By the numbers: Does circulating tumor cell enumeration have a role in metastatic breast cancer?

A 63-year-old postmenopausal woman was diagnosed with stage II (pT2N0M0), hormone receptor-positive, human epidermal growth factor receptor 2-negative breast cancer 9 years ago. Her treatment course included breast-conserving local therapy, four cycles of adjuvant chemotherapy with doxorubicin and cyclophosphamide, and 5 years of anastrozole. She developed persistent pain in the left hip 2 years after completing adjuvant endocrine therapy. Radiographic studies identified lesions in the left proximal femur and multiple vertebral bodies consistentwithskeletal metastases.Shestarted fulvestrant in addition tobone-modifyingtherapywithzoledronic acid. After 16 months, a nuclear medicine bone scan indicated likely progression in the bone metastases, prompting a switch to exemestane as second-line endocrine therapy. Six months later, a repeat bone scan identified new findings in the right humerus and scapula. Capecitabine was started as first-line chemotherapy at 1,500mgorally twice per day for 14 days on a 21-day cycle. The patient presents for a routine evaluation after three cycles of capecitabine and reports chronic waxing and waning discomfort in the left hip with weight bearing; left-sided-rib acute pain after she caught her grandson falling off the bed; and progressive dysesthesias, erythema, and capecitabine-related skin thickening and crackingonthe palms and soles.Arestaging bone scan reveals increased radiotracer activity in the left sixth ribandat theknownlesions in the righthumerusandright scapula.Computed tomography scans demonstrate increased focal sclerosis in the right scapula, indicative of either disease progression or treatment response. Plain radiographs identify a subtle fracture of the left sixth rib in the midclavicular line. Serum alkaline phosphatase is borderline increased, and the cancer antigen (CA) 27.29 has fluctuated in the range of 20 to 30U/mLsince she first presented with metastatic disease.Onthe basis of thenewleft rib discomfort and the bothersome toxicity from capecitabine, she inquires whether a change in systemic therapy is indicated.