Unanticipated Radiation Replanning for Stage III Non-small Cell Lung Cancer

Area of Science:

• Radiation Oncology
• Medical Physics
• Thoracic Oncology

Background:

• Stage III non-small cell lung cancer (NSCLC) requires precise radiation therapy (RT).
• Unanticipated changes in tumor or surrounding anatomy can necessitate RT replanning, impacting treatment delivery.
• Adaptive RT strategies aim to address these anatomical variations.

Purpose of the Study:

• To identify factors associated with unanticipated radiation therapy (RT) replanning in patients with stage III non-small cell lung cancer (NSCLC).
• To determine the frequency and reasons for RT replanning in this patient cohort.
• To evaluate the impact of RT replanning on patient outcomes.

Main Methods:

• Retrospective analysis of 144 patients with stage III NSCLC treated with radical RT between January 2016 and December 2019.
• Determination of the frequency and reasons for RT replanning using cone beam computed tomography (CBCT) data.
• Logistic regression analysis to identify predictors of replanning, with assessment of overall survival and local recurrence rates.

Main Results:

• 11% (16 out of 144) of patients required RT replanning.
• Replanning was primarily due to target shifts (10 patients), shrinkage (5 patients), or growth (1 patient) detected by CBCT.
• A larger planning target volume (primary and nodal) was a significant predictor of replanning (OR=2.5, P=.02).
• Overall survival (33.3 vs 36.3 months, P=.96) and local recurrence (25.0 vs 19.5 months, P=.28) were similar between replanned and non-replanned groups.

Conclusions:

• Approximately 11% of stage III NSCLC patients undergoing radical RT required replanning due to anatomical changes identified during treatment.
• Larger planning target volumes are associated with an increased likelihood of needing adaptive radiation therapy.
• RT replanning in this cohort did not significantly impact overall survival or local disease control.