De-Escalation Strategies in HPV-Associated Oropharynx Cancer-Are we Putting the Cart Before the Horse?

Are we ready for deintensification in human papillomavirus-positive oropharyngeal carcinomas?

PURPOSE OF REVIEW

Excellent outcomes following contemporary treatment of human papillomavirus (HPV)-positive oropharyngeal carcinoma (HPV+ OPC) have prompted the exploration of deintensification approaches to minimize treatment-related toxicities. This review describes the landscape of deintensification to date (up to November 2022).

RECENT FINDINGS

Although several deintensification trials have been published, none are practice changing. Three phase III randomized-controlled trials studying cetuximab and radiation therapy vs. standard chemoradiotherapy all showed inferior outcomes. Although some phase II trials reported favourable outcomes, they are often single-arm trials without an adequate control arm, thereby limiting the ability to modify practice.

SUMMARY

Substantial effort has been expended to explore deintensification options for selected HPV+ OPC patients aiming to avoid unnecessary toxicity. Strategies have included replacing cisplatin with cetuximab, reduced chemotherapy or radiotherapy intensity, reduction of radiotherapy volumes and risk stratification after trans-oral surgery or following induction chemotherapy. Challenges remain in the current deintensification landscape, including identifying the most suitable candidates along with a choice of most appropriate deintensification strategies. Promising selection criteria included either static baseline features or kinetic characteristics of clinical-biological parameters. Practice-changing trials remain elusive, and the search continues to attempt optimization of the therapeutic ratio for these patients.

GA-OH enhances the cytotoxicity of photon and proton radiation in HPV+ HNSCC cells

Introduction

Treatment-related toxicity following either chemo- or radiotherapy can create significant clinical challenges for HNSCC cancer patients, particularly those with HPV-associated oropharyngeal squamous cell carcinoma. Identifying and characterizing targeted therapy agents that enhance the efficacy of radiation is a reasonable approach for developing de-escalated radiation regimens that result in less radiation-induced sequelae. We evaluated the ability of our recently discovered, novel HPV E6 inhibitor (GA-OH) to radio-sensitize HPV+ and HPV- HNSCC cell lines to photon and proton radiation.

Methods

Radiosensitivity to either photon or proton beams was assessed using various assays such as colony formation assay, DNA damage markers, cell cycle and apoptosis, western blotting, and primary cells. Calculations for radiosensitivity indices and relative biological effectiveness (RBE) were based on the linear quadratic model.

Results

Our results showed that radiation derived from both X-ray photons and protons is effective in inhibiting colony formation in HNSCC cells, and that GA-OH potentiated radiosensitivity of the cells. This effect was stronger in HPV+ cells as compared to their HPV- counterparts. We also found that GA-OH was more effective than cetuximab but less effective than cisplatin (CDDP) in enhancing radiosensitivity of HSNCC cells. Further tests indicated that the effects of GA-OH on the response to radiation may be mediated through cell cycle arrest, particularly in HPV+ cell lines. Importantly, the results also showed that GA-OH increases the apoptotic induction of radiation as measured by several apoptotic markers, even though radiation alone had little effect on apoptosis.

Conclusion

The enhanced combinatorial cytotoxicity found in this study indicates the strong potential of E6 inhibition as a strategy to sensitize cells to radiation. Future research is warranted to further characterize the interaction of GA-OH derivatives and other E6-specific inhibitors with radiation, as well as its potential to improve the safety and effectiveness of radiation treatment for patients with oropharyngeal cancer.

p53 Modulates Radiosensitivity in Head and Neck Cancers-From Classic to Future Horizons

p53, initially considered a tumor suppressor, has been the subject of research related to cancer treatment resistance in the last 30 years. The unfavorable response to multimodal therapy and the higher recurrence rate, despite an aggressive approach, make HNSCC a research topic of interest for improving therapeutic outcomes, even if it is only the sixth most common malignancy worldwide. New advances in molecular biology and genetics include the involvement of miRNA in the control of the p53 pathway, the understanding of mechanisms such as gain/loss of function, and the development of different methods to restore p53 function, especially for HPV-negative cases. The different ratio between mutant p53 status in the primary tumor and distant metastasis originating HNSCC may serve to select the best therapeutic target for activating an abscopal effect by radiotherapy as a "booster" of the immune system. P53 may also be a key player in choosing radiotherapy fractionation regimens. Targeting any pathway involving p53, including tumor metabolism, in particular the Warburg effect, could modulate the radiosensitivity and chemo-sensitivity of head and neck cancers.

