FDG-PET/CT for treatment response assessment in head and neck squamous cell carcinoma: a systematic review and meta-analysis of diagnostic performance

Diffusion-Weighted MRI for Recurrent/Persistent Head and Neck Squamous-Cell Carcinoma After Radiotherapy: Systematic Review and Meta-Analysis

OBJECTIVE

To evaluate the accuracy of diffusion-weighted magnetic resonance imaging (DWI-MRI) in diagnosing persistent/recurrent head and neck squamous cell carcinomas (HNSCCs) after primary chemoradiotherapy (CRT).

DATA SOURCES

Scopus, PubMed/MEDLINE, and Cochrane Library databases were searched for relevant publications until April 18, 2023.

REVIEW METHODS

A systematic review and meta-analysis was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses of Diagnostic Test Accuracy statement. The search was conducted independently by 2 investigators. Methodological quality of included studies was assessed using the Quality Assessment of Diagnostic Studies-2 questionnaire. Extracted data were used to calculate the pooled DWI-MRI sensitivity, specificity, diagnostic odds ratio, and positive and negative likelihood ratio.

RESULTS

A total of 618 patients from 10 studies were included for calculation of diagnostic accuracy parameters. At the level of the primary tumor, the pooled sensitivity and specificity were, respectively, 0.96 (95% confidence interval [CI]: 0.89-1.00) and 0.81 (95% CI: 0.54-0.98) in the case of qualitative analysis, and, respectively, 0.79 (95% CI: 0.66-0.89) and 0.88 (95% CI: 0.77-0.96) for quantitative analysis. At the level of the neck, the pooled sensitivity and specificity were, respectively, 0.87 (95% CI: 0.75-0.95) and 0.84 (95% CI: 0.74-0.93) when images were analyzed qualitatively, and 0.79 (95% CI: 0.60-0.94) and 0.90 (95% CI: 0.82-0.97) when analyzed quantitatively.

CONCLUSION

DWI-MRI showed high diagnostic accuracy and should be considered if persistent/recurrent HNSCCs is suspected after primary CRT. No significant differences were found between qualitative and quantitative imaging assessment.

The molecular characteristics of recurrent/metastatic HPV-positive head and neck squamous cell carcinoma: A systematic review of the literature

OBJECTIVES

About 17% of patients with human papillomavirus (HPV)-positive head and neck squamous cell carcinoma (HNSCC), which is mainly comprised of oropharyngeal SCC (OPSCC), will experience disease recurrence, which is often considered incurable when manifested at a metastatic and/or recurrent stage. We conducted a critical qualitative systematic review. Our objectives were to provide an overview of the molecular landscape of recurrent/metastatic HPV-positive HNSCC as well as novel molecular biomarkers.

DESIGN

A literature review was conducted to identify studies reporting on the molecular characteristics of recurrent/metastatic HPV-positive HNSCC, novel molecular biomarkers and treatment options. The reviews of abstracts, full articles, and revision of the included studies, followed by data extraction and quality assessment were performed by three independent assessors. All primary literature, such as retrospective, prospective, and clinical trials as well as basic research studies were considered, and the final search was conducted at the end of February 2023. The level of evidence was rated using the guidelines published by the Oxford Centre for Evidence-based Medicine and quality was assessed using the Newcastle-Ottawa Scale criteria.

RESULTS AND CONCLUSIONS

The literature search resulted in the identification of 1991 articles. A total of 181 full articles were screened, and 66 articles were included in this analysis. Several studies reported that recurrent/metastatic HPV-positive HNSCC had higher rates of TP53 mutation and were genomically similar to HPV-negative HNSCC. The detection of circulating tumour tissue-modified HPV DNA (ctHPVDNA) as a specific biomarker has shown promising results for monitoring treatment response and recurrence in the subset of HPV-positive HNSCC. In addition, evidence for targeted therapy in recurrent/metastatic HPV-positive HNSCC has emerged, including agents that inhibit overexpressed EGFR. Studies of combination immunotherapy are also underway. Our review outlines the latest evidence on the distinct molecular profiles of recurrent/metastatic HPV-positive HNSCC as well as the clinical potential of ctHPVDNA testing in routine practice. More controlled and longitudinal studies are needed to identify additional molecular targets and to assess the performance and benefits of novel molecular biomarkers in clinical practice.

Role of 18F-FDG PET/CT in Head and Neck Squamous Cell Carcinoma: Current Evidence and Innovative Applications

This article provides an overview of the use of 18F-FDG PET/CT in various clinical scenarios of head-neck squamous cell carcinoma, ranging from initial staging to treatment-response assessment, and post-therapy follow-up, with a focus on the current evidence, debated issues, and innovative applications. Methodological aspects and the most frequent pitfalls in head-neck imaging interpretation are described. In the initial work-up, 18F-FDG PET/CT is recommended in patients with metastatic cervical lymphadenectomy and occult primary tumor; moreover, it is a well-established imaging tool for detecting cervical nodal involvement, distant metastases, and synchronous primary tumors. Various 18F-FDG pre-treatment parameters show prognostic value in terms of disease progression and overall survival. In this scenario, an emerging role is played by radiomics and machine learning. For radiation-treatment planning, 18F-FDG PET/CT provides an accurate delineation of target volumes and treatment adaptation. Due to its high negative predictive value, 18F-FDG PET/CT, performed at least 12 weeks after the completion of chemoradiotherapy, can prevent unnecessary neck dissections. In addition to radiomics and machine learning, emerging applications include PET/MRI, which combines the high soft-tissue contrast of MRI with the metabolic information of PET, and the use of PET radiopharmaceuticals other than 18F-FDG, which can answer specific clinical needs.

Diagnostic accuracy of NI-RADS for prediction of head and neck squamous cell carcinoma: a systematic review and meta-analysis

OBJECTIVES

This study aimed to assess the diagnostic performance of NI-RADS for the prediction of recurrence in patients treated for Head and Neck Squamous Cell Carcinoma (HNSCC).

METHODS

A literature search was conducted using various databases to identify relevant articles published from June 2016 onwards. We included studies reporting the diagnostic accuracy of NI-RADS in distinguishing recurrence in patients undergoing imaging surveillance, with pathologic results and/or follow-up as the reference standard. Summary estimates of diagnostic accuracy in terms of sensitivity, specificity, positive likelihood ratio (LR +), negative likelihood ratio (LR -), and diagnostic odds ratio (DOR) were calculated with the hierarchical summary receiver operating characteristic (HSROC) model. Meta-regression and subgroup analyses were conducted to investigate different clinical settings. Study quality was evaluated using the Quality Assessment of Diagnostic Accuracy Studies-2 tool.

RESULTS

A total of 12 studies were included in the current meta-analysis. The pooled sensitivity and specificity were 0.69 (95% CI 0.59-0.79) and 0.94 (95% CI 0.89-0.97), respectively. For the primary site, the pooled summary estimates were 0.67 (95% CI 0.53-0.78) and 0.95 (95% CI 0.90-0.97), for the nodal sites were 0.64 (95% CI 0.44-0.80) and 0.99 (95% CI 0.98-0.99), respectively. The recurrence rate for NI-RADS categories 1-3 was 0.03 (95% CI 0.02-0.05), 0.13 (95% CI 0.10-0.15), and 0.77 (95% CI 0.73-0.81). Meta-regression revealed that the type of analysis (per person vs. per site) and number of sites (≤ 200 vs. > 200) were significant factors associated with heterogeneity.

CONCLUSIONS

NI-RADS demonstrated high specificity but moderate sensitivity in patients after treatment for HNSCC. Summary estimates showed a significantly higher malignancy rate for NI-RADS category 3 compared to category 2.

The Effects of Human Papillomavirus Status and Treatment on the Positive Predictive Value of Post-radiotherapy 18F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography in Advanced Head and Neck Squamous Cell Carcinoma

AIMS

The high negative predictive value of post-chemoradiation (CRT) positron emission tomography-computed tomography (PET-CT) is well established in head and neck squamous cell cancers (HNSCC). The positive predictive value (PPV) remains under scrutiny, with increasing evidence that it is affected by several factors. The aim of this study was to assess the PPV of post-treatment PET-CT for residual nodal disease when stratified by treatment modality and tumour human papillomavirus (HPV) status.

