Dosimetric Analysis of HDR Brachytherapy vs. Stereotactic Ablative Radiation Therapy in Early-Stage Lung Cancer

Introduction

Stereotactic ablative radiotherapy (SABR) is the standard non-surgical treatment for early-stage non-small cell lung cancer (NSCLC), but unintentional irradiation of healthy lung tissue remains a concern. High-dose rate (HDR) bronchoscopic brachytherapy (BT) is a novel approach that may enhance dose conformity while reducing radiation exposure to adjacent normal tissues. To date, a comparative dosimetric analysis between HDR BT and modern SABR in lung cancer has not been performed. We hypothesize that HDR BT will demonstrate superior dose conformity, thereby reducing collateral radiation exposure compared to SABR.

Methods

In this study, patients who underwent robotic bronchoscopy between November 2020 and April 2022 at our institution under an IRB- approved protocol were considered. Patients were included if they had biopsy-confirmed stage IA NSCLC and were treated with SABR. Approved SABR plans were extracted from the electronic medical record, and corresponding single-channel HDR BT plans were simulated using identical prescription doses and fractionation schedules. Dose conformity index (CI) was calculated as the ratio of the prescription dose volume to the target volume and compared between both modalities using paired Student’s t-tests (α < 0.05 for statistical significance).

Results

Of 182 screened patients, 12 met inclusion criteria after exclusions for advanced disease, non-confirmed histology, or SABR not performed. Of those patients, 8 were excluded for lack of using active breathing control (ABC) to minimize target motion. The mean ± standard deviation (SD) tumor size was 1.4 ± 0.3 cm. SABR plans delivered 50 Gy in 4–5 fractions. Dosimetric analysis revealed that HDR BT achieved higher V95% (volume of target receiving at least 95% of prescription dose), suggesting improved dose coverage within the tumor, while also demonstrating a lower V25 % conformity index, indicating reduced irradiation of surrounding tissues.

Conclusions

This is the first dosimetric comparison of HDR BT and SABR for stage IA NSCLC. Our findings suggest that HDR BT offers improved dose conformity and potential for improved dose coverage within the target while minimizing low-dose exposure to adjacent lung tissue, which may reduce radiation-related toxicity. Prospective studies are warranted to further assess the clinical feasibility and therapeutic benefits of HDR BT in early-stage NSCLC.