A phase II study of buparlisib in relapsed or refractory thymomas

Thymic epithelial tumor medical treatment: A narrative review

Thymic epithelial tumors, a malignancy originating in the thymus, are the commonest primary neoplasm of the anterior mediastinum; however, among thoracic tumors, they have a relatively low incidence rare. Thymic epithelial tumors can be broadly classified into thymic carcinoma and thymoma. As the cornerstone of thymic tumor treatment, surgery is the preferred treatment for early-stage patients, whereas, for advanced unresectable thymic tumors, the treatment is chemoradiotherapy. Targeted therapy is less effective for thymic tumors. Moreover, the use of immune checkpoint inhibitors as another effective treatment option for advanced unresectable thymic tumors, particularly thymomas, is limited owing to immune-related adverse effects. Here, we have summarized all pertinent information regarding chemotherapy, especially preoperative neoadjuvant chemotherapy, and chemotherapy in combination with other treatments, and reviewed the effectiveness of these procedures and recent advances in targeted therapy. In addition, we analyzed the efficacy and safety of immune checkpoint inhibitors in thymic epithelial tumors, to provide a holistic treatment view.

Cell Culture Models for Translational Research on Thymomas and Thymic Carcinomas: Current Status and Future Perspectives

Cell culture model systems are fundamental tools for studying cancer biology and identifying therapeutic vulnerabilities in a controlled environment. TET cells are notoriously difficult to culture, with only a few permanent cell lines available. The optimal conditions and requirements for the ex vivo establishment and permanent expansion of TET cells have not been systematically studied, and it is currently unknown whether different TET subtypes require different culture conditions or specific supplements. The few permanent cell lines available represent only type AB thymomas and thymic carcinomas, while attempts to propagate tumor cells derived from type B thymomas so far have been frustrated. It is conceivable that epithelial cells in type B thymomas are critically dependent on their interaction with immature T cells or their three-dimensional scaffold. Extensive studies leading to validated cell culture protocols would be highly desirable and a major advance in the field. Alternative methods such as tumor cell organoid models, patient-derived xenografts, or tissue slices have been sporadically used in TETs, but their specific contributions and advantages remain to be shown.

Evolving treatment landscape in thymic epithelial tumors: From mechanism to therapy

Thymic epithelial tumors (TETs) are rare neoplasms of the anterior mediastinum that arise from thymic epithelial cells. Although surgery is the preferred treatment for resectable TETs, the options for unresectable or recurrent advanced-stage TETs are limited beyond platinum-based chemotherapy. The evolving landscape of TET treatments is marked by significant advancements in targeted therapies and immunotherapies, particularly with anti-angiogenic agents and immune checkpoint inhibitors (ICIs). While monotherapies demonstrated certain efficacy, the development of combination strategies is vital for improving patient outcomes. This review consolidates progress in anti-angiogenic therapies and ICIs, emphasizing the evolution of combination therapies of TETs. Furtherly, we particularly discuss new first-line strategies based on these advancements and emphasizes exploring novel treatments like antibody-drug conjugates, immunomodulatory drugs and cytokine-based agents for TETs. Mechanistically, the molecular features of TETs integrated with clinical diagnosis and targeted therapy, and immunophenotyping of TETs along with its impact on the efficacy and safety of immunotherapy are discussed. Thus, this review systemizes the development in the treatment landscape of TETs, integrating the corresponding molecular and immune mechanisms, aiming to provide new references for the treatment of TETs.

What Have We Learned from Molecularly Informed Clinical Trials on Thymomas and Thymic Carcinomas-Current Status and Future Directions?

Thymic epithelial tumors (TETs), which include thymomas and thymic carcinomas, are a rare, heterogeneous group of malignancies that originate from the thymus gland. As an important organ of immune cell development, thymic tumors, particularly thymomas, are often associated with paraneoplastic autoimmune disorders. The advances in targeted therapies for both solid and hematologic malignancies have resulted in improved patient outcomes, including better and more durable efficacy and improved toxicity. Targeted therapies have also been investigated in the treatment of TETs, though the results have largely been modest. These have included somatostatin-receptor-targeting therapies, KIT- and EGFR-directed tyrosine kinase inhibitors, epigenetic modulators, anti-angiogenesis agents, and agents targeting the cell proliferation and survival pathways and cell cycle regulators. Numerous investigated treatments have failed or underperformed due to a lack of a strong biomarker of efficacy. Ongoing trials are attempting to expand on previous experiences, including the exploration of effective drugs in early-stage disease. Novel combination therapy strategies are also undergoing evaluation, with the goal of augmenting efficacy and understanding the toxicity while expanding the biomarkers of efficacy and safety. With advances in technology to improve target identification and drug delivery, old targets may become new opportunities, and the subsequently developed drugs may find their place in the treatment of thymic tumors.