Novel Strategies for Managing Retropharyngeal Lymph Node Metastases in Head and Neck and Thyroid Cancer with Transoral Robotic Surgery (TORS)

Retropharyngeal metastases are encountered in a variety of head and neck malignancies, imposing significant surgical challenges owing to their distinct location and proximity to neurovascular structures. Radiotherapy is the recommended treatment in most cases owing to its oncological efficacy. However, retropharyngeal irradiation affects the superior pharyngeal constrictor muscles and parotid glands, with the potential for long-term dysphagia and xerostomia. A younger oropharyngeal and thyroid cancer patient demographic is trending, fueling interest in treatment de-escalation strategies. Consequently, reducing radiotoxicity and its long-term effects is of special relevance in modern head and neck oncology practice. Through its unique ability to safely extirpate these traditionally difficult-to-access retropharyngeal lymph nodes via a natural orifice, TransOral Robotic Surgery (TORS) can considerably lower the surgical morbidity of retropharyngeal lymph node dissection (RPLND), compared with current existing approaches. This review summarizes the latest developments in the field, exposing current research gaps and discusses specific clinical settings where TORS could enable treatment de-escalation. In early-stage node-negative oropharyngeal cancer, single-modality surgical treatment with TORS RPLND may improve risk stratification of metastasis and recurrence in this region. TORS RPLND is also a potentially viable treatment option in salvage of an isolated retropharyngeal node recurrence or in the primary setting of a thyroid malignancy with a single positive retropharyngeal node. In time, TORS RPLND may provide an alternative de-escalation strategy in these three scenarios. However, with the reported morbidities, further prospective trials with long-term follow-up data are required to prove oncological safety and functional benefits over existing strategies.

The accuracy of clinical neck staging for p16-positive and negative oropharyngeal cancer and its therapeutic implications

Purpose

Oropharyngeal squamous cell carcinoma (OPSCC) may be treated with primary surgery or primary (chemo)radiation. While surgery with concurrent neck dissection provides definitive pathological staging of the neck, non-surgical treatment relies on clinical staging for treatment planning. To assess the accuracy of clinical neck staging, we compared clinical to surgical staging after primary surgery in patients with p16-negative and p16-positive OPSCC.

Methods

Retrospective analysis of clinical, pathological, and oncologic outcome data of patients with OPSCC treated with primary surgery and bilateral neck dissection. Clinical and pathological nodal status were compared for p16-negative and p16-positive patients. Patients with occult metastatic disease were analyzed in detail.

Results

95 patients were included. 60.5% of p16-negative patients and 66.6% of p16-positive patients had pathologically confirmed metastatic neck disease. p16-positive patients had improved 24-month recurrence-free survival compared to p16-negative patients at 93.3% vs. 69.6%. Pathological N-status differed from clinical N-status in 36.8% of p16-negative patients vs. 31.6% of p16-positive patients. Occult metastatic disease was more common in p16-negative patients at 18.4% vs. 8.8% for p16-positive patients. Clinical detection sensitivity for extranodal extension was low overall; sensitivity was 27.3% and specificity was 91.6% for p16-negative patients vs. 61.5% and 80.0% for p16-positive patients, respectively.

Conclusion

Our data show a considerable degree of inaccuracy of clinical neck staging results in all OPSCC patients which needs to be taken into consideration during therapy planning. For p16-positive patients, these findings warrant attention in the context of therapy deintensification to avoid undertreatment.