MATERIALS AND METHODS

This was a retrospective cohort study in a tertiary oncology centre carried out between January 2013 and December 2019. Patients were radically treated with radiotherapy only/CRT for node-positive HNSCC. PET-CT nodal responses were categorised as complete, equivocal (EQR) or incomplete (ICR), and outcomes extracted from electronic records.

RESULTS

In total, 480 patients were evaluated, all had a minimum potential follow-up of 2 years, with a median of 39.2 months. The PPV of 12-week PET-CT was significantly different between HPV-positive (22.5%) and HPV-unrelated (52.7%) disease, P < 0.001. It was also significantly different between the CRT (24.8%) and radiotherapy-only (51.1%) groups, P = 0.001. The PPV of an EQR was significantly less than an ICR, irrespective of HPV status and primary treatment modality. In HPV-positive disease, the PPV of an EQR was 9.0% for the CRT group compared with 21.4% for radiotherapy only, P = 0.278. The PPV in those who achieved an ICR was 34.2% in the CRT group, significantly lower than 70.0% in the radiotherapy-only group, P = 0.03.

CONCLUSION

The PPV of 12-week PET-CT is significantly lower for HPV-positive compared with HPV-unrelated HNSCC. It is poorer in patients with HPV-positive disease treated with CRT compared with radiotherapy alone.

ACR Appropriateness Criteria® Staging and Post-Therapy Assessment of Head and Neck Cancer

Imaging of head and neck cancer at initial staging and as part of post-treatment surveillance is a key component of patient care as it guides treatment strategy and aids determination of prognosis. Head and neck cancer includes a heterogenous group of malignancies encompassing several anatomic sites and histologies, with squamous cell carcinoma the most common. Together this comprises the seventh most common cancer worldwide. At initial staging comprehensive imaging delineating the anatomic extent of the primary site, while also assessing the nodal involvement of the neck is necessary. The treatment of head and neck cancer often includes a combination of surgery, radiation, and chemotherapy. Post-treatment imaging is tailored for the evaluation of treatment response and early detection of local, locoregional, and distant recurrent tumor. Cross-sectional imaging with CT or MRI is recommended for the detailed anatomic delineation of the primary site. PET/CT provides complementary metabolic information and can map systemic involvement. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Diagnostic Performance of Response Assessment FDG-PET/CECT in HNSCC Treated With Definitive Radio(chemo)therapy Using NI-RADS

OBJECTIVE

To assess the diagnostic performance of response assessment 18F-fluorodeoxyglucose positron emission tomography/contrast-enhanced computed tomography (FDG-PET/CECT) following definitive radio(chemo)therapy in head and neck squamous cell carcinoma (HNSCC) using Neck Imaging Reporting and Data System (NI-RADS).

STUDY DESIGN

A retrospective analysis from a prospectively maintained dataset.

SETTING

Tertiary-care comprehensive cancer center in a low-middle-income country.

METHODS

Adults with newly diagnosed, biopsy-proven, nonmetastatic HNSCC treated with definitive radio(chemo)therapy were included. Posttreatment response assessment FDG-PET/CECT scans were retrospectively assigned NI-RADS categories (1-3) for the primary site, neck, and both sites combined. Locoregional recurrence occurring within 2-years was defined as the event of interest. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall accuracy were calculated. Locoregional control stratified by NI-RADS categories was computed with the Kaplan-Meier method and compared using the log-rank test.

RESULTS

Posttreatment FDG-PET/CECT scans were available in 190 patients constituting the present study cohort. Sensitivity, specificity, PPV, NPV, and overall accuracy of the NI-RADS template for the primary site was 73.5%, 81.4%, 46.3%, 93.4%, and 80.0%, respectively. Similar metrics for the neck were 72.7%, 87.5%, 43.2%, 96.1%, and 85.8%, respectively. Combining primary site and neck, the corresponding metrics of diagnostic accuracy were 84.4%, 69.7%, 46.3%, 93.5%, and 73.2%, respectively. At a median follow-up of 40 months, Kaplan-Meier estimates of 2-year locoregional control were significantly higher for NI-RADS category 1 (94.2%) compared to NI-RADS category 2 (69.4%) and category 3 (20.4%), respectively (stratified log-rank p < .0001).

CONCLUSION

FDG-PET/CECT using the NI-RADS template is associated with good diagnostic performance and prognostic utility in HNSCC treated with definitive radio(chemo)therapy.

An Intensive 18F-Fludeoxyglucose-Positron Emission Tomography With Computed Tomography-Based Strategy of Follow-Up in Patients Treated for Head and Neck Squamous Cell Carcinoma Who Are Clinically Asymptomatic

Importance

Patients with head and neck squamous cell carcinoma (HNSCC) have a significant risk of locoregional recurrence within the first 2 years, with approximately two-thirds of patients experiencing such recurrence. While early recurrence detection may be associated with improved patient outcomes, the association of such detection with survival remains uncertain.

Objective

To investigate the association of an intensive posttreatment follow-up strategy using 18F-fludeoxyglucose-positron emission tomography with computed tomography (18FDG-PET/CT) with survival among patients with HNSCC.

Design, Setting, and Participants

This case-control study was conducted among patients treated at 1 of 3 locations in Brest, France (University Hospital, Military Hospital, or Pasteur Clinic). The statistical analysis was conducted from January to June 2023. All adults with histologically proven HNSCC who were treated with curative intent between January 1, 2006, and December 31, 2019, and achieved a complete response on imaging at 3 to 6 months were included. They had a minimum of 3 years of follow-up.

Exposures

Patients undergoing an intensive posttreatment follow-up strategy had 18FDG-PET/CT (PET/CT group) at months 12, 24, and 36, chosen at the discretion of ear, nose, and throat surgeons.

Main Outcomes and Measures

Overall survival (OS) at 3 years.

Results

Among 782 patients with HNSCC (642 males [82.1%]; median [IQR] age, 61 [56-68] years), 497 patients had 18FDG-PET/CT during follow-up and 285 patients had conventional follow-up (CFU group). Cox regression analysis showed an association between undergoing 18FDG-PET/CT and lower risk of death (odds ratio, 0.71; 95% CI, 0.57-0.88; P = .002) after adjustment for covariates (age, sex, comorbidities, primary location, stage, surgeon, year of treatment, and treatment). The mean (SD) 3-year OS was significantly better in the PET/CT vs CFU group (72.5% [2.0%] vs 64.3% [2.9%]; P = .002). Analysis based on American Joint Committee on Cancer stage showed significantly better mean (SD) 3-year OS for advanced stages III and IV in the PET/CT group (373 patients) vs CFU group (180 patients; 68.5% [2.4%] vs 55.4% [3.8%]; P < .001), while no significant difference was observed between patients with stage I or II HNSCC. Analysis based on primary tumor site revealed significantly longer mean (SD) 3-year OS for oropharyngeal tumor in the PET/CT group (176 patients) than the CFU group (100 patients; 69.9% [3.5%] vs 60.5% [5.0%]; P = .04).

Conclusions and relevance

This case-control study found that use of 18FDG-PET/CT in the standard annual CFU of HNSCC was associated with a 3-year survival benefit, with a larger benefit for patients with advanced initial tumor stage (III-IV) and oropharyngeal disease.

Post-treatment 18F-fludeoxyglocuse-positron emission tomography in human papillomavirus-associated oropharyngeal cancer

BACKGROUND

Human papillomavirus association has changed the landscape of treatment for oropharyngeal squamous cell carcinoma; it remains to be seen whether current post-treatment surveillance schedules are effective.

OBJECTIVE

Evaluate whether post-treatment surveillance of oropharyngeal cancer through FDG-PET imaging is modified by human papillomavirus association.

METHODS

A prospective cohort analysis of retrospective data was conducted for patients undergoing treatment of oropharyngeal cancer between 2016 and 2018. This study was conducted at a single large tertiary referral center in Brisbane, Australia.

