More accurate than MRI measurement of tumor size in breast cancer by using the peri-tumoral halo uptake layer method of the 18F-FDG PET/CT scan.

OBJECTIVE: To evaluate the reliability of a method using the peri-tumoral halo layer (PHL) for assessing tumor size in breast cancer patients on the fluorine-18-fluorodeoxy glucose positron emission tomography/computed tomography (18F-FDG PET/CT) scan compared to MRI and pathology. SUBJECTS AND METHODS: Among 121 patients with breast cancer who underwent both 18F-FDG PET/CT and MRI between March 2013 and June 2016, 59 patients were included in this study. Exclusion criteria were as follows: history of neoadjuvant therapy, history of pre-operative mammotome, insufficient pathologic/radiologic size report, clustered tumor, positive tumor resection margin, 18F-FDG non-avid tumor. The PHL was examined by two nuclear medicine physicians. Tumor sizes (longest diameters) on 18F-FDG PET/CT were estimated using margins defined as the inner line of the PHL. Pathologic tumor sizes were utilized as reference standards. RESULTS: The PHL of each tumor was most commonly designated as the 20%-30% band of the maximum standardized uptake value (SUVmax) it exhibited an inverse correlation with tumor SUVmax. Tumor size on 18F-FDG PET/CT showed a more linear correlation with pathology than that on MRI (r2=0.91 vs 0.65). In Bland-Altman analysis, 18F-FDG PET/CT showed significantly lower bias in size difference relative to pathology, compared with MRI (0.6±9.6cm vs. -1.9±17.3cm). Fluorine-18-FDG PET/CT showed more accurate T staging with pathology, especially in T3 cases, than MRI. CONCLUSION: A method of tumor size determination, using PHL on 18F-FDG PET/CT, showed more linear relationship and smaller size differences with pathology than MRI (average 0.6 vs. 1.9cm). It provides sufficient reliability and reproducibility for measuring tumor size in breast cancer.

Follow-up bone scan in breast cancer patients: what is the appropriate interpretation of purely rib uptake?

AIM: Although rib uptake is frequently detected in follow-up bone scans of breast cancer patients, few studies have assessed its clinical significance. PATIENTS AND METHODS: Among 1208 breast cancer patients who underwent a bone scan between 2011 and 2014, 157 patients presented with newly detected rib uptake at follow-up. Patients who had underlying bone metastases (n=8) or had simultaneous new uptake in sites other than the rib (n=13) were excluded. The patients enrolled finally were those who had purely rib uptakes. The location, intensity, and final diagnosis of the uptake were evaluated by nuclear medicine physicians. RESULTS: A total of 275 new instances of rib uptake were detected in follow-up bone scans of 136 patients. These were more frequently located on the ipsilateral side of the breast cancer (61.1%) and the anterior arc (65.1%), and they presented as moderate to intense (93.1%) uptakes. Among these, 265 lesions in 130 patients turned out to be benign fractures (96.4%), whereas only 10 lesions in six patients were metastases. The proportion of metastases was significantly higher if the uptake was linear or if the patient had recurrence. It was marginally higher if the uptake was located in the posterior arc. The proportion of metastases within the radiation field was significantly lower in patients with a history of irradiation. CONCLUSION: Newly detected purely rib uptake on a follow-up bone scan in patients who have been treated for breast cancer is mostly because of fractures and rarely signals metastasis. However, if the patient has disease recurrence, metastasis should strongly be suspected, particularly when uptake is linear or located in the posterior arc.