Hyperprogression during anti-PD-1/PD-L1 therapy in patients with recurrent and/or metastatic head and neck squamous cell carcinoma.

Background: Pembrolizumab and nivolumab are immune checkpoint inhibitors targeting PD-1 that have recently been approved in pretreated recurrent and/or metastatic head and neck squamous cell carcinoma (R/M HNSCC) patients. In the clinic, some patients seem not only not to benefit from anti-PD-L1/PD-1 agents but rather to experience an acceleration of tumor growth kinetics (TGK).

Patients and methods: We retrospectively compared TGK on immunotherapy and TGK on last treatment in patients with R/M HNSCC treated with PD-1/PD-L1 inhibitors in four French centers. The TGK ratio (TGKR, ratio of the slope of tumor growth before treatment and the slope of tumor growth on treatment) was calculated. Hyperprogression was defined as a TGKR ≥ 2.

Results: From September 2012 to September 2015, 34 patients were identified. Patterns of recurrence included exclusive loco-regional recurrence in 14 patients, exclusive distant metastases in 11 patients, and both in 9 patients. No pseudo-progression was observed. Hyperprogression was observed in 10 patients (29%), including 9 patients with at least a locoregional recurrence, and only 1 patient with exclusively distant metastases. Hyperprogression significantly correlated with a regional recurrence (TGKR ≥ 2: 90% versus TGKR < 2: 37%, P = 0.008), but not with local or distant recurrence. Hyperprogression was associated with a shorter progression-free survival (PFS) according to RECIST (P = 0.003) and irRECIST (P = 0.02), but not with overall survival (P = 0.77).

Conclusions: Hyperprogression was observed in 29% of patients with R/M HNSCC treated with anti-PD-L1/PD-1 agents and correlated with a shorter PFS. It occurred in 39% of patients with at least a locoregional recurrence and 9% of patients with exclusively distant metastases. No pseudo-progressions were reported. Mechanisms and causality of hyperprogression should further be assessed through prospective controlled studies.