Radiomics Predicts for Distant Metastasis in Locally Advanced Human Papillomavirus-Positive Oropharyngeal Squamous Cell Carcinoma

Simple Summary

There is strong evidence that locally advanced human papillomavirus positive (HPV+) oropharyngeal squamous cell carcinoma (OPSCC) carries a significantly better prognosis than HPV negative OPSCC, suggesting the possibility of treatment de-escalation and, therefore, toxicity reduction in this patient population. The lack of success in clinical trials towards this end presses the need to risk stratify locally advanced HPV+ OPSCC patients who can safely have treatment de-escalated. The present study had recourse to radiomics for this purpose and showed that radiomics has the ability to discriminate patients with locally advanced HPV+ OPSCC who went on to develop distant metastasis after completion of definitive chemoradiation or radiation alone. The implications of this study aid in demonstrating the potential pivotal role of radiomics in predictive risk assessment and personalizing therapy for this patient population.

Abstract

(1) Background and purpose: clinical trials have unsuccessfully tried to de-escalate treatment in locally advanced human papillomavirus positive (HPV+) oropharyngeal squamous cell carcinoma (OPSCC) with the goal of reducing treatment toxicity. The aim of this study was to explore the role of radiomics for risk stratification in this patient population to guide treatment. (2) Methods: the study population consisted of 225 patients with locally advanced HPV+ OPSCC treated with curative-intent radiation or chemoradiation therapy. Appearance of distant metastasis was used as the endpoint event. Radiomics data were extracted from the gross tumor volumes (GTVs) identified on the planning CT, with gray level being discretized using three different bin widths (8, 16, and 32). The data extracted for the groups with and without distant metastasis were subsequently balanced using three different algorithms including synthetic minority over-sampling technique (SMOTE), adaptive synthetic sampling (ADASYN), and borderline SMOTE. From these different combinations, a total of nine radiomics datasets were derived. Top features that minimized redundancy while maximizing relevance to the endpoint were selected individually and collectively for the nine radiomics datasets to build support vector machine (SVM) based predictive classifiers. Performance of the developed classifiers was evaluated by receiver operating characteristic (ROC) curve analysis. (3) Results: of the 225 locally advanced HPV+ OPSCC patients being studied, 9.3% had developed distant metastases at last follow-up. SVM classifiers built for the nine radiomics dataset using either their own respective top features or the top consensus ones were all able to differentiate the two cohorts at a level of excellence or beyond, with ROC area under curve (AUC) ranging from 0.84 to 0.95 (median = 0.90). ROC comparisons further revealed that the majority of the built classifiers did not distinguish the two cohorts significantly better than each other. (4) Conclusions: radiomics demonstrated discriminative ability in distinguishing patients with locally advanced HPV+ OPSCC who went on to develop distant metastasis after completion of definitive chemoradiation or radiation alone and may serve to risk stratify this patient population with the purpose of guiding the appropriate therapy.

Radiotherapy biobanking: current landscape, opportunities, challenges, and future aspirations

Half of all cancer patients receive radiotherapy, which makes a substantial contribution to their long‐term disease control/cure. There are significant inter‐patient differences in response, both in terms of efficacy and toxicity (frequently delayed onset) which are difficult to predict. With the introduction of technological improvements (e.g. stereotactic body radiotherapy and proton therapy) and development of combination therapies (e.g. radiotherapy and immune checkpoint inhibition), predictive biomarkers are needed even more. Whilst genomic studies have contributed significantly to predictions of response to anticancer therapy, there is no doubt that more information can be gathered from patient tissue samples. Patients are willing to donate their tissues to biobanks and wish them to be used as widely as possible for high‐quality research. We report here a survey of the current practices in the UK from several groups collecting material from patients in radiotherapy trials and have identified barriers to collecting and sharing data and samples. We believe the current situation represents a significant missed opportunity to improve the personalisation of radiotherapy. We propose a greater involvement of patients and/or their advocates, a standardisation of the patient information leaflet, consent form content and data set, with easy linkage to clinical data, which would facilitate widespread sample and data discovery and availability to other researchers. The greater sharing of data and samples, nationally and internationally, would facilitate robust multicentre studies and avoid duplication of effort.

