The role of postoperative radiotherapy for thymomas: a multicentric retrospective evaluation from three Italian centers and review of the literature

Postoperative radiotherapy results in 192 epithelial thymic tumours patients with 10 years of follow-up

PURPOSE

To assess the prognostic factors and patterns of failure of patients consecutively treated with surgery and postoperative radiation therapy (PORT) for thymic epithelial tumours (TET).

PATIENTS AND METHODS

Data from 192 TET patients who were operated and received PORT at a single centre from 1990 to 2019 was retrospectively analysed.

RESULTS

Most patients had thymoma (77 %, B247%), were classified Masaoka-Koga stage III (35 %) or IV (32 %) and had a R0 (75 %) resection. Radiotherapy was delivered at a median dose of 50.4 Gy (range, 42-66 Gy; ≥ 60 Gy in 17 %), 63 (33 %) patients were treated by intensity-modulated radiation therapy and elective nodal radiotherapy was used for 37 %. At a median follow-up of 10.9 years, the 10-year overall survival (OS) and progression-free survival (PFS) rates were 62 % (95 % CI: 54-70 %) and 47 % (95 % CI: 39-55 %), respectively. Locoregional recurrence (LRR) occurred in 72/192 (38 %) patients, distributed as 6 local, 45 regional and 21 both local and regional. LRR were mainly located to the pleura: 66/72 (92 %) and 16/72 (22 %; 16/192 in total, 8 %) were in-field. Distant relapse (DR) were observed in 30 patients (16 %), resulting in 10-year locoregional (LRC) and distant control rates of 58 % (95 % CI: 50-66 %) and 82 % (95 % CI: 77-88 %), respectively. In the multivariate analysis, Masaoka-Koga stage (HR [hazard ratio]: 1.9; p = 0.001), thymic carcinomas/neuroendocrine tumours (TC) (HR: 1.6; p = 0.045) and ECOG PS > 1 (HR: 1.9; p = 0.02) correlated with poorer OS. Higher Masaoka-Koga stage (HR: 2.6; p < 0.001) associated with a decreased LRC but not R1 status (HR: 1.2; p = 0.5) or WHO histology classification. TC (HR: 3.4; p < 0.001) and a younger age (HR: 2.5; p = 0.02) correlated with DR.

CONCLUSION

Approximately one-third of the TET in our study experienced a LRR, mainly to the pleura, and 8% in total were in-field. The place of radiotherapy should be better defined in higher risk thymoma patients within prospective randomized studies.

Surgical, Radiation, and Systemic Treatments of Patients With Thymic Epithelial Tumors: A Systematic Review

INTRODUCTION

Thymic epithelial tumors are rare and are classified as thymoma, thymic carcinoma, and thymic neuroendocrine tumors. The objective of this systematic review was to evaluate the treatment options for patients with thymic epithelial tumors.

METHODS

This systematic review was developed by Ontario Health (Cancer Care Ontario)'s Program in Evidence-Based Care and by the Lung Cancer Disease Site Group. MEDLINE, EMBASE, and the Cochrane Library were searched for studies comparing surgical, radiotherapy, or systemic treatments against any combination of these treatments in patients with thymic epithelial tumors. Meta-analyses were conducted with clinically homogenous studies.

RESULTS

A total of 106 studies were included, mainly from observational studies. There was an overall survival benefit with postoperative radiotherapy for patients with thymic carcinoma (hazard ratio = 0.65, 95% confidence interval: 0.47-0.89) and for patients with thymoma (hazard ratio = 0.70, 95% confidence interval: 0.59-0.82), especially for those with a high risk for mortality. Patients with thymic carcinoma or thymoma had a response to chemotherapy. Selection bias affected the results for studies that evaluated neoadjuvant chemotherapy or minimally invasive surgical techniques. Furthermore, the overall survival benefit found for adjuvant chemotherapy may have been confounded by the administration of postoperative radiotherapy.

CONCLUSIONS

For patients with thymoma or thymic carcinoma, the literature is of low quality and subject to bias. There were overall survival benefits with postoperative radiotherapy. The results of this systematic review were used to inform treatment recommendations in a clinical practice guideline. Future large-scale prospective studies that control for confounders are needed.

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.

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.

The Prognostic Value of Postoperative Radiotherapy for Thymoma and Thymic Carcinoma: A Propensity-Matched Study Based on SEER Database

(1) Objectives: The effect of postoperative radiotherapy (PORT) for thymoma and thymic carcinoma remains controversial. This study aimed to investigate the prognostic value of PORT for thymoma and thymic carcinoma in a population-based registry. (2) Methods: This retrospective study used the Surveillance, Epidemiology, and End Results (SEER) database to identify patients diagnosed with thymoma and thymic carcinoma between 2010 and 2019. Propensity score matching was performed to adjust statistical influences between the PORT and non-PORT groups. (3) Results: A total of 2558 patients with thymoma (n = 2138) or thymic carcinoma (n = 420) were included. In the multivariate analysis, PORT was an independent prognostic factor for OS (overall survival; p < 0.001) and CSS (cancer-specific survival; p = 0.001) in thymoma and an independent prognostic factor for OS in thymic carcinoma (p = 0.018). Subgroup analyses revealed that PORT was beneficial to OS and CSS in patients with Masaoka-Koga stage IIB-IV thymoma (OS: IIB, p < 0.001; III-IV, p = 0.005; CSS: IIB, p = 0.015; III-IV, p = 0.002) and stage IIB thymic carcinoma (OS: p = 0.012; CSS: p = 0.029). (4) Conclusion: This propensity-matched analysis identified the prognostic value of PORT in thymoma and thymic carcinoma based on the SEER database. For patients with stage IIB-IV thymoma and stage IIB thymic carcinoma, PORT was associated with improved OS and CSS. A more positive attitude towards the use of PORT for nonlocalized thymoma and thymic carcinoma may be appropriate.

Outcomes of extended surgical resections for locally advanced thymic malignancies: a narrative review

BACKGROUND AND OBJECTIVE

Thymic malignancies represent the most common anterior mediastinal neoplasms, as well as rare and challenging tumors. Surgery is the cornerstone in the treatment of thymic malignancies, although a multidisciplinary approach is mandatory, for both, locally advanced or metastatic disease. In our narrative review, we explored the recent literature to investigate clinical and radiological assessment, multimodality approach and outcomes of locally advanced thymic tumors. More than one-third of patients affected by an anterior mediastinal mass are asymptomatic at diagnosis. In case of locally advanced thymoma, symptoms are related to compression or invasion of adjacent structures, such as the superior vena cava (SVC), innominate veins and pericardium. Paraneoplastic syndromes, such as myasthenia gravis (MG), are related to release of antibodies, hormones and cytokines.

METHODS

Diagnostic methods must be chosen accurately to avoid unnecessary surgical resections, to define the best strategy of care, and to plan the surgical strategy. Therefore, each case must be evaluated in a multidisciplinary context, where surgery plays an essential role.

KEY CONTENT AND FINDINGS

In this narrative review, we describe indications and surgical techniques for the treatment of locally advanced thymoma; focusing on oncological outcomes after different approaches.

CONCLUSIONS

In conclusion, aggressive surgery is always indicated, when possible, and when a complete resection can be planned, yet, the multidisciplinary approach is mandatory, in case of both locally or metastatic advanced disease.