Immunotherapy in thymic epithelial tumors: tissue predictive biomarkers for immune checkpoint inhibitors

Thymic epithelial tumors (TETs) are rare malignant neoplasms arising in the thymus gland. Nevertheless, TETs, including thymomas (TMs), thymic carcinomas (TCs), and thymic neuroendocrine neoplasms (TNENs), are the most common mediastinal malignancies overall. A multidisciplinary approach is required for the appropriate diagnostic and therapeutic management of TETs. To date, the main therapeutic strategies are largely depended on the stage of the tumor and they include surgery with or without neoadjuvant or adjuvant therapy, represented by platinum-based chemotherapy, radiotherapy or chemoradiotherapy. Immune checkpoint inhibitors (ICIs) are ongoing under evaluation in the advanced or metastatic diseases despite the challenges related to the very low tumor mutation burden (TMB) and the high incidence of immune-related adverse events in TETs. In this regard, predictive impact of tissue biomarkers expression such as programmed cell death ligand-1 (PD-L1), and other emerging biomarkers, as well as their optimal and shared interpretation are currently under evaluation in order to predict response rates to ICIs in TETs.

Thymic Carcinoma Management Patterns among International Thymic Malignancy Interest Group (ITMIG) Physicians with Consensus from the Thymic Carcinoma Working Group

INTRODUCTION

Thymic carcinomas are rare epithelial malignancies with limited data to guide management.

METHODS

To identify areas of agreement and variability in current clinical practice, a 16-question electronic survey was given to members of the International Thymic Malignancy Interest Group (ITMIG). Areas of controversy were discussed with the Thymic Carcinoma Working Group and consensus was achieved, as described.

RESULTS

A total of 100 ITMIG members responded. There was general agreement regarding the role for multimodality therapy with definitive surgical resection in physically fit patients with advanced but resectable disease. Areas of controversy included the need for histologic confirmation before surgery, the role of adjuvant therapy, the optimal first-line chemotherapy regimen, and the recommended treatment course for marginally resectable disease with invasion into the great vessels, pericardium, and lungs.

CONCLUSIONS

The results of the questionnaire provide a description of the management of thymic carcinoma by 100 ITMIG members with a specific interest or expertise in thymic malignancies. Although there was agreement in some areas, clinical practice appears to vary significantly. There is a great need for collaborative research to identify optimal evaluation and treatment strategies. Given the need for multimodality therapy in many cases, a multidisciplinary discussion of the management of patients with thymic carcinoma is critical.

Correlation between S-1 treatment outcome and expression of biomarkers for refractory thymic carcinoma

BACKGROUND

Thymic carcinoma is a rare cancer with minimal evidence of a survival benefit following chemotherapy. An oral fluoropyrimidine of S-1, however, is the recommended active cytotoxic chemotherapy agent for refractory thymic carcinoma based on a case series, whereas sunitinib or everolimus are recommended as molecular-targeted agents based on Phase II trials. We retrospectively investigated the efficacy of S-1 for refractory thymic carcinoma and performed a biomarker analysis.

METHODS

We assessed the clinicopathological variables of 14 consecutive patients who underwent S-1 for refractory thymic carcinoma and correlated the clinical outcomes with potential biomarkers using paraffin-embedded cancer tissues of eight patients in the cohort.

RESULTS

A total of 178 thymic malignancies were identified, of whom 14 patients included 12 cases of squamous cell carcinoma, one lymphoepithelioma-like carcinoma, and one undifferentiated carcinoma. Six patients exhibited a partial response (42.9 %: 95 % confidence interval [CI], 21.4-67.4) and the disease control rate was 85.7 % (60.0-96.0 %). After a median follow-up of 24.2 months, the median progression-free survival was 8.1 months (range, 2.6-12.2 months), and median overall survival was 30.0 months (range, 6.2-41.9 months). No significant correlation between biomarker expression and response was noted. However, thymidine synthase (TS)/dihydropyrimidine dehydrogenase and TS/orotate phosphoribosyltransferase were observed.

