Performance of [18F]FDG-PET/CT Imaging in First Recurrence of Invasive Lobular Carcinoma.

Background: Invasive lobular carcinoma accounts for 10 to 15% of all breast cancers. The first objective of this retrospective study was to assess the diagnostic performance of FDG-PET/CT scanning in women previously treated for invasive lobular carcinoma with suspected first recurrence. The secondary objectives were to evaluate the impact of PET/CT in a change in treatment and its prognostic value on specific survival.

Methods: Patients in whom a PET/CT scan was performed from January 2011 to July 2019 in our Cancer Research Center were enrolled. Recurrence was suspected based on clinical symptoms, abnormal findings on conventional imaging, and/or elevated tumor markers. The diagnosis of recurrence was established by the oncologist after integration of all clinical, biological, histological, imaging, and follow-up data. Prognostic factors of recurrence as predicted by PET were determined using univariate logistic regression. KI67, mitotic index, or grade of mitosis were tested. Survival curves were compared using the log-rank test. Sixty-four patients (mean age: 60.3; SD = 12.4 years) were enrolled. The average time from initial diagnosis of the primary tumor to suspicion of recurrence was 5.2 ± 4.1 years. Forty-eight patients (75%) were judged to have recurrence by the oncologist: 7 local and 41 metastatic, with mainly bone ( = 24), lymph node ( = 14) and liver ( = 10) metastases.

Results: Sensitivity, specificity, and positive and negative predictive values of PET/CT to predict recurrence were, respectively: 87%, 87%, 95%, and 70%. SUVmax at recurrence sites was generally high (mean: 6.4; SD = 2.9). False negative PET/CT results occurred with local ( = 2), peritoneal ( = 2), meningeal ( = 1), or bladder ( = 1) recurrences. In 40 patients with available histopathological data from suspected sites of recurrence, 30 PET/CT were true positive. In four patients, primary lung ( = 1) or gastric ( = 1) tumors or lymphomas ( = 2) were found. The detection of a recurrence resulted in a change in treatment in 44/48 patients (92%). No association between recurrence predicted by PET and biological biomarkers was found. Median specific survival appears shorter in patients with metastatic recurrence versus patients with local or no recurrence on PET/CT ( = 0.067).

Conclusions: FDG-PET/CT is an effective and reliable tool for the detection of invasive lobular carcinoma recurrence, although certain recurrence sites specific to this histological type can impair its diagnostic performance.