Capabilities of positron emission tomography/computed tomography in a comparative assessment of the effect of various targeted therapy options in patients with <i>EGFR</i>-mutated non-small-cell lung cancer

BACKGROUND: No publications in the Russian medical literature have examined the potential of positron emission tomography combined with computed tomography through a comparative evaluation of the effect of various targeted therapies involving tyrosine kinase inhibitors in patients with non-small cell lung cancer and mutations in the EGFR gene. AIM: To explore the capabilities of positron emission tomography combined with computed tomography based on the RECIST 1.1 criteria and changes in SUVmax and SUVmean metabolic parameters for the comparative assessment of the tumor response to targeted monotherapy and combination therapy with tyrosine kinase inhibitors in patients with EGFR-mutant non-small cell lung cancer. MATERIALS AND METHODS: The 2019–2022 examination records of positron emission tomography combined with computed tomography with 18F-fluorodeoxyglucose (18F-FDG) in 105 patients with non-small cell lung cancer were analyzed, including 75 patients with EGFR-activating mutation. The radiation exposure was adjusted individually and ranged from 45 to 90 mSv. The volume activity of the 18F-FDG radiopharmaceutical was 260–500 MBq. The change in the total largest diameters of the target lesions and SUVmax and SUVmean metabolic parameters were assessed before treatment initiation and 1.5–2.0 months after it. The follow-up duration for the changes in positron emission tomography combined with computed tomography findings in 17 patients with non-small cell lung cancer was at least 12 months. RESULTS: According to positron emission tomography combined with computed tomography images and SUVmax and SUVmean changes, disease progression was significantly less common (p = 0.043 and p =0.029) in patients with EGFR-mutant non-small cell lung cancer from Groups 2 and 3 who received combination therapy with tyrosine kinase inhibitors and bevacizumab or chemotherapy than in Group 1 and control group (4.2% vs. 20.0%–21.8%). An insignificant trend (p =0.092) to a higher partial response to therapy (58.3% vs. 40.0%) was noted. Similar changes in the total largest diameters of the target lesions at the early stage of therapy appeared to be not significant (p =0.187). Within the long-term follow-up of some patients with non-small cell lung cancer, in at least 50% of cases, changes in the total largest lesion diameters are consistent with the relevant SUVmax and SUVmean alterations found in the first control study. CONCLUSIONS: Based on the positron emission tomography combined with computed tomography data and alterations in SUVmax and SUVmean metabolic parameters, the early tumor response to combined therapy with tyrosine kinase inhibitors and bevacizumab or chemotherapy compared with targeted monotherapy with tyrosine kinase inhibitors or chemotherapy of the control group was characterized by a significantly lower rate of metabolic disease progression, although a similar tendency of the change in the total largest diameters of target lesions according to RECIST 1.1. was not significant. Changes in SUVmax and SUVmean metabolic parameters at the early stage of therapy are at least 50% faster than similar changes in the total largest diameters of the target lesions, which can be used for the timely identification of patients with a high risk of further progression as determined by RECIST 1.1.