Machine Learning-assisted immunophenotyping of peripheral blood identifies innate immune cells as best predictor of response to induction chemo-immunotherapy in head and neck squamous cell carcinoma - knowledge obtained from the CheckRad-CD8 trial

PURPOSE

Individual prediction of treatment response is crucial for personalized treatment in multimodal approaches against head-and-neck squamous cell carcinoma (HNSCC). So far, no reliable predictive parameters for treatment schemes containing immunotherapy have been identified. This study aims to predict treatment response to induction chemo-immunotherapy based on the peripheral blood immune status in patients with locally advanced HNSCC.

METHODS

The peripheral blood immune phenotype was assessed in whole blood samples in patients treated in the phase II CheckRad-CD8 trial as part of the pre-planned translational research program. Blood samples were analyzed by multicolor flow cytometry before (T1) and after (T2) induction chemo-immunotherapy with cisplatin/docetaxel/durvalumab/tremelimumab. Machine Learning techniques were used to predict pathological complete response (pCR) after induction therapy.

RESULTS

The tested classifier methods (LDA, SVM, LR, RF, DT, and XGBoost) allowed a distinct prediction of pCR. Highest accuracy was achieved with a low number of features represented as principal components. Immune parameters obtained from the absolute difference (lT2-T1l) allowed the best prediction of pCR. In general, less than 30 parameters and at most 10 principal components were needed for highly accurate predictions. Across several datasets, cells of the innate immune system such as polymorphonuclear cells, monocytes, and plasmacytoid dendritic cells are most prominent.

CONCLUSIONS

Our analyses imply that alterations of the innate immune cell distribution in the peripheral blood following induction chemo-immuno-therapy is highly predictive for pCR in HNSCC.

Combining radiotherapy and immunotherapy in definitive treatment of head and neck squamous cell carcinoma: review of current clinical trials

Background Head and neck squamous cell carcinoma (HNSCC) presents as locally advanced disease in a majority of patients and is prone to relapse despite aggressive treatment. Since immune checkpoint inhibitors (ICI) have shown clinically significant efficacy in patients with recurrent/metastatic HNSCC (R/M HNSCC), a plethora of trials are investigating their role in earlier stages of disease. At the same time, preclinical data showed the synergistic role of concurrently administered radiotherapy and ICIs (immunoradiotherapy) and explained several mechanisms behind it. Therefore, this approach is prospectively tested in a neoadjuvant, definitive, or adjuvant setting in non-R/M HNSCC patients. Due to the intricate relationship between host, immunotherapy, chemotherapy, and radiotherapy, each of these approaches has its advantages and disadvantages. In this narrative review we present the biological background of immunoradiotherapy, as well as a rationale for, and possible flaws of, each treatment approach, and provide readers with a critical summary of completed and ongoing trials. Conclusions While immunotherapy with ICIs has already become a standard part of treatment in patients with R/M HNSCC, its efficacy in a non-R/M HNSCC setting is still the subject of extensive clinical testing. Irradiation can overcome some of the cancer's immune evasive manoeuvres and can lead to a synergistic effect with ICIs, with possible additional benefits of concurrent platinum-based chemotherapy. However, the efficacy of this combination is not robust and details in trial design and treatment delivery seem to be of unprecedented importance.