Immune checkpoints in thymic epithelial tumors: challenges and opportunities

Immunotherapy in thymic epithelial tumors: an attractive dilemma

Thymomas and thymic carcinomas are the most prevalent tumors that develop in the thymus's epithelial tissue. Thymomas are malignant tumors that develop from the epithelial cells of the thymus and frequently include mixed populations of lymphocytes. In contrast, thymic carcinomas are also tumors of the thymic epithelium, but they are characterized by a lack of lymphocytes, exhibit more aggressive behavior, and are associated with a poorer prognosis. Surgical intervention is the primary approach for managing resectable cases, while advanced, unresectable tumors are treated with platinum-based chemotherapy. The recurrence of the disease can happen months to years after initial treatment. Some patients do benefit from biologic therapies, but there is still a significant need for new treatment options. Immune checkpoint inhibitors have proven safe and clinically effective, improving survival in various cancers. However, their use in thymic cancers is currently limited to treating recurrent thymic carcinoma due to potential immune toxicity risks. This manuscript reviews the current applications of immunotherapy for thymic epithelial tumors and discusses strategies to enhance safety and expand treatment options for patients with these cancers.

Immunotherapy for Thymomas and Thymic Carcinomas: Current Status and Future Directions

Thymic epithelial tumors are a histologically diverse group of cancers arising from the epithelial compartment of the thymus. These tumors are characterized by a low tumor mutation burden, a lack of actionable genomic changes, and, especially with thymomas, defects in immune tolerance. Surgery is the mainstay of the management of resectable disease, whereas advanced, unresectable tumors are treated with platinum-based chemotherapy. Disease recurrence can occur months to years after frontline treatment. Although several options are available for conventional treatment of recurrent thymic tumors, response rates are generally low, and treatment-related toxicity can affect quality of life. A subset of patients benefit from biologic therapies, but there remains an unmet need for the development of new treatments. Immune checkpoint inhibitors are safe, clinically active, and have contributed to an improvement in survival for patients with a wide variety of cancers. However, the application of these revolutionary treatments for thymic cancers is limited to their use for the management of recurrent thymic carcinoma because of the risk of immune toxicity. In this paper, we review the current uses of immunotherapy for the management of thymic epithelial tumors and highlight potential strategies to improve safety and broaden the application of these treatments for patients with thymic cancers.

Myasthenia Gravis Associated With Pembrolizumab for Relapsed Lung Cancer After Thymoma Resection

Immunotherapy has demonstrated clinical efficacy in patients with thymic epithelial tumors; however, there is the potential risk of serious immune-related adverse events (irAEs). Here, we report a case of myasthenia gravis (MG) associated with pembrolizumab treatment that developed after thymoma resection in a patient with lung adenocarcinoma. Symptoms of MG occurred 16 days after pembrolizumab administration and progressed rapidly, necessitating mechanical ventilation and tracheostomy. Even after tumor resection, careful monitoring is crucial for patients with thymic tumors being managed with immune checkpoint therapy, particularly regarding the development of severe irAEs.

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.

Efficacy and safety of nivolumab for patients with pre-treated type B3 thymoma and thymic carcinoma: results from the EORTC-ETOP NIVOTHYM phase II trial

BACKGROUND

Thymic malignancies are rare intrathoracic tumors, which may be aggressive and difficult to treat. They represent a therapeutic challenge in the advanced/metastatic setting, with limited treatment options after the failure of first-line platinum-based chemotherapy. They are frequently associated with autoimmune disorders that also impact oncological management.

MATERIALS AND METHODS

NIVOTHYM is an international, multicenter, phase II, two-cohort, single-arm trial evaluating the activity and safety of nivolumab [240 mg intravenously (i.v.) q2 weeks] alone or with ipilimumab (1 mg /kg i.v. q6 weeks) in patients with advanced/relapsed type B3 thymoma or thymic carcinoma, after exposure to platinum-based chemotherapy. The primary endpoint is progression-free survival rate at 6 months (PFSR-6) based on RECIST 1.1 as per independent radiological review.