RESULTS

Two-hundred and twenty-four patients were recruited for the purposes of the study, 193 (86%) with HPV-associated disease. In this cohort FDG-PET had a sensitivity of 48.3%, specificity of 72.6%, positive predictive value of 23.7%, and negative predictive value of 88.8% in detecting disease recurrence.

CONCLUSIONS

FDG-PET in HPV-associated oropharyngeal cancer has significantly lower positive predictive value when compared to non-HPV-associated oropharyngeal cancer. Caution should be used when interpreting positive post-treatment FDG-PET.

Surveillance of head neck cancer: Case for personalized and standardized surveillance

Although surgery, radiotherapy, chemotherapy, or combined treatment often elicits an initial satisfactory response, relapses are frequently observed within two years. Current surveillance methods, including clinical exams and imaging evaluations, have not unambiguously demonstrated a survival benefit, most probably due to a lack of sensitivity in detecting very early recurrence. Current guidelines advise post-treatment surveillance of head and neck cancer (HNC) patients should involve scheduled appointments with a variety of practitioners. The benefits of prolonged routine follow-up on survival have not been proven. Increasing numbers of HNC survivors raise the burden to provide efficient and effective care.

Predicting local persistence/recurrence after radiation therapy for head and neck cancer from PET/CT using a multi-objective, multi-classifier radiomics model

Objectives

Accurate identifying head and neck squamous cell cancer (HNSCC) patients at high risk of local persistence/recurrence (P/R) is of importance for personalized patient management. Here we developed a multi-objective, multi-classifier radiomics model for early HNSCC local P/R prediction based on post-treatment PET/CT scans and clinical data.

Materials and methods

We retrospectively identified 328 individuals (69 patients have local P/R) with HNSCC treated with definitive radiation therapy at our institution. The median follow-up from treatment completion to the first surveillance PET/CT imaging was 114 days (range: 82-159 days). Post-treatment PET/CT scans were reviewed and contoured for all patients. For each imaging modality, we extracted 257 radiomic features to build a multi-objective radiomics model with sensitivity, specificity, and feature sparsity as objectives for model training. Multiple representative classifiers were combined to construct the predictive model. The output probabilities of models built with features from various modalities were fused together to make the final prediction.

Results

We built and evaluated three single-modality models and two multi-modality models. The combination of PET, CT, and clinical data in the multi-objective, multi-classifier radiomics model trended towards the best prediction performance, with a sensitivity of 93%, specificity of 83%, accuracy of 85%, and AUC of 0.94.

Conclusion

Our study demonstrates the feasibility of employing a multi-objective, multi-classifier radiomics model with PET/CT radiomic features and clinical data to predict outcomes for patients with HNSCC after radiation therapy. The proposed prediction model shows the potential to detect cancer local P/R early after radiation therapy.

Imaging of human papilloma virus associated oropharyngeal squamous cell carcinoma and its impact on diagnosis, prognostication, and response assessment

The clinical behaviour and outcomes of patients with oropharyngeal cancer (OPC) may be dichotomised according to their association with human papilloma virus (HPV) infection. Patients with HPV-associated disease (HPV+OPC) have a distinct demographic profile, clinical phenotype and demonstrate considerably better responses to chemoradiotherapy. This has led to a reappraisal of staging and treatment strategies for HPV+OPC, which are underpinned by radiological data. Structural modalities, such as CT and MRI can provide accurate staging information. These can be combined with ultrasound-guided tissue sampling and functional techniques (such as diffusion-weighted MRI and 18F-fludeoxyglucose positron emission tomography-CT) to monitor response to treatment, derive prognostic information, and to identify individuals who might benefit from intensification or deintensification strategies. Furthermore, advanced MRI techniques, such as intravoxel incoherent motion and perfusion MRI as well as application of artificial intelligence and radiomic techniques, have shown promise in treatment response monitoring and prognostication. The following review will consider the contemporary role and knowledge on imaging in HPV+OPC.

Combined PET-CT and MRI for response evaluation in patients with squamous cell anal carcinoma treated with curative-intent chemoradiotherapy

OBJECTIVES

To assess the effectiveness of fluorine-18 fluorodeoxyglucose (FDG) positron-emission tomography-computed tomography (PET-CT) and magnetic resonance imaging (MRI) for response assessment post curative-intent chemoradiotherapy (CRT) in anal squamous cell carcinoma (ASCC).

METHODS

Consecutive ASCC patients treated with curative-intent CRT at a single centre between January 2018 and April 2020 were retrospectively identified. Clinical meta-data including progression-free survival (PFS) and overall survival (OS) outcomes were collated. Three radiologists evaluated PET-CT and MRI using qualitative response assessment criteria and agreed in consensus. Two-proportion z test was used to compare diagnostic performance metrics (sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy). Kaplan-Meier analysis (Mantel-Cox log-rank) was performed.

RESULTS

MRI (accuracy 76%, PPV 44.8%, NPV 95.7%) and PET-CT (accuracy 69.3%, PPV 36.7%, NPV 91.1%) performance metrics were similar; when combined, there were statistically significant improvements (accuracy 94.7%, PPV 78.9%, NPV 100%). Kaplan-Meier analysis demonstrated significant differences in PFS between responders and non-responders at PET-CT (p = 0.007), MRI (p = 0.005), and consensus evaluation (p < 0.001). Cox regression analysis of PFS demonstrated a lower hazard ratio (HR) and narrower 95% confidence intervals for consensus findings (HR = 0.093, p < 0.001). Seventy-five patients, of which 52 (69.3%) were females, with median follow-up of 17.8 months (range 5-32.6) were included. Fifteen of the 75 (20%) had persistent anorectal and/or nodal disease after CRT. Three patients died, median time to death 6.2 months (range 5-18.3).

CONCLUSION

Combined PET-CT and MRI response assessment post-CRT better predicts subsequent outcome than either modality alone. This could have valuable clinical benefits by guiding personalised risk-adapted patient follow-up.

KEY POINTS

• MRI and PET-CT performance metrics for assessing response following chemoradiotherapy (CRT) in patients with anal squamous cell carcinoma (ASCC) were similar. • Combined MRI and PET-CT treatment response assessment 3 months after CRT in patients with ASCC was demonstrated to be superior to either modality alone. • A combined MRI and PET-CT assessment 3 months after CRT in patients with ASCC has the potential to improve accuracy and guide optimal patient management with a greater ability to predict outcome than either modality alone.

Dual time point imaging in locally advanced head and neck cancer to assess residual nodal disease after chemoradiotherapy

Background

FDG-PET/CT has a high negative predictive value to detect residual nodal disease in patients with locally advanced squamous cell head and neck cancer after completing concurrent chemoradiotherapy (CCRT). However, the positive predictive value remains suboptimal due to inflammation after radiotherapy, generating unnecessary further investigations and possibly even surgery. We report the results of a preplanned secondary end point of the ECLYPS study regarding the potential advantages of dual time point FDG-PET/CT imaging (DTPI) in this setting. Standardized dedicated head and neck FDG-PET/CT images were obtained 12 weeks after CCRT at 60 and 120 min after tracer administration. We performed a semiquantitative assessment of lymph nodes, and the retention index (RI) was explored to optimize diagnostic performance. The reference standard was histology, negative FDG-PET/CT at 1 year, or > 2 years of clinical follow-up. The time-dependent area under the receiver operator characteristics (AUROC) curves was calculated.

Results

In total, 102 subjects were eligible for analysis. SUV values increased in malignant nodes (median SUV₁ = 2.6 vs. SUV₂ = 2.7; P = 0.04) but not in benign nodes (median SUV₁ = 1.8 vs. SUV₂ = 1.7; P = 0.28). In benign nodes, RI was negative although highly variable (median RI = − 2.6; IQR 21.2), while in malignant nodes RI was positive (median RI = 12.3; IQR 37.2) and significantly higher (P = 0.018) compared to benign nodes. A combined threshold (SUV₁ ≥ 2.2 + RI ≥ 3%) significantly reduced the amount of false-positive cases by 53% (P = 0.02) resulting in an increased specificity (90.8% vs. 80.5%) and PPV (52.9% vs. 37.0%), while sensitivity (60.0% vs. 66.7%) and NPV remained comparably high (92.9% vs. 93.3%). However, AUROC, as overall measure of benefit in diagnostic accuracy, did not significantly improve (P = 0.62). In HPV-related disease (n = 32), there was no significant difference between SUV₁, SUV₂, and RI in malignant and benign nodes, yet this subgroup was small.

