Pearls and Pitfalls in the Imaging of Targeted Therapy and Immunotherapy in Lung Cancer.

Most lung cancers are diagnosed at advanced stage when the cancer has metastasized outside the lung. These patients are not eligible for curative surgery or radiation therapy and treated with systemic therapy. Advances in the understanding of the biology of lung cancer has resulted in the development of targeted therapy aimed at specific genetic mutations identified with non-small cell lung cancer and immunotherapy that helps the immune system recognize tumors as foreign, stimulates the immune system, and removes the inhibition that allows growth and spread of cancer cells. Tumors treated with targeted or immunotherapies respond differently when compared with traditional chemotherapy and not captured by conventional response criteria such as the World Health Organization criteria and Response Evaluation Criteria in Solid Tumors. Therefore, several modified criteria have been developed to appropriately address the treatment response when using these novel agents. Numerous treatment-related side effects have been described that are important to recognize to avoid misinterpretation as worsening tumor and to ensure appropriate management.

Imaging of Malignant Pleural Mesothelioma: Pearls and Pitfalls.

Malignant pleural mesothelioma is a rare tumor arising from the pleural mesothelial cells. Imaging plays a crucial role in the diagnosis, staging, and management of patients with mesothelioma. Accurate staging to stratify patients into homogeneous groups is required to evaluate the effectiveness of multimodality therapeutic regimens. CT and PET/CT are recommended for the initial staging of MPM. MRI adds value to further assess invasion of the tumor into the diaphragm, chest wall, and mediastinum. This review will discuss pearls and pitfalls in the imaging of mesothelioma with emphasis on the roles of CT, MRI, and PET/CT.

Thymic Epithelial Neoplasms: Tumor-Node-Metastasis Staging.

Thymic epithelial neoplasms are a group of malignant tumors that includes thymoma, thymic carcinoma, and thymic neuroendocrine tumors. Although several staging systems have been developed over the years for use with these cancers, they have been interpreted and implemented in a nonuniform manner. Recently, the International Association for the study of Lung Cancer and the International Thymic Malignancy Interest Group developed a tumor-node-metastasis staging system that has been universally accepted and correlates with patient survival and outcomes. Although pathologic staging is determined by histologic examination of the resected tumor, imaging plays an important role in clinical staging and is important for informing therapeutic decisions.

Esophageal Cancer: Tumor-Node-Metastasis Staging.

Esophageal cancer is an uncommon malignancy that ranks sixth in terms of mortality worldwide. Squamous cell carcinoma is the predominant histologic subtype worldwide whereas adenocarcinoma represents the majority of cases in North America, Australia, and Europe. Esophageal cancer is staged using the American Joint Committee on Cancer and the International Union for Cancer Control TNM system and has separate classifications for the clinical, pathologic, and postneoadjuvant pathologic stage groups. The determination of clinical TNM is based on complementary imaging modalities, including esophagogastroduodenoscopy/endoscopic ultrasound; endoscopic ultrasound-fine-needle aspiration; computed tomography of the chest, abdomen, and pelvis; and fluorodeoxyglucose PET/computed tomography.

Response rates to single-agent chemotherapy after exposure to immune checkpoint inhibitors in advanced non-small cell lung cancer.

INTRODUCTION: Exploratory analysis of clinical trials in various tumor types have demonstrated potential improvements in overall response rate (ORR) to chemotherapy after exposure to vaccine-based immunotherapy. The objective of this retrospective study was to determine if single-agent chemotherapy (3rd-line or beyond) would yield improved ORR when given after exposure to programmed death-(ligand)1 inhibitors (anti-PD1) in metastatic non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: We queried the Thoracic GEMINI database of MD Anderson Cancer Center for patients treated between 06/12 and 11/16 who received at least one single-agent chemotherapy as 3rd-line or beyond, following progression after platinum-based chemotherapy and anti-PD1. We evaluated efficacy outcomes to each therapy, including ORR by RECIST version 1.1, progression-free survival (PFS), and overall survival (OS). RESULTS: Out of 306 anti-PD1-treated patients registered in the database, 28 met eligibility criteria - 54% were male, median age was 66 years, 82% had adenocarcinoma, and 71% were former/current smokers. The anti-PD1 and single-agent chemotherapy most commonly used were nivolumab (86%) and docetaxel (50%), respectively. ORR to single-agent chemotherapy after exposure to anti-PD1 was 39% (11/28 patients, 8 confirmed). In contrast, ORR to first-line chemotherapy in this cohort was 37%. Liver metastasis was the only factor associated with response to single-agent chemotherapy on univariate analysis (p<0.05). CONCLUSION: In NSCLC patients, the confirmed ORR to single-agent chemotherapy after immunotherapy exposure was higher as compared to historical data from the pre-anti-PD1 era, and approached ORR to first-line platinum-based chemotherapy. Further investigation of a possible immunotherapy-induced chemosensitization effect is warranted.

