2377 - Optimizing Fractionation Strategies for Early-Stage NSCLC: Real-World Toxicity and Outcomes from a Statewide Consortium
Presenter(s)
L. Higgins1, S. R. Miller1, H. Yin2, M. Schipper3, M. M. Matuszak1, M. Zaki4, J. A. Hayman3, A. F. Dragovic1, M. M. Dominello5, D. P. Bergsma1, P. A. Paximadis6, L. L. Kestin7, and S. Jolly1; 1Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, 2Department of Biostatistics, University of Michigan, Ann Arbor, MI, 3University of Michigan, Ann Arbor, MI, 4Covenant HealthCare, Saginaw, MI, 5Department of Radiation Oncology, Karmanos Cancer Center, Detroit, MI, 6Department of Radiation Oncology, Corewell Health South, St. Joseph, MI, 7Michigan Healthcare Professionals/GenesisCare USA, Farmington Hills, MI
Purpose/Objective(s): Many acceptable radiation dose and fractionation regimens exist for definitive treatment of early-stage non-small cell lung cancer (NSCLC). Hypofractionated (HypoRT) regimens are favored over stereotactic body radiation therapy (SBRT) for central or large lesions; however, comparative toxicity and outcomes data are limited. We previously identified factors influencing the use of HypoRT over SBRT within a statewide quality consortium. Here, we report observed toxicity and oncologic outcomes by fractionation.
Materials/Methods: Patients with early stage (T1-3N0M0) NSCLC were prospectively enrolled in a statewide quality consortium from September 2012 to January 2025. We defined SBRT as =5 fractions, HypoRT as 6-20 fractions, and conventional fractionation (cRT) as 1.8-2 Gy per fraction (Gy/Fx) for 25 or greater fractions. We excluded patients with multiple radiation plans or those not meeting definitions. Oncologic outcomes and physician-reported toxicities were collected prospectively. Fractionation and clinical factors were assessed for association with outcomes of interest.
Results: In total, 1,146 patients from 30 centers meeting inclusion criteria were enrolled: 848 received SBRT, 116 received HypoRT, and 182 received cRT. Among patients with T1 tumors, 93.6%, 4.6%, and 1.7% received SBRT, HypoRT, and cRT, respectively. This distribution was 52.9% SBRT, 22.3% hypoRT, and 24.8% cRT among T2 tumors and 10.4% SBRT, 18.2% hypoRT and 71.4% cRT among T3 tumors. Planning target volume was = 2 cm from the heart for 120 (14.1%) and = 2 cm from the esophagus for 64 (7.5%) SBRT patients. Cumulative incidence of lung and cardiac related hospitalization, accounting for death and hospice as competing risks, were similar across fractionations, although incidence of hospitalization for pneumonitis was lowest with SBRT (table 1). After adjusting for age and fractionation, only T-stage was associated with progression free survival (PFS) with a median follow up of 20 months. T2 tumors (HR 1.52) and T3 tumors (HR 1.83) demonstrated worse PFS than T1 tumors.
Conclusion: In a large prospective real-world dataset, incidence of lung or cardiac-related hospitalization was low following RT for early-stage lung cancer across fractionation regimens. PFS did not differ by fractionation after adjusting for T-stage. These findings highlight the safety of varied fractionation approaches within a statewide consortium.
Abstract 2377 - Table 1: Cumulative incidence fraction (CIF) of hospitalization events by fractionation
| 12 months % CIF (95% CI) | 24 months % CIF (95% CI) | Gray's test P-value | |
| Any lung event | 0.155 | ||
| cRT | 22.4 (13,33.4) | 22.4 (13,33.4) | |
| HypoRT | 22 (12.5,33.4) | 24.1(13.9,35.7) | |
| SBRT | 11.1 (8.6,14) | 16.2 (13.1,19.6) | |
| Any cardiac event | 0.51 | ||
| cRT | 6.4 (2.0,14.3) | 8.1 (3.0,16.7) | |
| HypoRT | 10 (4.0,19.2) | 11.9 (5.2,21.7) | |
| SBRT | 4.6 (3.1,6.6) | 7.6 (5.5,10.2) | |
| Pneumonitis hospitalization | |||
| cRT | 4.8 (1.2,12.1) | 4.8 (1.2,12.1) | 0.0001 |
| HypoRT | 3.3 (0.6,10.3) | 3.3 (0.6,10.3) | |
| SBRT | 0 | 0.4 (0.1,1.5) |