Efficacy of CDK4/6 Inhibitor in Treatment of Metastatic Breast Cancer and Colon Cancer

A 52-years old woman was diagnosed with an invasive left-sided ductal breast cancer, G3 – staged as T2N0M0; Estrogen (ER) 3+, Progesterone (PR) +, Human epidermal growth factor receptor 2 (HER 2) negative, Ki67-11%. She underwent a radical mastectomy, followed by adjuvant chemotherapy and hormone treatment with Tamoxifen. A year later she was diagnosed with a colorectal cancer-low grade, G1; histological results of adenocarcinoma - T3N1M1 with liver metastases. After a biopsy, which revealed that the metastases are coming from the breast (ER+/HER 2 (-) Breast cancer - (GATA (3+)), she was restaged as T3N1M0. The patient started treatment with Ribociclib 600mg/d + Letrozole 2,5mg/d with a partial response of the disease after three months of treatment. Due to G3 neutropenia, the dose was adjusted to 400 mg/d. Last restaging: October 2019 – complete response and a good quality of life. This case approves that the CDK (cyclin-dependent kinase) 4/6 inhibitors are able to manage visceral metastases and to provide long-term survival without worsening the quality of life. Her disease is successfully managed with CDK4/6 inhibitor together with hormonal therapy, which proves the effect of the CDK 4/6 inhibitors in treatment not only to breast cancer. Six months after there are no signs of relapse of the colon cancer. Despite the stage of the second cancer – T3N1M0, the patient did not undergo adjuvant treatment for the colon cancer.