18F-FDG retention index and biologic prognostic parameters in breast cancer

To analyze the correlation between [(18)F]-fluoro-2-deoxy-D-glucose (F-FDG) uptake assessed by positron emission tomography/computed tomography (PET/CT) in breast tumors and histopathologic and immunohistochemical prognostic factors.

Sixty-eight women with breast cancer were prospectively evaluated. PET/CT was requested in the initial staging previous to neoadjuvant chemotherapy (multicentric study).All the patients underwent a standard (18)F-FDG PET/CT followed by a delayed acquisition, 1 hour (PET-1) and 3 hours (PET-2) after FDG administration. Both examinations were evaluated qualitatively and semiquantitatively (SUV(max) values) in PET-1 (SUV-1) and in PET-2 (SUV-2). The percentage variation of the standard uptake values (retention index) between PET-1 and PET-2 was calculated.Clinical and metabolic stages were assessed according to TNM classification. All biologic prognostic parameters, such as the receptor status, p53 and c-erbB-2 expression, proliferation rate (Ki-67), and grading were determined from tissue of the primary tumor. Metabolic, clinical, and biologic parameters were correlated.

A positive relationship was found between the SUV(max), tumor size, clinical, and metabolic stages. SUV-1 and SUV-2 values showed significant statistical correlation (P < 0.05) with PET stage and tumor size assessed by PET. On the contrary, the retention index showed relation with clinical stage (P < 0.05).When related to the biologic parameters, retention index showed the best results, with positive and significant relation (P < 0.05), with histologic grade, and Ki-67 and c-erbB-2 expression. Isolated SUV values only showed significant relation to Ki-67 expression.

The retention index showed the best relation with biologic and clinical parameters compared with isolated SUVmax values for what could be a predictive marker of tumor biologic behavior.