Targeted Therapy as a Potential De-Escalation Strategy in Locally Advanced HPV-Associated Oropharyngeal Cancer: A Literature Review

The treatment landscape of locally advanced HPV-oropharyngeal squamous cell carcinoma (OPSCC) is undergoing transformation. This is because the high cures rates observed in OPSCC are paired with severe treatment-related, long-term toxicities. These significant adverse effects have led some to conclude that the current standard of care is over-treating patients, and that de-intensifying the regimens may achieve comparable survival outcomes with lower toxicities. Consequently, several de-escalation approaches involving locally advanced OPSCC are underway. These include the reduction of dosage and volume of intensive cytotoxic regimens, as well as elimination of invasive surgical procedures. Such de-intensifying treatments have the potential to achieve efficacy and concurrently alleviate morbidity. Targeted therapies, given their overall safer toxicity profiles, also make excellent candidates for de-escalation, either alone or alongside standard treatments. However, their role in these endeavors is currently limited, because few targeted therapies are currently in clinical use for head and neck cancers. Unfortunately, cetuximab, the only FDA-approved targeted therapy, has shown inferior outcomes when paired with radiation as compared to cisplatin, the standard radio-sensitizer, in recent de-escalation trials. These findings indicate the need for a better understanding of OPSCC biology in the design of rational therapeutic strategies and the development of novel, OPSCC-targeted therapies that are safe and can improve the therapeutic index of standard therapies. In this review, we summarize ongoing research on mechanism-based inhibitors in OPSCC, beginning with the salient molecular features that modulate tumorigenic processes and response, then exploring pharmacological inhibition and pre-clinical validation studies of candidate targeted agents, and finally, summarizing the progression of those candidates in the clinic.

Current status of systemic therapy in head and neck cancer

There are several controversies in the management of head and neck cancer (SCCHN). Although combined modality treatment is standard in locally advanced SCCHN (LA-SCCHN), the optimal timing of chemotherapy has been debated. Toxicity concerns with chemoradiation (CRT) using high dose cisplatin have prompted use of less intensive approaches. Weekly cisplatin and targeted therapies have been explored in randomized trials. Benefit of neoadjuvant chemotherapy in LA-SCCHN is debated due to lack of impact on overall survival, however, it remains a viable option in the Indian setting where many patients are not eligible for upfront surgery or definite CRT due to advanced stage and poor performance status (PS). The complexity of data of immune check point inhibitors (ICPi) in metastatic setting needs cautious interpretation till an ideal biomarker for their benefit is identified. Their significant cost and promising data of oral metronomic therapy has made the treatment landscape of metastatic SCCHN even more complex. To address these burning issues, we did a critical review of evidence of systemic therapy in SCCHN.

Survival Outcomes and Treatment Decision by Human Papillomavirus Status Among Patients With Stage IVC Head and Neck Squamous Cell Carcinoma

Purpose

To investigate the influence of human papillomavirus (HPV) status on survival outcomes and treatment decisions for patients with de novo stage IV head and neck squamous cell cancers (HNSCC).

Methods

Patients initially diagnosed with de novo stage IVC HNSCC between 2010 and 2015 were identified from the Surveillance, Epidemiology, and End Results database. Cox multivariable analyses were performed to determine prognostic factors associated with head and neck cancers specific survival (HNCSS) and overall survival (OS).

Results

We identified 303 patients who received chemotherapy in this study, including 52.5% of them had HPV-positive disease. HPV-positive HNSCC had better HNCSS (P < 0.001) and OS (P < 0.001) compared to those with HPV-negative disease. The results of Cox multivariable analyses showed that HPV-negative status (P = 0.007), N3 stage (P = 0.004), bone metastases (P < 0.001), and lung metastases (P = 0.003) were associated with worse HNCSS. Similar results were found regarding the OS. The sensitivity analyses indicated that HPV-positive HNSCC patients who were treated with radiotherapy had better survival outcomes. However, no survival benefits were found in those with HPV-positive disease receiving surgery. For HPV-negative patients, no survival benefit was observed among those treated with radiotherapy or surgery.

Conclusions

Approximately half of the stage IVC HNSCC patients are HPV-related. The presence of HPV infection appears to be strongly associated with the survival outcome in patients with de novo stage IV HNSCC. Determination of HPV status may help guide clinicians in prognostic assessment and treatment decision-making in this population.