Conclusions

DTPI did not improve the overall diagnostic accuracy of FDG-PET/CT to detect residual disease 12 weeks after chemoradiation. Due to differences in tracer kinetics between malignant and benign nodes, DTPI improved the specificity, but at the expense of a loss in sensitivity, albeit minimal. Since false negatives at the 12 weeks PET/CT are mainly due to minimal residual disease, DTPI is not able to significantly improve sensitivity, but repeat scanning at a later time (e.g. after 12 months) could possibly solve this problem. Further study is required in HPV-associated disease.

Longitudinal measurement of HPV copy number in cell-free DNA is associated with patient outcomes in HPV-positive oropharyngeal cancer

INTRODUCTION

Oropharyngeal squamous cell carcinoma (OPSCC) is increasing in global prevalence and is divided into two types dependent on association with human papillomavirus (HPV). Assay of HPV copy number in plasma cell-free DNA (cfDNA) provides a minimally invasive method for detecting and monitoring tumour-derived HPV, with potential for enhancing clinical care.

MATERIALS AND METHODS

In a prospectively recruited cohort of 104 OPSCC patients, we evaluate the utility of cfDNA droplet digital PCR (ddPCR) as a method for characterisation and longitudinal monitoring of patients with OPSCC.

RESULTS

ddPCR assay of pre-treatment plasma cfDNA for five HPV types showed overall 95% concordance with p16 immunohistochemistry and PCR analysis of tumour tissue. Longitudinal sampling in 48 HPV+ve patients, with median follow-up of 20 months, was strongly associated with patient outcomes. Persistently elevated cfDNA-HPV post-treatment was associated with treatment failure (2/2 patients) and an increase of cfDNA-HPV in patients whose HPV levels were initially undetectable post-treatment was associated with disease recurrence (5/6 patients). No recurrence was observed in patients in whom cfDNA-HPV was undetectable in all post-treatment samples. In two patients, sequential HPV measurement could have avoided surgical intervention which did not confirm recurrence.

CONCLUSION

The high concordance of pre-treatment plasma cfDNA-HPV analysis with tissue-based assays, together with the clinical associations of sequentially measured post-treatment cfDNA-HPV copy number add to a growing body of evidence that suggest utility of cfDNA-HPV ddPCR in management of OPSCC. Standardised clinical trials based on these data are now needed to assess the impact of such testing on overall patient outcomes.

Qualitative and quantitative methods in post-chemoradiation PET for head and neck cancer

OBJECTIVE

The aim of this study was to determine whether quantitative methods could aid in the evaluation of post-treatment head and neck scans, particularly taking human papillomavirus status into account.

METHODS

Clinical readings of positron emission tomography/computed tomography scans as well as standardized uptake value (SUV)max (and other metrics) of nodes visible on PET conducted on a total of 172 patients with head and neck squamous cell cancer were examined. Locoregional recurrence at 2 years was assessed. In total 88 of these patients had close enough follow-up to determine whether individual nodes were positive or negative, and 233 nodes on these patients were compared to surgical pathology notes or follow-up (if no path was available).

RESULTS

General negative predictive value (NPV) of complete response was 93% and an equivocal response was 89%; focusing on nodal recurrence, NPV was found to be 97% and positive predictive value (PPV) 46% if equivocal reads were treated as negative and NPV 98% and PPV 16% if equivocal reads were treated as positive. Using SUVmax of the hottest node with a cutoff of 3.4 gave NPV 97% and PPV 26%; a direct re-read (using 2 observers) gave NPV 98% and PPV 32% if equivocal reads were treated as negative, and NPV 99% and PPV 18% if equivocal reads were treated as positive. Using other first-order radiomics data such as SD and skewness did not improve this.

CONCLUSIONS

Quantitative data such as SUVmax does not show additional value over qualitative evaluation of response to chemoradiation in head and neck tumors.

Accurate preoperative staging with [68Ga]Ga-FAPI PET/CT for patients with oral squamous cell carcinoma: a comparison to 2-[18F]FDG PET/CT

OBJECTIVE

To evaluate the potential value of [⁶⁸Ga]Ga-labelled fibroblast activation protein inhibitor ([⁶⁸Ga]Ga-FAPI) positron emission tomography/computed tomography (PET/CT) in preoperative staging for patients with oral squamous cell carcinoma (OSCC) as compared to 2-[¹⁸F]fluoro-2-deoxy-D-glucose (2-[¹⁸F]FDG) PET/CT.

METHODS

Thirty-six treatment-naïve patients with OSCC who underwent 2-[¹⁸F]FDG and [⁶⁸Ga]Ga-FAPI PET/CT for preoperative staging were enrolled. The maximum standardised uptake value (SUV_max) of the primary tumour and suspected cervical metastatic lymph nodes, and the tumour-to-background ratio (TBR) of the primary tumour, were measured. The accuracy of two imaging modalities for preoperative diagnosis of metastatic lymph nodes was analysed. Histopathology served as the standard of reference.

RESULTS

Thirty-seven primary lesions of 36 patients were accurately detected by both [⁶⁸Ga]Ga-FAPI and 2-[¹⁸F]FDG PET/CT. Regarding primary tumours, the SUV_max and TBR of the two imaging modalities in stage T3-T4 were significantly higher than those of stage T1-T2 (all p < 0.05). On the patient analysis, the accuracy for the evaluation of N1-N3 neck status was 52.6% (10/19) for [⁶⁸Ga]Ga-FAPI PET/CT and 57.9% (11/19) for 2-[¹⁸F]FDG PET/CT. Notably, the accuracy for the evaluation of the N0 neck status between [⁶⁸Ga]Ga-FAPI and 2-[¹⁸F]FDG PET/CT was 100% (17/17) and 29% (5/17), respectively. Based on the patient, neck side and neck level, [⁶⁸Ga]Ga-FAPI PET/CT resulted in higher specificity and accuracy in diagnosing metastatic neck lymph nodes than 2-[¹⁸F]FDG PET/CT (all p < 0.05).

CONCLUSION

[⁶⁸Ga]Ga-FAPI PET/CT is a promising tool for preoperative staging of OSCC, and appears to reduce the false positivity seen with 2-[¹⁸F]FDG PET/CT for the detection of neck lymph node metastases.

KEY POINTS

• [⁶⁸Ga]Ga-FAPI PET/CT is a promising tool targeting cancer-associated fibroblasts with comparable diagnostic performance to 2-[¹⁸F]FDG PET/CT for identifying the primary lesions of OSCC. • [⁶⁸Ga]Ga-FAPI PET/CT showed higher specificity and accuracy for the evaluation of neck lymph node metastases of OSCC than 2-[¹⁸F]FDG PET/CT, especially for N0 neck status.

PET Imaging for Head and Neck Cancers

Head and neck cancers are commonly encountered cancers in clinical practice in the United States. Fluorine-18-fluorodeoxyglucose (¹⁸F-FDG) PET/CT has been clinically applied in staging, occult primary tumor detection, treatment planning, response assessment, follow-up, recurrent disease detection, and prognosis prediction in these patients. Alternative PET tracers remain investigational and can provide additional valuable information such as radioresistant tumor hypoxia. The recent introduction of ¹⁸F-FDG PET/MR imaging has provided the advantage of combining the superior soft tissue resolution of MR imaging with the functional information provided by ¹⁸F-FDG PET. This article is a concise review of recent advances in PET imaging in head and neck cancer.

End of treatment cone-beam computed tomography (CBCT) is predictive of radiation response and overall survival in oropharyngeal squamous cell carcinoma

BACKGROUND

Image guidance in radiation oncology has resulted in significant improvements in the accuracy and precision of radiation therapy (RT). Recently, the resolution and quality of cone beam computed tomography (CBCT) for image guidance has increased so that tumor masses and lymph nodes are readily detectable and measurable. During treatment of head and neck squamous cell carcinoma (HNSCC), on-board CBCT setup imaging is routinely obtained; however, this CBCT imaging data is not utilized to predict patient outcomes. Here, we analyzed whether changes in CBCT measurements obtained during a course of radiation therapy correlate with responses on routine 3-month follow-up diagnostic imaging and overall survival (OS).

