The purpose of this research study is to determine the safety, tolerability and dose of Ribociclib when combined with adjuvant radiation in women with high-risk ER+ breast cancer.
Once enrolled on study, patients will begin treatment with Ribociclib 400 mg daily at the same time as they initiate standard of care adjuvant radiation therapy- 50 Gy in 25 fractions or 42.56 Gy in 16 fractions +/- 10 Gy boost including comprehensive nodal. Paitents will continue treatment with Ribociclib for up to 6 weeks.
ER and/or PR-positive (≥ 1% positivity as determined by local pathology laboratory), HER2-negative breast cancer with > 3 lymph nodes involved on sentinel lymph node biopsy (SLNB) or axillary lymph node dissection (ALND) OR have between 1-3 lymph nodes involved AND have T3 disease OR have between 1-3 lymph nodes involved and grade 3 breast cancer.
Age ≥ 18
Patients must have undergone gross total excision of all locoregional disease with negative margins (i.e. no tumor on ink). At least 21 days must elapse between surgical treatment for breast cancer and initiation of study treatment.
Patients must have completed chemotherapy (either in neoadjuvant or adjuvant setting). If received adjuvant chemotherapy, chemotherapy must have completed at least 21 days prior to initiation of study treatment.
Prior history of radiation therapy to the chest wall and/or regional nodes is not allowed (but prior radiation therapy to other sites is permissible).
Prior history of CDK4/6 inhibitor therapy.
Patients who are pregnant or breastfeeding.
Patient with distant metastases of breast cancer beyond regional lymph nodes and/or evidence of breast cancer recurrence prior to study enrollment.