Radiotherapy for invasive thymoma and thymic carcinoma. Clinicopathological review

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.

Radiographic Predictors of Resectability in Thymic Carcinoma

BACKGROUND

The aim of this study was to assess preoperative computed tomography characteristics of thymic carcinomas and to investigate which features could predict an incomplete surgical resection. A secondary aim was to correlate preoperative imaging features with Masaoka stage.

METHODS

In this study, approved by our Institutional Review Board, two readers retrospectively reviewed preoperative computed tomography scans at our tertiary referral oncology center between 1994 and 2014. Imaging features analyzed included tumor morphology, infiltration of surrounding mediastinal fat, loss of surrounding fat plane, degree of contact between tumor and great vessels, and associated pulmonary or pleural abnormality. Surgical and pathologic records were reviewed for completeness of surgical resection and Masaoka stage.

RESULTS

Forty-one patients were included, with Masaoka stage I (n = 3), stage II (n = 4), stage III (n = 12), and stage IV (n = 22). Twenty-one patients (51%) had a complete surgical resection. Ten had microscopic residual disease (R1) with involved surgical margins at pathology, and 10 patients had macroscopic residual disease (R2) at surgery. In addition to lesion size, the feature associated with incomplete surgical resection was the degree of tumor contact with adjacent mediastinal vessels on the preoperative computed tomography image (p = 0.038). Many of the more common features associated with incomplete resection were also more likely to be present in patients with late Masaoka stage (III/IV), including infiltration of the mediastinal fat, which was present in all 34 patients with Masaoka stage III/IV compared with 5 patients (71%) with stage I/II (p = 0.03).

CONCLUSIONS

Preoperative computed tomography imaging features may help to identify patients at risk for an incomplete surgical resection.

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.

Surgical approach in thymectomy: Our experience and review of the literature

Aim

Thymectomy is the main treatment for thymoma and patients with myasthenia gravis (MG). The traditional approach is through a median sternotomy, but, recently, thymectomy through minimally invasive approaches is increasingly performed. Our purpose is an analysis and discussion of the clinical presentation, the diagnostic procedures and the surgical technique. We also consider post-operative complications and results, over a period of 5 years (May 2011–June 2016), in thymic masses admitted in our Thoracic Surgery Unit.

Methods

We analyzed 8 patients who underwent surgical treatment for thymic masses over a period of 5 years. 6 patients (75%) had thymoma, 2 patients (25%) had thymic carcinomas. 2 patients with thymoma (33%) had myasthenia gravis. We performed a complete surgical resection with median sternotomy as standard approach.

Results

One patient (12%) died in the postoperative period. The histological study revealed 6 (75%) thymoma and 2 (25%) thymic carcinomas. Post-operative morbidity occurred in 2 patients (25%) and were: pneumonia in 1 case (12%), atrial fibrillation and pleural effusion in 2 patients (25%). One patient with thymoma type A recurred at skeletal muscle 2-years after surgery.

Conclusions

Thymic malignancies are rare tumors. Surgical resection is the main treatment, but a multimodal approach is useful for many patients. Radical thymectomy is completed removing all the soft tissue in the anterior mediastinum between the two phrenic nerves and this is the most important factor in controlling myasthenia and influencing survival in patients with thymoma. Open (median sternotomy) approach has been the standard approach for thymectomy for the better visualization of the anatomical structures. Actually, video-assisted thoracoscopic surgery (VATS) thymectomy and robotic video-assisted thoracoscopic (R-VATS) approach versus open surgery has an equal if not superior oncological efficacy, better perioperative complications and survival outcomes.

Surgical and oncological outcomes of thoracoscopic thymectomy for thymoma

Thymoma remains the most common primary anterior mediastinal neoplasm. Surgical resection remains central to the treatment of thymoma, with thoracoscopic thymectomy (TT) being increasingly performed. This present review article aimed to summarize current studies comparing TT and open thymectomy (OT). Recently, most patients with Masaoka stage I-II thymoma have been receiving TT. This procedure is associated with a significantly shorter post-operative hospital stay, decreased intraoperative blood loss, and fewer complications compared with OT. Recurrence rates of thymoma after TT range from 0% to 6.7%, and the 5-year disease-free survival (DFS) ranges from 83.3% to 96%. The oncological outcomes of TT are comparable to that of OT. Masaoka stage and the World Health Organization (WHO) type classification are valuable predictors of the prognosis of thymoma; hence, the optimal treatment for thymoma should be performed according to these two. TT is less invasive, with equivalent oncological outcomes, when compared with the OT. Minimally invasive surgery including TT for stage I-II thymomas is becoming the mainstay of therapy.

Multidisciplinary management of thymic carcinoma

Thymic carcinomas represent approximately 10% of thymic tumors. In our approach to patients with thymic carcinoma, we emphasize multimodality treatment with close communication between the pathologist, thoracic surgeon, medical oncologist, and radiation oncologist. Given the paucity of high-quality clinical research data, treatment decisions are guided by a small amount of prospective trial data, retrospective reports, and clinical experience. Surgical management of thymic carcinoma must account for the more aggressive biology, higher degree of local invasion of neighboring structures, greater propensity for nodal metastasis, and higher risk of distant metastatic disease. Although surgical resection remains the most important component in the management of localized thymic tumors, radiation therapy (RT) may be used as adjuvant therapy after surgical resection or as the definitive treatment modality in patients who are deemed unresectable because of medical comorbidities or technical reasons. Systemic therapy for thymic carcinoma is used in two clinical scenarios: preoperative treatment and palliative therapy. First-line, platinum-based chemotherapy regimens are associated with response rates between 22% and 75%. Recent data from targeted therapy trials do not reveal a clear role for targeted therapies for patients with thymic carcinoma.

