Invasive thymoma: treatment with postoperative radiation therapy

American Radium Society Appropriate Use Criteria for Radiation Therapy in the Multidisciplinary Management of Thymic Carcinoma

Importance

Thymic carcinoma is rare, and its oncologic management is controversial due to a paucity of prospective data. For this reason, multidisciplinary consensus guidelines are crucial to guide oncologic management.

Objective

To develop expert multidisciplinary consensus guidelines on the management of common presentations of thymic carcinoma.

Evidence Review

Case variants spanning the spectrum of stage I to IV thymic carcinoma were developed by the 15-member multidisciplinary American Radium Society (ARS) Thoracic Appropriate Use Criteria (AUC) expert panel to address management controversies. A comprehensive review of the English-language medical literature from 1980 to 2021 was performed to inform consensus guidelines. Variants and procedures were evaluated by the panel using modified Delphi methodology. Agreement/consensus was defined as less than or equal to 3 rating points from median. Consensus recommendations were then approved by the ARS Executive Committee and subject to public comment per established ARS procedures.

Findings

The ARS Thoracic AUC panel identified 89 relevant references and obtained consensus for all procedures evaluated for thymic carcinoma. Minimally invasive thymectomy was rated as usually inappropriate (regardless of stage) due to the infiltrative nature of thymic carcinomas. There was consensus that conventionally fractionated radiation (1.8-2 Gy daily) to a dose of 45 to 60 Gy adjuvantly and 60 to 66 Gy in the definitive setting is appropriate and that elective nodal irradiation is inappropriate. For radiation technique, the panel recommended use of intensity-modulated radiation therapy or proton therapy (rather than 3-dimensional conformal radiotherapy) to reduce radiation exposure to the heart and lungs.

Conclusions and Relevance

The ARS Thoracic AUC panel has developed multidisciplinary consensus guidelines for various presentations of thymic carcinoma, perhaps the most well referenced on the topic.

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.

Thymic epithelial tumors: analysis of prognostic factors with emphasis on the role of adjuvant radiation therapy

BACKGROUND

The prognostic impacts of histopathological classification, Masaoka staging system, extent of surgery, and adjuvant treatment approaches in thymic epithelial tumors (TETs) were investigated.

MATERIAL AND METHODS

Records of 22 patients were retrospectively reviewed. Total thymectomy was performed on 5 patients and thymectomy on 17. Complete resection was achieved for 14 patients. Radiation therapy (RT) was considered for all patients with stage III or IV disease and all patients undergoing incomplete resections.

RESULTS

Local control had been achieved in all patients and all were alive with no evidence of disease (ANED) at 0.2-7.8 years (median, 2.3 years). Of 4 patients with stage II disease, 2 (favorable group) had undergone complete resections and 2 (intermediate group) had undergone incomplete resections. Those undergoing incomplete resections had received RT. Of these 4 patients, all were ANED. All 4 patients with Masaoka stage III disease that were involved in the study had undergone incomplete resections and had received RT. Also, these patients were ANED.

CONCLUSIONS

Patients with TETs undergoing less than complete resections might be referred for RT in the postoperative setting, while the role of RT in patients undergoing complete resections remains unclear.

Surgical Approaches for Stage IVA Thymic Epithelial Tumors

Thymic epithelial tumors (TET) are rare mediastinal neoplasms that can metastasize to the pleural space (stage IVA). Complete surgical resection remains the backbone of therapy for patients with early stage TET, however, the role of surgery in the management of patients with stage IVA disease is not fully defined. Published reports in this regard are mainly small, retrospective, and uncontrolled, with unclear inclusion criteria. Surgical options to manage pleural disease include metastasectomy, extrapleural pneumonectomy, and metastasectomy/pleurectomy combined with heated intrapleural chemotherapy. The choice of the most appropriate surgical strategy needs to be individualized according to the quantity and location of disease, the patient’s overall condition, as well as operator and institutional expertise. In the majority of cases, metastasectomy of pleural implants will be sufficient to achieve a complete resection. The available literature suggests that in selected patients with stage IVA TET, delivery of neoadjuvant chemotherapy followed by complete resection is a viable treatment option that can be associated with long-term survival.

Early-stage thymic carcinoma: is adjuvant therapy required?

Although the prognosis of advanced thymic carconoma remains poor, previous reports have shown survival rates of 70% to 100% in patients with Masaoka stage I or stage II of the disease who were treated with surgery followed by adjuvant therapy. However, the role of adjuvant therapy in these stages is controversial. We retrospectively evaluated the outcome of 4 patients with Masaoka stage II thymic carcinoma who were treated with surgery alone between 1992 and 2008. No patient had stage I of the disease. Primary tumors were preoperatively evaluated by chest X-ray and computed tomography. Needle biopsy was not performed because the tumors were clinically diagnosed as noninvasive thymomas. The largest diameter of the primary tumor was 65 mm. Mediastinal lymphadenopathy was not detected by computed tomography. All patients underwent transsternal thymectomy. Mediastinal lymph node dissection was not performed. None of the patients received adjuvant chemotherapy and/or irradiation. Histopathologic examination revealed squamous cell carcinoma in 3 patients and undifferentiated carcinoma in one. Pathologic invasion to the adjacent organs or lymph node metastasis was not detected. All patients were alive and free from relapse at a follow-up of 72 months (range, 12-167 months). Radical resection without adjuvant therapy could be a treatment option for early Masaoka stage thymic carcinoma with low-grade histology.

