Randomized Phase II Trial of Nivolumab With Stereotactic Body Radiotherapy Versus Nivolumab Alone in Metastatic Head and Neck Squamous Cell Carcinoma

Neoadjuvant immunoradiotherapy results in high rate of complete pathological response and clinical to pathological downstaging in locally advanced head and neck squamous cell carcinoma

BACKGROUND

Checkpoint inhibitors targeting programmed death receptor-1 (PD-1) have been tested in the neoadjuvant setting for the treatment of locoregionally advanced head and neck squamous cell carcinoma (HNSCC); however, response rates are modest. We hypothesized that adding stereotactic body radiation therapy (SBRT) to anti-PD-1 would be safe prior to definitive surgical resection and would enhance pathological response compared with historical cohorts of patients with locoregionally advanced HNSCC treated with checkpoint inhibitor alone.

METHODS

The Neoadjuvant Immuno-Radiotherapy Trial was an investigator-initiated single institution phase Ib clinical trial that enrolled patients with previously untreated locally advanced HPV-positive and HPV-negative HNSCC between 2018 and 2019. Eligible patients were treated with neoadjuvant SBRT at a total dose of either 40 Gy in 5 fractions or 24 Gy in 3 fractions, delivered in a 1-week timespan, with or without nivolumab, prior to definitive surgical resection. Patients were then planned for treatment with adjuvant nivolumab for 3 months. The primary safety endpoint was unplanned delay in surgery considered to be at least possibly related to neoadjuvant treatment. The primary efficacy endpoints included pathological complete response (pCR), major pathological response (mPR), and the rate of clinical to pathological downstaging after neoadjuvant treatment.

RESULTS

Twenty-one patients underwent neoadjuvant treatment, which was well tolerated and did not delay surgery, thus meeting the primary endpoint. Tissue responses were characterized by robust inflammatory infiltrates in the regression bed, plasma cells and cholesterol clefts. Among the entire study group, the mPR and pCR rate was 86% and 67%, respectively. Clinical to pathological downstaging occurred in 90% of the patients treated.

CONCLUSION

These data demonstrate that radiation delivered only to the gross tumor volume combined with immunotherapy was safe, resulted in a high rate of mPR and should be further evaluated as a locally focused neoadjuvant therapy for patients with head and neck cancer.

TRIAL REGISTRATION NUMBER

This study is registered with clinicaltrials.gov (NCT03247712) and is active, but closed to patient accrual.

The abscopal effect: a sense of DNA damage is in the air

Tumor metastasis is a singularly important determinant of survival in most cancers. Historically, radiation therapy (RT) directed at a primary tumor mass was associated infrequently with remission of metastasis outside the field of irradiation. This away-from-target or "abscopal effect" received fringe attention because of its rarity. With the advent of immunotherapy, there are now increasing reports of abscopal effects upon RT in combination with immune checkpoint inhibition. This sparked investigation into underlying mechanisms and clinical trials aimed at enhancement of this effect. While these studies clearly attribute the abscopal effect to an antitumor immune response, the initial molecular triggers for its onset and specificity remain enigmatic. Here, we propose that DNA damage-induced inflammation coupled with neoantigen generation is essential during this intriguing phenomenon of systemic tumor regression and discuss the implications of this model for treatment aimed at triggering the abscopal effect in metastatic cancer.

Radiotherapy in the Era of Immunotherapy With a Focus on Non-Small-Cell Lung Cancer: Time to Revisit Ancient Dogmas?

