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). 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 (TGK_R, ratio of the slope of tumor growth before treatment and the slope of tumor growth on treatment) was calculated. Hyperprogression was defined as a TGK_R ≥ 2. 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 (TGK_R ≥ 2: 90% versus TGK_R < 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). 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.

Novel patterns of response and progression to immunotherapy have been reported that are not observed with conventional cytotoxic or targeted anticancer treatments. A major breakthrough with immunotherapy is its potential to achieve durable responses in a subset of patients with advanced cancer that can be maintained several years even after stopping the treatment. No standardized definition of durable response exists in the literature, and the optimal duration of treatment in case of durable response is not clearly established. However, the majority of patients do not respond to immunotherapy. Initially reported in advanced melanoma patients, pseudoprogression occurs when tumor index lesions regress after initial progression, supporting the concept of treating some patients beyond progression. Overall, reported rates of pseudoprogression never exceeded 10%, meaning that the large majority of patients who have a disease progression will not eventually respond to treatment. The decision to pursue treatment beyond progression must therefore only be taken in carefully selected patients with clinical benefit, who did not experience severe toxicities with immunotherapy. Conversely, rapid progressions, called hyperprogressions, were reported by several teams with rates ranging from 4% to 29%. These observations need to be confirmed from randomized trials. It is essential to interrupt the treatment in patients with hyperprogression, in order to switch to another potentially active treatment. Finally, some patients experience dissociated responses, with some lesions shrinking and others growing. Local treatment with surgery or radiotherapy for growing lesions may be considered. Several immune-specific-related response criteria were developed to better capture benefits of immunotherapy. These criteria only address the pseudoprogression pattern of response, and do not capture the other patterns of response such as hyperprogression and dissociated response. The classic RECIST remains a reasonable and meaningful method to assess response to immunotherapy in the clinic.

To compare three-dimensional time-of-flight magnetic resonance (MR) angiography, MR imaging, and transfemoral four-vessel angiography in diagnosis and follow-up of cervical artery dissection. Eighteen patients with 19 extracranial internal carotid artery and five vertebral artery dissections were included in this prospective study. Blind interpretation of MR and angiographic images was made by two independent radiologists. MR angiography was more accurate than MR imaging in diagnosis of carotid dissection, although the difference was not statistically significant. In carotid artery dissection, respective sensitivity and specificity were 95% and 99% for MR angiography and 84% and 99% for MR imaging and in vertebral artery dissection were 20% and 100% for MR angiography and 60% and 98% for MR imaging. MR angiography is a reliable, noninvasive method for use in diagnosis and follow-up of extracranial internal carotid artery dissection. In vertebral artery dissection, however, conventional angiography remains useful.

Recent clinical results support the use of new immune checkpoint blockers (ICB), such as anti-PD-1 (e.g. nivolumab and pembrolizumab) and anti-PD-L1 antibodies. Radiological evaluation of ICB efficacy during therapy is challenging due to tumor immune infiltration. Changes of circulating tumor DNA (ctDNA) levels during therapy could be a promising tool for very accurate monitoring of treatment efficacy, but data are lacking with ICB. This prospective pilot study was conducted in patients with nonsmall cell lung cancer, uveal melanoma, or microsatellite-instable colorectal cancer treated by nivolumab or pembrolizumab monotherapy at Institut Curie. ctDNA levels were assessed at baseline and after 8 weeks (w8) by bidirectional pyrophosphorolysis-activated polymerization, droplet digital PCR or next-generation sequencing depending on the mutation type. Radiological evaluation of efficacy of treatment was carried out by using immune-related response criteria. ctDNA was detected at baseline in 10 out of 15 patients. At w8, a significant correlation (r = 0.86; P = 0.002) was observed between synchronous changes in ctDNA levels and tumor size. Patients in whom ctDNA levels became undetectable at w8 presented a marked and lasting response to therapy. ctDNA detection at w8 was also a significant prognostic factor in terms of progression-free survival (hazard ratio = 10.2; 95% confidence interval 2.5–41, P < 0.001) and overall survival (hazard ratio = 15; 95% confidence interval 2.5–94.9, P = 0.004). This proof-of-principle study is the first to demonstrate that quantitative ctDNA monitoring is a valuable tool to assess tumor response in patients treated with anti-PD-1 drugs.