Thymic neoplasms: a clinical update

Thymoma is a unique neoplasm of the anterior mediastinum that is frequently associated with indolent growth and a variety of paraneoplastic syndromes. One third of cases are detected during the evaluation of myasthenia gravis. Classification systems of thymoma have limited ability in accurately predicting prognosis and course of disease. Thus, staging is the only way to predict clinical behavior. Encapsulated tumors that are surgically resected carry the best prognosis. Adjuvant radiotherapy is recommended for incompletely excised and most invasive thymomas. Chemotherapy in anthracycline-based chemotherapy remains the most effective chemotherapy for neoadjuvant, adjuvant or palliative treatment.

Is There a Role of Postoperative Radiation Therapy in Completely Resected Stage I/II Thymic Epithelial Tumor?

PURPOSE

Retrospective analyses of patients with stage I-II thymic epithelial tumors (TET) who were treated with either surgery alone (S) or surgery plus postoperative radiation therapy (SRT) were conducted to evaluate the role of adjuvant radiation therapy (RT).

MATERIALS AND METHODS

A total of 110 stage I-II TET patients following complete resection were included in this study. Postoperative radiation therapy was recommended for those with aggressive histologic type and/or invasive features according to the surgeons' judgment during the operation. A median dose of 54.0 Gy (range, 44 to 60 Gy) focused on the primary tumor bed was administered to 57 patients (51.8%).

RESULTS

In all patients, the rates of overall survival, disease-specific survival, and disease-free survival at 10 years were 91.7%, 97.1%, and 95.8%, respectively. No significant differences in disease-specific survival (100% in the S group and 93.5% in the SRT group at 10 years, p=0.12) and disease-free survival (98.1% in the S group and 94.5% in the SRT group at 10 years, p=0.41) were observed between the treatment groups, although a significantly larger number of World Health Organization (WHO)-type B2-C (p<0.001) and Masaoka stage II (p=0.03) tumors were observed in the SRT group than in the S group. No local recurrence was observed in the SRT group. No grade 2 or greater RT-related toxicities were observed in the SRT group.

CONCLUSION

Excellent outcomes were achieved in patients with stage I-II TET who underwent complete resection. Considering excellent local control and low morbidity, adjuvant RT may be considered in high risk patients with WHO-type B2-C histology and Masaoka stage II.

Surgical management of stage III thymic tumors

Thymic tumors are classified as stage III when they clearly invade the surrounding structures: pericardium, great vessels (superior vena cava, innominate veins, ascending aorta, and main pulmonary artery), lung parenchyma, phrenic nerves, and chest wall. Surgical treatment with or without induction therapy should always aim to complete resection removing en bloc all the involved structures. Also, extended procedures are justified because only R0 resection allows long-term survival.

Technical advances of radiation therapy for thymic malignancies

Radiation therapy often plays a critical role in the treatment of thymic malignancies. However, because of the location of these tumors, historically patients have been at a significant risk for radiation-related toxicity such as pericardial effusions, radiation pneumonitis, long-term pulmonary fibrosis, and occasional long-term esophageal stricture, particularly for unresectable thymoma. Recent advancements in technology have provided the treating radiation oncologist with the ability to more accurately target the region at risk while sparing normal structures. In this review, we provide an overview of key advances in radiation techniques for thymoma over the past two decades. These techniques include 3D conformal therapy, intensity-modulated radiation therapy, 4D treatment planning, adaptive radiation therapy, and proton therapy. Each advancement has brought with it unique advantages in maintaining long-term disease control while improving quality of life in this manageable disease.

Radiotherapy for thymic neoplasms

The role of radiotherapy in the treatment of thymoma and thymic carcinoma has been evaluated by many investigators over the past two decades. The low incidence of these neoplasms has limited most published studies to small series spanning long time intervals or population-based studies. The exact indications and protocols for the use of radiotherapy as a part of the multidisciplinary approach to thymoma and thymic carcinoma are still unclear. However, a review of recent literature shows potential benefits for certain patients based on stage and grade of disease as well as the extent of surgical resection.

Prognostic predictors and long-term outcome of postoperative irradiation in thymoma: a study of 241 patients

The purpose of this study was to identify the prognostic predictors treated with postoperative irradiation in patients with thymoma. Two hundred forty-one patients with histologically confirmed thymoma were collected and retrospectively reviewed in this study. Fifty-four patients had stage I disease; 57, stage II; 120, stage III; 10, stage IV. One hundred sixty patients underwent total thymectomy; 63, partial resection; 18, debulking or biopsy. Patients were irradiated after surgery with median dose of 50 Gy by conventional fractionation. The overall survival rates at 5 and 10 years were 83.1% and 72.6%, respectively. The 10-year overall survival was 87% for stage I, 78.7% for stage II, 57.4% for stage III, and 24.3% for stage IV. The conclusions were drawn from this analysis. For stage I, the role of postoperative irradiation needed further investigation. For stage II-III, surgery and postoperative irradiation should be part of standard care. The favorable prognostic predictors were female, early stage, and surgical extirpation.