Video-assisted thoracoscopic surgery versus sternotomy in thymectomy for thymoma and myasthenia gravis

Thymectomy involves the removal of all the soft tissue in the pre-vascular plane of the anterior mediastinum between the two phrenic nerves. Surgical success in controlling myasthenia and the most important factor influencing survival in patients with thymoma depends on complete clearance of thymic tissue. Currently there is a perception that the open (median sternotomy) approach offers better visualisation of the thymic tissue. This perceived advantage is thought to justify the invasive nature of the procedure associated with increased morbidity. Video-assisted thoracoscopic surgery (VATS) for thymectomy has evolved significantly over the last decade, including bilateral and unilateral VATS (either left or right) approaches. The laterality of the approach remains largely on surgeon preferences, with the decision influenced by their experience and training. VATS offers superior illumination and magnification, particularly with the availability of advanced cameras with variable angles that provide better exposure and lighting of the operative field. The use of three-dimensional-operating imaging has also revolutionised the VATS technique. VATS thymectomy is a superior and radical technique in minimising access trauma and removing all thymic tissue that may be scattered in the anterior mediastinum and cervical fat. Other advantages of VATS include less intraoperative blood loss, early removal of chest drains, less requirement for blood products, decreased inflammatory cytokine response, shorter hospital stay and superior cosmesis. There is also a decreased risk of respiratory and cardiac related complications compared to the open (sternotomy) technique. Furthermore, no significant difference has been found in long-term complications and survival rate between VATS and open approaches. Subsequently, the VATS approach should be encouraged as more surgeons are adopting the minimally invasive practice as routine.

Invasion of the great vessels or atrium predicts worse prognosis in thymic carcinoma

Purpose

We evaluated treatment outcomes of thymic carcinomas to determine prognostic factors for survival.

Materials and Methods

Between May 1988 and May 2009, 41 patients had pathologic diagnosis of thymic carcinoma in Seoul National University Hospital, Seoul, Korea. Of these, 40 patients were followed up to 188 months after treatment. The mean age of all patients was 58.3 years and male to female ratio was 23 to 17.

Results

Among 30 patients who underwent surgical resection, 26 achieved R0 resection and postoperative radiotherapy (PORT) was performed in 22 patients (73%). Various chemotherapeutic regimens were given with local treatment modalities, surgery and/or radiotherapy, in 12 patients. The 5-year locoregional control (LRC), distant metastasis-free survival, progression-free survival (PFS), and overall survival were 79.4%, 53.0%, 42.6%, and 63.6%, respectively. Patients with Masaoka stage I or II showed excellent prognosis of 5-year PFS around 90%. In advanced stages, invasion of the great vessels or atrium by thymic carcinomas was negative prognostic factor for PFS in univariate analysis. Lymph node involvement was statistically significant factor for LRC and PFS. Local or regional recurrence was infrequent after surgical resection followed by PORT, while distant metastasis was the major component of treatment failure.

Conclusion

Complete resection followed by PORT provided remarkable local control without severe acute toxicities in patients with stage II and favorable stage III thymic carcinoma. Invasion of the great vessels or atrium was statistically significant prognostic factor for PFS.

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.

Results of a Surgical Resection for Patients with Thymic Carcinoma

Objectives:

This study investigated the clinical features of patients with complete resection of thymic carcinoma.

Patients and Methods:

The clinical records from 11 patients who underwent a complete resection of thymic carcinoma were retrospectively reviewed.

Results:

Twelve of 22 patients underwent a resection (a complete resection in 11 and an incomplete in 1). Six of the 11 patients with complete had confirmed recurrent tumors. The 5-year survival rate was 45.4%, and the median survival time was 50.6 months. The patients who underwent complete resection showed significantly better prognosis than cases with incomplete resection and inoperable cases ( p = 0.048). Three of the 6 patients had a recurrence within 1 year. Frequent sites of recurrence were the pleura, pericardium, and lung.

Conclusions:

A complete resection improved the prognosis of thymic carcinoma. Further prospective studies regarding postoperative adjuvant therapy are necessary to prevent local recurrence after a surgical resection for thymic carcinoma.

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.

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.

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.

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.

Thymoma: update for the new millennium

Thymomas are relatively common tumors of the anterior superior mediastinum. They are usually relatively slowly growing tumors and their prognosis depends on the macroscopic and microscopic invasion of surrounding tissues. Surgery is the mainstay treatment of thymomas, and complete resection represents one of the most important prognostic factors in this disease. Other important prognostic indicators include the tumor stage and size and the presence of symptoms. Postoperative radiotherapy is indicated in tumors with invasion of surrounding tissues, even if resection was radical, since it improves local control and survival. Cytotoxic chemotherapy has been employed in several relatively small phase II studies and in advanced disease has been demonstrated to produce a 50%-80% objective response rate. Neoadjuvant cytotoxic chemotherapy and/or external beam radiotherapy has been used with some success in patients with tumors which are not readily resectable. Novel antiproliferative systemic agents, with both cytotoxic and cytostatic mechanisms of action, are being tested in ongoing prospective clinical trials.

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.