Radiation-induced immune effects have been extensively deciphered over the last few years, leading to the concept of the dual immune effect of radiotherapy with both immunostimulatory and immunosuppressive effects. This explains why radiotherapy alone is not able to drive a strong anti-tumor immune response in most cases, hence underlining the rationale for combining both radiotherapy and immunotherapy. This association has generated considerable interest and hundreds of trials are currently ongoing to assess such an association in oncology. However, while some trials have provided unprecedented results or shown much promise, many hopes have been dashed. Questions remain, therefore, as to how to optimize the combination of these treatment modalities. This narrative review aims at revisiting the old, well-established concepts of radiotherapy relating to dose, fractionation, target volumes and organs at risk in the era of immunotherapy. We then propose potential innovative approaches to be further assessed when considering a radio-immunotherapy association, especially in the field of non-small-cell lung cancer (NSCLC). We finally propose a framework to optimize the association, with pragmatic approaches depending on the stage of the disease.

Delayed Response After Confirmed Progression (DR) and Other Unique Immunotherapy-Related Treatment Concepts in Cutaneous Squamous Cell Carcinoma

Non-melanoma skin cancers are one of the most common cancers diagnosed worldwide, with the highest incidence in Australia and New Zealand. Systemic treatment of locally advanced and metastatic cutaneous squamous cell carcinomas has been revolutionized by immune checkpoint inhibition with PD-1 blockade. We highlight treatment issues distinct to the management of the disease including expansion of the traditional concept of pseudoprogression and describe delayed responses after immune-specific response criteria confirmed progressive disease with and without clinical deterioration. We term this phenomenon “delayed response after confirmed progression (DR)”. We also discuss the common development of second primary tumors, heterogeneous disease responses, and expanding clinical boundaries for immunotherapy use.

Programmed Death-1/Programmed Death-Ligand 1-Axis Blockade in Recurrent or Metastatic Head and Neck Squamous Cell Carcinoma Stratified by Human Papillomavirus Status: A Systematic Review and Meta-Analysis

Background

Programmed death-1/programmed death-ligand 1 (PD-1/PD-L1) inhibitors have provided clinical benefit to head and neck squamous cell carcinoma (HNSCC) patients in recent clinical trials. However, it remains unclear as to whether human papillomavirus (HPV) status is associated with improved clinical outcome of anti-PD-1 or anti-PD-L1 immunotherapy in HNSCC.

Methods

PubMed, EMBASE, Cochrane Library, and Web of Science were systematically searched up to February 28, 2021. Published clinical trials of HNSCC patients treated with only PD-1 or PD-L1 inhibitors were selected. The primary or secondary outcome of these studies included objective response rate (ORR) stratified by HPV status. The pooled odds ratio (OR) and hazard ratio (HR) were estimated using a fixed-effect model.

Results

A total of seven eligible studies comprising 814 patients were included. The ORR of HPV positive HNSCC patients was significantly higher than that of HPV negative HNSCC patients (OR = 1.77; 95%CI = 1.14-2.74; P = 0.01), and this favorable effect occurred in pooled anti-PD-L1 trials (OR = 2.66; 95%CI = 1.16-6.11; P = 0.02). In comparison, the pooled OR was 1.51 in anti-PD-1 trials (95%CI = 0.90-2.54; P = 0.12). Survival analysis indicated that HPV positive HNSCC patients had a lower risk of overall death as compared to HPV negative HNSCC patients (HR = 0.77; 95%CI = 0.60–0.99; P = 0.04).

Conclusions

HPV positive HNSCC patients display improved outcomes with PD-1/PD-L1 axis blockade as compared to HPV negative HNSCC patients. These improved outcomes are likely driven to a greater extent by anti-PD-L1 inhibitors. However, randomized controlled trials with greater numbers of patients are needed for validation of these early findings.

Radiation dose and fraction in immunotherapy: one-size regimen does not fit all settings, so how does one choose?