The management of thymoma: a systematic review and practice guideline

INTRODUCTION

Thymoma is a rare tumor for which there is little randomized evidence to guide treatment. Because of the lack of high-quality evidence, a formal consensus-based approach was used to develop recommendations on treatment.

METHODS

A systematic refview of the literature was performed. Recommendations were formed from available evidence and developed through a two-round modified Delphi consensus approach.

RESULTS

The treatment recommendations are summarized as follows: Stage I--complete resection of the entire thymus without neoadjuvant or adjuvant therapy. Stage II--complete resection of the entire thymus with consideration of adjuvant radiation for high-risk tumors. Stage IIIA--surgery either initially or after neoadjuvant therapy, or surgery followed by adjuvant therapy. Stage IIIB--treatment may include a combination of chemotherapy, radiation, and/or surgery, or if technically possible, surgery in combination with chemoradiotherapy (concurrent cisplatin based). For bulky tumors, consideration should be given to sequential chemotherapy followed by radiation. Stage IVA--as per stage III, with surgery only if metastases can be resected. Stage IVB--treatment on an individual case basis (no generic recommendations). Recurrent disease--consider surgery, radiation, and/or chemoradiation. Chemoradiation should be considered in all medically inoperable and technically inoperable patients.

CONCLUSION

Consensus was achieved on these recommendations, which serve to provide practical guidance to the physician treating this rare disease.

Postoperative radiotherapy after surgical resection of thymoma: differing roles in localized and regional disease

PURPOSE

To analyze the Surveillance, Epidemiology and End Results (SEER) registry data to determine the impact of postoperative radiotherapy (PORT) for thymoma and thymic carcinoma (T/TC).

METHODS AND MATERIALS

Patients with surgically resected localized (LOC) or regional (REG) malignant T/TC with or without PORT were analyzed for overall survival (OS) and cause-specific survival (CSS) by querying the SEER database from 1973-2005. Patients dying within the first 3 months after surgery were excluded. Kaplan-Meier and multivariate analyses with Cox proportional hazards were performed.

RESULTS

A total of 901 T/TC patients were identified (275 with LOC disease and 626 with REG disease). For all patients with LOC disease, PORT had no benefit and may adversely impact the 5-year CSS rate (91% vs. 98%, p = 0.03). For patients with REG disease, the 5-year OS rate was significantly improved by adding PORT (76% vs. 66% for surgery alone, p = 0.01), but the 5-year CSS rate was no better (91% vs. 86%, p = 0.12). No benefit was noted for PORT in REG disease after extirpative surgery (defined as radical or total thymectomy). On multivariate OS and CSS analysis, stage and age were independently correlated with survival. For multivariate CSS analysis, the outcome of PORT is significantly better for REG disease than for LOC disease (hazard ratio, 0.167; p = 0.001).

CONCLUSIONS

Our results from SEER show that PORT for T/TC had no advantage in patients with LOC disease (Masaoka Stage I), but a possible OS benefit of PORT in patients with REG disease (Masaoka Stage II-III) was found, especially after non-extirpative surgery. The role of PORT in T/TC needs further evaluation.

Adjuvant Radiotherapy for Thymic Epithelial Tumor

OBJECTIVE

To determine whether the use of adjuvant radiation in the treatment of invasive thymic tumors affects survival and to identify prognostic factors.

METHODS

The files of 47 patients with thymic tumors treated by adjuvant radiation in our institute from 1984 to 2003 were reviewed for data on prognosis and survival. All patients underwent thoracotomy followed by either total macroscopic resection (n = 42) or biopsy (n = 5). The radiation dose ranged from 26 to 60 Gy.

RESULTS

Median duration of follow-up was 10.6 years. Overall 5-year survival was 73% (60%-88%): 77% for thymoma (n = 35/45) versus 33% for thymic carcinoma (n = 2/6) (P = 0.14). Better survival was associated with lower disease stage (II vs. III/IVA, P = 0.01), resection (P = 0.0004), myasthenia gravis at presentation (P = 0.04), and higher radiation dose (<or=45 vs. >45 Gy, P = 0.02); sex, smoking, tumor size, pathology, and margin status had no effect. Locoregional relapse occurred in 11 patients and distant metastasis in 4. The 5-year disease-free survival was 67% (52%-86%), with a median time to recurrence of 8.3 years. The better overall survival and disease-free survival associated with higher doses of radiation were also true for stage II patients. On multivariate analyses after adjusting for age, higher disease stage and lower radiation dose were found to adversely affect overall survival and disease-free survival. Thymic carcinoma had an impact only on disease-free survival.

CONCLUSION

Postoperative radiation therapy to doses above 45 Gy may improve the disease-free and overall survival of patients with invasive thymoma, especially stage II. Thymic carcinoma has a worse prognosis.