MATERIALS/METHODS

Patients with oropharyngeal primary tumors who received radiation therapy between 2015 and 2018 were included. Anatomical measurements were collected of largest nodal conglomerate (LNC) at CT simulation, end of radiation treatment (EOT CBCT), and routine 3-month post-RT imaging. At each timepoint anteroposterior (AP), mediolateral (ML) and craniocaudal (CC) measurements were obtained and used to create a 2-dimensional (2D) maximum.

RESULTS

CBCT data from 64 node positive patients were analyzed. The largest nodal 2D maximum and CC measurements on EOT CBCT showed a statistically significant correlation with complete response on 3-month post-RT imaging (r = 0.313, p = 0.02 and r = 0.318, p = 0.02, respectively). Furthermore, patients who experienced a 30% or greater reduction in the CC dimension had improved OS (Binary Chi-Square HR 4.85, p = 0.028).

CONCLUSION

Decreased size of pathologic lymph nodes measured using CBCT setup imaging during a radiation course correlates with long term therapeutic response and overall survival of HNSCC patients. These results indicate that CBCT setup imaging may have utility as an early predictor of treatment response in oropharyngeal HNSCC.

Systematic Review and Meta-Analysis of Post-Treatment PET/CT in HPV-Associated Oropharyngeal Cancer

OBJECTIVE

To perform a systematic review with meta-analysis to investigate the utility of post-treatment PET/CT specifically in HPV-associated oropharyngeal squamous cell carcinoma following curative intent treatment.

METHODS

Random-effects meta-analysis was used to pool data from 7 observational studies (2013-2019) obtained from a database search of PubMed, Web of Science, and EMBASE using an a priori protocol with dual independent evaluation for inclusion, risk of bias assessment for acceptable methodology, and extraction of data for analysis. PET/CT results, treatment failure, imaging and interventions subsequent to PET/CT findings, and efficacy of salvage therapy were extracted.

RESULTS

Of the 907 post-treatment scans, PET/CT results were largely negative (76.2%; 95% CI, 63.4-85.6) and least often positive (11.3%; 95% CI, 8.8-14.4). PET/CT results were equivocal for 22.5% (95% CI, 12.5-36.9) and equivocal/positive for 34.2% of patients (95% CI, 25.1-44.5). Patients with an initial positive scan had the highest treatment failure rates (43.1%; 95% CI, 21.4-67.7) and those with an initial negative scan had the lowest rates (7.4%; 95% CI, 5.7-9.7). The equivocal and equivocal/positive scans had intermediate prevalence of 16.5% (95% CI, 9.4-27.6) and 16.7% (95% CI, 9.1-28.7), respectively.

CONCLUSION

The low treatment failure rate following a negative PET/CT scan is reassuring, but the data are consistent with treatment failure rates up to 9.7% suggesting follow-up of these patients is prudent. Additionally, the low positive predictive value for treatment failure observed alludes to use of post-treatment PET/CT in HPV-associated disease frequently leading to unnecessary subsequent imaging and intervention.

The ability of post-chemoradiotherapy DWI ADCmean and 18F-FDG SUVmax to predict treatment outcomes in head and neck cancer: impact of human papilloma virus oropharyngeal cancer status

OBJECTIVES

To evaluate the ability of post-chemo-radiotherapy (CRT) diffusion-weighted-MRI apparent diffusion coefficient (ADCmean) and 18F-FDG PET maximum standardized uptake value (SUVmax) to predict disease-free survival (DFS) in head and neck squamous cell carcinoma (HNSCC), and to determine whether this ability is influenced by human papillomavirus oropharyngeal cancer (HPV-OPC) status.

METHODS

This prospective cohort observational study included 65 participants (53 male, mean ± SD age 59.9 ± 7.9 years, 46 HPV-OPC) with stage III or IV HNSCC. Primary tumour and nodal ADCmean (pre-treatment, 6- and 12-weeks post-CRT) and SUVmax (12-weeks post-CRT) were measured. Variables were compared with 2-year DFS (independent t-test/Mann-Whitney test) and overall DFS (Cox regression), before and after accounting for HPV-OPC status. Variables were also compared between HPV-OPC and other HNSCC subgroups after stratifying for DFS.

RESULTS

Absolute post-CRT ADCmean values predicted 2-year DFS and overall DFS for all participants (p = 0.03/0.03, 6-week node; p = 0.02/0.03 12-week primary tumour) but not in the HPV-OPC subgroup. In participants with DFS, percentage interval changes in primary tumour ADCmean at 6- and 12-weeks were higher in HPV-OPC than other HNSCC (p = 0.01, 6 weeks; p = 0.005, 12 weeks). The 12-week post-CRT SUVmax did not predict DFS.

CONCLUSION

Absolute post-CRT ADCmean values predicted DFS in HNSCC but not in the HPV-OPC subgroup. Amongst participants with DFS, post-CRT percentage interval changes in primary tumour ADCmean were significantly higher in HPV-OPC than in other HNSCC. Knowledge of HPV-OPC status is crucial to the clinical utilisation of post-CRT DWI-MRI for the prediction of outcomes.

Correlations between DW-MRI and 18 F-FDG PET/CT parameters in head and neck squamous cell carcinoma following definitive chemo-radiotherapy

BACKGROUND

Posttreatment diffusion-weighted magnetic resonance imaging (DW-MRI) and 18F-fluorodeoxygluocose (18 F-FDG) positron emission tomography (PET) with computed tomography (PET/CT) have potential prognostic value following chemo-radiotherapy (CRT) for head and neck squamous cell carcinoma (HNSCC). Correlations between these PET/CT (standardized uptake value or SUV) and DW-MRI (apparent diffusion coefficient or ADC) parameters have only been previously explored in the pretreatment setting.

AIM

To evaluate stage III and IV HNSCC at 12-weeks post-CRT for the correlation between SUVmax and ADC values and their interval changes from pretreatment imaging.

METHODS

Fifty-six patients (45 male, 11 female, mean age 59.9 + - 7.38) with stage 3 and 4 HNSCC patients underwent 12-week posttreatment DW-MRI and 18 F-FDG PET/CT studies in this prospective study. There were 41/56 patients in the cohort with human papilloma virus-related oropharyngeal cancer (HPV OPC). DW-MRI (ADCmax and ADCmin) and 18 F-FDG PET/CT (SUVmax and SUVmax ratio to liver) parameters were measured at the site of primary tumors (n = 48) and the largest lymph nodes (n = 52). Kendall's tau evaluated the correlation between DW-MRI and 18 F-FDG PET/CT parameters. Mann-Whitney test compared the post-CRT PET/CT and DW-MRI parameters between those participants with and without 2-year disease-free survival (DFS).

RESULTS

There was no correlation between DW-MRI and 18 F-FDG PET/CT parameters on 12-week posttreatment imaging (P = .455-.794; tau = -0.075-0.25) or their interval changes from pretreatment to 12-week posttreatment imaging (P = .1-.946; tau = -0.194-0.044). The primary tumor ADCmean (P = .03) and the interval change in nodal ADCmin (P = .05) predicted 2-year DFS but none of the 18 F-FDG PET/CT parameters were associated with 2-year DFS.

CONCLUSIONS

There is no correlation between the quantitative DWI-MRI and 18 F-FDG PET/CT parameters derived from 12-week post-CRT studies. These parameters may be independent biomarkers however in this HPV OPC dominant cohort, only selected ADC parameters demonstrated prognostic significance. Study was prospectively registered at http://www.controlled-trials.com/ISRCTN58327080.

