Cisplatin, doxorubicin, and cyclophosphamide plus thoracic radiation therapy for limited-stage unresectable thymoma: an intergroup trial

Role of radiotherapy in the management of rare solid thoracic tumors of the adults

Thoracic tumors include more than one hundred histopathological subtypes. Rare thoracic malignancies can be defined as representing less than 1% of all thoracic tumors. The European Rare Cancer Surveillance Project (RARECARE) identified rarity as an incidence less than 6 for 100,000 people, with significant difference of prevalence between them. Modalities of treatment for these pathologies include surgery, radiotherapy, and systemic therapies. In this article, we aim to discuss role and techniques of radiotherapy in management of rare solid thoracic tumors in adults, focusing on different anatomical locations such as lung parenchyma, mediastinum, vessels, chest wall and pleural cavity.

Whole Exome Sequencing of Thymoma Patients Exhibiting Exceptional Responses to Pemetrexed Monotherapy

BACKGROUND

Pemetrexed is used for the chemotherapy of advanced thymoma. Exceptional responses of thymoma to pemetrexed treatment are not frequently observed. The underlying genetic mechanism of the exceptional responses remains unclear. We used whole-exome sequencing to explore the specific genomic aberrations that lead to an extreme and durable response.

METHODS

Whole-exome sequencing using NovaSeq6000 (150 bp paired-end sequencing) was performed on nine formalin-fixed paraffin-embedded tissues from patients with advanced thymomas treated with pemetrexed (two exceptional responders and seven typical responders).

RESULTS

We identified 284 somatic single-nucleotide variants (SNVs; 272 missense, 8 missense/splice-site, 3 stop-gain, and 1 stop-gain/splice-site), 34 insertions and deletions (Indels; 33 frameshift and one splice region), and 21 copy number variations (CNVs; 15 gains and six losses). No difference in the number of SNVs variants and distribution of deleterious Indels was observed between the exceptional and typical responders. Interestingly, arm-level chromosomal CNVs (15 gains and six losses) were detected in four patients, including an exceptional responder. The highest number of arm-level CNVs was observed in an exceptional responder.

CONCLUSION

Exceptional responders to pemetrexed for metastatic thymomas may be characterized by arm-level CNVs. Further, whole-genome and RNA sequencing studies should be performed.

The 100 most cited papers on thymoma: a bibliometric analysis

OBJECTIVES

The aim of this bibliometric analysis was twofold: to identify the 100 most cited research articles on thymoma and to highlight future research opportunities in light of past and current research efforts.

METHODS

The Web of Science database was queried to identify the 100 most cited articles on thymoma. Imformations relevant to scientific research were extracted and analyzed: first author, journal, impact factor, type of article, year of publication, country, organization and keywords.

RESULTS

The publication year of the top 100 most cited articles ranged from 1981 to 2018, and the number of citations ranged from 97 to 1182. Most of the included articles are original (75/100) and are mainly retrospective studies (52/75). The United States has the most published articles and citations, and the Annals of Thoracic Surgery is the most sourced journal (n = 16). Through VOSviewer analysis, high-density keywords mainly come from thymic carcinoma/invasive thymoma management, immune-related diseases, and laboratory research.

CONCLUSIONS

To our knowledge, this is the first bibliometric study on thymoma. We found most of the top 100 most cited articles are original and retrospective research. The United States has the published and cited works. Presently, the hot keywords for thymoma research has gradually tilted towards immune-related diseases and laboratory research.

Chinese expert consensus on the diagnosis and treatment of thymic epithelial tumors

Thymic epithelial tumors (TETs) are a relatively rare type of thoracic tumor, accounting for less than 1% of all tumors. The incidence of TETs is about 3.93/10000 in China, slightly higher than that of European and American countries. For resectable TETs, complete surgical resection is recommended. Radiotherapy or chemotherapy may be used as postoperative adjuvant treatment. Treatment for advanced, unresectable TETs consist mainly of radiotherapy and chemotherapy, but there is a lack of standard first- and second-line treatment regimens. Recently, targeted therapies and immune checkpoint inhibitors have shown promising outcomes in TETs. Based on the currently available clinical evidences and the opinions of the national experts, the Thymic Oncology Group of Yangtze River Delta Lung Cancer Cooperation Group (East China LUng caNcer Group, ECLUNG; Youth Committee) established this Chinese expert consensus on the clinical diagnosis and treatment of TETs, covering the epidemiology, diagnosis, treatment, prognosis and follow-up of TETs.

Rare thoracic cancers: a comprehensive overview of diagnosis and management of small cell lung cancer, malignant pleural mesothelioma and thymic epithelial tumours

Despite the progress in outcomes seen with immunotherapy in various malignancies, including nonsmall cell lung cancer, the benefits are less in small cell lung cancer, malignant pleural mesothelioma and thymic epithelial tumours. New effective treatment options are needed, guided via more in-depth insights into the pathophysiology of these rare malignancies. This review comprehensively presents an overview of the clinical presentation, diagnostic tools, staging systems, pathophysiology and treatment options for these rare thoracic cancers. In addition, opportunities for further improvement of therapies are discussed.

An Updated Review on Radiation Treatment Management in Thymus Cancers

This narrative review aims to summarize the currently available evidence for the role of radiation in the treatment of thymus cancers. Thymus cancers are rare, heterogeneous tumors with limited evidence to guide their clinical management. There remains some controversy over the role of radiation in the adjuvant and induction/definitive setting. We performed a systematic search of the MEDLINE/PubMed database, focusing on studies published within the last 30 years. Our search queried "thymoma [OR] thymic carcinoma [AND] radiation" and was limited only to prospective and retrospective studies and metanalyses, omitting books, documents, and reviews. Our search resulted in 174 total references, of which only 31 references were within the scope of interest ranging from 1988 to 2021. For resectable disease, there is prospective evidence to support the avoidance of postoperative radiation (PORT) in completely resected Masaoka stage I thymoma, but there is a lack of prospective evidence guiding the use of PORT in other situations. Several retrospective studies and metanalyses have suggested a benefit with PORT for positive margins and advanced stage disease, although it remains controversial whether PORT is beneficial for all completely resected Masaoka stage II thymoma. For unresectable disease, induction chemotherapy followed by reassessment of resectability is the preferred management. Prospective evidence exists to support the use of induction chemoradiation for patients unable to tolerate anthracycline-based chemotherapy and the use of definitive chemoradiation for those unable to undergo surgery. An effective multidisciplinary approach is the optimal strategy for achieving the best outcomes in patients with thymus cancers.

Hypofractionated Radiation Therapy Combined With Weekly Chemotherapy in Patients With Unresectable or Recurrent Thymic Epithelial Tumor: A Prospective, Single-Arm Phase 2 Study (GASTO-1042)

PURPOSE

This prospective phase 2 study aimed to evaluate the efficacy and safety of hypofractionated radiation therapy (HRT) combined with concurrent weekly chemotherapy in patients with unresectable or recurrent thymic epithelial tumors (TETs).

METHODS AND MATERIALS

Patients with unresectable or recurrent intrathoracic TETs that could be encompassed within the radiation fields were enrolled. HRT using intensity modulated radiation therapy (IMRT) technique was administered with 3 different levels of radiation doses (51 Gy/17 fractions (fx), 48 Gy/12 fx, and 45 Gy/9 fx; biologically effective dose of 66.3-67.5Gy), combined with weekly docetaxel (25 mg/m²) and nedaplatin (25 mg/m²). Weekly thymosin α1 (1.6 mg) was administered from the start to 2 months after radiation therapy. The objective response rate (ORR), progression-free survival (PFS), overall survival (OS), health-related quality of life (QOL), and toxicity were recorded.