Recent evidence indicates that ionizing radiation can enhance immune responses to tumors. Advances in radiation delivery techniques allow hypofractionated delivery of conformal radiotherapy. Hypofractionation or other modifications of standard fractionation may improve radiation’s ability to promote immune responses to tumors. Other novel delivery options may also affect immune responses, including T-cell activation and tumor-antigen presentation changes. However, there is limited understanding of the immunological impact of hypofractionated and unique multifractionated radiotherapy regimens, as these observations are relatively recent. Hence, these differences in radiotherapy fractionation result in distinct immune-modulatory effects. Radiation oncologists and immunologists convened a virtual consensus discussion to identify current deficiencies, challenges, pitfalls and critical gaps when combining radiotherapy with immunotherapy and making recommendations to the field and advise National Cancer Institute on new directions and initiatives that will help further development of these two fields.

This commentary aims to raise the awareness of this complexity so that the need to study radiation dose, fractionation, type and volume is understood and valued by the immuno-oncology research community. Divergence of approaches and findings between preclinical studies and clinical trials highlights the need for evaluating the design of future clinical studies with particular emphasis on radiation dose and fractionation, immune biomarkers and selecting appropriate end points for combination radiation/immune modulator trials, recognizing that direct effect on the tumor and potential abscopal effect may well be different. Similarly, preclinical studies should be designed as much as possible to model the intended clinical setting. This article describes a conceptual framework for testing different radiation therapy regimens as separate models of how radiation itself functions as an immunomodulatory ‘drug’ to provide alternatives to the widely adopted ‘one-size-fits-all’ strategy of frequently used 8 Gy×3 regimens immunomodulation.

Avelumab plus standard-of-care chemoradiotherapy versus chemoradiotherapy alone in patients with locally advanced squamous cell carcinoma of the head and neck: a randomised, double-blind, placebo-controlled, multicentre, phase 3 trial

BACKGROUND

Chemoradiotherapy is the standard of care for unresected locally advanced squamous cell carcinoma of the head and neck. We aimed to assess if addition of avelumab (anti-PD-L1) to chemoradiotherapy could improve treatment outcomes for this patient population.

METHODS

In this randomised, double-blind, placebo-controlled, phase 3 study, patients were recruited from 196 hospitals and cancer treatment centres in 22 countries. Patients aged 18 years or older, with histologically confirmed, previously untreated, locally advanced squamous cell carcinoma of the oropharynx, hypopharynx, larynx, or oral cavity (unselected for PD-L1 status), an Eastern Cooperative Oncology Group performance status score of 0 or 1, and who could receive chemoradiotherapy were eligible. Patients were randomly assigned (1:1) centrally by means of stratified block randomisation with block size four (stratified by human papillomavirus status, tumour stage, and nodal stage, and done by an interactive response technology system) to receive 10 mg/kg avelumab intravenously every 2 weeks plus chemoradiotherapy (100 mg/m2 cisplatin every 3 weeks plus intensity-modulated radiotherapy with standard fractionation of 70 Gy [35 fractions during 7 weeks]; avelumab group) or placebo plus chemoradiotherapy (placebo group). This was preceded by a single 10 mg/kg avelumab or placebo lead-in dose given 7 days previously and followed by 10 mg/kg avelumab or placebo every 2 weeks maintenance therapy for up to 12 months. The primary endpoint was progression-free survival by investigator assessment per modified Response Evaluation Criteria in Solid Tumors, version 1.1, in all randomly assigned patients. Adverse events were assessed in patients who received at least one dose of avelumab or placebo. This trial is registered with ClinicalTrials.gov, NCT02952586. Enrolment is no longer ongoing, and the trial has been discontinued.

