Abstract 1175P
Background
Treatment-related pneumonitis is a significant concern in locally advanced non-small cell lung cancer (NSCLC) patients undergoing definitive chemoradiation (CRT). The incidence and predictors of pneumonitis in the era of consolidative durvalumab have yet to be fully elucidated. In this large, single institution, retrospective analysis, we analyze factors associated with grade 2+ pneumonitis in NSCLC patients treated on the Pacific regimen.
Methods
We identified all patients treated at our institution with definitive CRT followed by consolidative durvalumab from 2018 to 2021. Those with <3 months of follow-up were excluded. Clinical documentation and imaging were used to determine grade 2+ pneumonitis events, which required: 1) pulmonary symptoms requiring prolonged steroid taper, oxygen, and/or admission; and 2) radiographic findings consistent with pneumonitis. Cox proportional hazards regression models were applied to determine association between variables and pneumonitis.
Results
One-hundred fifty patients met inclusion. Median number of durvalumab cycles received was 12. Most patients received standard dose durvalumab every 2 weeks and 17 (11.3%) received high dose (1500 mg) durvalumab every 4 weeks for at least one cycle. At a median follow-up of 15 months, 36 pneumonitis events occurred with a 1-year cumulative incidence of 25.7% (95% CI: 19.2-34.2). Grade 3+ and 5 pneumonitis occurred in 11 and 2 patients, respectively. Univariate and multivariate predictors of pneumonitis are listed in the table. Age, stage, prior radiation, total lung V20Gy, proton therapy, high dose durvalumab, and lymphocyte count were not predictive. Kaplan-Meier estimates of overall survival at 1 and 3 years were 88.7% and 55.5%, respectively. Table: 1175P
Predictors of pneumonitis V5Gy (%). Percentage of volume receiving at least 5 Gy. All p-values <0.05
| Univariate | HR (95% CI) |
| Durvalumab cycles | 0.92 (0.87-0.96) |
| Total lung | |
| Volume | 0.68 (0.49-0.96) |
| Mean dose | 2.66 (1.16-6.12) |
| Ipsilateral lung | |
| Volume | 0.51 (0.28-0.94) |
| Mean dose | 1.71 (1.09-2.71) |
| V5Gy (%) | 1.24 (1.03-1.50) |
| V10Gy (%) | 1.26 (1.04-1.52) |
| V10Gy (cc) | 9.85 (1.44-67.42) |
| V20Gy (%) | 1.28 (1.02-1.60) |
| V40Gy (%) | 1.30 (1.02-1.67) |
| Contralateral lung | |
| Volume | 0.52 (0.28-0.97) |
| Mean dose | 2.42 (1.13-5.19) |
| V40Gy (%) | 2.34 (1.28-4.28) |
| Multivariate | HR (95% CI) |
| Durvalumab cycles | 0.92 (0.88-0.97) |
| Contralateral lung mean dose | 4.75 (1.09-20.68) |
Conclusions
We report a risk of pneumonitis higher than that seen on RTOG 0617 and comparable to the Pacific study. Multiple lung dosimetric factors were found to be predictive of grade 2+ pneumonitis. Larger lung volume was protective.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.