Symptomatic pituitary metastasis of malignant thymoma

Pituitary metastases from malignant thymoma are extremely rare. We report an 86 year-old-man with pituitary metastasis of malignant thymoma who complained of visual impairment and right ptosis. A pituitary lesion, which was partially removed by trans-sphenoidal surgery, was pathologically similar to the primary lesion and was diagnosed as pituitary metastasis of malignant thymoma. One autopsied case of pituitary metastasis of malignant thymoma has been found in the literature, and one case of this condition has been previously described in life. The present paper is the second report of symptomatic pituitary metastasis of malignant thymoma. Surgical removal of the pituitary lesion is a reasonable choice for the relief of progressive visual symptoms and for good quality of life in these patients.

World Health Organization histologic classification: An independent prognostic factor in resected thymomas

The histologic classification of thymoma remained controversial since 1999, when the World Health Organization (WHO) Consensus Committee published a histologic typing system for tumours of thymus. Clinical features, postoperative relapsing rates, and survival of patients with thymoma were evaluated with reference to the WHO histologic classification, based on a series of 178 patients, submitted to surgery between 1988 and 2000. There were 21 type A, 49 type AB, 45 type B1, 50 type B2 and 13 type B3 tumours. The invasiveness of tumours was 23.8%, 51%, 73.3%, 82% and 100% for types A, AB, B1, B2 and B3 tumours, respectively. The frequency of invasion of the great vessels increased according to the tumour type in the order A (0%), AB (4%), B1 (6.6%), B2 (22%), and B3 (23%). The 10-year disease-free survival was 95%, 90%, 85%, 71% and 40% for types A, AB, B1, B2 and B3, respectively. According to the Masaoka staging system, the disease-free survival rates were 94%, 88% and 66% for stages I, II and III, respectively, at 10 years. No stage IVA thymomas reached 10 years follow-up. Overall survival at 10 years were 88% and 25% when complete and incomplete resection were considered. By multivariate analysis, Masaoka staging system, WHO histologic classification and complete resection were significant independent prognostic factors, whereas age- and sex-associated myasthenia gravis were not. The present study demonstrated the World Health Organization histologic classification a good prognostic factor, such as completeness of surgical resection and Masaoka staging system.

Treatment of recurrent thymic tumors

Surgery is the cornerstone of therapy for recurrent thymic tumors. The pattern of recurrence is, however, less defined. Between 1966 and 1988, we operated on 83 patients with thymoma, 11 of whom underwent surgery for recurrence (group I). In 1989, we initiated a prospective multimodality protocol and have enrolled 128 patients with 9 (7%) recurrences since (group II). In group I, 1 patient was originally at stage I, 2 were at stage II, 5 at stage III, and 3 at stage IV. The patients underwent 1 (#10) or 2 (#1) reoperations and 5 showed histological progression of malignancy. One patient died postoperatively, 6 died of disease, and 3 are alive and disease free 18 to 22 years after the first operation. In group 2, no patient was originally at stage I, 1 was at stage II, 4 were at stage III, and 4 at stage IV. Reoperation (5 patients) was followed by chemotherapy and 2 showed histological progression of disease. One patient died after 2 years, and 4 patients are alive after 6 to 11 years. All recurrent tumors were thymomas with cortical differentiation. Early onset of recurrence was a negative prognostic factor. Thymomas can recur also at early stages. A multimodality approach is indicated also for early stage lesions based on histology.

Radiation therapy in the management of thymic tumors

Thymic tumors including thymomas, thymic carcinomas, and thymic carcinoid tumors, are relatively infrequent. These tumors with a wide spectrum of histological and biological features may exhibit an indolent clinical course (thymomas) or manifest an aggressive behavior (thymic carcinoma) with a high risk of relapse and metastasis. Successful management of these tumors depends on accurate diagnosis, thorough staging, proper assessment of patient health status, and selection of treatment modality. Surgery remains the mainstay of therapy whereas radiation therapy plays an important role in subtotally resected or unresectable cases. The risk of side effects and late sequelae is generally low when proper radiation technique is employed. This review examines the current role of radiation therapy in the management of these tumors.

Treatment of thymoma: a comparative study between Thailand and the United States and a review of the literature

This article provides a unique perspective on thymoma by describing the clinical scenarios from 2 diverse patient populations followed by an update. A comparative chart review was conducted on patients diagnosed at 2 university-based hospitals, 1 in the United States and 1 in Thailand. A comprehensive review of the literature was then performed through MEDLINE for articles between 1980 and 2002. During the last 23 years, charts from 16 patients at each institution were available for review. The most common presenting symptoms were myasthenia gravis (47%), dyspnea (25%), and chest discomfort (19%) and are similar to those reported in the literature. The primary treatment of stages I-III disease included surgery with or without radiation. Trimodality therapy with surgery, radiotherapy, and chemotherapy was pursued in 43% of patients with stage IV disease in the United States, whereas no patients from Thailand underwent this regimen. Median overall survivals were 124 and 76 months in the Thai and the US groups, respectively (P = 0.76). No major differences in the clinical features were observed between the 2 institutions, although a trend toward more advanced disease was seen in the United States. Surgery and radiation remain the backbone of treatment, but the role for chemotherapy is increasing.