Best Practices: Application of NI-RADS for Posttreatment Surveillance Imaging of Head and Neck Cancer

Imaging surveillance is an important component of posttreatment management of head and neck cancers. There is variability in the surveillance regimen used by various practitioners and institutions, with no official National Comprehensive Cancer Network guidelines for patients showing no symptoms beyond 6 months posttreatment. Moreover, imaging of the neck after treatment is a complex examination with significant interreader heterogeneity, particularly in terms of the manner in which degree of suspicion for disease recurrence is expressed. The Neck Imaging Reporting and Data System (NI-RADS) was introduced by the American College of Radiology (ACR) in 2018 as a practical guide for the interpreting radiologist. NI-RADS is a proposed interpretive framework that can be applied to any standardized or institutional surveillance imaging protocol. NI-RADS simplifies communication between radiologists and referring clinicians and provides management guidance linked to specific levels of suspicion. The ACR NI-RADS Committee also provided general best practice recommendations for imaging surveillance modality and timing in the 2018 white paper. This article will review existing literature regarding choice of modality and timeline for surveillance in treated cancer of the head and neck. NI-RADS will then be presented as an approach to imaging reporting, interpretation, and design of next steps in management.

Head and neck imaging surveillance strategy for HPV-positive oropharyngeal carcinoma following definitive (chemo)radiotherapy

PURPOSE

To describe the utilization pattern of head and neck (HN) surveillance imaging and explore the optimal strategy for radiologic "residual" lymph node (LN) surveillance following definitive (chemo)radiotherapy (RT/CRT) in human papillomavirus (HPV)+ oropharyngeal carcinoma (OPC).

METHODS

All HPV+ OPC patients who completed RT/CRT from 2012 to 2015 were included. Schedule and rationale for post-treatment HN-CT/MRI were recorded. Imaging findings and oncologic outcomes were evaluated.

RESULTS

A total of 1036 scans in 412 patients were reviewed: 414 scans for first post-treatment response assessment and 622 scans for the following reasons: follow-up of radiologic "residual" LN(s) (293 scans/175 patients); local symptoms (227/146); other (17/16); unknown (85/66). Rate of scans with "unstated" reason varied significantly among clinicians (3-28%, p < 0.001) and none of them yielded any positive imaging findings. First post-treatment scans identified 192 (47%) patients with radiologic "residual" LNs. Neck dissection (ND) was performed in 28 patients: 16 immediately (6/16 positive), 10 after one follow-up scan (2/10 positive), and 2 after 2nd follow-up scan (1/2 positive). Thirty patients had >2 consecutive follow-up scans at 2-3-month intervals, and none showed subsequent imaging progression or regional failure.

CONCLUSIONS

Pattern of HN imaging utilization for surveillance varied significantly among clinicians. Imaging surveillance reduces the need for ND. However, routine HN-CT/MR surveillance without clinical symptoms/signs does not demonstrate proven value in identifying locoregional failure or toxicity. Radiologic "residual" LNs without adverse features are common. If two subsequent follow-up scans demonstrate stable/regressing radiologic "residual" LNs, clinical surveillance without further imaging appears to be safe in this population.

Positron Emission Tomography-Computed Tomography Surveillance after (Chemo)Radiotherapy in Advanced Head and Neck Squamous Cell Cancer: Beyond the PET-NECK Protocol

AIMS

To evaluate the implementation of 18-fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) surveillance after (chemo)radiotherapy, to compare outcomes for those who achieved a complete (CR), equivocal (EQR) and incomplete (ICR) nodal response on 12-week PET-CT according to their human papillomavirus (HPV) status, and to assess the safety of ongoing surveillance beyond 12 weeks in the HPV-positive EQR group.

MATERIALS AND METHODS

All patients with node-positive head and neck squamous cell carcinoma (HNSCC) treated with (chemo)radiotherapy between January 2013 and September 2017 were identified. PET-CT responses were classified as CR, ICR or EQR. Patient outcomes were obtained from electronic records.

RESULTS

In total, 236 patients with a minimum of 2 years of follow-up were identified. The mean age was 59 years; 79.3% had N2 disease; 77.1% of patients had oropharyngeal cancer and 10.1% had squamous cell carcinoma of unknown primary, of whom 82.0% (169) were HPV positive; 78.0% received chemoradiotherapy. The median time from the end of radiotherapy to PET-CT was 91 days. Of the HPV-related HNSCC, 60.4% achieved CR, 29.0% EQR and 10.6% ICR. With a median follow-up of 41.7 months, there was no difference in survival between patients with HPV-related HNSCC achieving CR and EQR (median overall survival not reached for both, P = 0.67) despite the omission of immediate neck dissection in 98.0% of the EQR group.

CONCLUSION

Patients with HPV-positive HNSCC who have achieved EQR have comparable survival outcomes to those who achieved a CR despite the omission of immediate neck dissections; this shows the safety of ongoing surveillance beyond 12 weeks in this group of patients.

Predictive Value of Diffusion, Glucose Metabolism Parameters of PET/MR in Patients With Head and Neck Squamous Cell Carcinoma Treated With Chemoradiotherapy

Purpose: This study aims to evaluate the predictive value of the pretreatment, metabolic, and diffusion parameters of a primary tumor assessed with PET/MR on patient clinical outcomes.

Methods: Retrospective evaluation was performed using PET/MR image data sets acquired using the single tracer injection dual imaging of 68 histologically proven head and neck cancer patients 4 weeks before receiving definitive chemoradiotherapy (CRT). PET/MR was performed before the CRT and 12 weeks after the CRT for response evaluation. Image data (PET and MRI diffusion-weighted imaging [DWI]) was used to specify the maximum standard uptake value, the peak lean body mass corrected, SUV_max, the metabolic tumor volume, the total lesion glycolysis (SUV_max, SUL_peak, MTV, and TLG), and the mean apparent diffusion coefficient (ADC_mean) of the primary tumor. Based on the results of the therapeutic response evaluation, two patient subgroups were created: one with a viable tumor and another without. Metabolic and diffusion data, from the pretreatment PET/MR and the therapeutic response, were correlated using Spearman's correlation coefficient and Wilcoxon's test.

Results: After completing the CRT, a viable residual tumor was detected in 36/68 (53%) cases, and 32/68 (47%) patients showed complete remission. However, no significant correlation was found between the pretreatment parameter, ADC_mean (p = 0.88), and the therapeutic success. The PET parameters, SUV_max and SUL_peak, MTV, and TLG (p = 0.032, p = 0.01, p < 0.0001, p = 0.0004) were statistically significantly different between the two patient subgroups.

Conclusion: This study found that MRI-based (ADC_mean) data from FDG PET/MR pretreatment could not be used to predict therapeutic response although the PET parameters SUV_max, SUL_peak, MTV, and TLG proved to be more useful; thus, their inclusion in risk stratification may also be of additional value.

The declining role of post-treatment neck dissection in human papillomavirus-associated oropharyngeal cancer

BACKGROUND AND PURPOSE

Human papillomavirus-associated oropharyngeal cancer (HPV+ OPC) with regional lymph node metastases has a good prognosis following (chemo)radiation therapy (C/RT) but lymph nodes may remain detectable for several months. Delayed [¹⁸F]-Fluorodeoxyglucose positron emission tomography/computed tomography (PET) can identify patients who may avoid post-treatment neck dissection (PTND). We investigated the rate of PTND in HPV+ OPC treated with C/RT and delayed PET-directed management of the neck.

MATERIALS AND METHODS

This is a retrospective cohort study from a prospectively updated institutional database. Eligible patients were treated between January 2005 and July 2017 with a minimum of 18 months follow up, had node-positive, non-distant metastatic HPV+ OPC and were treated with RT (70 Gy/35#/5 per week) with concurrent Cisplatin or Cetuximab, or accelerated RT alone (68 Gy/34#/6 per week). The primary endpoint was rate of PTND. Secondary endpoints were locoregional failure free survival (LRFFS), regional failure free survival (RFFS), distant metastatic failure free survival (DMFFS), overall survival (OS) and oropharyngeal cancer-specific survival (CSS).

RESULTS

418 patients were eligible. Nineteen patients (4.5%) received a PTND. None of the tested variables were associated with an increased risk of PTND. Five-year probabilities for LRFFS, RFFS, DMFS, OS and CSS were, 91.2% (95% CI 88.3-94.2), 93.4% (95% CI 90.8-96.0), 91.2% (95% CI 88.3-94.2), 86.4% (95% CI 83.0-90.1) and 90.2% (95% CI 87.1-93.4), respectively.

