Palbociclib Plus Letrozole for the Treatment of Metastatic Breast Cancer: An Illustrative Case Scenario

CASE STUDY Betty, a 66-year-old white female, was diagnosed with stage IIB, T2N1M0, estrogen receptor/progesterone receptor–positive, HER2-negative breast cancer in 2007. It was detected on screening mammography when she was age 59, and she was confirmed to be postmenopausal at the time. She has no family history of breast cancer. Betty has never smoked but enjoys drinking alcohol, normally with dinner and typically limited to 1 drink of hard liquor per day. Her medical history includes type 2 diabetes mellitus and hypertension, which are adequately controlled with metformin and lisinopril. Betty is married and a retired teacher. She has four healthy adult children and five grandchildren. She noted that although she was always thin as a child, she was never able to lose the weight she gained during her pregnancies. Currently, her body mass index (BMI) is around 29 kg/m2. She enjoys ballroom dancing with her husband, gardening, and walking her dog and she is an active member at her church. Betty and her family were shocked to hear about her diagnosis. After a discussion with her oncologist, a treatment plan was devised. Her Eastern Cooperative Oncology Group performance status at diagnosis was 0. Initial treatment consisted of neoadjuvant chemotherapy with dose-dense doxorubicin/cyclophosphamide (AC) × 4 cycles followed by weekly paclitaxel × 12 cycles. Betty tolerated treatment relatively well. However, she was hospitalized once after cycle 3 of AC for neutropenic fever. Her subsequent cycle was followed with pegfilgrastim. Repeat imaging after AC treatment revealed a good overall response. Other adverse effects from treatment included fatigue and nausea for a few days after each cycle. Residual grade 1 neuropathy secondary to her treatment with paclitaxel, with a potential contribution from her history of diabetes, was a long-term complication. Following completion of her neoadjuvant therapy, she had a lumpectomy and then radiation therapy. Adjuvant endocrine therapy with the aromatase inhibitor (AI) anastrozole was given for 5 years, which she completed in late 2012. Bone health was monitored with dual-energy x-ray absorptiometry screening. Mild osteopenia was noted during AI therapy, and she was given twice-daily calcium plus vitamin D supplementation. Annual surveillance diagnostic breast mammography along with biannual history and physical examinations showed no signs of disease recurrence.