Thymic carcinoma: state of the art review

Thymic carcinoma is a rare neoplasm with distinct clinical and pathological characteristics. The prognosis is often poor with an aggressive course that belies its numerical rarity. Potentially prognostic factors for survival include histopathologic grade, clinical stage, and resectability of the tumor. Five-year survival rates for all patients are approximately 30-50%, with a significant survival time differential between low-grade and high-grade neoplasms. Owing to the paucity of cases, optimal management of thymic carcinoma has yet to be defined. At present, a multimodality approach involving aggressive surgical resection, platinum-based combination chemotherapeutic interventions, and radiotherapy represent the preferred therapeutic approach. Though our knowledge remains somewhat speculative at present, several scientific, technological and therapeutic innovations may have a potentially significant impact on the future of this disease.

Long-term outcome after multimodality treatment for stage III thymic tumors

BACKGROUND

Surgery remains the cornerstone of therapy for thymic tumors, but the optimal treatment for advanced, infiltrative lesions is still controversial. The introduction of multimodality protocols has substantially modified survival and recurrence rate. We reviewed our 13-year prospective experience with multimodality treatment of stage III thymoma and thymic carcinoma.

METHODS

Since 1989 we have prospectively used a multimodality approach in 45 stage III thymic tumors. Sixteen patients (35%) had myasthenia gravis. Twenty-three patients (51%) had pure or predominantly cortical thymoma (group 1), 11 (24.5%) had well-differentiated thymic carcinoma (group 2), and 11 (24.5%) had thymic carcinoma (group 3). Tumors that were not considered radically resectable at preoperative workup underwent biopsy and induction chemotherapy (15 patients, 33%) followed by surgical resection; all patients were referred for adjuvant chemoradiotherapy.

RESULTS

No operative mortality was recorded; 1 treatment-related death during adjuvant chemotherapy was observed in group 1. Complete resection was feasible in 91% of patients in groups 1 and 2 and 82% in group 3. The overall 10-year survival was 78%. Ten-year survival for groups 1 and 2 was 90% and 85%, respectively; 8-year survival for group 3 was 56%. During follow-up, tumor recurrence was noted in 3 patients (13%) from group 1, 3 (27%) from group 2, and 3 (27%) from group 3.

CONCLUSIONS

Multimodality treatment with induction chemotherapy (when required) and adjuvant chemoradiotherapy offers encouraging results for stage III thymic tumors; the outcome is more favorable for cortical thymoma and well-differentiated thymic carcinoma.

Therapy for thymic epithelial tumors: a clinical study of 1,320 patients from Japan

BACKGROUND

Surgery remains the mainstay of treatment for thymic epithelial tumors, and radiation and chemotherapy also have been applied widely as adjuvant and palliative procedures.

METHODS

We compiled records of 1,320 patients with thymic epithelial tumors who were treated from 1990 to 1994 in 115 institutes certified as special institutes for general thoracic surgery by The Japanese Association for Chest Surgery.

RESULTS

Patients with stage I thymoma were treated with only surgery, and patients with stage II and III thymoma and thymic carcinoid underwent surgery and additional radiotherapy. Patients with stage IV thymoma and thymic carcinoma were treated with radiation or chemotherapy. The Masaoka clinical stage is an excellent predictor of the prognosis of thymoma and thymic carcinoma, but not thymic carcinoid. In stage III and IV thymoma, the 5-year survival rates of total resection, subtotal resection, and inoperable groups were 93%, 64%, and 36%, respectively. On the other hand, in thymic carcinoma, the 5-year survival rates of total resection, subtotal resection, and inoperable groups were 67%, 30%, and 24%, respectively. Prophylactic mediastinal radiotherapy could not prevent local recurrences effectively in patients with totally resected stage II and III thymoma. Adjuvant therapy including radiation or chemotherapy did not improve the prognosis in patients with totally resected III and VI thymoma and thymic carcinoma.

CONCLUSIONS

Total resection is the most important factor in the treatment of thymic epithelial tumors. There is value in debulking surgery in invasive thymoma, but not in thymic carcinoma. We doubt that adjuvant therapy is valuable for patients with totally resected invasive thymoma and thymic carcinoma.

Hrad17 expression in thymoma

OBJECTIVES

We used palindromic polymerase chain reaction-driven complementary deoxyribonucleic acid differential display to identify and isolate a gene, the human homolog of the Schizosaccharomyces pombe checkpoint gene rad17 (Hrad17), from colon cancer tissue. The loss of checkpoint control in mammalian cells results in genomic instability, leading to the amplification, rearrangement, or loss of chromosomes--events associated with tumor progression. We hypothesized that the Hrad17 may be expressed in thymoma, especially in invasive thymoma. We attempted to determine the influence of Hrad17 expression on clinicopathological features for patients with thymoma who had undergone surgery.

METHODS

Expression of Hrad17 messenger ribonucleic acid (RNA) was evaluated by reverse transcription-polymerase chain reaction using a LightCycler in 38 thymomas and 10 adjacent histologically normal thymus samples from patients for whom follow-up data was available.