State of the Art: MR Imaging of Thymoma.

Thymoma is the most common primary malignancy of the anterior mediastinum and the most common thymic epithelial neoplasm, but it is a rare tumor that constitutes less than 1% of adult malignancies. Computed tomography (CT) is currently the imaging modality of choice for distinguishing thymoma from other anterior mediastinal masses, characterizing the primary tumor, and staging the disease. However, magnetic resonance imaging is also effective in evaluating and characterizing anterior mediastinal masses and staging thymoma in patients with contraindications to contrast-material-enhanced CT such as contrast allergy and/or renal failure.

Thymoma originating in a giant thymolipoma: a rare intrathoracic lesion.

Thymolipoma is a rare, slow-growing, benign tumor that arises from the anterior mediastinum and corresponds to 2% to 9% of all thymic neoplasms. We present the case of a 49-year-old man who had a large heterogeneous mass with areas of soft tissue and fat tissue located on the anterior mediastinum and right hemithorax. After resection, histologic analysis confirmed the diagnosis of a giant thymolipoma containing solid components that corresponded to thymomas B1, B2, and B3. We discuss the occurrence of an atypical variant of thymolipoma containing three types of thymomas inside.

FDG PET-CT aids in the preoperative assessment of patients with newly diagnosed thymic epithelial malignancies.

INTRODUCTION: Advanced thymoma (stage III and IV) is difficult to detect by computed tomography (CT), yet it is important to distinguish between early (stage I and II) and advanced disease before surgery, as patients with locally advanced tumors require neoadjuvant chemotherapy to enable effective resection. This study assessed whether the amount of fluorodeoxyglucose (FDG) uptake can predict advanced thymoma and whether it can separate thymoma from thymic cancer. METHODS: We retrospectively reviewed FDG positron emission tomography (PET)-CT scans of 51 consecutive newly diagnosed patients with thymic epithelial malignancy. PET-CT findings documented focal FDG activity: SUVmax, SUVmean, SUVpeak, and total body volumetric standardized uptake value (SUV) measurements. These were correlated with Masaoka-Koga staging and World Health Organization classification. Wilcoxon ranked sum tests were used to assess association between SUV and pathological stage, cancer type, and classification. RESULTS: Among the study patients, 37 had thymoma, 12 thymic carcinoma, and 2 thymic carcinoid. Higher focal FDG uptake was seen in patients with type B3 thymoma than in those with type A, AB, B1, or B2 thymoma (p < 0.006). FDG uptake was higher in patients with thymic carcinoma or carcinoid than in patients with thymoma (p < 0.0003), with more variable associations with volumetric SUV measurements. There was no significant association observed between higher focal FDG uptake and advanced-stage disease in thymoma patients (p > 0.09), although greater FDG-avid tumor volume was significantly associated with advanced disease (p < 0.03). CONCLUSIONS: Focal FDG uptake cannot predict advanced thymoma but is helpful in distinguishing thymoma from thymic carcinoma, or the more aggressive thymoma, type B3.

Role of imaging in the diagnosis, staging, and treatment of thymoma.

Thymoma is a rare mediastinal neoplasm but is the most common primary neoplasm of the anterior mediastinum. There have been only a few published reports assessing this disease. Furthermore, many of these reports are from a single institution and span several decades, which may lead to potentially misleading conclusions related to diagnosis, staging, and treatment. Computed tomography is the imaging modality of choice for evaluating thymoma and can help distinguish thymoma from other anterior mediastinal abnormalities. Tumor stage and extent of resection are the most important prognostic factors. Tumors that are encapsulated and are amenable to complete resection have a good prognosis, whereas invasive and unresectable tumors have a poor prognosis regardless of their histologic characteristics. Radiologists must be aware of the full spectrum of imaging findings of thymoma, the standard guidelines for diagnostic evaluation, and how imaging findings affect therapeutic decisions.