Single institution toxicity of definitive chemoradiation and maintenance durvalumab in locally advanced non-small cell lung cancer.

e20554 Background: The paradigm for locally advanced non-small cell lung cancer has been markedly altered to include maintenance durvalumab (D) post completion of definitive chemoradiation (CRT) following the publication of the Pacific trial in 2018. The toxicity of this treatment has not been well evaluated in the real-world setting. Methods: We identified 42 patients (pts) with Stage IIB-IIIC NSCLC treated at Mayo Clinic Rochester between 6/1/2018 and 10/1/2020 who received definitive CRT followed by maintenance D. Data were abstracted by retrospective chart review under an IRB approved protocol. Results: Median age was 66 yrs (range 47-90) and 62% were women. Primary lung cancer histology included 19 adenocarcinoma, 20 squamous cell, and 3 adenosquamous. The distribution of stages was: IIB (4/42), IIIA (15/42), IIIB (19/42), IIIC (4/42). Approximately half of patients had PDL1 expression > 25% (20/42). With a median follow up of 12.2 months (calculated from first cycle of D; range 4.2-30.5 months), 14 had completed one year of maintenance D, 16 were receiving ongoing D, and 10 stopped D early with 6/12 discontinuing due to disease progression (4/6 local progression, 2/6 distant progression). Other reasons for discontinuation (5/10) included grade 3 colitis, grade 2 hepatitis, aspergillus lung infection, and flare of autoimmune disorders. One quarter of patients experienced grade 2 radiation pneumonitis (RP; 10/42) with median time to development of RP 78 days from end of CRT and 45 days from start of D. RP was determined by multidisciplinary review of imaging and treatment fields. 17/42 patients developed immune related adverse events (see Table for details). There was minimal overlap between the patients who experienced pneumonitis and immune related toxicity; 2/17 had both pneumonitis and immune related toxicity (hepatitis, thyroiditis). Conclusions: In our early experience with the Pacific regimen, 29% of patients did not complete D due to either toxicity or progression during D administration. Pneumonitis was common (10/42 patients) although there were no grade 3 events. Nearly half of the patients developed an immune-related adverse event. Further analysis is needed to evaluate the real-world toxicity of this treatment as well as oncologic outcomes.[Table: see text]