FDG PET and FES PET Predict PFS on Endocrine Therapy—Letter

We read with interest the study by Kurland and colleagues (1) that was recently published in Clinical Cancer Research. They evaluated the ability of 18F-fluorodeoxyglucose (FDG) PET and 18F-fluoroestradiol (FES) PET to predict progression-free survival (PFS) in 84 patients treated by salvage endocrine therapy for luminal metastatic breast cancer (MBC).Previous studies suggested that FES PET imaging performed at a single time point before beginning a novel line of endocrine therapy could be helpful to predict response in patients with pretreated luminal MBC (2, 3). In those studies, a defined cutoff [value of 1.5 (2) or 2 (3)] for the standardized uptake values (SUV) was applied to separate tumors sensitive to the treatment (high SUV values) from those who are resistant (low SUV values).Unfortunately, in the study from Kurland and colleagues, none of the qualitative or quantitative parameters measured on FES PET imaging performed before beginning the hormonal therapy was predictive of PFS. On the opposite, FDG uptake was a good indicator of patient's outcome with shorter PFS in the case of metastases with high FDG uptake. Similarly, in the case of patients with luminal tumors without pretreatment, FDG uptake measured at a single time point before neoadjuvant chemotherapy (4) or before initial surgery (5) has been associated with patient's survival. These results suggest that FDG PET is more likely to predict outcome than the FES PET does.However, in the study from Kurland and colleagues, although FES PET was not predictive of patient's survival in the whole population, this imaging was of interest to better stratify the patients having high FDG uptake. Finally, three subgroups were identified: those with a good prognosis (in the case of tumors with low FDG uptake), those with a bad prognosis (tumor with high FDG uptake and low FES uptake), and those with an intermediate prognosis (tumor with high FDG uptake and high FES uptake).In conclusion, although previous studies showed that FES PET was a good indicator of response to endocrine therapy, the study from Kurland suggests that FES imaging has limited value in terms of prognosis. FDG imaging seems more helpful than FES PET to predict patient outcome. Nevertheless, FES imaging could be of interest in addition to FDG PET. The predictive and prognostic value of the two PET imaging and their additional role need to be investigated in a multicenter prospective study with a larger cohort of patients.See the Response, p. 3475No potential conflicts of interest were disclosed.

Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.