18F-FDG PET/CT in staging and delineation of radiotherapy volume for head and neck cancer

The Role of Positron Emission Tomography for the Management of Sinonasal Malignancies: A Systematic Review

BACKGROUND

Positron emission tomography (PET) scan is a valuable imaging modality widely used in the management of cancers. Its usage is well defined for most head and neck malignancies. However, there is a lack of consensus regarding the utility of PET scan for sinonasal malignancies. This is highlighted by the latest international consensus statement on endoscopic skull base surgery.

OBJECTIVE

This systematic review aims to clarify the role of PET scan in the management of sinonasal malignancies.

METHODS

We conducted a comprehensive literature search using PubMed, MEDLINE, EMBASE, Web of Science, CINAHL, and Cochrane databases for research studies of interest. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) updated statement was used to guide the review.

RESULTS

In total, 1807 articles were assessed for eligibility. Thirty-nine original papers, published between 2004 and 2021, met inclusion criteria. Seven articles focused on the role of PET scan for inverted papilloma, 23 for sinonasal carcinoma, 4 for melanoma, and 3 for lymphoma, and finally, 3 articles focused on the use of specific PET scan tracers for sinonasal malignancies. Qualitative summaries for each potential role of PET scans were provided. In general, included studies were retrospective in nature with low level of evidence.

CONCLUSIONS

In general, and across all types of sinonasal malignancies, PET scan yielded positive results regarding detection and initial staging. It was also considered as the modality of choice for detection of distant metastases, except in the case of sinonasal lymphoma. PET scan's main limit resides in its inability to detect lesions in or close to the metabolic activity of the brain.

Risk Stratification Using 18F-FDG PET/CT and Artificial Neural Networks in Head and Neck Cancer Patients Undergoing Radiotherapy

This study retrospectively analyzed the performance of artificial neural networks (ANN) to predict overall survival (OS) or locoregional failure (LRF) in HNSCC patients undergoing radiotherapy, based on 2-[¹⁸F]FDG PET/CT and clinical covariates. We compared predictions relying on three different sets of features, extracted from 230 patients. Specifically, (i) an automated feature selection method independent of expert rating was compared with (ii) clinical variables with proven influence on OS or LRF and (iii) clinical data plus expert-selected SUV metrics. The three sets were given as input to an artificial neural network for outcome prediction, evaluated by Harrell’s concordance index (HCI) and by testing stratification capability. For OS and LRF, the best performance was achieved with expert-based PET-features (0.71 HCI) and clinical variables (0.70 HCI), respectively. For OS stratification, all three feature sets were significant, whereas for LRF only expert-based PET-features successfully classified low vs. high-risk patients. Based on 2-[¹⁸F]FDG PET/CT features, stratification into risk groups using ANN for OS and LRF is possible. Differences in the results for different feature sets confirm the relevance of feature selection, and the key importance of expert knowledge vs. automated selection.

FDG-PET/CT identified distant metastases and synchronous cancer in squamous cell carcinoma of the head and neck: the impact of smoking and P16-s

PURPOSE

Whole-body FDG-PET-CT is widely used at diagnosis of squamous cell carcinoma of the head and neck (SCCHN) but may identify suspicious lesions outside the neck that require investigation. This study evaluated the impact of smoking and P16-status on the incidence of malignant disease outside the head and neck region in newly diagnosed patients with SCCHN.

METHODS

All PET-positive foci outside the head-neck area were registered in 1069 patients planned for postoperative or curative intent radiotherapy with whole-body FDG-PET/CT from 2006 to 2012. All patient files were retrospectively investigated and clinical parameters, tobacco use, HPV (P16)-status and subsequent malignant disease registered.

RESULTS

Malignancy outside the neck was diagnosed in 9% of smokers, 2% of never-smokers, and 5% of patients with P16-positive oropharyngeal squamous cell carcinoma (OPSCC). Clinically suspicious PET-positive foci outside the head-neck were malignant in 55% of smokers, 34% of never-smokers, and in 38% of P16-pos OPSCC. All but two patients with cancer occurring outside the head and neck region were smokers.

CONCLUSION

Malignancy outside the neck at diagnosis was more frequent in smokers compared to non-smokers or P16-pos OPSCC. A high proportion of clinically suspicious PET-positive foci were non-malignant.

Recent advances of PET imaging in clinical radiation oncology

Radiotherapy and radiation oncology play a key role in the clinical management of patients suffering from oncological diseases. In clinical routine, anatomic imaging such as contrast-enhanced CT and MRI are widely available and are usually used to improve the target volume delineation for subsequent radiotherapy. Moreover, these modalities are also used for treatment monitoring after radiotherapy. However, some diagnostic questions cannot be sufficiently addressed by the mere use standard morphological imaging. Therefore, positron emission tomography (PET) imaging gains increasing clinical significance in the management of oncological patients undergoing radiotherapy, as PET allows the visualization and quantification of tumoral features on a molecular level beyond the mere morphological extent shown by conventional imaging, such as tumor metabolism or receptor expression. The tumor metabolism or receptor expression information derived from PET can be used as tool for visualization of tumor extent, for assessing response during and after therapy, for prediction of patterns of failure and for definition of the volume in need of dose-escalation. This review focuses on recent and current advances of PET imaging within the field of clinical radiotherapy / radiation oncology in several oncological entities (neuro-oncology, head & neck cancer, lung cancer, gastrointestinal tumors and prostate cancer) with particular emphasis on radiotherapy planning, response assessment after radiotherapy and prognostication.