Impact of immune-related adverse events (irAE) onset on disease response and survival in patients (pts) with head-neck cancer treated with immune check point inhibitors (ICI).

6028 Background: ICI or combination chemo-immunotherapy are the mainstay of therapy for metastatic head-neck squamous cell carcinoma (mHNSCC) due to durable responses in certain pts. irAEs have emerged as a new challenge in the management of these pts. Some studies suggest a positive correlation between irAE onset and ICI efficacy in other cancers, however, whether such an association exists in HNSCC remains incompletely explored. Methods: We performed a retrospective, single-center cohort study of pts ≥ 18 years of age, with histologically confirmed mHNSCC who received ≥ 1 dose of ICIs at the University of Virginia Comprehensive Cancer Center, VA, USA between 2013-2022. Demographics, disease and treatment characteristics, and clinical outcomes related to irAEs and ICI re-challenge were analyzed. IrAEs were graded using CTCAE v4.0 criteria by chart review. Independent sample t-tests and chi-square analyses were used for univariate comparisons. Median PFS and OS from ICI therapy initiation were estimated using Kaplan-Meier methodology and censored at date of last follow up. P-values 1 irAE. The most common irAEs were hypothyroidism (30.4%), dermatitis (14.3%), and hepatitis (10.7%). CTCAE ≥G3 irAEs were seen in 22.6% pts (n=12). These included hepatitis (n=3), colitis (n=3), hypothyroidism (n=1), arthritis (n=1), pneumonitis (n=1), adrenal insufficiency (n=1), vasculitis (n=1), and cardiomyopathy (n=1). Men (62% vs 37%, p= 0.015) and pts with prior radiation therapy (83% vs 17%, p=0.047) were more likely to experience irAEs. Treatment interruption/discontinuation occurred in 43% pts with irAEs. Topical/supportive therapy was required in 52.8%, and 35.8% required systemic corticosteroids, with more than half experiencing complete irAE resolution. A statistically significant association was observed between irAE onset and objective response rate (68% vs 39%, p= 0.009). 12 pts underwent ICI re-challenge, resulting in partial response in 3 (25%), stable disease in 4 (33.3%) and progressive disease in 3 (25%) pts. There was no statistically significant difference in PFS (4.9 vs 9.7 months, p = 0.731) or OS (30.5 vs 21 months, p = 0.159) in irAE vs non-irAE groups, respectively. Conclusions: irAEs onset was associated with improved best response to ICI therapy in mHNSCC. Although OS was numerically superior in the irAE group, it did not meet statistical significance. ICI re-challenge is feasible in select pts, however further studies are needed to evaluate long term benefit of ICI re-challenge.