Osteoradionecrosis after radiation therapy for head and neck cancer: differentiation from recurrent disease with CT and PET/CT imaging

Cancer Pain: Radiotherapy as a Double-Edged Sword

Cancer pain is a common issue for patients, especially in the advanced stages of cancer, and significantly affects the quality of life (QoL), treatment tolerance, and overall treatment outcomes. Pain may be caused by primary tumors, metastases, or as a consequence of the inflammatory reaction of tissues surrounding the tumor following radiotherapy (RT). Effective pain management is crucial, especially with RT being a key method for alleviating cancer pain, particularly in cases of bone and soft tissue metastases. RT provides relief for 60-80% of patients by reducing tumor size and mitigating associated pain. Radiotherapy itself can also induce pain, especially radiation-induced neuropathic pain, which may require further treatment. Despite these potential side effects, RT remains an essential tool in managing cancer pain, though careful management of its toxicities is necessary to improve patient QoL and survival.

Iatrogenic Head and Neck Necrosis of Bone and Soft Tissue in Cancer Patients

BACKGROUND

Cancer patients are at risk of developing a wide range of treatment-related toxicities that may affect the head and neck region. Iatrogenic necrosis of bone and soft tissue in this area represents a distinct clinical entity characterized by significant complexities and challenges, arising as a consequence of radiotherapy (osteoradionecrosis) or the administration of bone-modifying and/or antiangiogenic therapies (medication-related osteonecrosis of the jaw).

OBJECTIVE

This review provides a comprehensive understanding of this potentially highly impactful complication of cancer therapy and antiresorptive therapy by examining its pathophysiology, risk factors, clinical presentation, and management strategies.

RESULTS

Risk factors associated with these conditions include radiotherapy-related variables, medication-related factors, and local predisposing conditions.

CONCLUSION

This review highlights the importance of preventive strategies, including comprehensive dental evaluations and the development of personalized treatment plans before, during, and after cancer therapy, as well as when patients are undergoing or are expected to undergo treatment with bone-modifying medications. By addressing these critical aspects, clinicians can better manage and mitigate the impact of this challenging complication on the quality of life and morbidity outcomes.

Radiographic classification of mandibular osteoradionecrosis: A blinded prospective multi-disciplinary interobserver diagnostic performance study

BACKGROUND & PURPOSE

Osteoradionecrosis (ORN) of the jaw is a severe complication affecting up to 15% of head and neck cancer patients treated with radiotherapy. The ClinRad system, endorsed by ASCO/ISOO/MASCC, incorporates radiographic features for ORN severity classification, but variability in imaging use and specialty expertise may impact diagnostic accuracy. This study benchmarks physician performance in diagnosing and staging ORN across specialties and imaging modalities.

MATERIALS & METHODS

A retrospective diagnostic validation study was conducted at MD Anderson Cancer Center, involving 20 physicians from oral oncology, radiation oncology, surgery, and neuroradiology. Participants reviewed 85 de-identified imaging sets (CT and orthopantogram (OPG)) from 30 patients with confirmed ORN, diagnosing and staging cases using the ClinRad system. ROC analysis assessed diagnostic accuracy, while intra- and inter-observer agreement was measured using Cohen's and Fleiss kappa statistics.

RESULTS

Paired CT-OPG imaging significantly improved diagnostic performance across specialties (p < 0.001), with AUC values ranging from 0.79 (residents) to 0.98 (surgeons). However, inter- and intra-rater agreement remained low, with median Fleiss kappa values of 0.22, 0.13, and 0.05 for ClinRad stages 0/1, 2, and 3, respectively. No specialty demonstrated significantly superior diagnostic accuracy (p > 0.05).

CONCLUSION

This study establishes a benchmark for radiographic ORN detection, revealing diagnostic variability across specialties. Findings emphasize the need for standardized imaging protocols, interdisciplinary training, and multimodal imaging to improve diagnostic accuracy.

Skull base osteoradionecrosis: from pathogenesis to treatment

PURPOSE OF REVIEW

This review aims to provide a comprehensive analysis of skull base osteoradionecrosis (ORN), a severe and rare complication of radiotherapy for head and neck malignancies. It explores pathogenesis, clinical presentation, diagnostic strategies, and management approaches, emphasizing the importance of multidisciplinary care in addressing this challenging condition.

RECENT FINDINGS

Skull base ORN results from radiotherapy-induced tissue damage, characterized by hypovascularity, hypoxia, and necrosis, often compounded by secondary infections. Advances in radiotherapy techniques, such as intensity-modulated radiotherapy and heavy particles, have reduced ORN incidence, though cases persist, particularly in high-dose radiotherapy fields. Emerging treatments, including hyperbaric oxygen therapy and the pentoxifylline-tocopherol protocol, show promise but lack robust evidence for standardized use. Surgical interventions, especially those incorporating vascularized tissue reconstruction, have demonstrated favorable outcomes in refractory cases. Recent studies underscore the utility of multimodal imaging techniques, including MRI and PET/CT, for distinguishing ORN from tumor recurrence.

SUMMARY

Skull base ORN represents a complex and potentially life-threatening condition requiring tailored, multidisciplinary management. Although advancements in diagnostics and therapeutics have improved outcomes, significant challenges remain, particularly in developing standardized protocols. Further research is needed to refine treatment strategies and improve evidence-based practices for this entity.

Navigating treatment ambiguities in head and neck squamous cell carcinoma: A retrospective analysis of equivocal PET-CT findings and decision-making strategies following primary non-surgical treatment

Post-treatment positron emission tomography/computed tomography (PET-CT) scans for head and neck cancer are challenging due to radiation-induced inflammation, leading to equivocal results. The decision by the Leeds-Mid Yorkshire multidisciplinary team (MDT) to proceed with a targeted biopsy or a second PET-CT reflects the uncertainty of balancing timely intervention and potential delays in patient outcomes. A review of the Leeds-Mid Yorkshire radiology database identified 34 head and neck cancer patients with equivocal PET-CT results following chemoradiation between 2019 and 2023. This audit aims to inform the future clinical management of equivocal findings in head and neck squamous cell carcinoma (SCC). Among the 34 analysed cases, oropharyngeal cancer was the most common (n = 28, 70%). All PET-CT reports indicated partial metabolic response, leading to two main management strategies: a second PET-CT (n = 4, 12%) or other interventions (n = 30, 88%). Kaplan-Meier analysis indicated no difference in disease-specific survival between the second PET-CT group and other-interventions group (log rank = 0.758). Similarly, there was no significant difference in overall survival between patients in the two groups, as determined by the log-rank test (p = 0.498). Decision making in this patient cohort is complex and requires MDT input. Our analysis found no significant survival difference between second PET-CT scans and other intervention (for example, biopsy) pathways. We recommend that for primary and nodal sites, radiological reports should include qualitative and quantitative assessments, clear categorisation (negative, positive, or equivocal), and standardised uptake values (SUVmax).