FINDINGS

Between Dec 12, 2016, and Jan 29, 2019, from 907 patients screened, 697 patients were randomly assigned to the avelumab group (n=350) or the placebo group (n=347). Median follow-up for progression-free survival was 14·6 months (IQR 8·5-19·6) in the avelumab group and 14·8 months (11·6-18·8) in the placebo group. Median progression-free survival was not reached (95% CI 16·9 months-not estimable) in the avelumab group and not reached (23·0 months-not estimable) in the placebo group (stratified hazard ratio 1·21 [95% CI 0·93-1·57] favouring the placebo group; one-sided p=0·92). The most common grade 3 or worse treatment-related adverse events were neutropenia (57 [16%] of 348 patients in the avelumab group vs 52 [15%] of 344 patients in the placebo group), mucosal inflammation (50 [14%] vs 45 [13%]), dysphagia (49 [14%] vs 47 [14%]), and anaemia (41 [12%] vs 44 [13%]). Serious treatment-related adverse events occurred in 124 (36%) patients in the avelumab group and in 109 (32%) patients in the placebo group. Treatment-related deaths occurred in two (1%) patients in the avelumab group (due to general disorders and site conditions, and vascular rupture) and one (<1%) in the placebo group (due to acute respiratory failure).

INTERPRETATION

The primary objective of prolonging progression-free survival with avelumab plus chemoradiotherapy followed by avelumab maintenance in patients with locally advanced squamous cell carcinoma of the head and neck was not met. These findings may help inform the design of future trials investigating the combination of immune checkpoint inhibitors plus CRT.

FUNDING

Pfizer and Merck KGaA, Darmstadt, Germany.

Re-irradiation with concurrent and maintenance nivolumab in locally recurrent and inoperable squamous cell carcinoma of the head and neck: A single-center cohort study

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Combination of in-field ReRT and nivolumab for locally recurrent HNSCC is feasible.

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No unexpected radiation-related toxicity occurred.

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CRP-, hemoglobin-levels, and neutrophil/lymphocyte ratio were associated with LPFS.

Background

The rate of loco-regional recurrences for locally advanced head and neck squamous cell carcinoma (HNSCC) following standard treatment reaches up to 50%, accompanied by a probability of 20% to develop a second primary tumor in the head and neck region.

Methods

Ten patients with inoperable, in-field recurrence of HNSCC following previous primary or adjuvant radiotherapy (RT) in combination with concurrent platinum-based chemotherapy were re-irradiated with 60 Gray in 30 fractions between December 2017 and January 2020 with concurrent and maintenance nivolumab administration. Data were retrospectively collected and compared with patients who underwent re-irradiation (ReRT) with concurrent cisplatin following propensity score matching (PSM). Local progression-free survival (LPFS) and overall survival (OS) were visualized using Kaplan-Meier method (log-rank test).

Results

All patients completed ReRT. Median number of applied courses of nivolumab was 12 (range, 3–38). OS rate was 50% at 12 months and the median OS was 11 (range, 2–23) months. Six and 12 month LPFS rates were 60% and 30%, respectively. Median LPFS was 8 (range, 2–19) months. OS and LPFS rates were not inferior to those of patients treated with concurrent cisplatin. No unexpected radiation-related toxicity occurred. A total of four patients developed any-grade immune-related adverse events of which two presented with grade 3 toxicities. One patient died within 3 weeks after ReRT. Higher blood levels of CRP (p = 0.004), lower levels of hemoglobin (p = 0.029) and higher neutrophil/lymphocyte ratio (p = 0.004) were associated with impaired LPFS. Higher recursive portioning analysis (RPA) class was associated with impaired LPFS (p = 0.022) and OS (p = 0.024).

Conclusion

The combination of ReRT and nivolumab for locally recurrent HNSCC was feasible without occurrence of unexpected toxicities. Combined radioimmunotherapy might offer an effective treatment option for carefully selected pre-irradiated patients ineligible for salvage surgery.

Is There a Benefit of Combining Immunotherapy and Radiotherapy in Bladder Cancer?

Immune checkpoint inhibitors have transformed the management of patients with metastatic urothelial cancer, by leading to long-term response and prolongation of survival in a subset of patients. Unfortunately, only one in five patients with metastatic urothelial cancer responds to anti-programmed death ligand-1 ([AQ1]anti-PD-1) monotherapy. Preclinical and early clinical evidence indicates that radiotherapy not only acts locally, but also exerts systemic anti-tumour effects by modulating the immune system. It is hypothesised that combining checkpoint inhibitors with radiotherapy might enhance an anti-tumour immune response and increase response rates. So far, a handful of early phase clinical trials have been performed seeking to answer this question in urothelial cancer patients. The current review summarises the available preclinical and clinical evidence on radiotherapy/immunotherapy combinations in locally advanced and metastatic bladder cancer and suggests future avenues worthy of exploration.