Immunotherapy and Targeted Therapies Efficacy in Thymic Epithelial Tumors: A Systematic Review

BACKGROUND

Thymic epithelial tumors (TET) are rare neoplasms of the anterior mediastinum. Surgery is the mainstay treatment for resectable TET, whereas systemic treatments are reserved for unresectable and metastatic tumors. The development of new treatments, such as immune checkpoint inhibitors (ICI) and targeted therapies, with promising results in other types of solid tumors, has led to the investigation of their potential efficacy in TET. The study of tumor microenvironments (TME) is another field of investigation that has gained the interest of researchers. Taking into account the complex structure of the thymus and its function in the development of immunity, researchers have focused on TME elements that could predict ICI efficacy.

MATERIALS AND METHODS

The primary objective of this systematic review was to investigate the efficacy of ICI in TET. Secondary objectives included the toxicity of ICI, the efficacy of targeted therapies in TET, and the evaluation of the elements of TME that may be predictive factors of ICI efficacy. A literature search was conducted in February 2023 using the Ovid Medline and SciVerse Scopus databases.

RESULTS

2944 abstracts were retrieved, of which 31 were retained for the systematic review. Five phase II and one retrospective study assessed ICI efficacy. The overall response rate (ORR) varied from 0% to 34%. Median progression-free survival (PFS) ranged from 3.8 to 8.6 months, being lower in thymic carcinoma (TC) (3.8-4.2 months). Median overall survival (OS) ranged from 14.1 to 35.4 months. Treatment-related adverse events occurred in 6.6% to 27.3% of patients. Sixteen studies assessed targeted therapies. The most active molecule was lenvatinib, with 38% ORR in patients with TC while no activity was detected for imatinib, erlotinib plus bevacizumab, and saracatinib. Ten studies assessed TME elements that could predict ICI efficacy. Four studies focused on the tumor-infiltrating immune cells suggesting improved outcomes in patients with TC and high tumor-infiltrating lymphocyte densities. Another study showed that CD8+, CD20+, and CD204+ tumor-infiltrating immune cells in cancer stroma might be prognostic biomarkers in TC. Another study identified the immune-related long non-coding RNAs as a predictor of response to ICI. Tumor mutational burden was identified as a predictive factor of ICI efficacy in one study.

CONCLUSIONS

Despite study heterogeneity, this review shows that ICI could be a therapeutic option for selected patients with TET that are not amenable to curative radical treatment after first-line chemotherapy.

Unraveling molecular networks in thymic epithelial tumors: deciphering the unique signatures

Thymic epithelial tumors (TETs) are a rare and diverse group of neoplasms characterized by distinct molecular signatures. This review delves into the complex molecular networks of TETs, highlighting key aspects such as chromosomal abnormalities, molecular subtypes, aberrant gene mutations and expressions, structural gene rearrangements, and epigenetic changes. Additionally, the influence of the dynamic tumor microenvironment on TET behavior and therapeutic responses is examined. A thorough understanding of these facets elucidates TET pathogenesis, offering avenues for enhancing diagnostic accuracy, refining prognostic assessments, and tailoring targeted therapeutic strategies. Our review underscores the importance of deciphering TETs' unique molecular signatures to advance personalized treatment paradigms and improve patient outcomes. We also discuss future research directions and anticipated challenges in this intriguing field.

Genetic profile of thymic epithelial tumors in the Japanese population: an exploratory study examining potential therapeutic targets

Background

Thymic epithelial tumors (TETs) are prone to developing in East Asian populations. However, little is known about the genomic profile of TETs in East Asian populations, and the genomic aberrations in TETs have not yet been fully clarified. Thus, molecular targeted therapies for patients with TETs have not been established. This prospective study was conducted to explore the genetic abnormalities of surgically resected TETs in a Japanese cohort and to identify clues for carcinogenesis and potential therapeutic targets in TETs.

