These findings—particularly increases in circulating T-cell–expressing checkpoint receptors such as PD-1—support various studies in development that seek to integrate immunotherapy into treatment of [squamous cell carcinoma of the head and neck] and could serve as a point of reference for biomarkers.
Jonathan Schoenfeld, MD, MPhil, MPH
Definitive radiation, with or without chemotherapy, induces a combination of immune-stimulating and inhibitory effects in patients with squamous cell carcinoma of the head and neck, according to research presented by Jonathan Schoenfeld, MD, MPhil, MPH, at the 2016 Multidisciplinary Head and Neck Cancer Symposium in Scottsdale, Arizona.1
Immune therapy, particularly immune checkpoint blockade, has dramatically impacted oncology, with promising data emerging across multiple solid tumors including head and neck cancer, explained Dr. Schoenfeld, a radiation oncologist at Dana-Farber Cancer Institute and Brigham and Women’s Hospital in Boston. “Preliminary studies have demonstrated response, particularly to inhibition of the PD-1 [programmed cell death protein 1] receptor in the metastatic setting,” he said. However, immunotherapy in the curative setting remains relatively unexplored.
Rationale for the Trial
Definitive chemoradiation is an established form of treatment for squamous cell carcinoma across multiple head and neck subsites.
“Both chemotherapy and radiation have long been appreciated for their immunosuppressive properties, but more recent data largely derived from animal models and human case reports suggest potential immune effects that may synergize, in some cases, with immune therapy,” said Dr. Schoenfeld.
Dr. Schoenfeld and his colleagues sought to survey the immune effects in a prospective cohort of patients receiving definitive radiation with or without chemotherapy, to confirm the results of a pilot study and to guide future studies.
“We had initially conducted a pilot study enrolling a heterogeneous group of patients that suggested that radiation might impact systemic levels of certain chemokines, such as CXCL9, CXCL10, and CXCL16; specific T-cell subsets; and myeloid-derived suppressor cells,” he said.
They attempted to confirm these results in a more homogeneous group of patients treated with conventionally fractionated radiation (≤ 2 Gy/d) for squamous cell carcinoma of the head and neck.
Peripheral blood was collected from 16 consecutive patients with squamous cell carcinoma of the head and neck undergoing curative-intent radiation therapy, at two or more time points during the beginning (week 1) and end (weeks 6–7) of therapy.
The study population was 90% male with a median age of 59 years; the median radiation dose was 70 Gy. Most patients were treated to the oropharynx for p16-positive disease, and the majority also received concurrent cisplatin-based chemotherapy for stage IV disease metastatic to regional lymph nodes.
The investigators used multiplex assays and the enzyme-linked immunosorbent assay to evaluate cytokine and serum PD-1 ligand (PD-L1) levels. Flow cytometry was performed on peripheral blood mononuclear cells to quantify circulating immune cell populations.
Select patient samples were analyzed in more depth using proteomic arrays to identify targets of circulating IgG antibodies over more than 9,000 potential targets, and multiplex polymerase chain reaction and high-throughput deep sequencing were also performed on T-cell receptor genes.
The investigators compared circulating levels of chemokines and peripheral blood mononuclear cells before and after treatment. “CXCL10, which has been reported in some cases to be produced by tumor cells associated with unfavorable outcome, was decreased over the course of treatment in the majority of patients,” Dr. Schoenfeld said. CXCL16 was also increased in the majority of patients, whereas no change was observed in circulating CXCL9.
“We also saw significant increases in the percent of circulating regulatory T-cells as well as myeloid-derived suppressor cells,” he added.
According to the investigators, changes in peripheral CD8-positive cells were relatively modest in some patients and pronounced in others. “Looking at peripheral CD8-positive T cells, you can see that by the end of treatment, PD-1–expressing T cells accounted for upward of 10% or even 15% of all circulating CD8-positive T cells in select patients,” Dr. Schoenfeld added.
Increases in serum PD-L1 levels mirrored increases in CD8-positive T cells over the course of therapy, and an increase in the diversity of antigens targeted by antibody responses over the course of treatment was seen in all three patients in whom this was evaluated, according to the researchers.
The investigators used seromic profiling to examine changes in IgG antibody signal over the course of treatment. “The majority of potential antibody targets did not show a significant change in signal before and after treatment; however, there were select targets that showed a significant increase in antibody signal at the end as compared to the beginning of treatment, representing potential targeting of tumor neoantigens, although ongoing work is attempting to confirm this,” he stated.
Interpretation of Findings
Altogether, the researchers’ findings suggest that definitive treatment for squamous cell carcinoma of the head and neck impacts systemic immunity via cytokine, T-cell, and potentially antibody effects. “Specifically, radiation with or without chemotherapy induces a combination of immune-stimulating and immune-inhibitory effects,” said Dr. Schoenfeld.
“Radiation-induced cell death may cause changes in circulating chemokines and may also cause liberation of tumor antigens that can then be presented by antigen-presenting cells, potentially leading to antibody responses as well as T-cell responses,” he added. These positive effects, however, are likely balanced by inhibitory effects on regulatory T cells and potentially on checkpoint-expressing T cells, he warned.
It is unknown whether changes in circulating immunologic markers correlate with effects on the tumor microenvironment, but the findings support complex immunologic effects of fractionated chemoradiation therapy as well as mechanisms for potential synergy between chemotherapy, radiation therapy, and immunotherapy in squamous cell carcinoma of the head and neck.
“These findings—particularly increases in circulating T-cell–expressing checkpoint receptors such as PD-1—support various studies in development that seek to integrate immunotherapy into treatment of [squamous cell carcinoma of the head and neck] and could serve as a point of reference for biomarkers,” said Dr. Schoenfeld. ■
Disclosure: Dr. Schoenfeld reported no potential conflicts of interest.
1. Sridharan V, Margalit D, Curreri S, et al: Systemic immunologic effects of definitive radiation in head and neck cancer. 2016 Multidisciplinary Head and Neck Cancer Symposium. Abstract 2. Presented February 18, 2016.
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