Avelumab, a PD-L1 Inhibitor, in Combination with Hypofractionated Radiotherapy and the Abscopal Effect in Relapsed Refractory Multiple Myeloma

Lessons Learned

Despite the initial optimism for using immune checkpoint inhibition in the treatment of multiple myeloma, subsequent clinical studies have been disappointing.

Preclinical studies have suggested that priming the immune system with various modalities in addition to checkpoint inhibition may overcome the relative T‐cell exhaustion or senescence; however, in this small data set, radiotherapy with checkpoint inhibition did not appear to activate the antitumor immune response.

Background

Extramedullary disease (EMD) is recognized as an aggressive subentity of multiple myeloma (MM) with a need for novel therapeutic approaches. We therefore designed a proof‐of‐principle pilot study to evaluate the synergy between the combination of the anti–PD‐L1, avelumab, and concomitant hypofractionated radiotherapy.

Methods

This was a single‐arm phase II Simon two‐stage single center study that was prematurely terminated because of the COVID‐19 pandemic after enrolling four patients. Key eligibility included patients with relapsed/refractory multiple myeloma (RRMM) who had exhausted or were not candidates for standard therapy and had at least one lesion amenable to radiotherapy. Patients received avelumab until progression or intolerable toxicity and hypofractionated radiotherapy to a focal lesion in cycle 2. Radiotherapy was delayed until cycle 2 to allow the avelumab to reach a study state, given the important observation from previous studies that concomitant therapy is needed for the abscopal effect.

Results

At a median potential follow‐up of 10.5 months, there were no objective responses, one minimal response, and two stable disease as best response. The median progression‐free survival (PFS) was 5.3 months (95% confidence interval [CI]: 2.5–7.1 months), and no deaths occurred. There were no grade ≥3 and five grade 1–2 treatment‐related adverse events.

Conclusion

Avelumab in combination with radiotherapy for patients with RRMM and EMD was associated with very modest systemic clinical benefit; however, patients did benefit as usual from local radiotherapy. Furthermore, the combination was very well tolerated compared with historical RRMM treatment regimens.

Overcoming Resistance to Immune Checkpoint Inhibitors in Head and Neck Squamous Cell Carcinomas

Preclinical data suggest that head and neck squamous cell carcinomas (HNSCC) may evade immune surveillance and induce immunosuppression. One mechanism of immune evasion involves the expression of programmed death ligand-1 (PD-L1) in tumor and immune cells, which is, to date, the only biomarker routinely used in clinical practice to select patients with advanced HNSCCs more likely to benefit from anti-PD-1 therapy. Nonetheless, PD-L1 expression alone incompletely captures the degree of sensitivity of HNSCCs to PD-1 inhibitors. Most patients exposed to anti-PD-1 antibodies do not respond to therapy, suggesting the existence of mechanisms of de novo resistance to immunotherapy. Furthermore, patients that initially respond to PD-1 inhibitors will eventually develop acquired resistance to immunotherapy through mechanisms that have not yet been completely elucidated. In this article, we will provide an overview of the immune landscape of HNSCCs. We will briefly describe the clinical activity of inhibitors of the PD-1/PD-L1 axis in this disease, as well as biomarkers of benefit from these agents that have been identified so far. We will review pre-clinical and clinical work in cancers in general, and in HNSCCs specifically, that have characterized the mechanisms of de novo and acquired resistance to immunotherapy. Lastly, we will provide insights into novel strategies under investigation to overcome resistance to immune checkpoint inhibitors.

