Left Breast cancer 0.8 cm with lumpectomy done. 1 sentinel lymph nodes

Treatment Plan: For this 51-year-old postmenopausal woman with a small (0.8 cm) invasive hormone receptor-positive, HER2-negative breast cancer, low proliferation index (Ki-67 of 3%), one positive sentinel lymph node, and a low Oncotype DX Recurrence Score of 9 indicating low risk, chemotherapy is not indicated as it is unlikely to provide benefit NICE NG101 Sehdev et al. 2026. She has undergone breast-conserving surgery (lumpectomy) and radiotherapy, which are appropriate local treatments NICE NG101 Hong & Xu 2022.

Endocrine Therapy: The current endocrine treatment is appropriate: she completed 3.5 years of tamoxifen and recently transitioned to an aromatase inhibitor (AI), reflecting standard practice to optimize adjuvant endocrine therapy in postmenopausal women with estrogen receptor (ER) positive disease NICE NG101 Sehdev et al. 2026. Continuing AI therapy to complete at least 5 years of endocrine treatment is recommended to reduce recurrence risk NICE NG101 Hong & Xu 2022. Given her high ER (270/300) and progesterone receptor (PR) (285/300) expression and low Ki-67, she likely has luminal A-like biology, which is associated with excellent prognosis on endocrine therapy alone NICE NG101,Höller et al. 2023 Sehdev et al. 2026 Höller et al. 2023.

Use of CDK4/6 Inhibitors: CDK4/6 inhibitors (e.g., abemaciclib or ribociclib) in the adjuvant setting are currently recommended for patients at high risk of recurrence, often defined as having ≥4 positive nodes, larger tumors (≥5 cm), higher grade, or Ki-67 ≥20% NICE NG101 Sehdev et al. 2026. This patient’s tumor is small, low grade with Ki-67 at 3%, and only one positive sentinel node, and her low Recurrence Score further supports her low risk status. Therefore, adjuvant CDK4/6 inhibitor therapy is not indicated or routinely recommended in her case NICE NG101 Sehdev et al. 2026. Limited benefit would be expected given her tumor and clinical features.

Additional Adjuvant Therapies: Given postmenopausal status and node-positive disease, consideration of adjuvant bisphosphonate therapy (e.g., zoledronic acid) to reduce the risk of bone recurrence and improve survival is recommended after discussing benefits and risks with the patient NICE NG101 Sehdev et al. 2026. There is no indication for BRCA or PARP inhibitor therapy unless germline mutations are identified.

Summary: In summary, the appropriate treatment plan for this patient is to continue endocrine therapy with the aromatase inhibitor to complete at least 5 years of adjuvant endocrine treatment, without chemotherapy or CDK4/6 inhibitor given her low risk by clinical and genomic criteria, plus adjuvant bisphosphonates consideration NICE NG101 Sehdev et al. 2026. Close clinical follow-up and support for adherence and management of endocrine therapy side effects should be provided. Enrollment in clinical trials could be considered if available.