Evaluation of PET-detected nodal upstaging and planning target volume expansion in esophageal cancer radiotherapy planning.

BACKGROUND

While 18F-fluorodeoxyglucose positron emission tomography (FDG-PET/CT) is known to influence staging, its quantitative impact on clinically meaningful target volume expansion remains incompletely characterized. We evaluated whether PET-detected nodal upstaging is associated with significant planning target volume (PTV) expansion.

METHODS

Fifty consecutive eligible patients with esophageal cancer undergoing computed tomography (CT)- and PET-based radiotherapy planning between January 2018 and January 2022 were retrospectively analyzed, with no predefined target sample size. Clinically significant PTV expansion was predefined as a > 10% increase from CT-based to PET-based planning. Associations between PET-detected nodal upstaging and PTV expansion were evaluated using Fisher's exact test, logistic regression, receiver operating characteristic (ROC) analysis, and nonparametric testing. Given the limited number of events, a parsimonious multivariable model and threshold sensitivity analyses were additionally performed.

RESULTS

Patients with nodal upstaging had a significantly higher risk of > 10% PTV expansion (48.0% vs. 16.7%; absolute risk difference 31.3%, 95% CI 6.7-55.9%; p = 0.032). The median percent PTV change was significantly higher in patients with nodal upstaging (9.49% vs. 0.31%; Wilcoxon p < 0.001). In a parsimonious multivariable model adjusting for tumor length, nodal upstaging remained independently associated with clinically significant PTV expansion (odds ratio (OR) 4.38, 95% confidence interval (CI) 1.12-17.10; p = 0.033). Model discrimination was acceptable (area under the curve (AUC) 0.7254), with stable performance on bootstrap internal validation (bootstrap mean AUC 0.733). Sensitivity analyses using alternative expansion thresholds (> 5%, > 10%, and > 15%) demonstrated directionally consistent associations. Patients meeting the PTV expansion threshold also demonstrated significantly greater increases in lung dose-volume burden (mean lung dose, and lung volumes receiving 5 Gy and 20 Gy; all p < 0.001) in paired dosimetric comparison, supporting the clinical relevance of this threshold.

CONCLUSION

During esophageal cancer radiotherapy planning, PET-detected nodal upstaging was independently associated with clinically meaningful target volume expansion. The association was consistent across alternative expansion thresholds and in bootstrap internal validation, and a paired lung dose-volume comparison indicated that the expansion threshold corresponds to a measurable increase in lung dose burden.