RESULTS

Fifty eligible patients enrolled from August 1, 2018, to July 1, 2020, were analyzed. Most patients (82.0%) had stage IVB tumors. Patients had IMRT-HRT (36-51 Gy in 9-17 fx, median biologically effective dose of 67.2 Gy) and concurrent weekly docetaxel/nedaplatin (2-4 cycles). During a median follow-up of 25.0 months (14.0-40.0), the ORR was 83.7%, the 2-year PFS was 59.1%, and the 2-year OS was 90.0%. There was 1 (2.0%) in-field recurrence while 19 (38.0%) patients developed out-of-field recurrence. Grade 3 pneumonitis was observed in 1 patient (2.0%). The ORR, 2-year PFS, 2-year OS, and toxicity were similar among 3 dose levels. Fourteen (28.0%) patients had 2 to 4 courses of radiation therapy because of recurrent diseases. Only 1 suffered from grade 1 pulmonary fibrosis during follow-up. Most patients (88%) maintained a stable QOL within 1 year after radiation therapy.

CONCLUSIONS

IMRT-HRT and concurrent weekly docetaxel/nedaplatin was effective and well tolerated in unresectable or recurrent TETs. Considering the common out-of-field recurrence, this combined regimen could be an option for repeated radiation therapy. Thymosin α1 might help lower the incidence of pneumonitis and maintain the QOL.

SEOM-GECP-GETTHI Clinical Guidelines for the treatment of patients with thymic epithelial tumours (2021)

Thymic epithelial tumours (TET) represent a heterogeneous group of rare malignancies that include thymomas and thymic carcinoma. Treatment of TET is based on the resectability of the tumour. If this is considered achievable upfront, surgical resection is the cornerstone of treatment. Platinum-based chemotherapy is the standard regimen for advanced TET. Due to the rarity of this disease, treatment decisions should be discussed in specific multidisciplinary tumour boards, and there are few prospective clinical studies with new strategies. However, several pathways involved in TET have been explored as potential targets for new therapies in previously treated patients, such as multi-tyrosine kinase inhibitors with antiangiogenic properties and immune checkpoint inhibitors (ICI). One third of patient with thymoma present an autoimmune disorders, increasing the risk of immune-related adverse events and autoimmune flares under ICIs. In these guidelines, we summarize the current evidence for the therapeutic approach in patients with TET and define levels of evidence for these decisions.

Therapeutic options in thymomas and thymic carcinomas

INTRODUCTION

Radical surgery is the best therapeutic option for thymic malignancies. However, patients with advanced or recurrent thymic malignancies often require chemotherapy or radiotherapy. Since thymic malignancies are rare cancers, the efficacy and safety of treatments have been verified based on small Phase 2 trials or retrospective studies.

AREA COVERED

We comprehensively reviewed the treatment strategies for thymic malignancies, including surgery, radiotherapy, and pharmacotherapy, including cytotoxic chemotherapy, molecular-targeted therapy, and immunotherapy. Additionally, we reviewed specific situations, such as pleural dissemination, central nervous system metastasis, and paraneoplastic syndrome.

EXPERT OPINION

Cytotoxic chemotherapy remains the standard option in pharmacotherapy. However, multikinase inhibitors, such as sunitinib and lenvatinib, and immune checkpoint inhibitors including pembrolizumab have been developed to treat thymic carcinomas. Now, a Phase 2 study is evaluating whether lenvatinib plus pembrolizumab benefits patients with type B3 thymoma or thymic carcinoma. Phosphatidylinositol 3-kinase/AKT/ mammalian target of rapamycin inhibitors may contribute to disease control and octreotide scan is only applicable to somatostatin analogues. Although the genomic characteristics of thymic malignancies have been analyzed, few actionable mutations have been detected in general. The development of a treatment strategy using combination pharmacotherapy is anticipated.

Induction Therapy Followed by Surgery for Unresectable Thymic Epithelial Tumours

Background and Objectives

The treatment of unresectable thymic epithelial tumours (TETs) remains controversial. Here, we present the efficacy and safety of induction therapy followed by surgery for unresectable TET.

Methods

Eighty-one patients with unresectable TETs treated with induction therapy followed by surgery were selected from a retrospective review of consecutive TETs from January 2005 to January 2021. Clinicopathological data were analyzed to assess tumour responses, resectability, adverse events, progression-free survival (PFS) and overall survival (OS).

Results

Induction therapy produced a major tumour response rate of 69.1%, a tumour response grade (TRG) 1-3 rate of 84.0% and an R0 resection rate of 74.1%. The most common toxic effects were all-grade neutropenia (35.8%) and anaemia (34.6%). The 10-year OS and PFS rates were 45.7% and 35.2%. Multivariate analysis showed that ypTNM stage, ypMasaoka stage, complete resection, and TRG were significant independent prognostic factors. Exploratory research revealed that different induction modalities and downstaging of T, N, M, TNM, or Masaoka classifications did not significantly alter the pooled hazard ratio for survival.

Conclusions

Induction therapy followed by surgery is well tolerated in patients with unresectable TETs, with encouraging R0 resection rates. Multimodality management provides good control of tumors for unresectable TET patients.

Thymic tumours and their special features

Thymic tumours are rare thoracic malignancies, that may be aggressive and difficult to treat. The pillars of the management include pathological review, consideration of differential diagnoses, staging and multidisciplinary discussion. Assessment of resectability is key to drive the treatment sequencing. Association with autoimmune diseases, especially myasthenia gravis, is observed, which impacts the oncological management. Networks are being built at the national and international levels. This article provides an overview of the most recent findings in the diagnosis, staging, histology, and management strategies of thymic tumours.

Thymic tumours are rare and heterogeneous tumours. Management is based on multidisciplinary discussion and networking.https://bit.ly/3kYAZ7u

Functional apoptosis profiling identifies MCL-1 and BCL-xL as prognostic markers and therapeutic targets in advanced thymomas and thymic carcinomas

BACKGROUND

Multi-omics studies have shown a high and lack of common driver mutations in most thymomas (TH) and thymic carcinomas (TC) that hamper the development of novel treatment approaches. However, deregulation of apoptosis has been proposed as a common hallmark of TH and TC. BH3 profiling can be utilized to study the readiness of living cancer cells to undergo apoptosis and their dependency on pro-survival BCL-2 family proteins.

METHODS

We screened a cohort of 62 TH and TC patient samples for expression of BCL-2 family proteins and used the TC cell line 1889c and native TH for dynamic BH3 profiling and treatment with BH3 mimetics.

RESULTS

Immunohistochemical overexpression of MCL-1 and BCL-xL was a strong prognostic marker of TH and TC, and BH3 profiling indicated a strong dependency on MCL-1 and BCL-xL in TH. Single inhibition of MCL-1 resulted in increased binding of BIM to BCL-xL as an escape mechanism that the combined inhibition of both factors could overcome. Indeed, the inhibition of MCL-1 and BCL-xL in combination induced apoptosis in a caspase-dependent manner in untreated and MCL-1-resistant 1889c cells.

