Abstract 334P
Background
A secondary analysis was performed to evaluate the association of radiotherapy (RT) parameters (RTP) with outcomes in limited stage small cell lung cancer.
Methods
Central review of RT plans and diagnostic imaging was completed. Clinical variables and RTP were analyzed with univariable (UVA) and multivariable analyses (MVA) for association with adverse events (AE) using logistic regression models and overall survival (OS) using Cox proportional hazards models. Baseline variables and RTP were compared between study arms and treatment types using Kruskall-Wallace tests and the Chi-square test for continuous and categorical variables, respectively. All findings identified as statistically significant (SS) represent two-sided p-values ≤0.05.
Results
507 patients (of 638 in primary anlaysis) were included (Table). Those treated with intensity modulated RT (IMRT) vs 3D (3D conformal RT) were more likely to have N3 stage and a higher number of involved nodal stations (NINS) (SS). With twice daily (BID): IMRT was associated with lower heart V30 (volume receiving X Gy), V40, V45, lung mean, V20, and larger lung V5, esophageal (eso) max dose (SS). With daily (QD): IMRT was associated with lower heart V30, V40, V45, V60 and larger lung V5, V10, and eso max (SS).With BID: NINS, eso V45, and N stage were associated with grade 2+ (G2+) and grade 3+ (G3+) esophagitis on UVA (SS). The association persisted with V45, N stage (G2+) and NINS (G3+) on MVA (SS).With QD: NINS, eso V60, V70, and N stage were associated with G2+ and G3+ esophagitis on UVA (SS). With BID: RTP were not associated with pulmonary AE. With QD: Lung V10 and V20 were associated with G2+ pneumonitis on UVA (SS). RTP were not found to correlate with cardiac AE or OS in either arm (BID or QD).
Table 334PKey baseline characteristics and funding
| BID | QD | |
| Patients treated with 3DCRT | 125 | 106 |
| Patients treated with IMRT | 136 | 140 |
| Patients with N1 stage | 38 | 53 |
| Patients with N2 stage | 161 | 140 |
| Patients N3 stage | 62 | 53 |
| Median NINS (number of involved nodal stations) per patient | 3 | 3 |
Support: U10CA180821, U10CA180882; U10CA180868. https://acknowledgments.alliancefound.org
Conclusions
Despite increased disease burden, IMRT was associated with similar survival and improved cardiac, pulmonary, and eso dose sparing. Clinically relevant esophagitis and pneumonitis correlated with RTP and NINS.
Clinical trial identification
NCT00632853.
Legal entity responsible for the study
Alliance for Clinical Trials in Oncology.
Funding
This study was supported by grants U10CA180821 and U10CA180882 from the National Cancer Institute (NCI) of the National Institutes of Health (NIH) (the Alliance for Clinical Trials in Oncology); by grants UG1CA189824, UG1CA233247, UG1CA233253, UG1CA233327, UG1CA233329, and U10CA180868 from the NIH (NRG); by Imaging and Radiation Oncology Core Grant U24 CA180803; and by grant KL2TR001421 from the National Center for Advancing Translational Sciences of the NIH). In addition, the study was supported by Alliance National Clinical Trials Network grants U10 CA180821 (Alliance for Clinical Trials in Oncology Operation) and U10 CA180882 (Statistics and Data Management Center for the Alliance for Clinical Trials in Oncology).
Disclosure
K. Smith: Financial Interests, Personal, Stocks/Shares, Spouse participates in Employee Stock Purchase Plan (ESPP): Varian. J.D. Bradley: Financial Interests, Personal, Advisory Board: AstraZeneca, Mevion, Genentech; Non-Financial Interests, Personal, Other, Consultant (honorariums waived): AstraZeneca. All other authors have declared no conflicts of interest.