CONCLUSIONS

S-1 for refractory thymic carcinoma offered clinical activity and achieved an 85 % disease control rate. Although the biomarkers did not correlate with clinical outcome, the study results showed efficacy of S-1 as a cytotoxic chemotherapy for refractory thymic carcinoma, which warrants future investigation.

Targeted therapy for thymic epithelial tumors: a new horizon? Review of the literature and two cases reports

Surgical resection remains the cornerstone of therapy for early-stage thymic epithelial tumors (TETs), while in advanced or recurrent forms, a multimodality approach incorporating radiation and chemotherapy is required. Given the absence of effective treatment options for metastatic/refractory TETs and the poor related prognosis, there is a compelling need to identify promising 'drugable' molecular targets. Initial reports of activity from targeted agents in TETs derived from anecdotal cases have been often associated with specific activating mutations. Only in recent years, several agents have been formally investigated into prospective clinical trials, with varying success rates. We reviewed the literature on targeted therapy in TETs along with two cases of thymoma achieving striking responses to sorafenib in combination with lapatinib.

[Thymus cancers: A clinical observation]

INTRODUCTION

Thymic tumors including thymomas, thymic carcinomas, and thymic carcinoid tumors are rare tumors with an incidence of 0.13/100,000.

MATERIALS AND METHODS

A literature search was performed to identify recent findings on epidemiology, classification, and various therapeutic approaches.

RESULTS

These tumors with a wide spectrum of histologic and biologic features may be clinically unapparent for a long time or show a very aggressive behavior with local invasion and distant metastases. Surgical resection is the mainstay in stage I and II thymomas, whereas in stage III thymomas and in thymomas with pleural dissemination surgery in context of a multimodal treatment should be discussed. Thymic tumors are chemoreactive. Targeted therapies show poor results and should only be considered in the palliative situation after failure of chemotherapy.

CONCLUSION

The new TNM (T: tumor, N: node, M: metastasis) classification of thymic tumors will help to identify the best treatment options.

State of the art of genetic alterations in thymic epithelial tumors

The rapid advent of technology in recent years has resulted in a substantial increase in our knowledge of the molecular underpinnings of thymic epithelial tumors. In addition to previously described chromosomal aberrations and alterations in DNA methylation, genome sequencing has helped unravel hitherto unknown mutations in these tumors. Attempts are also being made to develop gene signatures to help in the identification of patients likely to benefit from adjuvant therapy. Some of the recently identified genetic alterations have the potential to serve as targets for biological therapy, thus opening newer avenues for treatment of thymic epithelial tumors and increasing the number of effective options for treatment of recurrent or refractory disease.

Response to cytotoxic chemotherapy in patients previously treated with palliative-intent chemotherapy for advanced thymic carcinoma

BACKGROUND

Clinical efficacy of second- and later-line chemotherapy for patients with thymic carcinoma previously treated with chemotherapy remains uncertain; limited data are available about this carcinoma because of its rarity. The aim of this study was to investigate effective chemotherapy for patients with thymic carcinoma previously treated with chemotherapy using a retrospective analysis of responses and times to event.

PATIENTS AND METHODS

We conducted a retrospective review of the medical records of 23 advanced thymic carcinoma patients previously treated with palliative-intent chemotherapy between 1980 and 2014 in our institution. Clinical demographic characteristics, agents, response, and time to treatment failure for each treatment line and overall survival were reviewed. Factors expected to be associated with survival rates were analyzed. Differences in survival were assessed using Kaplan-Meier analysis and univariate and multivariate Cox proportional hazards regression analyses.

RESULTS

The study included 13 men (56.5%) and 10 women (43.5%). The median age at diagnosis was 58.5 years. The most common histological subtypes were squamous cell carcinoma (16 patients [69.6%]), followed by neuroendocrine carcinoma (4 patients [17.4%]). The objective response rates of first-, second-, third-, and fourth-line chemotherapy were 60.9%, 39.1%, 23.1%, and 25.0%, respectively. The median survival time was 18.8 months (95% confidence interval, 7.5-40.9 months). Uni- and multivariate analyses of all assessed variables failed to identify any statistically significant indicators of overall survival.

CONCLUSION

Patients with thymic carcinoma previously treated with palliative-intent chemotherapy might respond to second- or later-lines of cytotoxic chemotherapy.