CONCLUSION

TH and TC are exquisitely dependent on the pro-survival factors MCL-1 and BCL-xL, making them ideal candidates for co-inhibition by BH3 mimetics. Since TH show a heterogeneous dependency on BCL-2 family proteins, upfront BH3 profiling could select patients and tailor the optimal therapy with the least possible toxicity.

METTL3-dependent MALAT1 delocalization drives c-Myc induction in thymic epithelial tumors

BACKGROUND

Thymic epithelial tumors (TETs) are rare neoplasms, originating from epithelial thymic cells. The oncogenic potential of these rare neoplasms is still largely undefined, and a deeper molecular characterization could result in a relevant advance in their management, greatly improving diagnosis, prognosis and treatment choice. Deregulation of N6-methyladenosine (m⁶A) RNA modification, catalyzed by the METTL3/METTL14 methyltransferase complex, is emerging as a relevant event in cell differentiation and carcinogenesis. Various studies have reported that altered expression of METTL3 is associated with an aggressive malignant phenotype and favors migration and invasiveness, but its role in Thymic Tumors remains unknown.

RESULTS

In this study, we characterized that METTL3 contributes to Thymic Epithelial Tumor phenotype. We evidenced that METTL3 is overexpressed in tumor tissue compared to normal counterpart. Silencing of METTL3 expression in thymic carcinoma cells results in reduced cell proliferation and overall translation rate. Of note, METTL3 is responsible for the induction of c-MYC expression in TET cells. Specifically, high expression of c-MYC protein is enabled by lncRNA MALAT1, which is methylated and delocalized by METTL3. Interestingly, blocking of c-MYC by using JQ1 inhibitor cooperates with METTL3 depletion in the inhibition of proliferation and induction of cell death.

CONCLUSION

This study highlighted METTL3 as a tumor promoter in Thymic tumors and c-MYC as a promising target to be exploited for the treatment of TET.

Radiotherapy for thymic epithelial tumours: a review

Thymic epithelial tumours (TETs) represent a rare disease, yet they are the most common tumours of the anterior mediastinum. Due to the rare occurrence of TETs, evidence on optimal treatment is limited. Surgery is the treatment of choice in the management of TETs, while the role of postoperative radiotherapy (PORT) remains unresolved. PORT remains debated for thymomas, especially in completely resected stage II tumours, for which PORT may be more likely to benefit in the presence of aggressive histology (WHO subtype B2, B3) or extensive transcapsular invasion (Masaoka-Koga stage IIB). For stage III thymoma, evidence suggests an overall survival (OS) benefit for PORT after complete resection. For incompletely resected thymomas stage II or higher PORT is recommended. Thymic carcinomas at any stage with positive resection margins should be offered PORT. Radiotherapy plays an important role in the management of unresectable locally advanced TETs. Induction therapy (chemotherapy or chemoradiation) followed by surgery may be useful for locally advanced thymic malignancies initially considered as unresectable. Chemotherapy only is offered in patients with unresectable, metastatic tumours in palliative intent, checkpoint inhibitors may be promising for refractory diseases. Due to the lack of high-level evidence and the importance of a multidisciplinary approach, TETs should be discussed within a multidisciplinary team and the final recommendation should reflect individual patient preferences.

The safety and efficacy of Cyberknife® for thymic malignancy

PURPOSE

To evaluate the safety and efficacy of Cyberknife® (CK) for the treatment of primary or recurring thymic tumours.

MATERIALS AND METHODS

We retrospectively reviewed 12 patients (16 tumour lesions) with primary or recurring thymic tumours who were treated with CK between March 2008 and October 2017. Their data was stored in prospectively collected database. Kaplan-Meier method was used to calculate survival curves.

RESULTS

Five patients (41.7%), who had inoperable disease or refused surgery, were treated with CK initially, and 7 patients (58.3%) were treated with CK when they had recurrence diseases. The disease sites treated with CK were primary tumour site (5), regional lymph nodes (4), tumour bed (3), chest wall (2), pleura (1), and bone (1). The median target volume was 43.8 cm³ (range, 13.1-302.5cm³) for the 16 tumour lesions. The median follow-up time was 69.3 months (range, 9.7-124.8 months). The median survival time was 48.2 months, and the 5-year and 10-year OS rates were 68.2% and 45.5%, respectively. A high response rate for the tumour lesions irradiated with CK was obtained. Only one patient (8%) experienced in-field recurrence, and the 5-year local recurrence free survival was 90.9%. A case indicated that CK may induce the abscopal effect, which provides the potential to combine CK and immunotherapy. No severe radiation related toxicities were observed, and no treatment related death occurred.

CONCLUSION

CK treatment resulted in good outcomes, particularly local control, with minimal side effects, in highly selected patients with primary and recurring thymic tumours. More studies with larger sample are needed.

Multimodality approach in treatment of thymic tumors

Thymic tumors are rare neoplasms showing important clinical and pathologic polymorphisms ranging from low-mitotic encapsulated tumors to a highly aggressive and disseminating one. Complete resection of the tumor with surrounding fatty and mediastinal tissue is of paramount importance and provides good prognosis. Diagnosis of the tumor, radiologic evaluation and implementation of multimodal treatment including preoperative chemotherapy, radiotherapy, postoperative radiotherapy, adjuvant chemotherapy or radiotherapy are important components of the treatment strategy. Some of the stage III tumors can be resected without additional treatment, however, there is a good evidence to support administering preoperative and postoperative chemotherapy and postoperative radiotherapy in these patients providing higher complete resection rate and better survival. For stage IVA thymomas, surgery alone should not be considered as an effective approach and these tumors are considered as unresectable. Chemo/radiotherapy can be administered to those patients. Of those, postoperative chemotherapy and radiotherapy should be considered if these patients who were deemed to be previously unresectable become resectable. The combined modality treatment should provide prevention of locoregional and intrathoracic recurrence and eventually long-term survival with cure. New targeted therapies including agents against PI3K, CDK, and immune checkpoint PD-1/PD-L1 may lead to higher response rates with less toxicity.

Surgical treatment of pleural recurrence of thymoma: is hyperthermic intrathoracic chemotherapy worthwhile?

OBJECTIVES

Recurrence of thymoma is described in 10-30% of cases after surgical resection. Iterative surgery for thymoma pleural relapses (TPRs) is often part of a multimodal treatment. Hyperthermic intrathoracic chemotherapy (HITHOC) following macroscopic radical surgery is an option that combines the effects of mild hyperthermia with those of chemotherapeutic agents. We evaluated the effectiveness of surgery + HITHOC, compared with surgery alone, in the treatment of TPR.

METHODS

We retrospectively collected data of all patients who underwent surgery for TPR in our centre from 2005 to 2017. Relapses were treated by partial pleurectomy with radical intent, followed by HITHOC when not contraindicated. Patients were divided into 2 groups: surgery + HITHOC and surgery alone. We collected demographic and clinical data and analysed postoperative results together with oncological outcomes.

RESULTS

Forty patients (27: surgery + HITHOC, 13: surgery alone), mean age 49.8 (±13.7) years, were included in this study. There were no perioperative deaths. We experienced 33.3% perioperative morbidity in the surgery + HITHOC group compared with 23.1% in the surgery alone group (P = 0.71). The overall survival rate was comparable between the 2 groups (P = 0.139), whereas the local disease-free interval was 88.0 ± 15 months in the surgery + HITHOC group and 57 ± 19.5 months in the surgery alone group (P = 0.046). The analysis of factors affecting the outcomes revealed that radical surgery is related with a better survival rate whereas the local disease-free interval was significantly influenced by HITHOC.

