PET-CT for Early-Stage Breast Cancer

Although most patients with clinically node-negative, early-stage breast cancer do not undergo radiologic imaging to detect metastatic disease, patients with locally advanced disease typically undergo radiologic evaluation with bone scan and computed tomography (CT) of the chest, abdomen, and pelvis to confirm that a curative-intent strategy, including local therapy, should be recommended. Some clinicians advocate the use of positron emission tomography-CT (PET-CT) as a better tool to detect metastatic disease.

Canadian investigators conducted a randomized trial comparing ¹⁸F-labeled fluorodeoxyglucose PET-CT to conventional staging (bone scan, CT of the chest, abdomen, and pelvis) in 369 patients with clinical stage III (T0N2, T1N2, T2N2, T3N1,2 or T4) or IIb (T3N0, not T2N1) disease who were being considered for curative-intent therapy including surgery, radiation and systemic therapy. Due to concerns regarding PET's avidity for lobular cancers, only ductal carcinomas were included.

Overall, 23% of patients in the PET-CT arm were upstaged to stage IV disease compared with 11% in the conventional arm (absolute difference, 12.3%; P=0.002). As a result, treatment was changed in 81.3% of upstaged patients in the PET-CT arm and 95.2% in the conventional arm. PET-CT detected more distant metastases than conventional staging, and fewer patients in the PET-CT arm received combined modality therapy (absolute difference, 8.2%).

Interestingly, most of the occult metastatic disease was located in bone, and PET-CT was more sensitive in patients with estrogen receptor (ER)+ disease than in those with ER− disease. Upstaging in the small subset of patients with inflammatory breast cancer was similar with the two approaches. Patients who were upstaged largely were directed to palliative systemic therapy without a goal of cure, thus avoiding surgery and radiation therapy.