CONCLUSION

In a large cohort with good median follow up and protocolized C/RT, delayed PET-directed management of the neck affords a lower rate of PTND than reported in historical series without compromising disease control and survival.

Improving post-CRT neck assessment in patients with HPV-associated OPSCC (Review)

The positive predictive value (PPV) of 12-week post-therapy FDG-PET/CT is low in patients with Human Papillomavirus (HPV)-associated Oropharyngeal Squamous Cell Carcinoma (OPSCC) after treatment with definitive chemoradiation (CRT). Moreover, the diagnostic performance of post-CRT fine needle aspiration (FNA) in detecting persistent disease is unknown in this population. Given these important shortcomings in post-CRT treatment assessment, head and neck oncologists are limited in appropriately selecting patients for consolidative neck dissection, which results in over-treatment of a favorable risk population. Using the PubMed database, we performed a literature review of published series in HPV-associated OPSCC to investigate potential strategies for improvement of post-CRT neck assessment. Several different approaches were found, including continued surveillance with PET/CT, delayed timing of restaging PET/CT, initial response evaluation with multimodality or alternative imaging, and detection of circulating HPV DNA. At present, the optimal approach to post-CRT treatment assessment is unclear; further investigation and incorporation of new technologies and surveillance protocols will be highly beneficial for patients with HPV-associated OPSCC.

PET/CT in Surgical Planning for Head and Neck Cancer

Fluorine-18 (¹⁸F)-fluorodeoxyglucose (FDG) positron emission tomography fused with computed tomography (PET/CT) is a valuable tool in surgical planning for head and neck squamous cell carcinoma (HNSCC). If performed prior to biopsy or other surgical intervention, FDG-PET/CT has high sensitivity for the detection of the primary site in patients with cervical lymph node metastases from unknown primary origin and can be used to direct the surgical workup. FDG-PET/CT is superior to CT alone for detection of nodal metastases outside the expected pattern or distant metastases or second primary cancers and can greatly affect determination of appropriate management including surgical eligibility. Prior to the advent of PET/CT, many patients undergoing (chemo)radiation-based therapy had planned post-treatment neck dissection; FDG-PET/CT now has a proven role in the evaluation of recurrent or persistent disease amenable to salvage surgery and enables safe avoidance of planned postradiation neck dissection with a high negative predictive value. Specifically for this important application, two standardized reporting metrics may be used in the head and neck anatomic region: the "Hopkins criteria" and the "Neck Imaging Reporting and Data System"; both systems produce a formalized evaluation and recommendation based on PET/CT findings. The role of PET/CT as a replacement for elective neck dissection or examination under anesthesia remains controversial but deserves further study. FDG-PET/CT has a wide-ranging impact on the surgical management of patients with HNSCC and should be used routinely in patients with unknown primary nodal disease and those presenting with advanced-stage cancers at initial staging and to assess treatment response.

Does a 6-point scale approach to post-treatment 18F-FDG PET-CT allow to improve response assessment in head and neck squamous cell carcinoma? A multicenter study

PURPOSE

Response assessment to definitive non-surgical treatment for head and neck squamous cell carcinoma (HNSCC) is centered on the role of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET-CT) 12 weeks after treatment. The 5-point Hopkins score is the only qualitative system available for standardized reporting, albeit limited by suboptimal positive predictive value (PPV). The aim of our study was to explore the feasibility and assess the diagnostic accuracy of an experimental 6-point scale ("Cuneo score").

METHODS

We performed a retrospective, multicenter study on HNSCC patients who received a curatively-intended, radiation-based treatment. A centralized, independent qualitative evaluation of post-treatment FDG-PET/CT scans was undertaken by 3 experienced nuclear medicine physicians who were blinded to patients' information, clinical data, and all other imaging examinations. Response to treatment was evaluated according to Hopkins, Cuneo, and Deauville criteria. The primary endpoint of the study was to evaluate the PPV of Cuneo score in assessing locoregional control (LRC). We also correlated semi-quantitative metabolic factors as included in PERCIST and EORTC criteria with disease outcome.

RESULTS

Out of a total sample of 350 patients from 11 centers, 119 subjects (oropharynx, 57.1%; HPV negative, 73.1%) had baseline and post-treatment FDG-PET/CT scans fully compliant with EANM 1.0 guidelines and were therefore included in our analysis. At a median follow-up of 42 months (range 5-98), the median locoregional control was 35 months (95% CI, 32-43), with a 74.5% 3-year rate. Cuneo score had the highest diagnostic accuracy (76.5%), with a positive predictive value for primary tumor (Tref), nodal disease (Nref), and composite TNref of 42.9%, 100%, and 50%, respectively. A Cuneo score of 5-6 (indicative of residual disease) was associated with poor overall survival at multivariate analysis (HR 6.0; 95% CI, 1.88-19.18; p = 0.002). In addition, nodal progressive disease according to PERCIST criteria was associated with worse LRC (OR for LR failure, 5.65; 95% CI, 1.26-25.46; p = 0.024) and overall survival (OR for death, 4.81; 1.07-21.53; p = 0.04).

CONCLUSIONS

In the frame of a strictly blinded methodology for response assessment, the feasibility of Cuneo score was preliminarily validated. Prospective investigations are warranted to further evaluate its reproducibility and diagnostic accuracy.

Post-treatment 18F-FDG PET/CT for predicting survival and recurrence in patients with advanced-stage head and neck cancer undergoing curative surgery

OBJECTIVES

Pre- and post-treatment ¹⁸F-FDG PET/CT may have a prognostic role in human cancers. ¹⁸F-FDG PET/CT after primary surgery for head and neck cancer might also predict survival. Therefore, we evaluated the prognostic value of post-treatment ¹⁸F-FDG PET/CT in primary surgical patients with advanced-stage head and neck squamous cell carcinoma (HNSCC).

MATERIALS AND METHODS

This prospective study involved 225 patients with previously untreated advanced-stage HNSCC who underwent primary surgery with or without postoperative radiotherapy or chemoradiotherapy. The patients also had ¹⁸F-FDG PET/CT scanning at a median 6 months after surgery. Post-treatment ¹⁸F-FDG PET/CT was considered positive, based on interpretation by experienced nuclear medicine physicians with integrating clinical information. Positive and negative predictive values (PPV and NPV) for positive ¹⁸F-FDG PET/CT in association with recurrence were calculated. Predictors for positive post-treatment ¹⁸F-FDG PET/CT were evaluated using binary logistic regression. Survival analysis was performed using Cox proportional hazard regression analysis.

RESULTS

PPV and NPV for post-treatment PET/CT for overall recurrence were 75.8% and 98.7%, respectively. A positive post-treatment PET/CT was an independent predictive factor for overall and disease-free survival (both P < 0.001). Five-year overall survival rates for patients with positive and negative PET/CT were 48.1% and 92.3%, respectively. Corresponding 5-year disease-free survival rates were 22.5% and 82.4%, respectively. Perineural invasion, positive resection margin, positive pathological node, and extranodal extension were the independent predictors of positive ¹⁸F-FDG PET/CT (all P < 0.05).

CONCLUSIONS

Post-treatment ¹⁸F-FDG PET/CT predicts survival and recurrence in patients undergoing curative surgery for advanced-stage HNSCC.

Quantification of 18F-fluorodeoxyglucose uptake to detect residual nodal disease in locally advanced head and neck squamous cell carcinoma after chemoradiotherapy: results from the ECLYPS study

BACKGROUND

The Hopkins criteria were introduced for nodal response evaluation after therapy in head and neck cancer, but its superiority over quantification is not yet confirmed.

METHODS

SUV_{body weight} thresholds and lesion-to-background ratios were explored in a prospective multicenter study of standardized FDG-PET/CT 12 weeks after CRT in newly diagnosed locally advanced head and neck squamous cell carcinoma (LAHNSCC) patients (ECLYPS). Reference standard was histology, negative FDG-PET/CT at 12 months after treatment or ≥ 2 years of negative follow-up. Area under the receiver operator characteristics curves (AUROC) were estimated and obtained thresholds were validated in an independent cohort of HNSCC patients (n = 127).

