Resectable Thymoma: Treatment Outcome and Prognostic Factors in the Late Adolescent and Adult Age Group

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.

Elective Nodal Irradiation as Adjuvant Radiotherapy for Advanced Thymomas and Thymic Carcinomas

INTRODUCTION

We evaluated the clinical outcome of patients with stage III to IV thymomas (Ts) or stage II to IV thymic carcinomas (TCs) treated with complete thymectomy and local radiation therapy (LRT, targeting the tumor bed and anterior mediastinal areas only) or elective nodal irradiation (ENI, targeting the entire mediastinal and supraclavicular regions).

MATERIALS AND METHODS

Data from 47 patients diagnosed with Ts or TCs and treated with surgery and adjuvant RT from May 2002 to May 2015 were analyzed. The standard RT dose was 50.4 Gy in 28 fractions; patients with a positive resection margin received a further 4 to 10 Gy. Survival outcomes determined at 5 years included local recurrence-free survival, regional recurrence-free survival, distant metastasis-free survival, and overall survival.

RESULTS

Five-year local recurrence-free survival was similar in both groups (LRT, 94.7% vs. ENI, 96.2%; P = .849). Significant differences were seen in 5-year regional recurrence-free survival (LRT, 55.1% vs. ENI, 83.7%; P = .006); however, tumor size was seen to be a significant factor (< 7 cm, 95.2% vs. ≥ 7 cm, 48.9%; P < .001), and the LRT group contained a greater proportion of patients with ≥ 7-cm tumors (70% vs. 33%). Multivariate analysis demonstrated that tumor size was the only significant prognostic factor (P < .001). No differences in 5-year overall survival were seen (LRT, 91.7% vs. ENI, 100%; P = .106).

CONCLUSION

ENI may not be indicated in all cases, as additional benefit in reducing recurrence or improving survival was not predominant. LRT seems to be a feasible option with favorable patient outcomes.

Postoperative radiotherapy and tumor recurrence after complete resection of stage II/III thymic tumor: a meta-analysis of cohort studies

BACKGROUND

Whether postoperative radiotherapy (PORT) is effective for reducing the recurrence risk in patients who received complete resection of the stage II or III thymic tumors has not been determined. A meta-analysis was performed by combining the results of all available controlled trials.

METHODS

PubMed, Cochrane's Library, and the Embase databases were searched for studies which compared the recurrence data for patients with complete resection of the stage II or III thymic tumors assigned to an observing group, or a PORT group. A random effect model was applied to combine the results.

RESULTS

Nineteen studies, all designed as retrospective cohort studies were included. These studies included 663 patients of PORT group and 617 patients of observing group. The recurrence rate for the patients in PORT group and observing group were 12.4% and 11.5%, respectively. Results of our study indicated that PORT has no significant influence on recurrent risk in patients with stage II or III thymic tumor after complete resection (odds ratio 1.02, 95% confidence interval 0.55-1.90, P=0.96). When stratified by stages, our meta-analyses did not indicate any significant effects of PORT on recurrent outcomes in either the stage II or the stage III patients. Moreover, subsequent analysis limited to studies only including patients with thymoma or thymic carcinoma also did not support the benefits of PORT on recurrent outcomes.

CONCLUSION

Although derived from retrospective cohort studies, current evidence did not support any benefit of PORT on recurrent risk in patients with complete resection of the stage II or III thymic tumors.