RESULTS

From April 2018 to February 2020, 55 patients were enrolled in 15 centers from 5 countries. Ten patients (18%) had type B3 thymoma and 43 (78%) had thymic carcinoma. The majority were male (64%), and the median age was 58 years. Among the 49 eligible patients who started treatment, PFSR-6 by central review was 35% [95% confidence interval (CI) 22% to 50%]. The overall response rate and disease control rate were 12% (95% CI 5% to 25%) and 63% (95% CI 48% to 77%), respectively. Using the Kaplan-Meier method, median progression-free survival and overall survival by local assessment were 6.0 (95% CI 3.1-10.4) months and 21.3 (95% CI 11.6-not estimable) months, respectively. In the safety population of 54 patients, adverse events (AEs) of grade 1/2 were observed in 22 (41%) patients and grade 3/4 in 31 (57%) patients. Treatment-related AEs of grade 4 included one case of neutropenia, one case of immune-mediated transaminitis, and two cases of myocarditis.

CONCLUSIONS

Nivolumab monotherapy demonstrated an acceptable safety profile and objective activity, although it has been insufficient to meet its primary objective. The second cohort of NIVOTHYM is currently ongoing to assess the combination of nivolumab plus ipilimumab.

Immunotherapy of thymic epithelial tumors: molecular understandings and clinical perspectives

Immunotherapy has emerged to play a rapidly expanding role in the treatment of cancers. Currently, many clinical trials of therapeutic agents are on ongoing with majority of immune checkpoint inhibitors (ICIs) especially programmed death receptor 1 (PD-1) and its ligand 1 (PD-L1) inhibitors. PD-1 and PD-L1, two main immune checkpoints, are expressed at high levels in thymic epithelial tumors (TETs) and could be predictors of the progression and immunotherapeutic efficacy of TETs. However, despite inspiring efficacy reported in clinical trials and clinical practice, significantly higher incidence of immune-related adverse events (irAEs) than other tumors bring challenges to the administration of ICIs in TETs. To develop safe and effective immunotherapeutic patterns in TETs, understanding the clinical properties of patients, the cellular and molecular mechanisms of immunotherapy and irAEs occurrence are crucial. In this review, the progress of both basic and clinical research on immune checkpoints in TETs, the evidence of therapeutic efficacy and irAEs based on PD-1 /PD-L1 inhibitors in TETs treatment are discussed. Additionally, we highlighted the possible mechanisms underlying irAEs, prevention and management strategies, the insufficiency of current research and some worthy research insights. High PD-1/PD-L1 expression in TETs provides a rationale for ICI use. Completed clinical trials have shown an encouraging efficacy of ICIs, despite the high rate of irAEs. A deeper mechanism understanding at molecular level how ICIs function in TETs and why irAEs occur will help maximize the immunotherapeutic efficacy while minimizing irAEs risks in TET treatment to improve patient prognosis.

Immune checkpoint blockers in patients with unresectable or metastatic thymic epithelial tumours: A meta-analysis

BACKGROUND

For patients with advanced thymic epithelial tumours (TET), there is no standard second-line treatment after platinum-based chemotherapy. Although immune checkpoint blockers (ICB) are a potential treatment strategy, their efficacy seems limited with an increased risk of immune-related adverse events (ir-AEs), thus hampering their application in daily clinical practice.

METHODS

We performed a meta-analysis to better evaluate the existing evidence about the activity and safety of ICB in the setting of unresectable or metastatic advanced TET previously treated with platinum-based chemotherapy.

RESULTS

Six phase I/II trials met the eligibility criteria including a total of 166 evaluable patients (77% thymic carcinoma, 23% thymoma) evaluable for activity after being treated with pembrolizumab, nivolumab, avelumab or atezolizumab. The overall response rate to ICB was 18.4% (95% CI: 12.3-26.5), and the one-year progression-free survival rate and one-year overall survival rate were 26.0% (95% CI: 19.6-34.6) and 66.9% (95% CI: 59.6-75.2%), respectively. The incidence of grade 3-5 ir-AEs was 26.4%, with 17.1% in thymic carcinoma and 58.3% in thymoma.

CONCLUSIONS

Despite the absence of a robust demonstration of efficacy in the context of randomised trials, our results suggest ICB as a potential strategy in patients with pretreated TET, mainly among patients with thymic carcinoma. Close monitoring is strongly advised to detect severe immune-toxicity.