Radiotherapy and Immunotherapy for Head and Neck Cancer: Current Evidence and Challenges

Immune checkpoint inhibitors (ICI) have revolutionized cancer treatment over the past decade. However, although the immune landscape suggests a strong rationale for the use of these agents in patients with head and neck squamous cell carcinoma, the available clinical evidence indicates that most patients currently do not respond to ICI monotherapy. Radiotherapy is a primary treatment modality for many patients with locally advanced head and neck cancer. While ionizing radiation traditionally has been thought to act in a purely cytotoxic fashion, a growing body of preclinical studies have demonstrated additional profound immunomodulatory effects. Consequently, there has been a surge of interest in the potential synergy between radiotherapy and immunotherapy, both the potential for radiotherapy to augment the systemic anti-tumor immune response and the potential for immunotherapy to improve in-field tumor response to radiation. In this review, we summarize the current preclinical and clinical evidence for radioimmunotherapy, with a particular focus on studies directly relevant to head and neck squamous cell carcinoma, as well as existing challenges and future directions for this emerging field.

Radiation and Immunotherapy in Upper Gastrointestinal Cancers: The Current State of Play

Radiotherapy remains one of the contemporary cornerstones of cancer treatment in the neoadjuvant, curative, adjuvant and palliative settings, either in isolation or as a multimodal approach. Moreover, recent advances in targeted immune checkpoint therapy have firmly established immunotherapy as the fourth pillar in cancer therapy alongside surgery, chemotherapy and notably radiotherapy. There is emerging evidence to suggest both radioresistance and reduced efficacy of immune checkpoint blockade (ICB) are potentiated by the tumour microenvironment (TME) and in fact modulating aspects of this immunosuppressive milieu is instrumental to unlocking anti-tumour immunity. The response rates of Upper Gastrointestinal (UGI) malignancies to ICB remains modest at 10–15%, compared to melanoma at 20–40%. Harnessing the effects of radiotherapy through remodelling of the TME using ICB as a radiosensitisor is an avenue showing promise. Here we explore the rationale behind combining radiotherapy with ICB, as a symbiotic relationship in shifting the balance in favour of anti-tumour immunity. We discuss the effects of radiotherapy on immunogenic cell death, the concept of the abscopal effect, the importance of the cGAS STING pathway, and their relevance in the context of the tumour microenvironment. Furthermore, dosing and timing of radiotherapy and ICB is now being evaluated for its synergistic effects on host tumour immunity, and we review the ongoing efforts and current available literature for single agent and dual agent ICB in combination multimodal therapy for both locally advanced operable and metastatic disease of the upper gastrointestinal tract.

Oligometastatic Disease Management: Finding the Sweet Spot

Hematogenous dissemination represents a common manifestation of squamous cell carcinoma of the head and neck, and the recommended therapeutic options usually consist of systemically administered drugs with palliative intent. However, mounting evidence suggests that patients with few and slowly progressive distant lesions of small size may benefit from various local ablation techniques, which have already been established as standard-of-care modalities for example in colorectal and renal cell carcinomas and in sarcomas. In principle, serving as radical approaches to eradicate cancer, these interventions can be curative. Their impact on local control and overall survival has been shown in numerous retrospective and prospective studies. The term oligometastatic refers to the number of distant lesions which should generally not surpass five in total, ideally in one organ. Currently, surgical resection remains the method of choice supported by the majority of published data. More recently, stereotactic (ablative) body radiotherapy (SABR/SBRT) has emerged as a viable alternative. In cases technically amenable to such local interventions, several other clinical variables need to be taken into account also, including patient-related factors (general health status, patient preferences, socioeconomic background) and disease-related factors (primary tumor site, growth kinetics, synchronous or metachronous metastases). In head and neck cancer, patients presenting with late development of slowly progressive oligometastatic lesions in the lungs secondary to human papillomavirus (HPV)-positive oropharyngeal cancer are the ideal candidates for metastasectomy or other local therapies. However, literature data are still limited to say whether there are other subgroups benefiting from this approach. One of the plausible explanations is that radiological follow-up after primary curative therapy is usually not recommended because its impact on survival has not been unequivocal, which is also due to the rarity of oligometastatic manifestations in this disease. At the same time, aggressive treatment of synchronous metastases early in the disease course should be weighed against the risk of futile interventions in a disease with already multimetastatic microscopic dissemination. Therefore, attentive treatment sequencing, meticulous appraisal of cancer extension, refinement of post-treatment surveillance, and understanding of tumor biology and kinetics are crucial in the management of oligometastases.

