PURPOSE Although immune-checkpoint inhibitors (ICIs) have emerged as therapeutic options for recurrent and/or metastatic head and neck squamous cell carcinoma (R/M-HNSCC), concerns have been raised on exceptional acceleration of tumor growth during treatment with ICIs, a condition described as hyperprogressive disease (HPD). This study examined the incidence, potential predictors, and clinical impact of HPD in R/M-HNSCC.

METHODS We retrospectively collected data of patients with R/M-HNSCC treated with ICIs between January 2013 and June 2018 from 11 medical centers in Korea. HPD was defined as tumor growth kinetics ratio (TGKr) > 2, which was calculated by comparing TGK on ICIs with that before treatment with ICIs.

RESULTS Of 125 patients, 68 (54.4%) obtained progressive disease as their best responses (progressors). HPD was identified in 18 (26.5% of progressors, 14.4% of total) patients. Relatively younger age, primary tumor of oral cavity, and previous locoregional irradiation were significant predictors of HPD according to multivariable analysis (p = 0.040, 0.027, and 0.015, respectively). Compared to patients without HPD, patients with HPD had significantly shorter median progression-free survival (PFS) (1.2 vs. 3.4 months, p < 0.001) and overall survival (OS) (3.4 vs. 10.7 months, p = 0.047). However, interestingly, HPD did not significantly affect the therapeutic benefit of post-ICIs chemotherapy.

CONCLUSIONS Younger patients with oral cavity cancer or prior treatment with locoregional radiotherapy could be regarded potential risk groups for HPD in patients with R/M-HNSCC treated with ICIs. Although HPD could consistently predict poorer survival outcomes, patients who experienced HPD with ICIs should not be excluded from the subsequent salvage chemotherapy treatments.