"PET/CT Variants and Pitfalls in Lung Cancer and Mesothelioma"

Insights into lung cancer diagnosis and clinical management using [18F]F-fibroblast activation protein inhibitor (FAPI)-42 positron emission tomography/computed tomography (PET/CT)

PURPOSE

Accurate diagnosis and staging of lung cancer are critical for optimal clinical management. Fibroblast activation protein inhibitor (FAPI) imaging has emerged as a promising modality with superior detection capabilities for lung cancer. We hypothesized that [1⁸F]FAPI-42 PET/CT would enhance diagnosis, TNM staging, and influence oncologic management in patients with suspected or confirmed lung cancer.

METHODS

In this retrospective study, 155 patients with clinically suspected or confirmed lung cancer underwent both conventional imaging and [1⁸F]FAPI-42 PET/CT scans within a one-week interval, without any intervening treatment. Lesions were visually assessed and categorized to evaluate the diagnostic capability of [18F]FAPI-42 PET/CT. Tracer activity was quantified using maximum standardized uptake values (SUVmax) and tumor-to-background ratios. TNM staging was independently determined by a board-certified radiologist or nuclear medicine physician using both imaging modalities, and discrepancies were assessed. Changes in TNM staging were documented and evaluated for their impact on clinical management.

RESULTS

Of the 155 patients, 99 were evaluated for primary lesion diagnosis and staging. Pathological examination confirmed malignant tumors in 87 patients and benign tumors in 12. The diagnostic sensitivity and positive predictive value of [18F]FAPI-42 PET/CT for detecting primary lung tumors were 96.77% and 92.78%, respectively. Malignant lesions exhibited significantly higher SUVmax compared to benign lesions (5.2 vs. 1.5, P = 0.0002), with an area under the ROC curve of 0.87. In total, 1,556 malignant lesions were identified among patients with lung cancer, and [18F]FAPI-42 PET/CT demonstrated a diagnostic accuracy of 95.50%. However, its sensitivity for detecting adrenal metastases was lower at 33.33%, with a specificity of 100% and an accuracy of 53.85%. The use of [18F]FAPI-42 PET/CT resulted in changes in TNM staging for 46% of patients, leading to upstaging in 58 patients and downstaging in 5. These staging adjustments directly impacted clinical management in 34 patients, prompting modifications in treatment plans.

CONCLUSION

[18F]FAPI-42 PET/CT is a promising modality for lung cancer diagnosis and staging, demonstrating high sensitivity and specificity. Its use significantly altered TNM staging in nearly half of the patients, directly impacting oncologic management and treatment planning. However, its limited sensitivity for detecting adrenal metastases underscores the need for additional imaging techniques.

Current Status of Staging and Restaging Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is the most frequent aggressive tumor affecting the pleura, accounting for over 38,000 deaths worldwide. It originates from the mesothelial cells and is mostly associated to asbestos exposure. Depending on the extent of the disease, the management of MPM varies from surgical intervention to a combination of systemic chemotherapy, immunotherapy, and radiation therapy. Major International scientific societies provide continuous updates on proper management of the disease, including recommendations on the optimal imaging algorithms, which are crucial for determining effective treatment options and optimizing clinical outcomes. However, despite the continuous efforts to improve patients' prognosis, median overall survival remains poor, ranging from 8 to 14 months. And even in case of initial response to treatment, local or distant recurrences represent almost a certainty, requiring appropriate imaging for the assessment of tumor sites. The aim of the present article is to illustrate the current status of imaging for staging and restaging of MPM, not forgetting most recent novelties in the diagnostic work-up of the disease.

68Ga-FAPI-04 PET/CT in Non-Small Cell Lung Cancer: Accurate Evaluation of Lymph Node Metastasis and Correlation with Fibroblast Activation Protein Expression

Fibroblast activation protein (FAP) is a promising diagnostic and therapeutic target in various solid tumors. This study aimed to assess the diagnostic efficiency of 68Ga-labeled FAP inhibitor (FAPI)-04 PET/CT for detecting lymph node metastasis in non-small cell lung cancer (NSCLC) and to investigate the correlation between tumor 68Ga-FAPI-04 uptake and FAP expression. Methods: We retrospectively enrolled 136 participants with suspected or biopsy-confirmed NSCLC who underwent 68Ga-FAPI-04 PET/CT for initial staging. The diagnostic performance of 68Ga-FAPI-04 for the detection of NSCLC was evaluated. The final histopathology or typical imaging features were used as the reference standard. The SUVmax and SUVmean, 68Ga-FAPI-avid tumor volume (FTV), and total lesion FAP expression (TLF) were measured and calculated. FAP immunostaining of tissue specimens was performed. The correlation between 68Ga-FAPI-04 uptake and FAP expression was assessed using the Spearman correlation coefficient. Results: Ninety-one participants (median age, 65 y [interquartile range, 58-70 y]; 69 men) with NSCLC were finally analyzed. In lesion-based analysis, the diagnostic sensitivity and positive predictive value of 68Ga-FAPI-04 PET/CT for detection of the primary tumor were 96.70% (88/91) and 100% (88/88), respectively. In station-based analysis, the diagnostic sensitivity, specificity, and accuracy for the detection of lymph node metastasis were 72.00% (18/25), 93.10% (108/116), and 89.36% (126/141), respectively. Tumor 68Ga-FAPI-04 uptake (SUVmax, SUVmean, FTV, and TLF) correlated positively with FAP expression (r = 0.470, 0.477, 0.582, and 0.608, respectively; all P ≤ 0.001). The volume parameters FTV and TLF correlated strongly with FAP expression in 31 surgical specimens (r = 0.700 and 0.770, respectively; both P < 0.001). Conclusion: 68Ga-FAPI-04 PET/CT had excellent diagnostic efficiency for detecting lymph node metastasis, and 68Ga-FAPI-04 uptake showed a close association with FAP expression in participants with NSCLC.