Pre-treatment and post-treatment nasopharyngeal carcinoma imaging: imaging updates, pearls and pitfalls

PURPOSE

Nasopharyngeal carcinoma (NPC) is endemic in Southeast Asia, requiring precise imaging for personalized treatment. This review highlights key imaging challenges and updates from recent literature, emphasizing findings that impact oncological management.

METHODS

We discuss common and uncommon clinical entities, detailing salient imaging features and diagnostic distinctions to aid accurate interpretation.

RESULTS

In the pre-treatment setting, leveraging the characteristic MR signals and spread patterns of NPC aids in defining the tumor volume for accurate staging and radiotherapy contouring. Key diagnostic challenges include differentiating tumor from benign hyperplasia, skull base osteomyelitis, and other skull base tumors. Perineural tumor spread, radiological extranodal extension and nodal necrosis further refine primary tumor and nodal assessment. In the post-treatment setting, the key question is whether tumor recurrence exists. Diagnostic challenges involve distinguishing tumor recurrence from scar tissue, post-radiation nasopharyngeal necrosis, or hypertrophied cervical ganglia. For recurrences, endoscopic nasopharyngectomy has emerged as the preferred approach over open surgery or re-irradiation. The text highlights characteristic post-treatment appearances and emphasizes recognizing these patterns to avoid misinterpretation and guide appropriate management.

CONCLUSION

Imaging plays a pivotal role in NPC precision oncology. Mastering imaging pearls and pitfalls empowers radiologists to provide clinicians with reliable, actionable guidance.

Radiographic classification of mandibular osteoradionecrosis: A blinded prospective multi-disciplinary interobserver diagnostic performance study

Background

Osteoradionecrosis of the jaw (ORNJ) is a debilitating complication that affects up to 15% of head and neck cancer patients who undergo radiotherapy. The ASCO/ISOO/MASCC-endorsed ClinRad severity classification system was recently proposed (and recommended in the latest ASCO guidelines) to incorporate radiographic findings for determining ORNJ severity based on the vertical extent of bone necrosis. However, variability in imaging modalities and specialty-specific knowledge may contribute to disparities in diagnosing and classifying ORNJ. This study aims to evaluate and benchmark multi-specialty physician performance in diagnosing and severity classification of ORNJ using different radiographic imaging.

Methods

A single institution retrospective diagnostic validation study was conducted at The University of Texas MD Anderson Cancer Center involving 20 healthcare providers across varying specialties including oral oncology, radiation oncology, surgery, and neuroradiology. Participants reviewed 85 de-identified imaging sets including computed tomography (CT) and orthopantomogram (OPG) images from 30 patients with confirmed ORN, with blinded replicates (n=10) for assessment of intra-observer variability and asked to diagnose and stage ORNJ using the ClinRad system. Diagnostic performance was assessed using ROC curves; intra- and inter-observer agreement were measured with Cohen's and Fleiss kappa, respectively. Sub-analyses considered physician specialty, years of clinical experience and level of confidence.

Results

Paired CT-OPG imaging improved ORNJ diagnostic performance across all specialties, with AUC values ranging from 0.79 (residents) to 0.98 (surgeons). Inter- and intra-rater agreements for ORNJ detection were limited, with median (IQR) Fleiss and Cohen's kappa values of 0.38 (0.22) and 0.08 (0.17), respectively. Slight to fair inter-rater agreement in severity classification ORNJ was observed with median (IQR) Fleiss kappa values of 0.22, 0.13, and 0.05 for stages 0/1, 2, and 3, respectively. The most commonly reported radiographic features for confirmed ORNJ cases staged as ClinRad grade 1 or 2 were "bone necrosis confined to alveolar bone" (22.7%), "bone necrosis involving the basilar bone or maxillary sinus" (14.8%), and "bone lysis/sclerosis" (20.0%).

Conclusion

This study establishes an essential benchmark for physician detection of radiographic ORNJ. The significant variability in diagnostic and severity classification observed across specialties emphasizes the need for standardized imaging protocols and specialist training as well as highlights the value of multimodality imaging.

Identification and management of recurrent oral squamous cell carcinoma in the clinical presentation of osteoradionecrosis: a single-center case series for treatment experience sharing

INTRODUCTION

Radiotherapy is an integral component of the comprehensive and sequential treatment approach for advanced oral squamous cell carcinoma (OSCC). One of the significant complications associated with radiotherapy is osteoradionecrosis (ORN), which most frequently affects the mandible. Differentiating between osteoradionecrosis (ORN) and recurrent oral squamous cell carcinoma (ORSCC) can be challenging when relying solely on clinical and radiologic characteristics. The diagnosis becomes even more difficult when bone necrosis of jaw presents as the first clinical symptom.

OBJECTIVES

This study aims to present the clinical manifestations and treatment processes of patients at our institution who have developed bone necrosis of jaw after radiotherapy and subsequently diagnosed with recurrent oral squamous cell carcinoma (ORSCC).

CASE PRESENTATION

We have collected six patients with recurrent oral squamous cell carcinoma (ORSCC) who developed bone necrosis of jaw after radiotherapy. These patients subsequently underwent surgical repair and reconstruction and were eventually diagnosed with ORSCC. We present a case series reviewing their basic characteristics, radiological reports, surgical treatment, and pathological diagnosis. All six patients initially presented with oral or facial pain and were diagnosed with osteoradionecrosis (ORN) through imaging studies. All patients underwent surgical treatment, with free flaps used to repair postoperative defects. Among them, five patients were diagnosed with tumor recurrence through preoperative or intraoperative frozen biopsy, and one patient was confirmed with recurrence in the osseous resection through postoperative examination.

CONCLUSION

Identified ORSCC in the suspected ORN of the jaw following radiotherapy is relatively rare, yet it poses identification challenges and can significantly impact treatment decisions. Consequently, surgeons must remain vigilant and ensure clear pathological diagnoses for suspicious patients, either before or during surgery.

Inflammatory Lesions of the Jaws

This article defines the fascial and spatial anatomy of the suprahyoid neck region, delineates the role of CT and MR imaging, discusses the inflammatory conditions of the jaws and adjacent spaces and their clinical symptomatology, and illustrates the appearance of these conditions.