CONCLUSIONS

The safety and feasibility of HITHOC in the treatment of TPR are already known, even if it should be reserved for selected patients. Surgery + HITHOC seems to be associated with a longer local disease-free time compared to surgery alone.

Role of modern neoadjuvant chemoradiotherapy in locally advanced thymic epithelial neoplasms

PURPOSE

To improve resectability in patients with stage III-IVA thymic epithelial neoplasms, neoadjuvant chemotherapy and radiotherapy are considered. This retrospective study aimed to investigate the efficacy and safety of neoadjuvant therapies using modern techniques in thymic epithelial neoplasms.

METHODS

We included 32 patients with Masaoka stage III-IV disease treated at our institution from January 2010 to December 2017. Data regarding clinicopathologic characteristics, treatment protocols, toxicities, and survival were collected. Response was evaluated according to the Response Evaluation Criteria in Solid Tumours 1.1. Survival was assessed using the Kaplan-Meier method. Adverse events were graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0.

RESULTS

Neoadjuvant radiotherapy alone, chemotherapy alone, sequence chemoradiotherapy, and concurrent chemoradiotherapy were administered to 10 (31.3%), 9 (28.1%), 3 (9.4%), and 10 (31.3%) patients, respectively. Twenty-nine patients (90.6%) underwent R0 resection. The median follow-up time was 38.0 months (3.3-109.5 months). After neoadjuvant therapy, 18 patients (56.3%) achieved partial response and 14 (43.8%) had stable disease. Pathologic complete response was achieved in 6 patients (18.8%), all of whom had thymic carcinoma. The 5-year overall and progression-free survival rates were 90.9% and 67.5%, respectively. For patients with thymic carcinoma, the 5-year overall and progression-free survival rates were 80.0% and 66.2%, respectively. Grade 3 toxicities were observed in only 1 patient (leukopenia).

CONCLUSIONS

For patients with primary unresectable thymic neoplasms, neoadjuvant chemoradiotherapy is an efficient and safe choice, with favorable response and survival and moderate toxicities. Patients with thymic carcinoma might benefit more from neoadjuvant therapies.

Thymic Malignancy-Updates in Staging and Management

Thymomas are relatively indolent tumors that present with locally advanced disease in 30% of the patients. Thymic carcinoma is a more aggressive histology with shorter disease-free and overall survival. Early-stage tumors are managed best with complete resection. Multimodal therapy is the standard of care for locally advanced tumors and neoadjuvant therapy may help improve respectability. Stage and complete resection are the strongest prognostic factors for long-term survival. Based on early experience, targeted and immunotherapies have shown limited promise in advanced disease.

Importance of resection for locoregional disease control in Masaoka stage IVA thymic neoplasms

BACKGROUND AND OBJECTIVES

It is unclear if a specific strategy for simultaneous treatment of primary thymic neoplasms and pleural metastases confers benefit for Masaoka stage IVA disease. We reviewed our experience with thymic neoplasms with concurrent pleural metastases to identify factors influencing outcomes.

METHODS

Records of patients who presented with stage IVA thymic neoplasms from 2000 to 2018 were assessed. Multivariate Cox proportional hazards analyses were completed to determine predictors of progression-free and overall survival.

RESULTS

Forty-eight patients were identified, including 34 (71%) who underwent surgery. Median overall and progression-free survival were 123 and 21 months, respectively. The extent of resection varied, and was most commonly thymectomy plus partial pleurectomy (22, 65%). Median progression-free survival for patients who underwent surgical resection versus those who had not was 24 versus 12 months (P = .018). Following surgical resection, mediastinal recurrence was uncommon (2, 6%, vs 7, 50% nonoperatively). Five-year survival rates in these groups were suggestive of possible benefit to surgery (87% vs 68%).

CONCLUSIONS

Thymic neoplasms with pleural dissemination represents a treatment challenge. As part of a multidisciplinary approach, surgery appears to be associated with more favorable long-term results, although selection bias may account for some of the survival differences observed.

Intensity Modulated Radiation Therapy Plus Etoposide/Cisplatin for Patients With Limited Advanced Unresectable Thymic Epithelial Tumors: A Prospective Phase 2 Study

PURPOSE

This prospective phase 2 study evaluated the efficacy and safety of intensity modulated radiation therapy plus etoposide/cisplatin (EP) for patients with unresectable thymic epithelial tumors (TETs).

METHODS AND MATERIALS

Patients with limited advanced unresectable TETs whose lesions could be encompassed within radiation fields were enrolled in this study. Two cycles of EP (75 mg/m² etoposide and 25 mg/m² cisplatin on days 1-3 and days 29-31) were administered concurrently with radiation therapy, followed by 2 cycles after radiation therapy. The primary endpoint was the objective response rate. The secondary endpoints were the progression-free survival rate, overall survival rate, and incidence of adverse events.

RESULTS

Fifty-six patients were enrolled between June 2011 and May 2018. Twenty-two and 34 patients had thymomas and thymic carcinomas, respectively. The median age was 52 (range, 21-76) years, and 30 patients (53.6%) were men. Eight patients (14.3%) had stage III tumors, 6 (10.7%) had stage IVA tumors, and 42 (75.0%) had stage IVB tumors. The objective response rate was 85.7% (95% confidence interval, 76.3%-95.2%). With a median follow-up of 46 (range, 7-101) months, the 1-, 2-, and 5-year progression-free survival rates were 66.1%, 48.0%, and 29.5%, and the 1-, 2-, and 5-year overall survival rates were 91.0%, 76.2%, and 56.2%, respectively. The most common grade 3 to 4 adverse event was leukopenia (42.9%). Pulmonary fibrosis was also observed (5.3%).

CONCLUSIONS

Because intensity modulated radiation therapy with EP is effective and safe for limited advanced unresectable TETs, it could be a suitable treatment option for such patients.

Activation of the mTOR/ Akt pathway in thymic epithelial cells derived from thymomas

The pathogenesis of thymic epithelial tumors remains poorly elucidated. The PIK3/Akt/mTOR pathway plays a key role in various cancers; interestingly, several phase I/II studies have reported a positive effect of mTOR inhibitors in disease control in thymoma patients. A major limit for deciphering cellular and molecular events leading to the transformation of thymic epithelial cells or for testing drug candidates is the lack of reliable in vitro cell system. We analyzed protein expression and activation of key players of the Akt/ mTOR pathway namely Akt, mTOR, and P70S6K in eleven A, B and AB thymomas as well as in normal thymuses. While only Akt and phospho-Akt were expressed in normal thymuses, both Akt and mTOR were activated in thymomas. Phospho-P70S6K was expressed in all thymic tumors whatever their subtypes, and absent in normal thymus. Interestingly, we report the activation of Akt, mTOR and P70S6 proteins in primary thymic epithelial cells maintained for short period of time after their derivation from seven AB and B thymomas. Finally, we showed that rapamycin (100 nM) significantly reduced proliferation of thymoma- derived epithelial cells without inducing cell death. Our results suggest that the activation of the Akt/ mTOR pathway might participate to the cell proliferation associated with tumor growth. Ultimately, our data enhance the potential role of thymic epithelial cells derived from tissue specimens for in vitro exploration of molecular abnormalities in rare thymic tumors.