Metastasis-directed therapy for oligometastasis and beyond

Metastasis-directed therapy (MDT)-local therapy that is intended to eradicate specific metastatic lesions-has hitherto been used with varying degrees of clinical efficacy and acceptance as a meaningful therapy for metastatic disease. Over the past 25 years, however, the momentum for using MDT to manage patients with metastatic solid tumours has increased, driven by several factors. Among these factors is the recognition that patients with limited metastatic burden could potentially derive survival benefits from MDT. Furthermore, although current systemic therapies are increasingly effective, they are infrequently curative. In addition, technological advances have broadened the spectrum of metastatic lesions that can be treated with ablative intent. Here we aim to briefly review the status of evidence for the clinical benefit of MDT based on current data mainly from trials in patients with oligometastatic disease, discuss the myriad of clinical states that might fall under and beyond the definition of oligometastasis, review technological advances in MDT and their applications beyond oligometastasis, and discuss the need for the continued co-evolution of MDT and systemic therapy as we seek to understand which patients with metastatic cancer can achieve durable remission and how to optimally manage those who cannot.

The head and neck cancer genome in the era of immunotherapy

The recent success of immunotherapy in head and neck squamous cell carcinoma (HNSCC) has necessitated a new perspective on the cancer genome. Here we review recent advances in the carcinogenesis and molecular genetics of HNSCC with an eye on their implications for cancer immunity. Newer sequencing technologies have recently facilitated dissection of the complex interaction between the HPV virus, tumor, host factors, and the tumor microenvironment (TME) that help shed light on how the immune system interacts with head and neck malignancies.

Challenges in Combining Immunotherapy with Radiotherapy in Recurrent/Metastatic Head and Neck Cancer

Immunotherapy with immune checkpoint inhibitors (ICI) has recently become a standard part of the treatment of recurrent or metastatic head and neck squamous cell carcinoma (R/M HNSCC), although the response rates are low. Numerous preclinical and clinical studies have now illuminated several mechanisms by which radiotherapy (RT) enhances the effect of ICI. From RT-induced immunogenic cancer cell death to its effect on the tumor microenvironment and vasculature, the involved mechanisms are diverse and intertwined. Moreover, the research of these interactions is challenging because of the thin line between immunostimulatory and the immunosuppressive effect of RT. In the era of active research of immunoradiotherapy combinations, the significance of treatment and host-related factors that were previously seen as being less important is being revealed. The impact of dose and fractionation of RT is now well established, whereas selection of the number and location of the lesions to be irradiated in a multi-metastatic setting is something that is only now beginning to be understood. In addition to spatial factors, the timing of irradiation is as equally important and is heavily dependent on the type of ICI used. Interestingly, using smaller-than-conventional RT fields or even partial tumor volume RT could be beneficial in this setting. Among host-related factors, the role of the microbiome on immunotherapy efficacy must not be overlooked nor can we neglect the role of gut irradiation in a combined RT and ICI setting. In this review we elaborate on synergistic mechanisms of immunoradiotherapy combinations, in addition to important factors to consider in future immunoradiotherapy trial designs in R/M HNSCC.

