Standardized Uptake Values Correlate With PD-L1 Expression in Stage IV Lung Adenocarcinoma

Maximum standardized uptake value (SUVmax) in lung adenocarcinomas correlates with programmed death ligand 1 (PD-L1) expression levels and may help predict immunotherapy response in patients with stage IV cancers, according to a new report published in Frontiers in Medicine.

Lung adenocarcinoma has a high mortality rate, the authors noted, particularly in developing countries where a significant number of patients do not receive their diagnosis until their cancers have reached stage IV. As therapy for lung adenocarcinoma has evolved, the study investigators said PD-L1 testing has become a routine procedure to help identify the most appropriate treatment. For some patients, PD-L1–targeting monoclonal antibodies can be used.

“The binding of programmed cell death protein 1 (PD-1) with PD-L1 induces T-lymphocyte depletion or death,” the authors noted. “The inhibition of this signaling pathway has been shown to increase T-cell activity, boost antitumor immunity, and prevent tumor cells from evading host immune responses, representing a viable technique for successful tumor immunotherapy.”

Previous investigations have attempted to figure out whether one way to ascertain PD-L1 levels might be to use SUVmax levels. SUVmax has already been identified as a prognostic indicator in both early and advanced non–small cell lung cancer (NSCLC), the authors noted. However, to date no study has looked specifically at the relationship between PD-L1 levels and SUVmax in NSCLC. Moreover, the authors said there has been little research examining PD-L1 expression in patients with NSCLC within the Vietnamese population.

The authors therefore decided to see whether they could use ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/CT values to predict PD-L1 expression among patients with stage IV lung adenocarcinoma who sought treatment from a single hospital in Vietnam.

The-constructed a cohort of 86 patients with stage IV disease who underwent both PET/CT imaging and PD-L1 expression testing between February 2019 and November 2020. The patients, two-thirds of whom were men, had an average age of 62.23 years and 36% had epidermal growth factor receptor (EGFR) mutations.

PD-L1 expression testing showed that 40.7% of cases were PD-L1 negative (meaning PD-L1 was detected in less than 1% of the tumor). In 32.6% of cases, PD-L1 was detected in 1% to 49% of the tumor, and in 26.7% of cases, PD-L1 was detected in more than 50% of the tumor.

The mean (SD) SUVmax value was 11.09 (3.94); however, it was notably higher in PD-L1–positive tumors (12.24 [4.01]) than in PD-L1–negative tumors (9.43 [3.22]). Moreover, they found that SUVmax was significantly different not only between PD-L1–positive and –negative cases, but also between tumors that were weakly expressing PD-L1 and those strongly expressing PD-L1.

“SUVmax is considerably higher in patients with positive PD-L1 expression than in those with negative PD-L1 expression,” the authors said. “This finding suggests that combining the evaluation of PD-L1 expression and SUVmax in the primary tumor may help predict stage IV adenocarcinoma lung cancer prognosis.”

The authors said the question of the relationship between PD-L1 expression and SUVmax remains controversial, and they said their study has limitations, including its cross-sectional nature and small study population. They said glutamine transporters and hexokinase II should be included in future studies and that further research is necessary to better understand whether and how ¹⁸F-FDG can be used to predict immunotherapy response.

Reference

Tien Cong B, Cam Phuong P, Thai PV, et al. Prognostic Significance of PD-L1 Expression and Standardized Uptake Values in the Primary Lesions of Stage IV Adenocarcinoma Lung Cancer. Front Med (Lausanne). Published online May 13, 2022. doi:10.3389/fmed.2022.895401