Efficacy and toxicities of gemcitabine and cisplatin combined with endostar in advanced thymoma and thymic carcinoma

BACKGROUND

Thymoma and thymic carcinoma are rare thymic epithelial tumors. We investigated the efficacy of first-line gemcitabine and cisplatin (GP) chemotherapy versus gemcitabine and cisplatin chemotherapy combined with the anti-angiogenic drug endostar (GP + E) in advanced thymoma and thymic carcinoma.

METHODS

The records of 45 patients with invasive metastatic thymomas or thymic carcinomas treated with GP as first-line therapy between August 2008 and July 2017 at the Department of Respiratory Medicine, Peking University Cancer Hospital and Institute were retrospectively reviewed.

RESULTS

Eighteen patients (75%) in the GP + E group achieved a partial response and six (25%) had stable disease. In GP only group, nine (42.8%) patients achieved a partial response, 11 (52.4%) had stable disease, and one (4.8%) had progressive disease. The GP + E group had a significantly higher overall response rate (75% vs. 42.9%; P = 0.028), and median progression-free survival (PFS) and overall survival (OS) of 19 and 76 months, respectively. In the GP only group, median PFS and OS were 16 and 29 months, respectively. PFS and OS were not significantly different between the groups.

CONCLUSIONS

GP has moderate efficacy and could represent a suitable first-line therapy for thymic carcinoma and thymoma. Chemotherapy combined with endostar could improve the overall response rate, but did not prolong PFS or OS.

Role of Surgery in the Treatment of Masaoka Stage IVa Thymoma

PURPOSE

To analyze the role of surgery in patients with Masaoka stage IVa thymoma treated with multimodality therapy.

METHODS

Of 191 patients undergoing surgery for thymoma in our department between January 2002 and December 2015, 39 (20.4%) had Masaoka stage IVa. Histopathological tumor type, myasthenic status of the Osserman-Genkins score, Masaoka stage at the first surgery, neoadjuvant treatment, number and type of surgeries, and survival rates were recorded.

RESULTS

Thymoma B2 was the most common histopathological tumor type (n = 16, 41%). Twenty-six (66.7%) patients underwent primary surgeries for Masaoka stage IVa thymoma, whereas nine (23.1%) underwent secondary surgeries and four (10.3%) underwent tertiary surgeries for pleural or pericardial recurrences. Median survival was 132 ± 25 (82-181; 95% confidence interval [CI]) months. Overall 3-, 5-, and 10-year survival rates were 93%, 93%, and 56%, respectively.

CONCLUSION

Surgical treatment should be considered as a completion modality to oncological therapy and has the potential to provide long-term survival of Masaoka stage IVa in patients with thymoma. The type of surgery should be determined based on the invasiveness of the lesion.

Neuroendocrine tumors of the thymus: the oncologist point of view

Thymic malignancies represent a heterogeneous group of rare thoracic cancers, which are classified according to the World Health Organization (WHO) histopathologic classification that distinguishes thymomas from thymic carcinomas and neuroendocrine tumors; neuroendocrine thymic tumors (NETTs) exhibit the same histological spectrum as in other anatomical locations, although with different frequencies. NETTs represent around 2% of all neuroendocrine tumors, and about 5% of all thymic malignancies. Overall, the management of patients with NETTs tumors requires continuous multidisciplinary expertise at any step of the disease progression. Systemic treatment relies on cytotoxic chemotherapy, as well as on somatostatin analogues and everolimus. Systemic treatment may be delivered in a curative-intent approach, for patients presenting with locally-advanced tumor at the time of diagnosis, with invasion of intra-thoracic neighboring structures. In such cases, chemotherapy has been used in an induction setting, to reduce the tumor burden-possibly allowing subsequent surgery and/or radiotherapy-or as a postoperative treatment if the tumor was resectable upfront, to reduce the risk of recurrence and achieve prolonged disease control. Systemic therapies are also a palliative-intent treatment of unresectable, metastatic, and recurrent NETTs. Chemotherapy may then be an option for aggressive disease, but somatostatin analogues and everolimus are suitable as well. Alternative options are emerging through clinical trials. As no dedicated study has ever been conducted, recommendations for systemic treatment in NETTs have been mostly based on retrospective cohorts of limited numbers patients, especially in the advanced disease setting, and expert opinion based on experience from primary pulmonary, as well as gastro-intestinal neuroendocrine tumors, for which clinical trials have been conducted.

Prospective Study of Stereotactic Body Radiation Therapy for Thymoma and Thymic Carcinoma: Therapeutic Effect and Toxicity Assessment

Stereotactic body radiation therapy (SBRT) is an important modality in treatment of tumors. We hypothesized that SBRT can achieve excellent local control with limited toxicity in patients with thymic tumors. A single-institution prospective study was performed with 32 patients who underwent SBRT of thymoma and thymic carcinoma between 2005 and 2014. Thirty-two patients including 39 target lesions were analyses in this study. Almost half of the patients (46.9%) were type C by histopathology and more than half (56.3%) were classified into stage IVA or IVB. The median dose of SBRT for gross tumor volume (GTV) was 56 Gy (range 49–70 Gy). Results showed that the response rate was 96.9% after SBRT and the median tumor shrinkage rate was 62.2% (range 3.8–100%). For the patients with both stage II–III and type A-B (n = 6), the median PFS was 28 months. In-field failure was only observed in 4 patients, and outside-field failure was seen in 2 patients. The local control rate was 81.25%. Patients treated with SBRT had an excellent local control with mild toxicities, which suggests that SBRT is feasible for the patients with thymic tumors who are unable to undergo either surgery or conventionally fractionated radiation therapy.

Chemoradiotherapy for unresectable cases of thymic epithelial tumors: a retrospective study

BACKGROUND

Because of the rarity of thymic epithelial tumors (TETs), there is no treatment for managing unresectable tumors that is supported by a high level of evidence. We present here the clinical outcomes of concurrent or sequential chemoradiotherapy for patients with unresectable TETs.

METHODS

We collated records for 215 patients with TETs who were treated at our institution and focused on the 20 patients who underwent chemoradiotherapy without curative-intent surgical resection.

RESULTS

Six patients with thymoma (4%) and 14 patients with thymic carcinoma (19%) were treated with chemoradiotherapy. Six received concurrent therapy, and platinum-containing regimens were administered to 16 patients. The survival of patients with thymic carcinoma was poorer than that of patients with thymoma [median overall survival (OS), 64.1 and 31.4 months, respectively; P=0.059]. No significant difference in survival was observed between patients treated concurrently and sequentially (48.5 vs. 38.2 months, respectively, P=0.83) or between patients treated with platinum-containing regimens and other regimens (43.5 and 53.8 months, respectively, P=0.25).

CONCLUSIONS

Chemoradiotherapy for unresectable TETs can be beneficial, especially when administrated concurrently. Patients for concurrent chemoradiotherapy should be chosen carefully because of its effectiveness and toxicity.