RESULTS

Hrad17 transcripts were detected in all 38 tumor samples (8.789 +/- 7.337) at levels significantly higher than those in normal thymus samples (1.908 +/- 2.267, p < 0.0001). No relationship was seen between Hrad17 gene expression and age, gender, or pathological thymoma subtypes. Hrad17 mRNA expression in invasive thymomas (stage II-IV, 10.067 +/- 5.293) was significantly higher than that in stage I thymomas (5.193 +/- 4.485, p = 0.0168). Immunohistochemistry showed that Hrad17 protein was highly expressed in invasive thymoma tumor tissue but not within the normal thymus tissue.

CONCLUSIONS

Hrad17 was highly expressed in invasive thymoma.

Malignant thymoma: current status of classification and multimodality treatment

Classification, understanding of the pathophysiology, and treatment options of thymoma have changed during recent years. It is hoped that novel strategies will lead to a survival benefit in these patients. It has become clear that patients with thymoma are best treated with multimodality therapy. In this review, a pathologist, an immunologist, a surgeon, a radiotherapist, a pneumologist, and oncologists discuss the current status of classification and strategies for the treatment of patients with thymoma.

Postoperative radiotherapy in thymic carcinoma: treatment results and prognostic factors

PURPOSE

To analyze the treatment results and prognostic factors of patients with primary thymic carcinoma treated by total or subtotal tumor resection followed by radiotherapy alone.

METHODS AND MATERIALS

Between October 1987 and October 1997, 26 patients with thymic carcinoma were treated with complete or incomplete surgical resection and postoperative adjuvant irradiation without chemotherapy. The radiation was delivered with 10-MV X-ray given 5 days per week at 1.8 to 2 Gy per fraction. Total doses ranged from 40 to 70 Gy. All patients had at least 40 months of follow-up.

RESULTS

The 5-year overall survival rate, local control rate, and distant metastasis-free rate were 77%, 91%, and 57%, respectively. Several prognostic factors, including sex, age, extent of resection (total resection vs. subtotal resection), Masaoka staging (early Stage I + II vs. advanced Stage III + IV), pathology (low-grade vs. high-grade), and postoperative radiation dose (> or =60 Gy vs. <60 Gy), were evaluated in univariate analysis. The Masaoka staging system was the only statistically significant predictor in overall survival rate (p = 0.0482) and distant metastasis-free rate (p = 0.0193).

CONCLUSIONS

The Masaoka staging system is the most important prognostic factor in primary thymic carcinoma patients receiving postoperative radiotherapy alone. For resectable tumors, surgery and postoperative radiotherapy can achieve good local control, but the distant metastatic rate is still high. Further investigation of more effective chemotherapy is needed.

Postoperative radiotherapy for patients with completely resected thymoma: a multi-institutional, retrospective review of 103 patients

BACKGROUND

Optimal management of postoperative radiotherapy for patients with completely resected thymoma remains controversial. This study was conducted to assess the efficacy of postoperative mediastinal irradiation in patients with completely resected thymoma.

METHODS

The records of 103 patients with completely resected thymoma who received postoperative mediastinal irradiation during the period between 1979 and 1998 were reviewed. The distribution according to Masaoka stage was Stage I in 17 patients, Stage II in 61 patients, and Stage III in 25 patients. Fifty-two patients were treated with involved field (IF) irradiation, and 51 patients were treated with irradiation of the whole mediastinal field with or without boost (WM irradiation). The total radiation dose to the primary tumor bed was 30-61 grays (Gy), with a median dose of 40 Gy. No patients received chemotherapy during the initial treatment. The median follow-up of the 82 living patients was 112 months (range, 24-244 months).

RESULTS

The 10-year actuarial overall and disease free survival rates for all patients were 81% and 79%, respectively. The 10-year actuarial overall survival rate was 100% for patients with Stage I disease, 90% for patients with Stage II disease, and 48% for patients with Stage III disease. In the analysis, clinical stage alone had a statistically significant impact on both overall survival and disease free survival (P < 0.0001 for both). Recurrent disease was observed in 17 patients, and the pleura was the most frequent site of first recurrence. Of 12 patients who had pleural recurrences, 11 patients had pleural dissemination remote from the initial tumor site. No recurrence was observed in any of the 17 patients with Stage I disease, and 6 of 61 patients (10%) with Stage II disease and 11 of 25 patients (44%) with Stage III disease experienced recurrences. With regard to intrathoracic recurrences, there were no recurrences within the irradiated field in any of the 103 patients, and no dose response correlation was seen in intrathoracic control (incidence of intrathoracic recurrence: 2 of 19 patients in the group that received < 40 Gy, 6 of 45 patients in the group that received 40 Gy, and 7 of 39 patients in the group that received > 40 Gy). With respect to treatment field, mediastinal recurrences were observed in 4 of 52 patients (8%) who were treated with IF irradiation, whereas 0 of 51 patients who were treated with WM irradiation experienced mediastinal recurrences. Pleural-based recurrences were observed both in patients who were treated with IF irradiation (7 of 52 patients) and in patients who were treated with WM irradiation (5 of 51 patients). According to the degree of pathologic tumor invasion, 0 of 71 patients without pleural invasion had pleural-based recurrences (0 of 17 patients with Stage I disease, 0 of 51 patients with Stage II disease, and 0 of 3 patients with Stage III disease), whereas 12 of 32 patients (38%) with pleural invasion had pleural-based recurrences (4 of 10 patients with Stage II disease and 8 of 22 patients with Stage III disease).