The Role of Imaging in Mandibular Reconstruction with Microvascular Surgery

Imaging plays a critical role in the diagnosis, staging, and management of segmental mandibular defects. Imaging allows mandibular defects to be classified which aids in microvascular free flap reconstruction. This review serves to complement the surgeon's clinical experience with image-based examples of mandibular pathology, defect classification systems, reconstruction options, treatment complications, and Virtual Surgical Planning.

The added values of 18F-FDG PET/CT in differentiating cancer recurrence and osteoradionecrosis of mandible in patients with treated oral squamous cell carcinoma

BACKGROUND

Osteoradionecrosis (ORN) of the jaw requires a differential diagnosis to exclude cancer recurrence. Here, we sought to develop a scoring system comprising ¹⁸F-FDG PET/CT parameters for distinguishing between the two conditions in patients with oral squamous cell carcinoma (OSCC).

METHODS

The study consisted of 103 OSCC patients with suspected ORN of the jaw. All participants underwent ¹⁸F-FDG PET/CT imaging within 6 months of diagnostic histopathology. Following extraction of PET parameters, we identified clinical and imaging predictors of mandibular recurrence-free survival (MRFS) using receiver operating characteristic curve analysis and multivariate Cox regression models.

RESULTS

The results of histopathology revealed mandibular cancer recurrence in 24 patients (23.3%). Multivariate Cox regression analyses identified an age at diagnosis ≤ 52 years (P = 0.013), a location of the SUVmax voxel with soft tissue predominance (P = 0.019), and mandibular total lesion glycolysis (TLG) > 62.68 g (P < 0.001) as independent risk factors for MRFS. A scoring system was devised with scores from 0 (no risk factor) to 3 (presence of all three risk factors). High-risk patients with a score of 2-3 compared with score of 0-1 had a significantly higher likelihood of mandibular cancer recurrence (hazard ratio: 32.50, 95% confidence interval: 8.51-124.18, P < 0.001). The scoring system had a sensitivity of 87.50%, a specificity of 82.28%, and an accuracy of 83.50% for identifying mandibular cancer recurrence.

CONCLUSIONS

The scoring system of our study is clinically useful for identifying mandibular cancer recurrence in patients with suspected ORN of the jaw.

Application of Machine Learning for Differentiating Bone Malignancy on Imaging: A Systematic Review

An accurate diagnosis of bone tumours on imaging is crucial for appropriate and successful treatment. The advent of Artificial intelligence (AI) and machine learning methods to characterize and assess bone tumours on various imaging modalities may assist in the diagnostic workflow. The purpose of this review article is to summarise the most recent evidence for AI techniques using imaging for differentiating benign from malignant lesions, the characterization of various malignant bone lesions, and their potential clinical application. A systematic search through electronic databases (PubMed, MEDLINE, Web of Science, and clinicaltrials.gov) was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 34 articles were retrieved from the databases and the key findings were compiled and summarised. A total of 34 articles reported the use of AI techniques to distinguish between benign vs. malignant bone lesions, of which 12 (35.3%) focused on radiographs, 12 (35.3%) on MRI, 5 (14.7%) on CT and 5 (14.7%) on PET/CT. The overall reported accuracy, sensitivity, and specificity of AI in distinguishing between benign vs. malignant bone lesions ranges from 0.44–0.99, 0.63–1.00, and 0.73–0.96, respectively, with AUCs of 0.73–0.96. In conclusion, the use of AI to discriminate bone lesions on imaging has achieved a relatively good performance in various imaging modalities, with high sensitivity, specificity, and accuracy for distinguishing between benign vs. malignant lesions in several cohort studies. However, further research is necessary to test the clinical performance of these algorithms before they can be facilitated and integrated into routine clinical practice.

Osteoradionecrosis versus Cancer Recurrence: An Unresolved Clinical Dilemma

INTRODUCTION

Osteoradionecrosis is a rare and debilitating risk of definitive chemoradiotherapy for head and neck squamous cell carcinoma. It is difficult to distinguish between osteoradionecrosis and recurrent or progressive disease, as clinical and radiologic features may be similar. Our aim was to compare the clinical presentation and radiologic features of osteonecrosis with those of recurrent or progressive cancer.

METHODS

We conducted a single-center case series of 19 patients with head and neck squamous cell carcinoma diagnosed between 2011 and 2019 who subsequently developed clinical and/or radiological suspicion of osteoradionecrosis. The population was a referred sample from head and neck cancer physicians at Northwell Health Cancer Institute. Clinician notes and imaging reports were reviewed to assign a final diagnosis of either cancer, osteonecrosis, or indeterminate.

RESULTS

No differences were found in the clinical presentation or radiologic features between groups. Median time between treatment and development of symptoms was longer in patients with a final diagnosis of osteoradionecrosis than recurrent or progressive disease (5 vs. 3 months), but this difference was not statistically significant. Radiation dose and type were not associated with diagnosis. Mean standard uptake value maximums on positron emission tomography/computed tomography were significantly higher in the cancer group (median 14.8 vs. 9.1, p < 0.0152). At 1 year after first suspicion of osteoradionecrosis, 100% of osteoradionecrosis patients were alive, versus 28.6% of cancer patients.

DISCUSSION/CONCLUSION

There is significant overlap in clinical and radiologic features of osteoradionecrosis and cancer. Standard uptake maximums may be helpful in predicting diagnosis. Occurrence of symptoms within 6 months of completing chemoradiotherapy should raise the concern for malignancy.

18F-FDG PET/CT for early response assessment of jaw osteoradionecrosis after the PENTOCLO protocol: A promising imaging modality

INTRODUCTION

The Pentoxifylline, Tocopherol and Clodronate protocol (PENTOCLO) showed promising results for jaw osteoradionecrosis (ORN) management. However, the clinical and radiological improvements are often delayed, leading to unwanted long-term treatment, with potential loss of opportunity for more radical surgical treatments. Our objective was to assess the diagnosis performance of ¹⁸F-FDG PET/CT to early predict ORN response to the PENTOCLO protocol.

MATERIALS AND METHODS

All patients from our center who were treated with the PENTOCLO protocol and with a ¹⁸F-FDG PET/CT performed at diagnosis and three months after the end of antibiotherapy were retrospectively included. The PENTOCLO protocol was always combined with prior appropriate antibiotherapy for six weeks. The healing endpoint was divided into healing, stability or worsening, according to the combination of clinical and radiological assessments at the date of last follow-up. For each patient, the difference between the maximal standardized uptake value (ΔSUVmax) of the ORN lesion at three months and baseline were computed. Diagnostic performance of ¹⁸F-FDG PET/CT was evaluated by sensitivity, specificity and the area under the receiver operating characteristic curve (ROC-AUC) of ΔSUVmax.

