Positron emission tomography and sentinel lymph node dissection in breast cancer

Sentinel lymph node dissection (SLND) is emerging as the preferred method of axillary staging for breast cancer patients. To further the use of noninvasive techniques in breast cancer, positron emission tomography (PET) scans have been considered as an alternative axillary staging modality. In order to compare the 2 modalities, we studied 15 invasive breast cancer patients who had undergone a preoperative PET scan before sentinel lymphadenectomy. PET scans were compared to axillary pathology results, which were defined as the greatest diameter of nodal metastases. Primary tumor sizes ranged from 0.5 cm to 5.0 cm (median,1.5 cm) and all were ductal in origin except for 1 invasive lobular and 1 mucinous carcinoma. Ten women had completion axillary dissections. Sentinel lymph node dissection was successful in all patients with completion dissections and no false-negative results. Five patients had sentinel node metastases, but PET scans identified only 1 of these patients, resulting in 4 false-negative PET scans. Missed metastases ranged in size from a micrometastatic focus identified only by immunohistochemistry to a nodal tumor measuring 11 mm in diameter. In addition, 1 woman with a PET-positive axilla was tumor free by SLND and remains free of axillary recurrence 29 months postoperatively. Two women had mediastinal uptake by PET scanning and were found to be tumor free after computerized tomography. The results of this preliminary study suggest that PET scanning using current techniques can be used as an adjunct to SLND rather than as an alternative staging technique.