Standard 99mTc-MDP planar bone scan and 18F bone scan. Anterior and posterior views showing increase in uptake in vertebra and left rib. Image source: Seattle Nuclear/Journal of Nuclear Medicine Technology

PET/CT may be superior in evaluating women with suspected metastatic breast cancer, as evidenced by the high rate of pathologically confirmed osseous metastases in women with positive PET/CT and negative bone scintigraphy results, according to a study published in this month's issue of the Journal of Clinical Oncology.

In this retrospective, single-institution study researchers compared the diagnostic performance of integrated FDG PET/CT and bone scintigraphy in women with suspected metastatic breast cancer (MBC) with bone biopsy/fine-needle aspiration results when available.

Patrick Morris, MD, from the breast cancer medicine service at Memorial Sloan-Kettering Cancer Center in New York City, and colleagues identified women with suspected MBC who were evaluated with PET/CT and BSc (within 30 days) between Jan. 1, 2003 and June 30, 2008 through institutional databases.

The researchers reviewed electronic medical records, and classified radiology reports as positive, negative or equivocal for osseous metastases. A nuclear medicine radiologist (blinded to correlative and clinical endpoints) reviewed all equivocal PET/CT and BSc images and reclassified some reports. Final PET/CT and bone scintigraphy classifications were compared. Baseline patient/tumor characteristics and bone pathology were recorded and compared to the final imaging results, according to Morris and colleagues.

The researchers identified 163 women who had a median age of 52 years. Of these 32 percent had locally advanced breast cancer, 42 percent had been diagnosed with breast cancer less than 12 weeks before identification.

Overall, PET/CT and bone scintigraphy were highly concordant for reporting osseous metastases with 81 percent of the studies--20 percent were positive and 61 percent were negative, wrote Morris and colleagues.

The results of the study showed that 19 percent were discordant. Twelve of these had pathology confirming osseous metastases: nine were PET/CT positive and bone scintigraphy negative; one was PET/CT positive and bone scintigraphy equivocal; and two were PET/CT equivocal and bone scintigraphy negative, according to Morris and colleagues.

PET/CT also conferred the additional advantage of identifying nonosseous metastases, thereby potentially obviating the need for additional imaging. In the study, 62 percent of patients with positive PET/CT had evidence of nonosseous metastases. Of these patients, 6 percent had equivocal bone scintigraphy and 42 percent had negative bone scintigraphy, wrote the authors.

However, Morris and colleagues cautioned that in a subgroup of breast cancer associated with strong expression of estrogen and progesterone receptors might lead to potentially lower standard uptake values on PET.

“This study supports the use of PET/CT in detecting osseous metastases for suspected MBC. Bone scintigraphy may potentially be avoided in most patients undergoing PET/CT for suspected skeletal metastases. These results indicate that a prospectively conducted study evaluating the sensitivity and specificity of PET/CT in women with suspected MBC is warranted,” concluded Morris and colleagues.