CONCLUSIONS

The current results indicated that WM irradiation with a total dose of 40 Gy was effective in preventing mediastinal recurrence for patients with completely resected thymoma. However, in patients with pathologic pleural invasion of the tumor, mediastinal irradiation alone was insufficient to avoid pleural-based recurrence.

Spindle cell and mixed spindle/lymphocytic thymomas: an integrated clinicopathologic and immunohistochemical study of 81 cases

Forty-three cases of spindle cell thymoma (medullary, WHO type A) and 38 cases of mixed spindle/lymphocytic thymoma (WHO type AB) were studied for their clinicopathologic and immunohistochemical characteristics. Three histologic patterns of spindle cell thymoma were observed: short-spindled (57%), long-spindled (31%), and micronodular (12%). The short-spindled variant was composed of oval to short spindle cells commonly arranged in a hemangiopericytic or microcystic pattern. The long-spindled variant chiefly consisted of fibroblast-like epithelial cells mimicking fibrohistiocytic neoplasms. The micronodular variant was characterized by small nests of short spindle cells dispersed among a lymphoid stroma with frequent germinal centers. All kinds of spindle cell could be admixed with lymphocyte-rich "cortex"-like areas to constitute mixed spindle/lymphocytic thymomas. Immunohistochemically, the epithelial cells in up to 70% of the short-spindled and long-spindled variants of spindle cell thymoma and 90% of mixed spindle/lymphocytic thymomas were positive for CD20, whereas the epithelial cells in all micronodular spindle cell thymomas were negative. All of the spindle cell thymomas and most of the mixed spindle/lymphocytic thymomas in this study were found in stages I and II. Follow up of the patients did not disclose relapse or mortality directly resulting from the tumors. However, the prognosis of stage I and II spindle cell and mixed spindle/lymphocytic thymomas did not significantly differ from those of stage I and II thymomas of other types by a stage-matched survival analysis. Our data showed that spindle cell and mixed spindle/lymphocytic thymomas are distinctive in histologic pattern and immunohistochemical profile. When interpreted within the context of staging, spindle cell and mixed spindle/lymphocytic thymomas presenting in stages I and II most likely behave in an indolent fashion.

Thymoma

Thymomas are fascinating tumors because of their multifaceted clinical presentation, including an unrivaled frequency of associated paraneoplastic autoimmune diseases and an astounding histologic heterogeneity. Thus, thymomas challenge the clinician, pathologist, and immunologist alike with complex diagnostic and therapeutic problems in almost all fields of medicine, radiology, nuclear medicine, surgery, radiooncology, and pathology. This review highlights recent progress in these fields, including the new World Health Organization's classification of thymomas, and reports on the beginning discovery of the genetic basis of thymoma oncogenesis and the cellular and molecular immunopathology of thymoma-associated paraneoplastic autoimmunity.

Prognostic relevance of Masaoka and Müller-Hermelink classification in patients with thymic tumors

BACKGROUND

To compare the prognostic relevance of Masaoka and Müller-Hermelink classifications.

METHODS

We treated 71 patients with thymic tumors at our institution between 1980 and 1997. Complete follow-up was achieved in 69 patients (97%) with a mean follow up-time of 8.3 years (range, 9 months to 17 years).

RESULTS

Masaoka stage I was found in 31 patients (44.9%), stage II in 17 (24.6%), stage III in 19 (27.6%), and stage IV in 2 (2.9%). The 10-year overall survival rate was 83.5% for stage I, 100% for stage IIa, 58% for stage IIb, 44% for stage III, and 0% for stage IV. The disease-free survival rates were 100%, 70%, 40%, 38%, and 0%, respectively. Histologic classification according to Müller-Hermelink found medullary tumors in 7 patients (10.1%), mixed in 18 (26.1%), organoid in 14 (20.3%), cortical in 11 (15.9%), well-differentiated thymic carcinoma in 14 (20.3%), and endocrine carcinoma in 5 (7.3%), with 10-year overall survival rates of 100%, 75%, 92%, 87.5%, 30%, and 0%, respectively, and 10-year disease-free survival rates of 100%, 100%, 77%, 75%, 37%, and 0%, respectively. Medullary, mixed, and well-differentiated organoid tumors were correlated with stage I and II, and well-differentiated thymic carcinoma and endocrine carcinoma with stage III and IV (p < 0.001). Multivariate analysis showed age, gender, myasthenia gravis, and postoperative adjuvant therapy not to be significant predictors of overall and disease-free survival after complete resection, whereas the Müller-Hermelink and Masaoka classifications were independent significant predictors for overall (p < 0.05) and disease-free survival (p < 0.004; p < 0.0001).