Oncologic outcomes of human papillomavirus-associated oropharynx carcinoma treated with surgery alone: A 12-institution study of 344 patients

BACKGROUND

The oncologic outcomes of surgery alone for patients with American Joint Committee on Cancer 7th edition (AJCC 7th) pN2a and pN2b human papillomavirus-associated oropharynx squamous cell carcinoma (HPV+OPSCC) are not clear.

METHODS

The authors performed a 12-institution retrospective study of 344 consecutive patients with HPV+OPSCC (AJCC 7th pT0-3 N3 M0) treated with surgery alone with 6 months or more of follow-up using univariate and multivariate analyses.

RESULTS

The 2-year outcomes for the entire cohort were 91% (182 of 200) disease-free survival (DFS), 100% (200 of 200) disease-specific survival (DSS), and 98% (200 of 204) overall survival (OS). The 18 recurrences within 2 years were 88.9% (16 of 18) local and/or regional recurrences and 11.1% (2 of 18) distant metastases. Recurrences were not significantly associated with smoking, pT stage, or pN stage. The 16 patients with locoregional recurrences within 2 years all underwent successful salvage treatments (median follow-up after salvage: 13.1 months), 43.8% (7 of 16) of whom underwent salvage surgery alone for a 2-year overall salvage radiation need of 4.5% (9 of 200). The 2-year outcomes for the 59 evaluable patients among the 109 AJCC 7th pT0-2 N2a-N2b patients with 1 to 3 pathologic lymph nodes (LNs) were as follows: local recurrence, 3.4% (2 of 59); regional recurrence, 8.4% (5 of 59); distant metastases, 0%; DFS, 88.1% (52 of 59); DSS, 100% (59 of 59); OS, 96.7% (59 of 61); and salvage radiation, 5.1% (3 of 59).

CONCLUSIONS

With careful selection, surgery alone for AJCC 7th pT0-T2N0-N2b HPV+OPSCC with zero to 3 pathologic LNs without perineural invasion, extranodal extension, or positive margins results in high DFS, DSS, OS, and salvage treatment success. Because of the short-term follow-up, these data support further investigation of treatment de-escalation in this population.

Decreasing treatment burden in HPV-related OPSCC: A systematic review of clinical trials

INTRODUCTION

Favorable outcomes are observed after treatment with standard chemoradiotherapy (CRT) for Human papillomavirus (HPV)-related oropharyngeal squamous cell carcinoma (OPSCC) patients. The consistent growing interest on treatment-related toxicity burden, potentially jeopardizing survivors' quality of life, led clinicians to investigate possible de-escalation strategies.

MATERIALS AND METHODS

A comprehensive systematic literature search of clinical trials was performed through the EMBASE database to provide an overview of the de-escalation strategies spectrum. Additionally, hand searching and clinicaltrials.gov were also used.

RESULTS

Herein, we report and discuss different approaches to de-escalation of therapy, with respect to both local and systemic strategies.

CONCLUSIONS

Several promising de-escalation experiences have been published. However, while further evidence is awaited, no changes in the management nor deviation from the standard of care should be made outside of clinical trials.

Synergies Radiotherapy-Immunotherapy in Head and Neck Cancers. A New Concept for Radiotherapy Target Volumes-"Immunological Dose Painting"