A Review of the Place and Role of Radiotherapy in Thymoma

Thymomas, tumors that arise from the epithelial cells of the thymus gland, are the most common tumors of the anterior mediastinum despite their overall rarity. They are not classified together with malignancies although it is recognized that they can be invasive and persistent even after attempted treatment. Because of their rarity, optimal treatment protocols remain a challenging topic. Although surgery is recognized as the cornerstone of management, the role and benefit of use of postoperative radiotherapy (PORT), remains questionable. Unequivocal evidence, although exclusively from retrospective studies, indicates that stage I thymoma is adequately treated with complete resection alone. As for stage II there is still a need to better determine the indications of PORT. For stage III and IV, existing data point to the fact that PORT plays a significant role in the management of thymoma. In patients for whom radiotherapy (RT) is indicated, 50 Gy appears to be adequate for microscopic disease and higher doses should be used for macroscopic tumor. With advances in RT delivery techniques, which allow for higher doses to be delivered to larger areas affected by tumor while sparing normal tissue, it is prudent to identify a place for this modality in the optimal management of thymoma patients.

Postoperative radiotherapy for completely resected Masaoka stage III thymoma: a retrospective study of 65 cases from a single institution

Background

The role of adjuvant radiotherapy (RT) for patients with stage III thymoma after complete resection is not definite. Some authors have advocated postoperative RT after complete tumor resection, but some others suggested observation. In this study, we retrospectively evaluated the effect of postoperative RT on survival as well as tumor control in patients with Masaoka stage III thymoma.

Methods

Between June 1982 and December 2010, 65 patients who underwent complete resection of stage III thymoma entered the study. Fifty-three patients had adjuvant RT after surgery (S + R) and 12 had surgery only (S alone). Of patients who had adjuvant RT, 28 had three-dimensional conformal RT (3D-CRT)/intensity modulated RT (IMRT) and 25 had conventional RT. A median prescribed dose of 56 Gy (range, 28–60 Gy) was given.

Results

The median follow-up time was 50 months (range, 5–360 months). Five- and 10-year overall survival (OS) rates were 91.7% and 71.6%, respectively, for S + R and 81.5% and 65.2% for S alone (P = 0.5), respectively. In the subgroup analysis, patients with 3D-CRT/IMRT showed a trend of improved 5-year OS rate compared with conventional RT (100% vs. 86.9%, P =0.12). Compared with S alone, the 5-year OS rate was significantly improved (100% vs. 81.5%, P = 0.049). Relapses occurred in 15 patients (23.1%). There was a trend of lower crude local recurrence rates for S + R (3.8%) compared with S alone (16.7%) (P = 0.09), whereas the crude regional recurrence rates were similar (P = 0.9). No clear dose–response relationship was found according to prescribed doses.

Conclusions

Adjuvant 3D-CRT/IMRT showed potential advantages in improving survival and reducing relapse in patients with stage III thymoma after complete resection, whereas adjuvant RT did not significantly improve survival or reduce recurrence for the cohort as a whole. Doses of ≤ 50 Gy may be effective and could be prescribed for adjuvant RT. To confirm the role of adjuvant 3D-CRT/IMRT in patients who undergo a complete resection of thymoma, a multicenter randomized study should be performed.

Adjuvant radiotherapy for thymic epithelial tumors: a systematic review and meta-analysis

Adjuvant radiotherapy after complete resection of localized, invasive thymic epithelial tumors is considered by many to be the standard of care, despite little supporting literature. We hypothesized that individual studies may lack statistical power to demonstrate a reduction in recurrence with this approach, but meta-analysis of published data may allow for more adequate statistical evaluation. Analysis of data from 592 patients with completely resected stage II or III thymic epithelial tumors, however, revealed no statistically significant reduction in recurrence after adjuvant radiotherapy (odds ratio 1.05; 95% confidence interval: 0.63 to 1.75; p = 0.840). Additionally, the majority of publications suggest that the most common sites of recurrence are the lung, pleura, and diaphragm, even when incompletely resected patients are included.

Tumors of the mediastinum

Tumors of the mediastinum represent a wide diversity of disease states. The location and composition of a mass is critical to narrowing the differential diagnosis. The most common causes of an anterior mediastinal mass include the following: thymoma; teratoma; thyroid disease; and lymphoma. Masses of the middle mediastinum are typically congenital cysts, including foregut and pericardial cysts, while those that arise in the posterior mediastinum are often neurogenic tumors. The clinical sequelae of mediastinal masses can range from being asymptomatic to producing symptoms of cough, chest pain, and dyspnea. This article will review the anatomy of the mediastinum as well as the different clinical, radiographic, and prognostic features, and therapeutic options of the most commonly encountered masses.