RESULTS

24 patients were included with an average follow-up of 29.3 months. The healing, stability and worsening rate were 25%, 62.5% and 12.5% respectively. The AUC for discriminating worsening vs stability or healing was 0.92 (IC95 [0.81-1.00]). A ΔSUVmax greater than or equal to 0 was predictive of a worsening with a sensitivity and specificity of 84 and 66% respectively.

CONCLUSION

¹⁸F-FDG PET/CT imaging could be useful for early prediction of PENTOCLO treatment resistance with appropriate antibiotherapy.

Radiation-induced osteoradionecrosis of the ribs in a patient with breast cancer: A case report

Osteoradionecrosis of the chest wall after radiation therapy for breast cancer is rare; however, it is one of the most severe complications of radiation treatment. Radiologically, osteoradionecrosis can manifest as a focal lucent area in bone, periostitis, sclerosis, and cortical irregularity of bones on X-ray or computed tomography; therefore, differentiation from bone metastasis can be challenging. Associated insufficiency fractures, ulceration, and skin necrosis may also occur. We encountered a patient with osteoradionecrosis in the left anterior ribs after radiation therapy for breast cancer. Chest computed tomography revealed cortical irregularity with severe sclerotic changes of the anterior arc of the left fist to the fourth ribs. The patient's skin on the left chest wall exhibited ulceration with purulent discharge. Ultrasonography of the left chest wall revealed diffuse skin thickening with hyperechoic changes in the subcutaneous fat layer of the left chest wall with calcifications. The patient underwent rib resection and chest wall reconstruction. Recognizing characteristic imaging features of osteoradionecrosis is important for radiologists to differentiate it from bone metastasis and plan appropriate treatment.

Manifestations of radiation toxicity in the head, neck, and spine: An image-based review

BACKGROUND AND PURPOSE

Radiation therapy is an important component of treatment in patients with malignancies of the head, neck, and spine. However, radiation to these regions has well-known potential side effects, many of which can be encountered on imaging. In this manuscript, we review selected radiographic manifestations of therapeutic radiation to the head, neck, and spine that may be encountered in the practice of radiology.

METHODS

We conducted an extensive literature review of known complications of radiation therapy in the head, neck, and spine. We excluded intracranial and pulmonary radiation effects from our search. We selected complications that had salient, recognizable imaging findings. We searched our imaging database for illustrative examples of these complications.

RESULTS

Based on our initial literature search and imaging database review, we selected cases of radiation-induced tumors, radiation tissue necrosis (osteoradionecrosis and soft tissue necrosis), carotid stenosis and blowout secondary to radiation, enlarging thyroglossal duct cysts, radiation myelopathy, and radiation-induced vertebral compression fractures.

CONCLUSIONS

We describe the clinical and imaging features of selected sequelae of radiation therapy to the head, neck, and spine, with a focus on those with characteristic imaging findings that can be instrumental in helping to make the diagnosis. Knowledge of these entities and their imaging findings is crucial for accurate diagnosis. Not only do radiologists play a key role in early detection of these entities, but many of these entities can be misinterpreted if one is not familiar with them.

Response Evaluation Following Radiation Therapy With 18F-FDG PET/CT: Common Variants of Radiation-Induced Changes and Potential Pitfalls

Radiation therapy (RT) is one of the cornerstones in cancer treatment and approximately half of all patients will receive some form of RT during the course of their cancer management. Response evaluation after RT and follow-up imaging with ¹⁸F-Fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) can be complicated by RT-induced acute, chronic or consequential effects. There is a general consensus that ¹⁸F-FDG PET/CT for response evaluation should be delayed for 12 weeks after completing RT to minimize the risk of false-positive findings. Radiation-induced late side effects in normal tissue can take years to develop and eventually cause symptoms that on imaging can potentially mimic recurrent disease. Imaging findings in radiation induced injuries depend on the normal tissue included in the irradiated volume and the radiation therapy regime including the total dose delivered, dose per fraction and treatment schedule. The intent for radiation therapy should be taken in consideration when evaluating the response on imaging, that is palliative vs curative or neoadjuvant vs adjuvant RT. Imaging findings can further be distorted by altered anatomy and sequelae following surgery within the radiation field. An awareness of common PET/CT-induced changes/injuries is essential when interpreting ¹⁸F-FDG PET/CT as well as obtaining a complete medical history, as patients are occasionally scanned for an unrelated cause to previously RT treated malignancy. In addition, secondary malignancies due to carcinogenic effects of radiation exposure in long-term cancer survivors should not be overlooked. ¹⁸F-FDG PET/CT can be very useful in response evaluation and follow-up in patients treated with RT, however, variants and pitfalls are common and it is important to remember that radiation-induced injury is often a diagnosis of exclusion.

Factors Associated with Treatment Outcomes and Pathological Features in Patients with Osteoradionecrosis: A Retrospective Study

A standard treatment for osteoradionecrosis (ORN) has not yet been established because of the diversity. Therefore, identifying the risk factors for a poor prognosis is essential. This study retrospectively investigated the factors associated with the prognosis of ORN in 68 patients. Relevant clinical data of all patients were obtained. Of the patients, 16 who underwent extensive surgery underwent histopathological analysis. The necrotic changes of the anterior and posterior margins in the cortical and cancellous bones were investigated. Multivariate analyses showed statistically significant associations between poor prognosis in patients with ORN and high radiation dose (hazard ratio [HR] 1.15), orocutaneous fistula (HR 2.93), and absence of sequestration (HR 2.49). Histopathological analysis showed a viable anterior margin of the middle portion of the cortical bone for all recovered cases; in contrast, most cases (75%) with a poor prognosis showed necrotic changes. The anterior margin of the cancellous bone was viable and resilient to high irradiation, regardless of the prognosis. These results suggest that patients with orocutaneous fistula should receive early surgical intervention, even if the affected area is limited or asymptomatic. In extensive surgery, a sufficient safety margin of necrotic bone, particularly in the anterior region, is required to improve the prognosis.