FDG PET/CT for Staging and Restaging Malignant Mesothelioma

Malignant mesothelioma is an aggressive tumor originating from the mesothelial cells and presenting in general with a very poor prognosis. The pleural localization represents the prevailing disease site, while peritoneal involvement is commonly rare. The WHO classifies mesotheliomas into epithelioid, biphasic, and sarcomatoid histotypes, having diverse outcome with the sarcomatoid or biphasic forms showing the poorest prognosis. Given the peculiar rind-like pattern of growth, mesothelioma assessment is rather challenging for medical imagers. Conventional imaging is principally based on contrast-enhanced CT, while the role of functional and metabolic imaging is regarded as complementary. By focusing essentially on the staging and restaging role of [18F]FDG PET/CT in malignant mesotheliomas, the present review will summarize the available data present in literature and provide some hints on alternative imaging and future perspectives. Given the prevailing incidence of pleural disease, the majority of the information will be addressed on malignant pleural mesothelioma, although a summary of principal characteristics and imaging findings in patients with peritoneal mesothelioma will be also provided.

FDG PET/CT for Primary Staging of Lung Cancer and Mesothelioma

Lung cancer is the leading cause of cancer-related mortality in the United States. Accurate staging at initial diagnosis determines appropriate treatment and is the most important predictor of survival. Since 2018, the 8th edition of the TNM staging system has been used to stage lung cancer based on local tumor extent (T), nodal involvement (N), and metastases (M). 18 F fluorodeoxyglucose (FDG) PET/CT, which combines functional and anatomic imaging, is the standard of care and an integral part of clinical staging of patients with lung cancer. Malignant pleural mesothelioma (MPM), the most common primary malignant pleural tumor affecting the pleura is staged with 8th edition of TNM staging for MPM. 18 F FDG PET/CT is indicated in select patients who are surgical candidates to identify locally advanced tumor, nodal metastases, or extrathoracic metastases, which may preclude surgery.

[18F]FDG-PET/CT radiomics and artificial intelligence in lung cancer: Technical aspects and potential clinical applications

Lung cancer is the second most common cancer and the leading cause of cancer-related death worldwide. Molecular imaging using [¹⁸F]fluorodeoxyglucose Positron Emission Tomography and/or Computed Tomography ([¹⁸F]FDG-PET/CT) plays an essential role in the diagnosis, evaluation of response to treatment, and prediction of outcomes. The images are evaluated using qualitative and conventional quantitative indices. However, there is far more information embedded in the images, which can be extracted by sophisticated algorithms. Recently, the concept of uncovering and analyzing the invisible data extracted from medical images, called radiomics, is gaining more attention. Currently, [¹⁸F]FDG-PET/CT radiomics is growingly evaluated in lung cancer to discover if it enhances the diagnostic performance or implication of [¹⁸F]FDG-PET/CT in the management of lung cancer. In this review, we provide a short overview of the technical aspects, as they are discussed in different articles of this special issue. We mainly focus on the diagnostic performance of the [¹⁸F]FDG-PET/CT-based radiomics and the role of artificial intelligence in non-small cell lung cancer, impacting the early detection, staging, prediction of tumor subtypes, biomarkers, and patient's outcomes.

Joint EANM/SNMMI/ESTRO practice recommendations for the use of 2-[18F]FDG PET/CT external beam radiation treatment planning in lung cancer V1.0

PURPOSE

2-[18F]FDG PET/CT is of utmost importance for radiation treatment (RT) planning and response monitoring in lung cancer patients, in both non-small and small cell lung cancer (NSCLC and SCLC). This topic has been addressed in guidelines composed by experts within the field of radiation oncology. However, up to present, there is no procedural guideline on this subject, with involvement of the nuclear medicine societies.

METHODS

A literature review was performed, followed by a discussion between a multidisciplinary team of experts in the different fields involved in the RT planning of lung cancer, in order to guide clinical management. The project was led by experts of the two nuclear medicine societies (EANM and SNMMI) and radiation oncology (ESTRO).

RESULTS AND CONCLUSION

This guideline results from a joint and dynamic collaboration between the relevant disciplines for this topic. It provides a worldwide, state of the art, and multidisciplinary guide to 2-[18F]FDG PET/CT RT planning in NSCLC and SCLC. These practical recommendations describe applicable updates for existing clinical practices, highlight potential flaws, and provide solutions to overcome these as well. Finally, the recent developments considered for future application are also reviewed.