Prospective Evaluation of All-lesion Versus Single-lesion Radiotherapy in Combination With PD-1/PD-L1 Immune Checkpoint Inhibitors

Background

Local ablative treatments improve survival in patients with oligometastatic disease in addition to chemotherapy. The application of immune checkpoint inhibitors prolonged patients’ survival in different tumor entities. This raises the question if patients still benefit from intensified local treatments in combination with a more efficient systemic treatment with immune checkpoint inhibitors.

Methods

The prospective non-interventional ST-ICI trial investigates treatment with PD-1/PD-L1 (Programmed cell death protein 1/Programmed cell death 1 ligand 1) immune checkpoint inhibitors and radiotherapy in different tumor entities. Patients who started radiotherapy and immunotherapy concomitantly were included in this interim analysis. In this cohort patients with all-lesion radiotherapy (all tumor lesions irradiated, al-RT) were compared to patients with radiotherapy to only a single of their tumor lesions (single-lesion radiotherapy, sl-RT). Endpoints of the interim analysis were progression-free survival (PFS), overall survival (OS) and time to progression (TTP).

Results

A total of 104 patients were registered between April 2017 and August 2019. Fifty patients started immune checkpoint inhibitor treatment and radiotherapy concomitantly and were included. Most frequent tumor entities were non-small cell lung cancer (62%) followed by head and neck squamous cell cancer (26%). Most frequent location of radiotherapy was lung (34%) and central nervous system (20%). Median duration of follow-up was 8.6 months beginning with first administration of the immune-checkpoint-inhibitor. Median PFS was 9.2 months (95% CI, 5.8 – 12.6) in the al-RT group and 3.0 months (95% CI, 2.5 – 3.5) in the sl-RT group (p<0.001). Median OS was 11.6 months (95% CI, 8.1 - 15.1) in the al-RT group and 4.2 months (95% CI, 3.0 - 5.4) in the sl-RT group (p=0.007). Median TTP was not reached in the al-RT group compared to 4.6 months (95% CI, 1.1–8.0) in the sl-RT group (p=0.028). Univariate Cox regression analyses computed tumor entity, histology, central nervous system metastases, immunotherapy drug and al-RT as predictors of OS (with an effect p-value of ≤ 0.1). In the multivariable analysis only tumor entity and al-RT remained prognostic factors for OS.

Conclusion

Patients with PD-1/PD-L1 immune checkpoint inhibitor therapy benefit from local radiotherapy to all known lesions compared to single-lesion radiotherapy regarding PFS and OS.

Multivariable Analysis of 169 Cases of Advanced Cutaneous Melanoma to Evaluate Antibiotic Exposure as Predictor of Survival to Anti-PD-1 Based Immunotherapies

Recently antibiotic exposure has been associated with worse outcomes in patients undergoing treatment with antibodies directed against programmed cell death protein-1 (PD-1). We reviewed data of 1264 patients enrolled at Melanoma Skin and Ocular Tissue Repositories at University of Iowa Hospitals and Clinic. Reviewed data included patient demographics, prior medical history, baseline hematologic and disease parameters and outcomes including progression-free survival (PFS) and overall survival (OS). Cox regression models were used to determine predictive markers. Overall, 169 patients with advanced cutaneous melanoma received anti-PD-1 based therapies. Median follow up was 18.46 (range 0.89 to 62.52) months. On multivariable analysis brain metastasis, higher absolute neutrophil count (ANC) and lower absolute lymphocyte count were associated with poorer PFS while brain and liver metastasis and lower albumin were associated with poorer OS. Prior antibiotics, radiation as well as age, gender, basal metabolic index (BMI), smoking status, BRAF mutation, line of therapy (first or latter), prior treatments (ipilimumab or BRAF inhibitors), hemoglobin, neutrophil-to-lymphocyte ratio, white blood cell, platelet and eosinophil counts were not associated with PFS or OS in multivariable analysis. Contrary to some prior studies BMI, radiation, and antibiotics were not associated with PFS or OS.