Expression of PD-L1 and other immunotherapeutic targets in thymic epithelial tumors

Introduction

The thymus is a critical organ for the development of the adaptive immune system and thymic epithelial tumors (TETs; thymomas and thymic carcinomas) are often associated with auto-immune paraneoplastic conditions. However, the immunobiology of TETs is not well described. An evaluation of the tumor microenvironment, with particular focus on expression of immunotherapeutic targets, may facilitate and prioritize development of immunotherapy strategies for patients with TETs.

Methods

Tumor tissues from 23 patients with WHO Type B2/B3 thymoma (n = 12) and thymic carcinoma (n = 11) were identified and clinical outcomes were annotated. The expression of membranous PD-L1 on tumor cells, CD3+ and CD8+ tumor infiltrating lymphocytes (TILs), co-stimulatory (CD137, GITR, ICOS), and co-inhibitory immune checkpoint molecules (PD-1, CTLA-4, TIM-3) were assessed semi-quantitatively using immunohistochemistry.

Results

PD-L1 positivity (≥ 25% of tumor membrane expression) was frequent in TETs (15/23, 65%), more common in thymomas compared to thymic carcinomas (p<0.01), and was associated with longer overall survival (p = 0.02). TIM-3 and GITR were expressed in all TETs, including 18/23 and 12/23 with at least moderate/high expression, respectively. Moderate/high CD137 expression correlated with CD8+ (p = 0.01) and moderate/high GITR expression co-associated with PD-1 (p = 0.043).

Conclusions

TETs are characterized by frequent PD-L1 expression and PD-L1 is associated with improved survival, suggesting PD-L1 signaling may be biologically important in TETs. Robust expression of markers of immune activation and immunotherapeutic target molecules in TETs emphasizes the potential for development of anti-PD-1/PD-L1 therapies.

Polyparaneoplastic Manifestations of Malignant Thymoma: A Unique Case of Myasthenia, Autoimmune Hepatitis, Pure Red Cell Aplasia, and Keratoconjunctivitis Sicca

Thymomas are relatively uncommon malignancies of the anterior mediastinum and present with four distinct histological types based on the specific epithelial to lymphocyte ratio: spindle cell, epithelial predominant, lymphocyte predominant, or mixed. Each histologic type of thymoma has a propensity for local invasion and metastasis and can have a wide variety of paraneoplastic manifestations, myasthenia being the most common. We present a unique case of a 34-year-old African-American female who initially presented with a history of profound weakness with repetitive motion, shortness of breath, horizontal nystagmus, persistent anemia, keratoconjunctivitis sicca, and what was initially thought to be azithromycin-induced hepatitis. Upon left anterior thoracotomy with biopsy of the mediastinal mass, pathology yielded a lymphocyte-predominant (B1), Masaoka stage IVA invasive thymoma with pericardial extension. This case illustrates the clinical significance of considering a multitude of extrathymic paraneoplastic manifestations, each with a unique physiological mechanism.

Thymic Epithelial Tumors phenotype relies on miR-145-5p epigenetic regulation

BACKGROUND

Thymoma and thymic carcinoma are the most frequent subtypes of thymic epithelial tumors (TETs). A relevant advance in TET management could derive from a deeper molecular characterization of these neoplasms. We previously identified a set of microRNA (miRNAs) differentially expressed in TETs and normal thymic tissues and among the most significantly deregulated we described the down-regulation of miR-145-5p in TET. Here we describe the mRNAs diversely regulated in TETs and analyze the correlation between these and the miRNAs previously identified, focusing in particular on miR-145-5p. Then, we examine the functional role of miR-145-5p in TETs and its epigenetic transcriptional regulation.

METHODS

mRNAs expression profiling of a cohort of fresh frozen TETs and normal tissues was performed by microarray analysis. MiR-145-5p role in TETs was evaluated in vitro, modulating its expression in a Thymic Carcinoma (TC1889) cell line. Epigenetic transcriptional regulation of miR-145-5p was examined by treating the TC1889 cell line with the HDAC inhibitor Valproic Acid (VPA).

RESULTS

Starting from the identification of a 69-gene signature of miR-145-5p putative target mRNAs, whose expression was inversely correlated to that of miR-145-5p, we followed the expression of some of them in vitro upon overexpression of miR-145-5p; we observed that this resulted in the down-regulation of the target genes, impacting on TETs cancerous phenotype. We also found that VPA treatment of TC1889 cells led to miR-145-5p up-regulation and concomitant down-regulation of miR-145-5p target genes and exhibited antitumor effects, as indicated by the induction of cell cycle arrest and by the reduction of cell viability, colony forming ability and migration capability. The importance of miR-145-5p up-regulation mediated by VPA is evidenced by the fact that hampering miR-145-5p activity by a LNA inhibitor reduced the impact of VPA treatment on cell viability and colony forming ability of TET cells. Finally, we observed that VPA was also able to enhance the response of TET cells to cisplatin and erlotinib.

CONCLUSIONS

Altogether our results suggest that the epigenetic regulation of miR-145-5p expression, as well as the modulation of its functional targets, could be relevant players in tumor progression and treatment response in TETs.

[Preoperative Induction Therapy for Locally Advanced Thymic Tumors: A Retrospective Analysis Using the ChART Database]

背景与目的

探讨术前诱导治疗在胸腺瘤中的应用及其对局部进展期胸腺瘤预后的影响。

方法

收集中国胸腺肿瘤协作组（Chinese Alliance of Research for Thymomas, ChART）1994年1月1日至2012年12月31日回顾性数据库中局部进展期胸腺瘤（Masaoka-Koga分期为Ⅲ期-Ⅳa期）病例。分为诱导治疗组和直接手术组，对比分析两组的R0切除率、5年复发率及5年生存率等指标。诱导治疗组术后分期为Masaoka-Koga Ⅰ期-Ⅱ期的病例视为诱导治疗后降期。为更加精确评估诱导治疗效果，在剔除术后Ⅳ期病例的基础上，再次将诱导治疗组术后Masaoka-Koga Ⅰ期-Ⅲ期的病例与直接手术组Masaoka-Koga Ⅲ期的病例进行对比分析。

结果

ChART回顾性数据库1, 713例有效病例中，局部进展期胸腺瘤706例，仅68例（4%）作了术前诱导治疗，R0切除率为67.6%，5年复发率为44.9%，5年与10年生存率分别为49.7%和19.9%。其中17例诱导治疗后达到降期，降期亚组中胸腺瘤的比例高于胸腺癌（38.7% vs 13.9%, P=0.02）；与未降期亚组相比，降期亚组获得更高的5年生存率（93.8% vs 35.6%, P=0.013）。剔除术后Ⅳ期的病例后，直接手术组和诱导治疗组R0切除率接近（76.4% vs 73.3%, P=0.63），但5年生存率差异明显（85.2% vs 68.1%, P < 0.001），对于降期亚组，5年生存率优于直接手术组（93.8% vs 85.2%, P=0.438），未降期亚组5年生存率仅35.6%，明显差于降期亚组和直接手术组（P < 0.001）。

结论

术前诱导治疗目前尚未在局部进展期胸腺瘤中广泛应用，但ChART的回顾性数据研究显示通过有效的术前诱导治疗可以使难以彻底切除的病例降期后增加R0切除的机会，从而延长生存，特别是胸腺瘤的病例。这一初步结果将有助于未来的研究。

Induction Therapy for Thymoma

Thymomas are uncommon tumors that can present as locally advanced tumors in approximately 30% of the patients. Stage and complete resection are the strongest prognostic factors. For locally advanced tumors, induction treatment may improve the ability to achieve a complete resection. Combination treatment with cisplatin, doxorubicin, and cyclophosphamide is the most commonly used induction regimen. Similar rates of resectability are noted with the use of induction chemotherapy and chemoradiation therapy; however, more tumor necrosis is noted with the addition of radiation.