The combination of immune checkpoint inhibitors and definitive radiotherapy is investigated for the multimodal treatment of cisplatin non-eligible locally advanced head and neck cancers (HNC). In the case of recurrent and metastatic HNC, immunotherapy has shown benefit over the EXTREME protocol, being already considered the standard treatment. One of the biggest challenges of multimodal treatment is to establish the optimal therapy sequence so that the synergistic effect is maximal. Thus, superior results were obtained for the administration of anti-CTLA4 immunotherapy followed by hypofractionated radiotherapy, but the anti-PD-L1 therapy demonstrates the maximum potential of radio-sensitization of the tumor in case of concurrent administration. The synergistic effect of radiotherapy–immunotherapy (RT–IT) has been demonstrated in clinical practice, with an overall response rate of about 18% for HNC. Given the demonstrated potential of radiotherapy to activate the immune system through already known mechanisms, it is necessary to identify biomarkers that direct the “nonresponders” of immunotherapy towards a synergistic RT–IT stimulation strategy. Stimulation of the immune system by irradiation can convert “nonresponder” to “responder”. With the development of modern techniques, re-irradiation is becoming an increasingly common option for patients who have previously been treated with higher doses of radiation. In this context, radiotherapy in combination with immunotherapy, both in the advanced local stage and in recurrent/metastatic of HNC radiotherapy, could evolve from the “first level” of knowledge (i.e., ballistic precision, dose conformity and homogeneity) to “level two” of “biological dose painting” (in which the concept of tumor heterogeneity and radio-resistance supports the need for doses escalation based on biological criteria), and finally to the “third level“ ofthe new concept of “immunological dose painting”. The peculiarity of this concept is that the radiotherapy target volumes and tumoricidal dose can be completely reevaluated, taking into account the immune-modulatory effect of irradiation. In this case, the tumor target volume can include even the tumor microenvironment or a partial volume of the primary tumor or metastasis, not all the gross and microscopic disease. Tumoricidal biologically equivalent dose (BED) may be completely different from the currently estimated values, radiotherapy treating the tumor in this case indirectly by boosting the immune response. Thus, the clinical target volume (CTV) can be replaced with a new immunological-clinical target volume (ICTV) for patients who benefit from the RT–IT association (Image 1).

Potential therapeutic implications of the new tumor, node, metastasis staging system for human papillomavirus-mediated oropharyngeal cancer

PURPOSE OF REVIEW

The 8th edition tumor, node, metastasis (TNM) classification (TNM-8) introduced a new classification for human papillomavirus (HPV)-mediated oropharyngeal carcinoma (HPV+ OPC). This review summarizes its potential therapeutic implications focusing on literature published since 2018.

RECENT FINDINGS

The following are active research areas involved in clinical care and therapy relevant to TNM-8: tumor HPV testing and its clinical implications; stage I disease: treatment selection and lessons learned from recent deintensification trials; emerging strategies addressing stage II and III disease.

SUMMARY

The TNM-8 classification depicts prognosis of HPV+ OPC much more reliably compared with TNM-7. Among the advantages in outcome comparison and stratification for clinical trial entry and conduct, it also enables more satisfactory individual patient consultation to adequately estimate prognosis, and facilitates clinical and translational research. However, clinicians must remain mindful that the TNM classification is not a guideline for treatment but, instead, provides a framework for clinical research and treatment decision-making. The TNM-8 has potential to improve risk-tailored treatment algorithms for HPV+ OPC including selection of treatment modality (primary trans-oral surgery vs. radiotherapy, addition of chemotherapy) and adjusting the intensity of approaches. To realize these goals fully, it is apparent that the TNM-8 needs to evolve further.

Retropharyngeal Lymph Node Involvement in Oropharyngeal Carcinoma: Impact upon Risk of Distant Metastases and Survival Outcomes

The influence of retropharyngeal lymph node (RPLN) involvement on prognosis in oropharyngeal carcinoma remains poorly defined. The aim of this study was to assess the impact of RPLN involvement upon outcomes. A single-centre retrospective analysis of 402 patients with oropharyngeal carcinoma treated nonsurgically between 2010 and 2017 was performed. All had a baseline 2-[fluorine-18]-fluoro-2-deoxy-d-glucose (FDG) PET-CT and contrast-enhanced MRI and/or CT. RPLN status was determined by radiology review of cases with reported abnormal RPLN. Multivariate backwards logistic regression was used to examine impact on outcomes of factors. Abnormal RPLNs were identified in 40/402 (10%) of patients. Median follow up was 42.9 months. RPLN involvement was associated with inferior 3 year outcomes for overall survival (OS) (67.1% vs. 79.1%, p = 0.006) and distant metastases-free survival (DMFS) (73.9% versus 88.0%, p = 0.011), with no significant difference in local control (81.6% vs. 87.7%, p = 0.154) or regional control (80.7% vs. 85.4%, p = 0.252). On multivariate analysis abnormal RPLN, no concurrent chemotherapy and ongoing smoking were associated with inferior DMFS and OS, while advanced T stage was also associated with inferior OS. In summary, RPLN involvement, present in 10% of patients, was an independent prognostic factor for the development of distant disease failure translating into inferior OS. These findings need confirmation in future studies.