breast Cancer

Inclusion Criteria:

* Patients with histologically confirmed non-metastatic invasive breast cancer who will be undergoing neoadjuvant chemotherapy and have persistent disease at time of definitive surgery

  * Tumors must have ER/PR/HER2 status reported by available pathology report(s)
  * Both triple negative and hormone receptor positive patients are eligible for enrollment
* Completion of neoadjuvant chemotherapy

  * May not include capecitabine or 5-FU containing regimens
  * Resolution of adverse events from neoadjuvant chemotherapy including biochemical/hematologic to CTCAE v5.0 grade 1 or below (except alopecia) prior to initiation of study therapy
  * Recovery time between surgery and study therapy ≥ 4 weeks.
* Persistent invasive disease following neoadjuvant chemotherapy in either the breast, lymph node, or both ). Any residual tumor; lack of complete pathologic response.
* Patients planning to receive adjuvant radiation to the breast and/or regional nodes.
* Patients planning to receive capecitabine per the treating physician

Patients already receiving capecitabine as adjuvant therapy are eligible to enroll in this study, provided adverse events deemed by the treating physician as possibly, probably or definitely related to adjuvant capecitabine prior to study therapy have resolved to CTCAE v.5.0 grade 1 or below (except alopecia), and provided duration of planned capecitabine includes entire duration of planned radiotherapy.

* ECOG performance status 0 or 1
* Tamoxifen: patients who have received Tamoxifen as chemoprevention are still eligible.

Endocrine receptor therapies (Hormone receptor inhibitors) may not be given with study treatment.

* . Patients who have had radiation to the contralateral breast are eligible.
* Ability to understand and the willingness to sign a written informed consent document.

Exclusion Criteria:

* Pregnant or lactating females. Women who are pregnant or who become pregnant are excluded from this study because capecitabine is a chemotherapeutic agent with the potential for teratogenic or abortifacient effects. Because there is an unknown but potential risk for adverse events in nursing infants secondary to treatment of the mother with capecitabine, breastfeeding should be discontinued if the mother is treated with capecitabine. These potential risks may also apply to radiotherapy used in this study.
* Serious medical or psychiatric illness that in the judgement of the treating physician places the patient at risk \& would limit compliance with the study requirements.
* Inability to swallow or retain whole pills.
* Patients with known or suspected allergy to capecitabine or 5-FU.
* Contraindications to capecitabine or radiotherapy as determined by the treating physician including severe renal impairment (GFR \< 30).
* Prior radiation to the ipsilateral breast.