The clinical features, diagnosis and management of recurrent thymoma

Thymoma is a disease with malignant potential, which has a recurrence rate after complete resection ranging from 5 to 50 %. Multiple studies on the risk factors, treatment or prognosis have been reported. Many of them are controversial, however. In this review, we summarized some accepted risk factors, means of diagnosis and different treatments of recurrent thymoma. The risk factors of recurrent thymoma haven’t been well-studied, and its management remains controversial. We reviewed the literatures and found some key points which should be noticed during the surgery of initial thymoma. Although reoperation should be taken into account preferentially, multimodal treatments are also available. The prognosis are also been discussed.

Treatment Modalities and Outcomes in Patients With Advanced Invasive Thymoma or Thymic Carcinoma: A Retrospective Multicenter Study

INTRODUCTION

We investigated the relationships between treatment characteristics and long-term outcomes in patients with locally advanced thymoma or thymic carcinoma.

METHODS

We retrospectively reviewed 146 patients treated from 1980 to 2011 at 2 tertiary cancer care centers, 110 with Masaoka-Koga stages III to IVA invasive thymoma and 36 with stages I to IVA thymic carcinoma. Survival probabilities were estimated using the Kaplan-Meier method. Risk factors related to survival were identified by univariate and multivariate competing risk analysis, with overall survival (OS) as the competing risk. The Cox regression analysis was used to identify risk factors for OS.

RESULTS

Median follow-up time for all patients was 64 months. At 5 and 10 years, rates of OS and freedom from recurrence (FFR) were 81% and 58% and 81% and 65%, respectively. Of the patients who underwent surgery, trimodality treatment produced better survival compared with less aggressive treatment among patients with stage III disease (P=0.03). Among patients who underwent trimodality treatment, patients with stage III disease had better OS (P=0.03) and FFR (P<0.001) than those with stage IVA disease. On Cox regression analysis, decreased OS was associated with thymic carcinoma (hazard ratio [HR], 7.36; 95% confidence interval [CI], 2.38-22.77; P=0.001), R2/unresectable disease (HR, 8.45; 95% CI, 1.44-49.42; P=0.02), and an Eastern Cooperative Oncology Group performance score of 1 (HR, 8.14; 95% CI, 1.55-42.75; P=0.01) or 2 to 3 (HR, 29.60; 95% CI, 4.0-218.98; P=0.001) versus 0.

CONCLUSIONS

Aggressive treatment with chemotherapy, surgical resection, and postoperative radiation therapy can produce long-term survival for patients with invasive thymic malignancies.

Preoperative induction therapy for locally advanced thymic tumors: a retrospective analysis using the ChART database

BACKGROUND

To evaluate the role of preoperative induction therapy on prognosis of locally advanced thymic malignancies.

METHODS

Between 1994 and 2012, patients received preoperative induction therapies (IT group) in the Chinese Alliance for Research in Thymomas (ChART) database, were compared with those having surgery directly after preoperative evaluation (DS group). All tumors receiving induction therapies were locally advanced (clinically stage III-IV) before treatment and those turned out to be in pathological stage I and II were considered downstaged by induction. Clinical pathological characteristics were retrospectively analyzed. To more accurately study the effect of induction therapies, stage IV patients were then excluded. Only stage I-III tumors in the IT group and stage III cases in the DS group were selected for further comparison in a subgroup analysis.

RESULTS

Only 68 (4%) out of 1,713 patients had induction therapies, with a R0 resection of 67.6%, 5-year recurrence of 44.9%, and 5- and 10-year overall survivals (OS) of 49.7% and 19.9%. Seventeen patients (25%) were downstaged after induction. Significantly more thymomas were downstaged than thymic carcinomas (38.7% vs. 13.9%, P=0.02). Tumors downstaged after induction had significantly higher 5-year OS than those not downstaged (93.8% vs. 35.6%, P=0.013). For the subgroup analysis when stage IV patients were excluded, 5-year OS was 85.2% in the DS group and 68.1% in the IT group (P=0.000), although R0 resection were similar (76.4% vs. 73.3%, P=0.63). However, 5-year OS in tumors downstaged after induction (93.8%) was similar to those in the DS group (85.2%, P=0.438), both significantly higher than those not downstaged after induction (35.6%, P=0.000).

CONCLUSIONS

Preoperative neoadjuvant therapy have been used only occasionally in locally advanced thymic malignances. Effective induction therapy leading to tumor downstaging may be beneficial for potentially unresectable diseases, especially in patients with thymomas. These findings would be helpful to related studies in the future.

Diffuse high intensity PD-L1 staining in thymic epithelial tumors

INTRODUCTION

Blockade of the immune checkpoint programmed death receptor ligand-1 (PD-L1)/PD-1 pathway has well-established clinical activity across many tumor types. PD-L1 protein expression by immunohistochemistry is emerging as a predictive biomarker of response to these therapies. Here, we examine PD-L1 expression in a thymic epithelial tumor (TET) tissue microarray (TMA).

METHODS

The TMA contained 69 TETs and 17 thymic controls, with each case represented by triplicate cores. The TMA was stained with rabbit monoclonal antibody (clone 15; Sino Biological, Beijing, China) to human PD-L1. PD-L1 staining was scored based on intensity as follows: 0 = none, 1 = equivocal/uninterpretable, 2 = weak, and 3 = intermediate-strong. Those cases with all cores scoring three in the epithelial component were categorized as PD-L1 high and the remaining as PD-L1 low.

RESULTS

PD-L1 high scores were more frequent in TETs than in controls (68.1% versus 17.6%; p = 0.0036). PD-L1 scores and histology were significantly correlated, with higher intensity staining in World Health Organization (WHO). B2/B3/C TETs. Only 14.8% of TETs had PD-L1 staining of associated lymphocytes. In an adjusted analysis (age/sex), PD-L1 high TETs had a significantly worse overall survival (hazard ratio: 5.40, 95% confidence interval: 1.13-25.89; p = 0.035) and a trend for worse event-free survival (hazard ratio: 2.94, 95% confidence interval: 0.94-9.24; p = 0.064).

CONCLUSIONS

PD-L1 expression was present in all cases of TETs within the epithelial component but only in a minority in the lymphocytic component. TETs stained more intensely for PD-L1 than in controls, and PD-L1 high TETs were associated with more aggressive histology and worse prognosis. This study lends rationale to a clinical trial with anti-PD-1/PD-L1 therapy in this rare tumor type.

Prospective study of proton beam radiation therapy for adjuvant and definitive treatment of thymoma and thymic carcinoma: Early response and toxicity assessment

BACKGROUND AND PURPOSE

Radiation is an important modality in treatment of thymic tumors. However, toxicity may reduce its overall benefit. We hypothesized that double-scattering proton beam therapy (DS-PT) can achieve excellent local control with limited toxicity in patients with thymic malignancies.

METHODS AND MATERIALS

Patients with thymoma or thymic carcinoma treated with DS-PT between 2011 and 2015 were prospectively analyzed for toxicity and patterns of failure on an IRB-approved study.