Adverse Radiation Therapy Effects in the Treatment of Head and Neck Tumors

Whether used as a single modality or as part of a combined approach, radiation therapy (RT) plays an essential role in the treatment of several head and neck malignancies. Despite the improvement in radiation delivery techniques, normal structures in the vicinity of the target area remain susceptible to a wide range of adverse effects. Given their high incidence, some of these effects are referred to as expected postradiation changes (eg, mucositis, sialadenitis, and edema), while others are considered true complications, meaning they should not be expected and can even represent life-threatening conditions (eg, radionecrosis, fistulas, and radiation-induced neoplasms). Also, according to their timing of onset, these deleterious effects can be divided into four groups: acute (during RT), subacute (within weeks to months), delayed onset (within months to years), and very delayed onset (after several years).The authors provide a comprehensive review of the most important radiation-induced changes related to distinct head and neck sites, focusing on their typical cross-sectional imaging features and correlating them with the time elapsed after treatment. Radiologists should not only be familiar with these imaging findings but also actively seek essential clinical data at the time of interpretation (including knowledge of the RT dose and time, target site, and manifesting symptoms) to better recognize imaging findings, avoid pitfalls and help guide appropriate management. ^© RSNA, 2022.

Indolent enhancing spinal lesions mimicking spinal metastasis in pediatric patients with malignant primary brain tumors

Spinal metastasis from malignant primary brain tumors (MPBTs) in pediatric patients is rare and often appears as enhancing lesions on MRI. However, some indolent enhancing spinal lesions (IESLs) resulting from previous treatment mimic metastasis on MRI, leading to unnecessary investigation and treatment. In 2005-2020, we retrospectively enrolled 12 pediatric/young patients with clinical impression of spinal metastasis and pathological diagnosis of their spinal lesions. Three patients had MPBT with IESL, and 9 patients had malignant tumors with metastases. The histopathologic diagnosis of IESL was unremarkable marrow change. We evaluated their MRI, CT, and bone scan findings. The following imaging findings of IESL vs. spinal metastasis were noted: (1) IESLs appeared round/ovoid (3/3, 100%), whereas spinal metastasis appeared irregular (9/9, 100%) (P = 0.005); (2) target-shaped enhancement was noted in (3/3, 100%) vs. (0/9, 0%) of cases, respectively (P = 0.005); (3) pathologic fracture of the vertebral body was noted in (1/3, 33.3%) vs. (9/9, 100%) of cases, respectively (P = 0.045); (4) expansile vertebral shape was noted in (0/3, 0%) vs. (9/9, 100%) of cases, respectively (P = 0.005); (5) obliteration of the basivertebral vein was noted in (0/3, 0%) vs. (9/9, 100%) of cases, respectively (P = 0.005); and (6) osteoblastic change on CT was noted in (3/3, 100%) vs. (2/9, 22.2%) of cases, respectively (P = 0.034). IESL in pediatric patients with MPBT can be differentiated from metastasis based on their imaging characteristics. We suggest close follow-up rather than aggressive investigation and treatment for IESL.

Skull base osteomyelitis in patients with head and neck cancer: Diagnosis, management, and outcomes in a case series of 23 patients

BACKGROUND

Skull base osteomyelitis (SBO) is an infection of the central cranial bones, most commonly resulting from contiguous spread of infection from adjacent head and neck structures. SBO is a well-recognized complication of treatment of head and neck cancer (HNC) that results in significant morbidity.

METHODS

We conducted a retrospective chart review of HNC patients diagnosed with SBO.

RESULTS

SBO was commonly diagnosed with nasal endoscopy showing mucosal breakdown between the naso/oropharynx and skull base and with characteristic changes on CT/MRI. Culture data were often polymicrobial, inclusive of naso/oropharyngeal flora, but half of the patients additionally had antibiotic-resistant or atypical pathogens. The mean duration of antimicrobial therapy was 117 +/- 94 days. Recurrent SBO was found in half of the patients, associated with Pseudomonas aeruginosa and with persistent defects in the mucosa abutting the skull base.

CONCLUSIONS

Diagnosis and management of SBO in HNC patients are challenging. Recommendations to aid in clinical care are proposed.

LEVEL OF EVIDENCE

4, case series.

Imaging of Complications of Chemoradiation

Chemoradiation for head and neck cancer is associated with a variety of early and late complications. Toxicities may affect the aero-digestive tract (mucositis, salivary gland injury), regional osseous and cartilaginous structures (osteoradionecrosis (ORN) and chondronecrosis), vasculature (progressive radiation vasculopathy and carotid blow out syndromes), and neural structures (optic neuritis, myelitis, and brain injury). These may be difficult to distinguish from tumor recurrence on imaging, and may necessitate the use of advanced MRI and molecular imaging techniques to reach the correct diagnosis. Secondary radiation-induced malignancies include thyroid cancer and a variety of sarcomas that may manifest several years after treatment. Checkpoint inhibitors can cause a variety of adverse immune events, including autoimmune hypophysitis and encephalitis.

Imaging Features of Postradiotherapy Changes in Head and Neck Cancers

Radiation therapy is the mainstay in the treatment of head and neck cancers, in addition to surgery and chemotherapy. Expected radiotherapy changes evolving over time may be confused with recurrent tumor. Conversely, even residual or recurrent tumor in the setting of postradiotherapy changes may be difficult to identify clinically or even by radiological imaging. Therefore, it is important to be familiar with the temporal evolution of these changes. The purpose of this pictorial essay is thus to illustrate distinctly the expected radiotherapy changes and radiotherapy-related complications in the head and neck region and to differentiate them from tumor recurrence on routine cross-sectional imaging techniques (computed tomography and magnetic resonance imaging).

Side Effects of Oncologic Treatment in the Chest: Manifestations at FDG PET/CT

Fluorodeoxyglucose (FDG) PET/CT is a vital imaging technique used for staging, assessing treatment response, and restaging following completion of therapy in patients who are undergoing or have completed oncologic treatment. A variety of adverse effects from chemotherapy, targeted therapy, immunotherapy, and radiation therapy are commonly encountered in oncologic patients. It is important to be aware of the manifestations of these adverse effects seen on FDG PET/CT images to avoid misinterpreting these findings as disease progression. Furthermore, early identification of these complications is important, as it may significantly affect patient management and even lead to a change in treatment strategy. The authors focus on the FDG PET/CT manifestations of a broad spectrum of oncologic therapy-related adverse effects in the thorax, as well as some treatment-related changes that may potentially mimic malignancy. Online supplemental material is available for this article. ©RSNA, 2021.

