Abstract
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Objectives PET-CT, which is a molecular imaging tool, can be a useful technique for assessing tumor proliferation activity and predicting the malignant potential of certain tumors. Thus, we aimed to compare 18F-FDG uptake on PET/CT to tumor histologic features and Ki-67 proliferation index, and further investigate whether a correlation exists.
Methods Between January 2012 and December 2014, 43 patients (mean age, 47.6 years) with histologically confirmed breast cancer were recruited. They all underwent 18F-FDG PET/CT for initial staging before therapy. All cases were assigned to one of two groups according to the clinicopathological variables: age (≤45 years vs. >45 years), tumor size (≤2 cm vs. >2 cm), axillary nodal status (negative vs. positive metastasis), histological type (invasive ductal and invasive lobular), and the Ki-67 proliferation index (≤20 % vs. >20 %). The SUVmax measurements between groups were compared, and its correlations with tumor size and Ki-67 proliferation index were also assessed.
Results The mean size of the invasive tumors was 2.4±0.8 cm (range: 0.9-5.8 cm), and 21 patients had pT1 lesions (≤ 2 cm). In 19 patients positive axillary lymph nodes were detected. Thirty patients had low Ki-67 scores and 13 patients had high Ki-67 scores. In addition, the histological findings revealed invasive ductal carcinoma (IDC) in 35 patients and invasive lobular carcinoma (ILC) in eight patients. The mean SUVmax of the 43 tumors was 9.8±4.3 (range: 2.6-29.4). The mean SUVmax value for tumors >2 cm was higher than that of tumors ≤2 cm (11.2±4.5 vs. 8.5±2.4, p<0.05). The mean SUVmax for high Ki-67 subgroup (13.1±5.2) was higher than that for low Ki-67 subgroup (9.1±3.7, p<0.05). However, these factors including age, nodal status and histologic type did not show a significant relationship with SUVmax (Table 1). Based on Spearman correlation analysis, a positive correlation between 18F-FDG uptake (SUVmax) and Ki-67 (Spearman’s rho=0.87, P=0.004) as well as tumor size (Spearman’s rho=0.65, P=0.001) was observed (Figure 1). However, Ki-67 was not correlated with tumor size (Spearman’s rho=0.15, P=0.65).
Conclusions 18F-FDG uptake on PET/CT correlates significantly with Ki-67 proliferation index and tumor size in breast cancer. It has a potential value for identifying more aggressive behavior. This study was supported by National Natural Science Foundation of China (Grant No. 81471692).
Table 1. Relationships between clinicopathological factors and SUVmax
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