RESULTS

Twenty-seven consecutive patients were evaluated. Patients were a median of 56 years and had thymoma (85%). They were treated with definitive (22%), salvage (15%) or adjuvant (63%) DS-PT to a median of 61.2/1.8 Gy [CGE]. No patient experienced grade ⩾3 toxicity. Acute grade 2 toxicities included dermatitis (37%), fatigue (11%), esophagitis (7%), and pneumonitis (4%). Late grade 2 toxicity was limited to a single patient with chronic dyspnea. At a median follow-up of 2 years, 100% local control was achieved. Three-year regional control, distant control, and overall survival rates were 96% (95% CI 76-99%), 74% (95% CI 41-90%), and 94% (95% CI 63-99%), respectively.

CONCLUSIONS

This is the first cohort and prospective series of proton therapy to treat thymic tumors, demonstrating low rates of early toxicity and excellent initial outcomes.

Thymoma and thymic carcinomas

Thymomas (Ts) and thymic carcinomas (TCs) are rare tumours of the mediastinum with an incidence rate of 1.7/million per year in Europe. Histological classification is based on rate of non-malignant-appearing thymic epithelial cells and proportions of lymphocytes (A, AB, B1, B2, B3, and C), while staging system concerns localisation of the involved areas. Surgery is the mainstay of treatment with a 10-year survival of 80%, 78%, 75%, and 42% for stages I, II, III and IV, respectively, with an R0 resection. Radiotherapy has a role in selected cases (stage III patients or R1-2 residual) and platinum-based chemotherapy remains the standard of care for patients with advanced disease. A multimodality approach would be advisable when surgery is not recommended. Since molecular aberrations are poorly understood and few responses are reported, targeted therapies are yet being studied. In this review, we describe key aspects of clinical management for Ts and TCs.

Development of the international thymic malignancy interest group international database: an unprecedented resource for the study of a rare group of tumors

BACKGROUND

Our knowledge of thymic malignancies has largely been derived from small, single-institution series. Recognition of the need for broad collaboration led to the creation of the International Thymic Malignancy Interest Group (ITMIG) and the development of a large, centralized database to advance knowledge of these rare tumors.

METHODS

A multidisciplinary Database Committee was convened to define a common set of data elements a priori. Retrospective data were solicited from ITMIG members and collated using standardized fields. Patients with thymoma, thymic carcinoma, or thymic carcinoid were included.

RESULTS

Over a 6-month period, 47 institutions spanning 15 countries contributed a total of 6097 cases (mean, 129 [range, 10-1209]). The sex distribution was equal for thymomas, but there was a greater proportion of men with thymic carcinoma and thymic carcinoid (p < 0.0001). Nearly all cases (99%) were treated surgically. WHO type B2 was the most frequent histologic classification among thymomas, whereas squamous was the most common among thymic carcinomas. In total, 38% of patients with thymoma had myasthenia gravis compared with less than or equal to 5% for thymic carcinoma and thymic carcinoid. Median overall survival was 18.9 years (95% confidence interval [CI], 17.4-20.3) for thymoma, 6.8 years (95% CI, 5.5-7.9) for thymic carcinoma, and 7.5 years (95% CI, 6.5-8.5) for thymic carcinoid.

CONCLUSIONS

The rapid creation of the ITMIG database demonstrates the feasibility of international collaboration for this rare set of malignancies and attests to the engagement of its membership. This database represents the largest collective data set ever assembled and provides an unprecedented resource for research of these tumors.

Management of metastatic malignant thymoma with advanced radiation and chemotherapy techniques: report of a rare case

Malignant thymomas are rare epithelial neoplasms of the anterior superior mediastinum that are typically invasive in nature and have a higher risk of relapse that may ultimately lead to death. Here we report a case of an advanced malignant thymoma that was successfully treated with neoadjuvant chemotherapy followed by surgical resection and subsequently with advanced and novel radiation therapy techniques. A 65-year-old male was diagnosed with a stage IV malignant thymoma with multiple metastatic lesions involving the left peripheral lung and pericardium. Initial neoadjuvant chemotherapy with a cisplatin-based regimen resulted in a partial response allowing the inoperable tumor to become operable. Following surgical resection of the residual disease, the tumor recurred within a year. The patient then underwent a course of targeted three-dimensional intensity modulated radiation therapy (IMRT) and image-guided radiation therapy (IGRT). Five years after radiation therapy, the localized soft tissue thickening at the left upper lung anterior pleural space had resolved. Seven years after radiation therapy the tumor mass had completely resolved. No recurrences were seen and the patient is well even 8 years after IMRT/IGRT with a favorable outcome. Chemotherapy with targeted three-dimensional IMRT/IGRT should be considered the primary modality for the management of advanced malignant thymoma patients.

Long-term follow-up and prognostic factors for advanced thymic carcinoma

The aim of this study was to evaluate the long-term survival outcomes in patients with advanced thymic carcinoma and identify prognostic factors influencing the survival. We retrospectively analyzed 90 consecutive patients with pathologically confirmed advanced thymic carcinoma (Masaoka III and IV) in our institute, from December 2000 to 2012. Age, sex, clinical characteristics, laboratory findings, Masaoka and tumor node metastasis staging, pathologic grade, and treatment modalities were analyzed to identify prognostic factors associated with the progress-free survival (PFS) and the overall survival (OS) rates. Statistical analysis was conducted using SPSS, version 19.0 (SPSS, Inc, Chicago, IL). A total of 73 (81.1%) male and 17 (18.9%) female patients participated in the study. The median follow-up time was 75 months (range, 20-158 months). The 5-year PFS and OS rates were 23.6% (95% confidence interval [CI], 14.6%-33.8%) and 35.7% (95% CI, 25.1%-46.4%), respectively. The multivariate Cox regression model analysis showed that factors improving the PFS were the normal lactate dehydrogenase (LDH) level (P<0.001), Masaoka III stage (P=0.028), and radiotherapy (RT) (P<0.001). The LDH (P<0.001), T stage (P<0.001), and the pathologic grade (P=0.047) were independently prognostic of OS. Long-term follow-up of the advanced thymic carcinoma showed poor outcomes of PFS and OS. LDH, Masaoka stage, and RT affected the PFS, and LDH, T stage, and pathologic grade seemed to affect the OS. Establishing a better staging system for predicting outcomes would be warranted.

Available evidence and new biological perspectives on medical treatment of advanced thymic epithelial tumors

Thymic epithelial tumors (TETs) are rare primary mediastinal tumors arising from thymic epithelium. Their rarity and complexity hinder investigations of their causes and therapy development. Here, we summarize the existing knowledge regarding medical treatment of these tumors, and thoroughly review the known genetic aberrations associated with TETs and the present status of potential biological treatments. Epidermal growth factor receptor (EGFR), stem-cell factor receptor, insulin-like growth factor-1 receptor (IGF1R), and vascular endothelial growth factors (VEGF-A, VEGF-B, and VEGF-2) are overexpressed in TETs. EGFR overexpression in TETs is associated with higher stage, and IGF1R overexpression has poor prognostic value. Data indicate that anti-IGF1R monoclonal antibodies, and inhibitors of angiogenesis, somatostatin receptors, histone deacetylase, mammalian target of rapamycin, and cyclin-dependent kinases may be active against TETs. Continued investigations in this field could lead to advancement of targeted and biological therapies for TETs.