RESULTS

In ECLYPS, 124 patients were available for quantification. With a median follow-up of 20.4 months, 23 (18.5%) nodal neck recurrences were observed. A SUV₇₀ threshold of 2.2 (AUROC = 0.89; sensitivity = 79.7%; specificity = 80.8%) was identified as optimal metric to identify nodal recurrence within 1 year after therapy. For lesion-to-background ratios, an SUV₅₀/SUV_liver threshold of 0.96 (AUROC = 0.89; sensitivity = 79.7%; specificity = 82.8%) had the best performance. Compared with Hopkins criteria (AUROC = 0.81), SUV₇₀ and SUV₅₀/SUV_liver provided a borderline significant (p = 0.040 and p = 0.094, respectively) improvement. Validation of thresholds yielded similar AUROC values (SUV₇₀ = 0.93, SUV₅₀/SUV_liver = 0.95), and were comparable to the Hopkins score (AUROC = 0.91; not statistically significant).

CONCLUSION

FDG quantification detects nodal relapse in LAHNSCC patients. When using EARL standardized PET acquisitions and reconstruction, absolute SUV metrics (SUV₇₀ threshold 2.2) prove robust, yet ratios (SUV₅₀/SUV_liver, threshold 0.96) may be more useful in routine clinical care. In this setting, the diagnostic value of quantification is comparable to the Hopkins criteria.

TRIAL REGISTRATION

US National Library for Medicine, NCT01179360. Registered 11 August 2010, https://clinicaltrials.gov/ct2/show/NCT01179360.

FDG PET Hybrid Imaging

Molecular imaging with positron emission tomography (PET) using tumour-seeking radiopharmaceuticals has gained wide acceptance in oncology with many clinical applications. The hybrid imaging modality PET/CT (computed tomography) allows assessing molecular as well as morphologic information at the same time. Therefore, PET/CT represents an efficient tool for whole-body staging and re-staging within one imaging modality. In oncology, the glucose analogue 18-F-fluorodeoxyglucose (FDG) is the most widely used PET/CT radiopharmaceutical in clinical routine. FDG PET and FDG PET/CT have been used for staging and re-staging of tumour patients in numerous studies. This chapter will discuss the use and the main indications of FDG PET/CT in oncology with special emphasis on lung cancer, lymphoma, head and neck cancer, melanoma and breast cancer (among other tumour entities). A review of the current literature is given with respect to primary diagnosis, staging and diagnosis of recurrent disease. Besides its integral role in diagnosis, staging and re-staging of disease in oncology, there is increasing evidence that FDG PET/CT can be used for therapy response assessment (possibly influencing therapeutic management and treatment planning) by evaluating tumour control, which will also be discussed in this chapter.

Management of the neck after definitive chemoradiation in patients with HPV-associated oropharyngeal cancer: An institutional experience

PURPOSE

To investigate the multidisciplinary management of patients with Human Papilloma Virus (HPV)-associated oropharyngeal squamous cell carcinoma (OPSCC) and an incomplete nodal response on restaging PET/CT after definitive chemoradiation (CRT).

MATERIALS AND METHODS

A retrospective chart review was performed of patients diagnosed with node-positive HPV-associated OPSCC from 2012 to 2017, who underwent definitive upfront CRT, and had an incomplete response on post-therapy PET/CT according to NCCN criteria. Post-CRT PET/CT results, management decisions, and clinical outcomes were recorded.

RESULTS

Seventy-four patients with node-positive HPV-associated OPSCC were identified; 20 patients with incomplete neck response on PET/CT according to NCCN criteria were included in the final case series. Median follow-up time was 33 months. Patients were managed as follows: 8 underwent observation and surveillance imaging, 6 underwent ultrasound-guided fine needle aspiration (FNA), and 6 had immediate neck dissection. All the observed patients were disease-free at most recent follow-up. None of the patients who underwent immediate neck dissection had residual neck disease on pathological examination; two patients in this group ultimately developed metastatic disease. Among the 6 who underwent FNA, 1 individual had positive pathology, along with residual primary disease, for which the patient underwent salvage surgery. The 5 remaining individuals had negative FNA results, were subsequently observed, and remained free of disease.

CONCLUSIONS

This institutional experience supports the notion of a high threshold for neck dissection in this low-risk population; only 1 of 20 patients with suspicious PET/CT findings had residual disease in the neck. Moreover, these patients should be managed by a multidisciplinary tumor board (MTB) since current algorithms do not universally include HPV status. Finally, the use of restaging PET/CT to guide management of the neck can be improved with changes in terminology and consideration of FDG-avidity at the primary site and on pre-therapy scans.

Effect of F-18 Fluorodeoxyglucose Uptake by Bone Marrow on the Prognosis of Head and Neck Squamous Cell Carcinoma

The purpose of this study was to assess the relationship between F-18 fluorodeoxyglucose (FDG) uptake in bone marrow (BM) on positron emission tomography/computed tomography (PET/CT) and survival in patients with head and neck squamous cell carcinoma (HNSCC). We retrospectively enrolled 157 HNSCC patients who underwent staging FDG PET/CT and subsequent treatment. On PET/CT, primary tumor metabolic characteristics, mean FDG uptake of BM (BM SUV), and BM-to-liver uptake ratio (BLR) were measured. The prognostic significance of FDG uptake of BM for predicting disease progression-free survival and distant failure-free survival was assessed using a Cox proportional hazards regression model. In univariate analysis for disease progression-free survival, increased BM SUV and BLR were associated with poor survival. In multivariate analysis, BLR (p = 0.044; hazard ratio, 1.96), TNM stage (p = 0.014; hazard ratio, 2.87) and maximum FDG uptake of the primary tumor (p = 0.046; hazard ratio, 2.38) were independently associated with disease progression-free survival. For distant failure-free survival, BLR, TNM stage, tumor size, and metabolic parameters of the primary tumor showed prognostic significance in univariate analysis. However, none of the variables showed significance in multivariate analysis. FDG uptake of BM in HNSCC patients might be a significant predictor for disease progression-free survival. Further studies with large patient population are needed to validate the results.

Physician centred imaging interpretation is dying out - why should I be a nuclear medicine physician?

Radiomics, machine learning, and, more generally, artificial intelligence (AI) provide unique tools to improve the performances of nuclear medicine in all aspects. They may help rationalise the operational organisation of imaging departments, optimise resource allocations, and improve image quality while decreasing radiation exposure and maintaining qualitative accuracy. There is already convincing data that show AI detection, and interpretation algorithms can perform with equal or higher diagnostic accuracy in various specific indications than experts in the field. Preliminary data strongly suggest that AI will be able to process imaging data and information well beyond what is visible to the human eye, and it will be able to integrate features to provide signatures that may further drive personalised medicine. As exciting as these prospects are, they currently remain essentially projects with a long way to go before full validation and routine clinical implementation. AI uses a language that is totally unfamiliar to nuclear medicine physicians, who have not been trained to manage the highly complex concepts that rely primarily on mathematics, computer sciences, and engineering. Nuclear medicine physicians are mostly familiar with biology, pharmacology, and physics, yet, considering the disruptive nature of AI in medicine, we need to start acquiring the knowledge that will keep us in the position of being actors and not merely witnesses of the wonders developed by other stakeholders in front of our incredulous eyes. This will allow us to remain a useful and valid interface between the image, the data, and the patients and free us to pursue other, one might say nobler tasks, such as treating, caring and communicating with our patients or conducting research and development.

Emerging Opportunities for Digital PET/CT to Advance Locoregional Therapy in Head and Neck Cancer

The purpose of this article is to present the recent imaging advancements enabled by digital photon counting positron emission tomography detector technology and discuss its potential applications in the clinical management of head and neck cancer (HNC) and nodal metastases. ¹⁸F-fluorodeoxyglucose positron-emission tomography is a clinically useful biomarker for the detection, targeted biopsy, treatment planning, and therapeutic response assessment of HNC. This article highlights the current state of ¹⁸F-fluorodeoxyglucose positron-emission tomography imaging in HNC management as well as the emerging capabilities of the recently introduced digital photon counting positron emission tomography/computed tomography platform for more effective molecular and functional HNC imaging.