3430 - Minimizing Radiation Pneumonitis in Locoregionally Advanced NSCLC Receiving Consolidative Hypofractionated Thoracic Radiotherapy Following Chemoimmunotherapy
Presenter(s)
S. Beduk Esen1, S. Senyürek2, D. Sezen2, Y. Saglam3, A. I. Atasoy Sr1, F. Karaköse4, M. Budak4, M. Tintas4, M. Büyükköse1, M. Duman5, N. Kilic Durankus4, S. E. Oymak1, Y. Bolukbasi4, and U. Selek2,3; 1American Hospital Department of Radiation Oncology, Istanbul, Turkey, 2Koc University, School of Medicine, Department of Radiation Oncology, Istanbul, Turkey, 3VKV, American Hospital, Department of Radiation Oncology, Istanbul, Turkey, 4Koç University Faculty of Medicine Department of Radiation Oncology, Istanbul, Turkey, 5Koç University School of Medicine Department of Radiation Oncology, Istanbul, Turkey
Purpose/Objective(s): To assess the incidence and predictors of radiation pneumonitis (RP) among patients with non-small cell lung cancer (NSCLC) undergoing induction chemoimmunotherapy, consolidative hypofractionated thoracic radiotherapy (HFRT) and subsequent maintenance immunotherapy.
Materials/Methods: This retrospective study included 68 patients with stage IIB–IVB NSCLC treated between 2019 and 2025. All patients underwent 4DCT simulation, and target volumes were contoured on the average respiratory phase. RT was delivered using simultaneous-integrated boost (SIB) - intensity-modulated RT (IMRT). Lung dose evaluation was based on the expiratory phase (V50). The primary endpoint was the incidence of RP; secondary endpoints included predictors of RP in the immunotherapy era.
Results: Median age was 67 years (range: 33–80). Median albumin, pan-immune-inflammation-value (PIV), and systemic immune-inflammation index (SII) were 41.7 g/L, 510, and 1040.5 respectively. The most common regimen was carboplatin–paclitaxel (68%) and pembrolizumab (47%). Patients received a median of 4 chemotherapy (range: 2–7) and 4 immunotherapy (range: 1–10) induction cycles; 27 patients (40%) received concomitant immunotherapy. The median time between immunotherapy and RT was 3.7 weeks (range: 0-42.2 weeks). The total number of immunotherapy cycles were 11 (range: 2-78). The median prescribed RT dose was 52.5 Gy (range: 45–60) in 15 fractions. Treatment was well-tolerated with no grade 4-5 RP. Grade 2 and 3 RP occurred in 4 (5.8%) and 2 (2.9%) patients, respectively. Immunotherapy-related pneumonitis of grade 2, 3, and 5 was observed in 1 (3%), 3 (9%), and 1 (3%) patients, respectively. Two (6%) patients discontiued to systemic treatment due to immunotherapy-related pneumonitis. Older age and high serum albumin level at diagnosis significantly increased the risk of grade =2 RP (Table 1). Total and ipsilateral lung V16 and V20 Gy are marginally higher in patients with RP than those without.
Conclusion: Consolidative HFRT using SIB-IMRT after induction chemoimmunotherapy seems well tolerated in NSCLC, demonstrating low rates of severe RP. Particular caution should be exercised regarding grade =2 RP, especially in patients of older age and with high serum albumin levels at diagnosis. Keeping total and ipsilateral lung V16 and V20 Gy on expiratory phase as low as possible may help to mitigate the risk of clinically meaningful RP in the immunotherapy era.
| Clinical Parameters | Grade =2 RP (%) | Grade =2 RP (%) | P-value |
| Yes | No | ||
| Age (years) <65 =65 | 6 (100) 0 (0) | 21 (34) 41 (66) | 0.003* |
| Previous history of smoking Yes No | 3 (50) 3 (50) | 52 (84) 10 (16) | 0.079 |
| Concomitant Immunotherapy with RT Yes No | 3 (50) 3 (50) | 24 (39) 38 (61) | 0.675 |
| Albumin level at diagnosis | 46 (44.2-48.6) | 41.6 (4.8-48) | 0.014* |
| Total lung V16 (%) | 25.5 (13.9-30.0) | 19.0 (2.3-40.5) | 0.309 |
| Total lung V20 (%) | 20.0 (10.3-24.0) | 16.0 (1.3-21.4) | 0.375 |
| Ipsilateral lung V16 (%) | 44.7 (30.3-52.0) | 37.0 (3.9-68.0) | 0.284 |
| Ipsilateral lung V20 (%) | 40.8 (23.6-47.0) | 30.0 (2.4-60.0) | 0.238 |