Clinical Diagnostic Imaging Study of Osteoradionecrosis of the Jaw: A Retrospective Study

Radiation therapy (RT) plays a significant role in the management of head and neck malignancies. This study aimed to review the clinical symptoms and various imaging findings of osteoradionecrosis (ORN) and provide a clinical perspective on the development of ORN. The retrospective cohort was composed of 57 sites in 54 patients who had a history of RT and suspected ORN and 48 sites in 45 patients who were confirmed to have ORN. Image analyses included computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET)/CT, bone scintigraphy, and single-photon emission CT (SPECT). The irradiated tissue was damaged by RT, and the extent of damage was correlated with clinical symptoms. The bone marrow showed sclerotic changes and the devitalized bone showed bone resorption after invasive stimulation. Chronic trismus and pathological fracture are considered severe conditions, typically occurring in the last stage of ORN. Furthermore, neurological symptoms were an important sign of tumor recurrence, since diagnostic imaging was difficult. The possible treatment options vary depending on the stage of ORN. We speculate that bone sclerosis reactions and bone resorption are sequential reactions that seem to be protective measures of the bone to radiation injury.

Advances in Imaging for HPV-Related Oropharyngeal Cancer: Applications to Radiation Oncology

While there has been an overall decline of tobacco and alcohol-related head and neck cancer in recent decades, there has been an increased incidence of HPV-associated oropharyngeal cancer (OPC). Recent research studies and clinical trials have revealed that the cancer biology and clinical progression of HPV-positive OPC is unique relative to its HPV-negative counterparts. HPV-positive OPC is associated with higher rates of disease control following definitive treatment when compared to HPV-negative OPC. Thus, these conditions should be considered unique diseases with regards to treatment strategies and survival. In order to sufficiently characterize HPV-positive OPC and guide treatment strategies, there has been a considerable effort to diagnose, prognose, and track the treatment response of HPV-associated OPC through advanced imaging research. Furthermore, HPV-positive OPC patients are prime candidates for radiation de-escalation protocols, which will ideally reduce toxicities associated with radiation therapy and has prompted additional imaging research to detect radiation-induced changes in organs at risk. This manuscript reviews the various imaging modalities and current strategies for tackling these challenges as well as provides commentary on the potential successes and suggested improvements for the optimal treatment of these tumors.

Oral findings during follow-up of nasopharyngeal squamous cell carcinoma treatment: A case report

A 50-year-old woman with a long history of nasopharyngeal cancer (T2N2M0, squamous cell carcinoma) underwent chemoradiotherapy and surgery. In the past, to prevent tumor recurrence or metastasis, she underwent concurrent chemoradiotherapy or neck dissection. However, during a follow-up 10 years after the surgery, intense F-18 fluorodeoxyglucose uptake was detected in the oral area (SUVmax 6.0). A biopsy of the area with F-18 fluorodeoxyglucose uptake revealed pathological inflammation. Radiography showed the presence of a wisdom tooth, located at the F-18 fluorodeoxyglucose accumulation site, and pericoronitis of this tooth was detected. Our findings indicate the importance of considering the effect of inflammatory conditions, such as periodontal disease, in using F-18 fluorodeoxyglucose positron emission tomography/computed tomography during follow-up after head and neck cancer treatment.

Practical Approach to Radiopaque Jaw Lesions

Radiopaque lesions of the jaw are myriad in type and occasionally protean in appearance. In turn, the radiologic analysis of these lesions requires a systematic approach and a broad consideration of clinical and imaging characteristics to enable reliable radiologic diagnosis. Initially categorizing lesions by attenuation pattern provides a practical framework for organizing radiopaque jaw lesions that also reflects important tissue characteristics. Specifically, the appearance of radiopaque lesions can be described as (a) densely sclerotic, (b) ground glass, or (c) mixed lytic-sclerotic, with each category representing a distinct although occasionally overlapping differential diagnosis. After characterizing attenuation pattern, the appreciation of other radiologic features, such as margin characteristics or relationship to teeth, as well as clinical features including demographics and symptoms, can aid in further narrowing the differential diagnosis and lend confidence to clinical decision making. The authors review the potential causes of a radiopaque jaw lesion, including pertinent clinical and radiologic features, and outline a simplified approach to its radiologic diagnosis, with a focus on cross-sectional CT. An invited commentary by Buch is available online. ^©RSNA, 2021.

Osteoradionecrosis of the skull base

Radiation therapy (RT) is often necessary for the treatment of head and neck cancers. Osteoradionecrosis (ORN) is a rare, but potentially serious complication of RT. RT leads to the destruction of vasculature in radiated tissue causing hypoxia and tissue necrosis. ORN can occur in any bone, but bones with naturally poor blood supply appear to be more susceptible. Bones of the skull base are susceptible, with ORN occurring in the anterior, central, and lateral skull base. Risk factors include cancer type and location, radiation dose, and a variety of patient factors. Patients often present with pain, bleeding, and foul odor and are typically found to have exposed and necrotic bone. Treatment options vary depending on the severity, but typically include pentoxifylline and vitamin E as well as surgical debridement, with less evidence supporting hyperbaric oxygen therapy. Recognition and prompt treatment of ORN will allow for improved patient outcomes.

Osteoradionecrosis of the Occipitocervical Junction After Radiation for Head and Neck Cancer: A Report of 8 Cases

BACKGROUND

Osteoradionecrosis (ORN) refers to the degenerative changes seen in bone after local radiation, particularly in head and neck cancer. ORN can present as neck or facial pain and may be confused with tumor recurrence. Magnetic resonance imaging (MRI) and positron emission tomography (PET) scans are often inconclusive, requiring percutaneous biopsy to differentiate ORN from infection and recurrent disease. We reviewed the utility of preprocedural imaging in guiding the decision to biopsy in cases of ORN.

CASE DESCRIPTION

Eight patients with a history of prior head and neck cancer, radiation therapy, and suspected ORN at the skull base, occipitocervical junction, and atlantoaxial spine were identified retrospectively from a single academic medical center. In 4 cases, MRI findings and PET imaging were negative for recurrence. One patient in this group underwent an aborted biopsy. Four patients had MRI concerning for infection or recurrent tumor with PET-positive lesions. Three patients in this group underwent biopsy that was negative for recurrent tumor. One patient developed an arteriovenous fistula after biopsy. The fourth patient was observed and did not demonstrate progression at 5 months. At last follow-up for all patients, there was no evidence of tumor recurrence or metastasis at the index site to indicate a misdiagnosis for recurrent tumor.

CONCLUSIONS

This case series highlights that PET scanning may not be useful in predicting which patients will benefit from biopsy for ORN because no patients with PET-positive lesions had histopathologic evidence of tumor recurrence or metastasis on biopsy.