Methods

Genetic profiles of TETs were investigated using fresh-frozen specimens resected from operable cases with TETs. DNA sequencing was performed using a next-generation sequencing (NGS) gene panel test with Ion Reporter™ and CLC Genomics Workbench 11.0. The mutation sites were further confirmed by Sanger sequencing, digital droplet polymerase chain reaction (ddPCR), and TA cloning for validation.

Results

Among 43 patients diagnosed with anterior mediastinal tumors between January 2013 and March 2019, NGS and validation analyses were performed in 31 patients [29 thymomas and two thymic cancers (TCs)] who met the study criteria. Of these, 12 cases of thymoma types A, AB, B1, and B2 harbored the general transcription factor 2-I (GTF2I) mutation (L424H). Conversely, the mutation was not detected in type B3 thymoma or TC, suggesting that the GTF2I mutation existed in indolent types of TETs. Rat sarcoma viral oncogene (RAS) mutations were detected in three cases [Harvey RAS (HRAS) in two cases of type AB thymoma and neuroblastoma RAS (NRAS)] in one case of type B1 thymoma), and additional sex combs like 1 (ASXL1) mutation was present in one case of TC. All RAS mutations were observed in GTF2I-mutated cases.

Conclusions

The GTF2I mutation (L424H) is the most frequently occurring mutation in the limited histology of thymoma, consistent with those in the non-Asian population. HRAS and NRAS mutations co-occurred in cases harboring the GTF2I mutation. These findings suggest that the existence of the GTF2I mutation might be related to indolent types of TETs, and RAS mutations could be candidates as therapeutic targets in TETs.

Thymic Epithelial Tumors: An Evolving Field

Despite their rarity, thymic epithelial tumors (TETs) have attracted much interest over the years, leading to an impressive number of histological and staging classifications. At present, TETs are divided by the WHO classification into four main subtypes: type A, type AB, and type B thymomas (subdivided into B1, B2, and B3), and thymic carcinomas, going from the more indolent to the most aggressive ones. Among many debated staging proposals, the TNM and the Masaoka-Koga staging systems have been widely accepted and used in routine practice. The four-tiered histological classification is symmetrically mirrored by the molecular subgrouping of TETs, which identifies an A-like and an AB-like cluster, with frequent GTF2I and HRAS mutations; an intermediate B-like cluster, with a T-cell signaling profile; and a carcinoma-like cluster comprising thymic carcinomas with frequent CDKN2A and TP53 alterations and a high tumor molecular burden. Molecular investigations have opened the way to tailored therapies, such as tyrosine kinase inhibitors targeting KIT, mTOR, and VEGFR, and immune-checkpoints that have been adopted as second-line systemic treatments. In this review, we discuss the crucial events that led to the current understanding of TETs, while disclosing the next steps in this intriguing field.

Emerging therapies in thymic epithelial tumors (Review)

Thymic epithelial tumors (TETs), including thymomas and thymic carcinomas, are rare malignancies arising from the thymus gland. The optimal management requires a multidisciplinary approach. Standard first-line systemic treatment involves cytotoxic chemotherapeutic regimens; however, alternative options for systemic treatment are required. Current research focuses on the unique profile of immune-related pathogenic mechanisms of TETs, involving an overlap with certain autoimmune phenotypes, as well as on determining the landscape of oncogenic molecular alterations and the role of tumor angiogenesis. The aim of the present review is to summarize the current clinical investigation on immunotherapy and targeted agents in the management of TETs. Regarding immune checkpoint inhibitors, efficacy results are promising in certain subsets of patients; however, caution is required concerning their toxicity. Anti-angiogenic agents, mainly potent small-molecule inhibitors, have demonstrated antitumor activity in TETs, whereas other targeted agents, including KIT inhibitors and epigenetic agents, are associated with encouraging, yet still modest results for unselected populations, in the absence of predictive biomarkers. Future research should focus on identifying predictive biomarkers for patients with TETs, and should implement multicenter collaborations and appropriate clinical trials tailored for rare tumor types.