Medical Care
Postoperative radiotherapy has been used for invasive thymoma and incompletely resected thymoma.
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Commonly, radiotherapy has treated T tumors demonstrated to be unresectable on CT scan or with supraclavicular extension.
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Primary radiotherapy in unresectable stage III or stage IVa disease has controlled local disease with a 5-year survival rate of 45-50%. [2]
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Combination chemotherapy using cisplatin has been reported to have a response rating of 70-80%. Doxorubicin, vincristine, and cyclophosphamide have been used in combination chemotherapy.
The acquired immunodeficiency associated with thymoma should be treated with monthly replacement immunoglobulin (Ig) therapy. Replacement Igs may be intravenously or subcutaneously administered. Doses of intravenous Igs should be 300-400 mg/kg every 3 weeks or 400-500 mg/kg every 4 weeks with dose adjustment to maintain trough IgG levels above 500-600 mg/dL. In addition, prophylactic antibiotics may be required in addition to Ig replacement therapy to prevent bacterial infections in immunodeficient patients. Aggressive and long-term antibiosis is often required to treat bacterial infections in these patients. [22]
See Thymoma Treatment Protocols for more information.
Surgical Care
Because thymoma is usually well encapsulated and characterized by local spread, thymectomy can be curative in the early stages.
Encapsulated (stage I) tumors can usually be completely excised, and the local relapse rate is less than 5%. Currently, adjuvant radiotherapy and chemotherapy are not recommended for stage I thymomas that are completely resected. [31] The relapse rate increases in more invasive stages.
Surgery can be challenging because of the tendency of the tumor to surround blood vessels, bronchi, and other mediastinal structures. Excessive bleeding can complicate thymectomy of large tumors that have become vascular or lacunar.
Tumor recurrence can occur even after complete resection. [32]
Eighty-five percent of patients with myasthenia gravis (MG) have some histologic abnormality of the thymus.
Thymectomy is considered a routine treatment for MG. Reportedly, resection of the thymoma is associated with improvement in weakness in 25% of patients, and almost one half of patients without thymoma improve after thymectomy. [13]
A study of 153 patients by Werneck et al compared thymectomy with conservative treatment groups in paired patients at similar stages and found no statistical difference between the conservative treatment and thymectomy groups. [33]
Thymectomy is believed to improve muscle weakness in 25% of individuals with MG and thymoma and in 50% of patients with MG without thymoma.
Thymectomy results in resolution of red cell aplasia in 30% of persons with this disorder.
The acquired immunodeficiency phenotype does not improve after thymectomy, and, in some persons, immunodeficiency has occurred years after resection of a thymoma. [34]
Tables
Clinicopathologic Classification |
WHO Type |
Terminology of the Histogenetic Classification for the Histologic Subtypes of Thymic Epithelial Tumors |
Benign thymoma |
A AB |
Medullary thymoma Mixed thymoma |
Malignant thymomas, Category I |
B1 B2 B3 |
Predominantly cortical thymoma Cortical thymoma Well-differentiated thymic carcinoma |
Malignant thymomas, Category II |
C |
Epidermoid keratinizing (squamous cell) carcinoma Epidermoid nonkeratinizing carcinoma Lymphoepithelioma-like carcinoma Sarcomatoid carcinoma (carcinosarcoma) Clear cell carcinoma Mucoepidermoid carcinoma Undifferentiated carcinoma |
Cisplatin |
75 mg/m2 on day 1 |
3 courses repeated q3wk |
Epirubicin |
100 mg/m2 on day 1 |
|
Etoposide |
120 mg/m2 on days 1, 3, and 5 |
|
Surgery and radiation in patients with complete or partial response to chemotherapy |
4500 cGy if complete resection 6000 cGy if incomplete resection |
|
Cisplatin |
50 mg/m2 |
2-4 cycles q3wk |
Doxorubicin |
50 mg/m2 |
|
Cyclophosphamide |
500 mg/m2 |
|
Followed by radiation |
54 Gy to the primary tumor and lymph nodes |
|
Cisplatin |
75-100 mg/m2 on day 1 |
Repeated q3wk 3 times before surgery and 2 or 3 times after surgery |
Epirubicin hydrochloride |
100 mg/m2 on day 1 |
|
Etoposide |
120 mg/m2 on days 1, 3, and 5 |
|
Postoperative radiation in patients with radical resection |
30 Gy |
Delivered in 3 wk with 5 fractions per wk |
Postoperative radiation in patients with incomplete resection |
50 Gy |
Delivered in 5 wk with 5 fractions per wk |
Octreotide |
1.5 mg/d SC |
In patients shown to have somatostatin receptors |
Lanreotide |
30 mg/d SC q14d |
Switch to this longer-acting somatostatin analogue or depot form of octreotide if short-acting octreotide is well tolerated |
Prednisone |
0.6 mg/kg/d PO for 3 mo, then decreasing to 0.2 mg/kg |
|