Lumbar vertebral osteoradionecrosis: a rare case report with 10-year follow-up and brief literature review

Background

Osteoradionecrosis (ORN) is a complication that occurs after radiotherapy for head or neck malignancies. ORN of the spine is rare, with only few cases affecting the cervical spine reported to date. To our knowledge, no case of lumbar ORN has been reported. We report a rare case of ORN in the lumbar spine that occurred 2 years after radiotherapy and perform a literature review.

Case presentation

We present a case of lumbar ORN that occurred 2 years after radiotherapy for gallbladder carcinoma. The patient was successfully treated conservatively and followed up for > 10 years.

Conclusions

ORN of the spine is a rare complication of radiotherapy. Spinal ORN is clinically described as a chronic disease with a slow onset. The most common presenting symptom of spinal ORN is pain. However, as ORN progresses, spinal kyphosis and instability can lead to neurological compression and thus to induced myelopathy or radiculopathy. Treatment of spinal ORN is comprehensive, including orthosis, medication, hyperbaric oxygen therapy, surgery, and new treatment combinations of pentoxifylline and tocopherol. The surgical rate for spinal ORN is relatively high.

Potential role of post-treatment follow-up FDG-PET CT to detect mandibular osteoradionecrosis: A case report

It was hypothesized that fluorodeoxyglucose (FDG) uptake on post-treatment follow-up positron emission tomography with computed tomography (PET CT; using PET CT to monitor and rule out recurrence and metastasis of head and neck carcinoma) would be useful for detecting and understanding the disease state of osteoradionecrosis (ORN) of the jaw. The present study included 14 patients who developed mandibular ORN following radiation therapy (RT) for head and neck cancer and underwent follow-up PET CT several times following RT. Areas exhibiting FDG uptake were retrospectively assessed on post-treatment follow-up PET CT images and were classified into three types: Spot type: Only spot accumulation of FDG; localized type: Accumulation of FDG restricted to within the bone resorption area; extensive type: Accumulation of FDG extending into surrounding soft tissue. PET classification at the time of clinical diagnosis of mandibular ORN in the 14 patients demonstrated the extensive type in 43%, localized type in 36% and spot type in 21%. An increased area of FDG uptake around the ORN was revealed retrospectively on post-treatment follow-up FDG PET-CT images in 50% of patients. Alterations in PET classification included spot type to localized type in 36% and localized type to extensive type in 14%. A significantly increased number of patients with extensive-type ORN (P=0.026) required surgery. Post-treatment follow-up FDG-PET CT may be useful for early detection and better understanding of ORN.

Disease- and Treatment-related Complication on F-18-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Oncology Practice: A Pictorial Review

F-18-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) is routinely performed in oncology patients for various indications including staging, restaging, recurrence detection, and treatment response evaluation. Many disease- and treatment-related complications can be incidentally detected on PET/CT, which may be due to the complication of radiotherapy, chemotherapy, intervention, or primary tumor itself. Some of these complications could be life threatening and need urgent intervention. Therefore, these incidental findings should be recognized on PET/CT and immediately informed to the treating physicians if required urgent intervention.

Radiotherapy response evaluation using FDG PET-CT-established and emerging applications

Radiation therapy is a common component of curative cancer treatment. However, there is a significant incidence of treatment failure. In these cases, salvage surgical options are sometimes appropriate. Accurate assessment of response and early recognition of treatment success or failure is therefore critical to guide treatment decisions and impacts on survival and the morbidity of treatment. Traditionally, treatment response has depended upon the anatomical measurement of disease. However, this may not correlate well with the presence of disease, especially after radiotherapy. Combined positron emission tomography (PET) and CT imaging employs radioactive tracers to identify molecular characteristics of tissues. PET imaging exploits the fact that malignancies have characteristic molecular profiles which differ compared with surrounding tissues. The complementary anatomical and functional information facilitates accurate non-invasive assessment of surrogate biomarkers of disease activity.

Recurrent Malignancy in Osteoradionecrosis Specimen

PURPOSE

Osteoradionecrosis (ORN) is a well-known complication of head and neck radiation therapy. Statistically, the mandible is the most commonly affected site. The incidental finding of malignancy in the resection specimen has been documented but is somewhat rare. The aim of this review is to investigate the presence of recurrent carcinoma and sarcoma or new primary malignancies in resection specimens previously diagnosed and treated as ORN.

PATIENTS AND METHODS

This study is a retrospective case series. We conducted a chart review of all cases managed at the University of Miami Miller School of Medicine/Jackson Memorial Hospital. The inclusion criteria included a history of head and neck carcinoma treated with radiation of at least 6,000 cGy; clinical diagnosis of ORN; and surgical intervention with osseous resection for treatment of ORN. The study endpoint measured included microscopic evidence of malignancy in the resected ORN specimen. Additional data collected included gender, age, and type of primary pathology.

RESULTS

A total of 564 patients met the inclusion criteria. Of these patients, 14 had microscopic evidence of cancer in the specimen (2.48%) and 5 had a proven second primary malignancy in the foregut (1 in the lung, 0.18%, and 4 in the oropharynx, 0.70%). In 1 of the 14 patients, a high-grade sarcoma was diagnosed and the patient died within 1 year of diagnosis. In the treatment of our ORN patient population, a total of 19 malignancies were found collectively (3.37%). Of the 564 patients, 352 were men and 212 were women. The median age was 46 years (range, 33 to 97 years). Head and neck squamous cell carcinoma represented 531 cases in our sample, followed by 28 cases of salivary gland carcinoma and only 5 cases of sarcoma.

CONCLUSIONS

Although the finding of malignancy in ORN patients is relatively rare (3.37% in this study), oral and maxillofacial surgeons should be cognizant of its potential presence. The treatment of malignant disease is different than that of ORN, and a multidisciplinary treatment approach is recommended if a malignancy is diagnosed in an ORN patient.

Diffusion-weighted and PET/MR Imaging after Radiation Therapy for Malignant Head and Neck Tumors

Interpreting imaging studies of the irradiated neck constitutes a challenge because of radiation therapy-induced tissue alterations, the variable appearances of recurrent tumors, and functional and metabolic phenomena that mimic disease. Therefore, morphologic magnetic resonance (MR) imaging, diffusion-weighted (DW) imaging, positron emission tomography with computed tomography (PET/CT), and software fusion of PET and MR imaging data sets are increasingly used to facilitate diagnosis in clinical practice. Because MR imaging and PET often yield complementary information, PET/MR imaging holds promise to facilitate differentiation of tumor recurrence from radiation therapy-induced changes and complications. This review focuses on clinical applications of DW and PET/MR imaging in the irradiated neck and discusses the added value of multiparametric imaging to solve diagnostic dilemmas. Radiologists should understand key features of radiation therapy-induced tissue alterations and potential complications seen at DW and PET/MR imaging, including edema, fibrosis, scar tissue, soft-tissue necrosis, bone and cartilage necrosis, cranial nerve palsy, and radiation therapy-induced arteriosclerosis, brain necrosis, and thyroid disorders. DW and PET/MR imaging also play a complementary role in detection of residual and recurrent disease. Interpretation pitfalls due to technical, functional, and metabolic phenomena should be recognized and avoided. Familiarity with DW and PET/MR imaging features of expected findings, potential complications, and treatment failure after radiation therapy increases diagnostic confidence when interpreting images of the irradiated neck. Online supplemental material is available for this article.

