VAI TRÒ CỦA 18F-FDG PET/CT TRONG LẬP KẾ HOẠCH XẠ TRỊ Ở BỆNH NHÂN UNG THƯ PHỔI KHÔNG TẾ BÀO NHỎ GIAI ĐOẠN III

Abstract

Objective: To evaluate the role of 18F-FDG PET/CT in modifying disease stage, radiotherapy target volumes, and organ-at-risk dosimetric parameters in radiotherapy planning for patients with stage III non-small cell lung cancer (NSCLC).

Materials and methods: This paired cohort planning study was conducted in 101 patients with stage III NSCLC treated with definitive radiotherapy. For each patient, target volumes were initially delineated on conventional simulation CT and subsequently re-delineated with additional reference to 18F-FDG PET/CT images. Two corresponding three-dimensional conformal radiotherapy (3D-CRT) plans were generated using the same prescription dose and identical organ-at-risk constraints. Changes in disease stage, planning target volume (PTV) of the primary tumor, nodal PTV, total PTV, and organ-at-risk dosimetric parameters were compared using paired statistical tests.

Results: The mean age of the study population was 62.0 ± 8.9 years, with males accounting for 76.2%. PET/CT led to stage modification in 15 of 101 patients (15.0%), excluding cases with upstaging beyond the feasibility of definitive radiotherapy; among these, upstaging occurred in 13 patients (12.9%) and downstaging in 2 patients (2.0%). Changes in total PTV were observed in 38 of 101 patients (38.0%), including increases in 22 patients (22.0%) and decreases in 16 patients (16.0%); however, the difference in mean total PTV between CT-based and PET/CT-based plans was not statistically significant (276.6 cc vs. 275.2 cc; p = 0.753). Changes in primary tumor PTV were observed in 20 patients (19.8%), with no statistically significant difference in mean volume (p = 0.282). Nodal PTV changes occurred in 28 patients (27.7%), and PET/CT detected new nodal metastases in 21 patients (20.8%); however, the difference in mean nodal PTV did not reach statistical significance (p = 0.675). Regarding organ-at-risk dosimetry, no statistically significant differences were observed in spinal cord maximum dose (p = 0.871), lung V20 (p = 0.966), mean esophageal dose (p = 0.087), or heart V50 (p = 0.412). PET/CT-based planning was associated with a slight increase in the mean heart dose (8.50 Gy vs. 8.68 Gy; p = 0.036) and in the oesophageal V60 (5.31% vs. 5.66%; p = 0.014).

Conclusion: 18F-FDG PET/CT results in changes in disease staging and radiotherapy target volume delineation in a substantial proportion of patients with stage III NSCLC, particularly in nodal assessment. Integration of PET/CT into radiotherapy planning does not significantly affect most organ-at-risk dosimetric parameters, although a slight increase in mean heart dose was observed; the clinical significance of these findings warrants further investigation.