The relationship between histopathological data and parameters derived from F-18 FDG PET/BT in diagnosed breast cancer patients

Aim: In this study, we aimed to evaluate the relationship between histopathological and immunohistochemical subtypes of tumors in breast cancer patients, prognostic factors such as axillary lymph node involvement, and demographic data such as BMI, with the metabolic parameters derived from F-18 FDG PET/CT. Materials and Methods: The retrospective data of patients with histopathological diagnosis of breast cancer who did not undergo primary tumor surgery and who underwent F-18 FDG PET/CT for staging between January 2017 and December 2022 in the archive of Manisa Celal Bayar University Faculty of Medicine, Department of Nuclear Medicine were analyzed retrospectively. Demographic information (age, weight, height, body mass index [BMI]) and histopathological and immunohistochemical findings of the tumors were obtained retrospectively. SUVmax, SUVmean and SULmax measurements were performed within the regions of interest of the lesions in F-18 FDG PET/CT images. Metabolic tumor volume (MTV) and total lesion glycolysis (TLG) values were measured automatically by taking 42% of SUVmax value as a threshold value in the same region of interest. In addition, SUVmax and SULmax values were measured from intact liver parenchyma and compared with the SUVmax value of the primary lesion to calculate the primary lesion SUVmax/liver SUVmax ratio (SUVmaxTLR) and heterogeneity index (HI) by dividing SUVmax by SUVmean.Results: The study included 331 female patients. The ages of the patients ranged between 31 and 90 years with a mean age of 56.22±12.76 years. The mean BMI of the patients was 30.08±5.91 kg/m2. Patients were grouped into molecular subtypes according to estrogen (ER), progesterone (PR) levels and HER2 and Ki-67 positivity. In our study, 46 (13.9%) patients were Luminal A, 119 (36%) Luminal B HER2 negative, 90 (27.2%) Luminal B HER2 positive, 37 (11.2%) HER2 overexpressed and 39 (11.8%) Triple Negative. In addition, axillary lymph node metastasis was detected in 169 (51.1%) patients, while no axillary lymph node metastasis was observed in 162 (48.9%) patients. Metabolic parameters, especially SUVmax, SUVmean, TLG, SUVmaxTLR and SULmax values were found to be higher in ER and PR negative patients compared to ER and PR positive patients (p<0.001). There was no significant difference in metabolic parameters between HER2 positive and negative patients (p > 0.05). A statistically significant difference was found between the median values of all metabolic parameters except MTV and HI between the Ki-67 index negative and positive patient groups (p<0.001). Luminal A patients were found to have lower median values of SUVmax, SUVmean, TLG, SULmax and SUVmaxTLR parameters compared to other molecular subtypes (p<0.001). When the Triple Negative group was compared with other molecular subtypes individually, SUVmax, SUVmean, TLG, SUVmaxTLR and SULmax relationships were statistically significant. Conclusion: Higher metabolic parameters were detected in ER and PR negative breast cancer patients, indicating that these patients had more aggressive tumors. Ki-67 proliferation index positivity was also associated with higher metabolic activity. Between molecular subtypes, Luminal A group had lower metabolic activity and Triple Negative group had higher metabolic activity. Metabolic parameters were significantly higher in patients with lymph node metastasis. In obese patients, the usage of different metabolic parameters such as SULmax and SUVmaxTLR may be clinically more accurate.