Osteoradionecrosis of the subaxial cervical spine following treatment for head and neck carcinomas

OBJECTIVE

To study MRI and positron emission tomography (PET)/CT imaging of osteoradionecrosis (ORN) of the subaxial cervical spine, a serious long-term complication of radiation therapy (RT) for head and neck cancers that can lead to pain, vertebral instability, myelopathy and cord compression.

METHODS

This is a single-institution retrospective review of patients diagnosed and treated for ORN of the subaxial cervical spine following surgery and radiation for head and neck cancer.

RESULTS

We report PET/CT imaging and MRI for four patients, each with extensive treatment for recurrent head and neck cancer. Osteomyelitis (OM) and discitis are the end-stage manifestations of ORN of the subaxial spine.

CONCLUSION

ORN of the subaxial spine has variable imaging appearance and needs to be differentiated from recurrent or metastatic disease. Surgical violation of the posterior pharyngeal wall on top of the compromised vasculature in patients treated heavily with RT may pre-dispose the subaxial cervical vertebrae to ORN, with possible resultant OM and discitis. MRI and PET/CT imaging are complimentary in this setting. PET/CT images may be misinterpreted in view of the history of head and neck cancer. MRI should be utilized for definitive diagnosis of OM and discitis in view of its imaging specificity.

ADVANCES IN KNOWLEDGE

We identify the end-stage manifestation of ORN in the sub-axial spine on PET/CT and MRI to facilitate its correct diagnosis.

Osteoradionecrosis of the hyoid bone--a novel application of the Sonopet ultrasonic aspirator

A 66-year-old man with a history of squamous cell carcinoma of the right tonsil presented to the emergency department with two life-threatening episodes of haemoptysis 9 months after completion of chemoradiation. He was evaluated to rule out recurrent malignancy, and was determined to have osteoradionecrosis of his hyoid bone that had led to an oropharyngeal fistula. Given the proximity to branches of the external carotid, he was offered tracheostomy and resection of the protruding necrotic bone with ultrasonic bone aspirator, which was placed down the shaft of the laryngoscope to minimise damage to adjacent structures. He tolerated the procedure well with complete resolution of exposed bone on follow-up laryngoscopy.

Metastatic squamous cell carcinoma of the gingiva appearing as a solitary branchial cyst carcinoma: diagnostic role of PET/CT

We herein present a case of a left cervical cystic mass, for which the initial pathological diagnosis was branchial cleft cyst carcinoma (following complete mass excision). Thorough postoperative examinations, including with FDG positron emission tomography/computed tomography (PET/CT), revealed a primary tumor in the retromolar region of the left mandible. A 52-year-old female presented with a 2-month history of a painless, progressively enlarged left-sided neck mass. Fine-needle aspiration biopsy suggested a branchial cleft cyst. Physical examination revealed a 3 × 3-cm smooth, tender mass in the upper-left neck and anterior border of the sternocleidomastoid muscle. Examination using nasendoscopy and a strobolaryngoscope revealed no abnormalities of the nasal cavity, nasopharynx, oropharynx, hypopharynx or larynx. MRI of the neck revealed a solitary, round, cystic mass under the left parotid gland. The mass was excised completely. Pathologic results indicated a branchial cleft cyst carcinoma. According to the diagnostic criteria for a branchial cleft cystic carcinoma, PET/CT was performed to detect the occult primary site. PET/CT revealed high FDG uptake in the tooth root of the left mandible. Frozen sections of the mass were indicative of moderate, differentiated squamous cell carcinoma. The carcinoma in the retromolar region of the left mandible was locally excised under general anesthesia. A partial left maxillectomy, partial mandibulectomy, and left radical neck dissection were performed. The patient received postoperative concurrent chemoradiotherapy, and was disease-free at the 8-month follow-up. True branchial cleft cyst carcinoma is rare: once diagnosed, it should be distinguished from metastatic cystic cervical lymph and occult primary carcinoma. FDG PET/CT is useful in the identification of occult primary tumor.

FDG-PET/CT pitfalls in oncological head and neck imaging

OBJECTIVES

Positron emission tomography-computed tomography (PET/CT) with fluorine-18-fluorodeoxy-D-glucose (FDG) has evolved from a research modality to an invaluable tool in head and neck cancer imaging. However, interpretation of FDG PET/CT studies may be difficult due to the inherently complex anatomical landmarks, certain physiological variants and unusual patterns of high FDG uptake in the head and neck. The purpose of this article is to provide a comprehensive approach to key imaging features and interpretation pitfalls of FDG-PET/CT of the head and neck and how to avoid them.

METHODS

We review the pathophysiological mechanisms leading to potentially false-positive and false-negative assessments, and we discuss the complementary use of high-resolution contrast-enhanced head and neck PET/CT (HR HN PET/CT) and additional cross-sectional imaging techniques, including ultrasound (US) and magnetic resonance imaging (MRI).

RESULTS

The commonly encountered false-positive PET/CT interpretation pitfalls are due to high FDG uptake by physiological causes, benign thyroid nodules, unilateral cranial nerve palsy and increased FDG uptake due to inflammation, recent chemoradiotherapy and surgery. False-negative findings are caused by lesion vicinity to structures with high glucose metabolism, obscuration of FDG uptake by dental hardware, inadequate PET scanner resolution and inherent low FDG-avidity of some tumours.

CONCLUSIONS

The interpreting physician must be aware of these unusual patterns of FDG uptake, as well as limitations of PET/CT as a modality, in order to avoid overdiagnosis of benign conditions as malignancy, as well as missing out on actual pathology.

TEACHING POINTS

• Knowledge of key imaging features of physiological and non-physiological FDG uptake is essential for the interpretation of head and neck PET/CT studies. • Precise anatomical evaluation and correlation with contrast-enhanced CT, US or MRI avoid PET/CT misinterpretation. • Awareness of unusual FDG uptake patterns avoids overdiagnosis of benign conditions as malignancy.