Immunotherapy for Management of Thymic Epithelial Tumors: A Double-Edged Sword

Thymic epithelial tumors (TETs) are rare thoracic cancers that are broadly classified as thymomas and thymic carcinomas. Surgery is the cornerstone of management for early-stage disease. There are a limited number of effective treatment options for patients with advanced or recurrent disease. The occurrence of paraneoplastic autoimmune disorders in patients with TETs, especially thymomas, creates significant challenges for the development of immunotherapy, including immune checkpoint inhibitors, as a feasible treatment option. In addition, patients with TETs are at increased risk for the development of immune-mediated toxicity with a predilection for musculoskeletal and neuromuscular adverse events upon treatment with immunotherapy. The identification of biomarkers of response and toxicity is expected to play a key role in harnessing the benefits of immunotherapy for patients with TETs. In this paper we review the biology of TETs and the potential effects on the tolerability of immunotherapy. The results of clinical trials of immune checkpoint inhibitors for the treatment of advanced TETs are described to understand the potential risks and benefits of immunotherapy. We also provide an overview of future avenues for treatment with novel immunotherapeutic modalities and opportunities to develop biomarkers to improve the safety and tolerability of immunomodulatory treatments in patients with TETs.

Tolerability of Coronavirus Disease 2019 Vaccines, BNT162b2 and mRNA-1273, in Patients With Thymic Epithelial Tumors

INTRODUCTION

Defects in immunologic self-tolerance result in an increased risk for development of paraneoplastic autoimmune diseases (ADs) and immune-mediated toxicity in response to immune stimulation in individuals with thymic epithelial tumors (TETs). We conducted a survey to evaluate the tolerability of coronavirus disease 2019 (COVID-19) mRNA vaccines in patients with TETs, including individuals with preexisting AD.

METHODS

After reviewing published data on adverse events associated with the BNT162b2 (Pfizer, Inc., and BioNTech) and mRNA-1273 (ModernaTX, Inc.) mRNA vaccines, we designed and administered a questionnaire to participants at the following three time points: after each dose of vaccination and 1 month after the final dose. Questions related to AD and use of immunosuppressive drugs were included. Descriptive statistics were used to analyze data, and results were compared with previously described results related to the BNT162b2 and mRNA-1273 vaccines.

RESULTS

From February 26 to June 1, 2021, we administered the survey to 54 participants (median age = 58 y, thymoma = 33, preexisting AD = 19). Common adverse events included injection site pain, fatigue, and headaches. There were no vaccination-related hospitalizations or deaths. Autoimmune flares occurred in three patients (16%) after the first dose and three patients (17%) after the second dose. Most AD flares were mild and self-limited. One patient (2%) was diagnosed with having a new AD after vaccination.

CONCLUSIONS

Tolerability of COVID-19 mRNA vaccines in patients with TETs is comparable to the general population. Most patients with preexisting AD did not experience disease flares, and the development of new AD was rare. Patients with TETs should be encouraged to get vaccinated against COVID-19 owing to the documented benefits of vaccination and manageable risk profile.

Nivolumab treatment for metastatic thymic epithelial tumors

BACKGROUND

Metastatic and unresectable thymoma (T) or thymic carcinoma (TC) have limited treatment options, especially after first line.

METHODS

Patients with unresectable or recurrent thymic tumors who used minimum one dose of nivolumab at any line of treatment were evaluated retrospectively. Even though nivolumab was administered 3mg/kg dosage in PRIMER study, due to toxicity and financial concerns, we used low dose regimen mostly.

RESULTS

Among 46 unresectable and recurrent thymic epithelial tumors; 8 patients with TC (n = 3), T (n = 4) and mixt histology (n = 1) were reviewed. Three patients had myasthenia gravis history that had to be controlled before treatment. Four patients showed moderate (n = 2) or severe (n = 2) adverse events with nivolumab treatment. Interestingly, two severe adverse events were occurred at first dose even with 40 mg nivolumab and required cessation of treatment permanently. The median number of nivolumab received was four (range: 1-18). Best response was partial response. Two patients progressed at the 3rd and 5th month of treatment. Best duration of response for one patient with TC and one patient with T-B2 were 9 and 14 months, respectively. Median survival time after nivolumab was 7.4 months (range: 2-22.1).

CONCLUSIONS

After the results of the previous study could be supported by randomized prospective studies with more number of patients, nivolumab may be considered as an option in patients with thymic epithelial tumors who have received multiple line treatments. However, given the high rate of severe toxicities, there is need to find out a reliable marker to prediction patients who will derive benefit or exhibit toxicity.