Thymoma and Thymic Carcinoma: An Update of the WHO Classification 2004

When dealing with tumors of the thymus and mediastinum, both the surgeon and the pathologist are confronted with a vast variety of different pathohistologic entities, among which epithelial tumors, namely thymomas and thymic carcinomas, are the most frequent. Intimate knowledge of the different entities and their anticipated clinical outcome is required to meet diagnostic and therapeutic challenges. We herein briefly update the reader with the most important new changes in the 2004 WHO classification of tumors of the thymus and to important new trends in the treatment of some of these tumors.

Treatment of malignant thymoma

PURPOSE OF REVIEW

The present review reports findings in the field of epithelial tumors originating from the thymus from the past year and discusses these findings in the context of the literature.

RECENT FINDINGS

Epithelial tumors of the thymus are relatively common tumors of the anterior superior mediastinum. Thymomas are usually slowly growing tumors, and their prognosis depends on the macroscopic and microscopic invasion of surrounding tissues. Thymic carcinomas are more aggressive and less common tumors than thymomas and have been increasing in frequency in recent years. Surgery is the mainstay treatment of thymic malignancies, and complete resection represents the best prognostic factor in this disease. Postoperative radiotherapy may be indicated in tumors with invasion of surrounding tissues, but it is controversial in early-stage thymomas. Combination chemotherapy has been employed in several small studies and in advanced disease has been demonstrated to produce a 50-80% objective response rate. Neoadjuvant chemotherapy or external beam radiotherapy have been used with success in patients with tumors that are not readily resectable. Novel antiproliferative systemic agents are being investigated, based on a better understanding of the biology of these tumors.

SUMMARY

A better understanding of the clinical behavior of thymomas versus thymic carcinomas and systemic therapies targeted to biologically validated targets in these diseases will help improve efficacy of treatment.

Tumor recurrence and survival in patients treated for thymomas and thymic squamous cell carcinomas: a retrospective analysis

PURPOSE

Thymic epithelial tumors (TET) are rare epithelial neoplasms of the thymus with considerable histologic heterogeneity. This retrospective study focused on the correlation of WHO-defined TET histotypes with survival and tumor recurrence in a large cohort of patients receiving different modes of treatment.

PATIENTS AND METHODS

Two hundred twenty-eight patients were followed for up to 21 years (median, 60 months; range, 1 to 252 months) after primary surgery. Forty-two patients received adjuvant radiotherapy (mean dose, 53 Gy), and 33 patients received adjuvant chemotherapy.

RESULTS

Seventy-six (88%) of 86 patients with WHO type A, AB, and B1 thymomas were treated by surgery alone, with three tumor relapses after 3 to 10 years (median, 3.4 years). Twelve of 67 patients with WHO type B2 and B3 thymomas in Masaoka stages I and II were treated by adjuvant radiotherapy without evidence of tumor recurrence after 1 to 12 years (median, 4 years). Among 75 patients with B2 and B3 thymomas with incomplete resection or a tumor stage III or higher, the recurrence rate was 34% (n = 23) after 0.5 to 17 years (median, 5 years) in patients receiving adjuvant radiochemotherapy, compared to 78% (seven of nine patients) in patients without adjuvant radiochemotherapy. Incomplete tumor resection was associated with a high recurrence rate (65%) and a poor prognosis (P <.01).

CONCLUSION

The long-term outcome of TET patients is related to tumor stage, WHO histotype, completeness of surgical removal, and type of treatment. Prospective trials are warranted to formally address the efficacy of adjuvant therapy in the treatment of localized and advanced malignant TETs.