CONCLUSIONS

The consideration of staging and histology in thymic tumors has the potential to improve recurrence prediction and patient selection for combined treatment modalities.

Malignant thymoma with metastases to the gastrointestinal tract and ovary: a case report and literature review

This is the first clinical case report of a thoracic invasive thymoma metastatic to the ovary with disease noted in the entire abdomen including the pelvis 5 1/2 years after initial diagnosis. The involved areas of metastases include the distal ileum, peritoneal and serosal surfaces (including the surface of the distal colon, bladder, and pelvis), and the surface of the right ovary. The patient survived 13 years after her initial diagnosis and 7 1/2 years after discovery of her metastases. Thymomas are rare tumors but comprise the most common primary tumor of the anterior mediastinum. Extrathoracic metastases of malignant thymomas are also rare, and the literature reports that the most common sites for metastases are the liver, lung, lymph nodes, and bone. Extrathoracic disease is associated with a poor prognosis. The average time of survival after the diagnosis of metastases is 1.5 years.

Postoperative radiation therapy for completely resected invasive thymoma: prognostic value of pleural invasion for intrathoracic control

BACKGROUND

Optimal management of postoperative radiation therapy for completely resected invasive thymoma remains controversial. This study was conducted to assess the efficacy of postoperative mediastinal irradiation in patients with completely resected invasive thymoma.

METHODS

Between 1981 and 1996, 21 patients with completely resected invasive thymoma were referred for postoperative mediastinal irradiation. The distribution of Masaoka stages was stage II in 14 patients and stage III in seven patients. Nine patients had pleural invasion by the tumor. Thirteen patients were treated with a localized field and eight were treated with the whole mediastinal field with boost. The total dose to the primary tumor was 40-61 Gy (median: 52 Gy). The median follow-up time of the 16 living patients was 67 months (range: 29-202 months).

RESULTS

The 5- and 10-year actuarial overall survival rates in all patients were both 77%. Relapses were observed in five patients, in all of whom the sites of the first relapse involved pleural dissemination. There were no relapses within the irradiated field in any of the 21 cases. Five of nine (56%) patients with pleural invasion had relapse of pleural dissemination, while 0 of 12 (0%) patients without pleural invasion had relapse. In univariate analysis, pleural invasion had a statistically significant impact on intrathoracic control (P = 0.01).

CONCLUSIONS

The results indicated that pleural invasion might be predictive of pleural-based relapse for completely resected invasive thymoma. In patients with pleural invasion, mediastinal irradiation alone might be insufficient to avoid pleural-based relapse even after complete resection.

Thymoma: state of the art

Thymoma is the most common tumor of the anterior mediastinum. This tumor is associated with unique paraneoplastic syndromes, such as myasthenia gravis, hypogammaglobulinemia, and pure red cell aplasia. The rarity of this tumor, however, has somewhat obscured the optimal treatment for this disease. For the majority of patients who present with localized tumor, surgical extirpation remains the standard of choice. Adjuvant radiotherapy seems to improve local control and survival. In more advanced disease, systemic therapy has been demonstrated to produce a 50% to 80% objective response rate. These observations have led to the development of multimodality therapy for the treatment of patients with advanced thymoma. In this article, we will review the current perspectives on the management of early stage and advanced thymoma.

Radiotherapy for invasive thymoma and thymic carcinoma. Clinicopathological review

PURPOSE

This study reports clinicopathological features and outcome of thymic tumors. Twenty-seven patients with invasive thymoma and 6 patients with thymic carcinoma who had received radiotherapy either primary or postoperatively were analyzed retrospectively.

PATIENTS AND METHODS

All 33 patients were irradiated with a mean dose of 50 Gy after complete resection (16 patients), partial resection (9 patients) or biopsy (8 patients). Staging was done according to the Masaoka classification; there were 12 Stage II, 12 Stage III and 9 Stage IV patients.

RESULTS

In patients with invasive thymoma Stage II to IV (median follow-up 54.4 months) Kaplan-Meier estimates of overall survival (OS), disease-specific (DSS) and disease-free survival (DFS) at 5 years were 63.7% (95% confidence interval [CI], 42 to 84%), 88.3% (CI, 75 to 100%) and 77.4% (CI, 58 to 95%), respectively. Among the prognostic factors tested, such as age, myasthenia gravis, completeness of surgery and histologic subclassification, total radiation dose, and Masaoka Stage, the latter was the only significant predictor of improved survival (p = 0.04). Considering local control, radiation dose was a significant prognostic factor (p = 0.0006). In patients with thymic carcinoma (median follow-up 43.4 months) 5-year DSS, and DFS were 22.2% (CI, 0 to 60%) and 16.7% (CI, 0 to 46%), respectively. Thymoma as compared to thymic carcinoma had a statistically significant better DSS (p = 0.007) and DFS (p = 0.0007).

CONCLUSION

Postoperative radiotherapy with sufficient doses plays an important role as adjuvant treatment in complete or incomplete resected invasive Stage II to III thymoma. In unresectable thymoma Stage III to IV as well as in thymic carcinoma a multimodality approach should be considered to improve survival.