1 Departments of Neurosciences and 2 Surgical Sciences, Division of General Thoracic Surgery, Catholic University, Rome, Italy
*E-mail: mimgaletta@yahoo.com
Thymomas are often associated with autoimmune disorders, of which myasthenia gravis (MG) is by far the most common; moreover, an increased incidence of extrathymic tumors has been reported in these patients [13].
A center for MG at the Catholic University, Rome, has been active for >20 years; since 1996, clinical follow-up has also included thymoma patients without MG. We have compared thymoma cases both with and without MG in order to look for possible differences in the rate of additional malignancies.
We evaluated 107 patients operated on for thymoma in the period 19962002, with 6-months follow-up after surgery. Tumor histology was classified according to the World Health Organization (WHO) classification [4]. The presence of autoimmune diseases other than MG and immunosuppressive and adjuvant treatments were recorded. Extrathymic malignancies were diagnosed on the basis of chart review, periodic patient examinations and analysis of the hospital tumor registry. Statistical analysis was performed using the chi-square test with Yates correction and Students t-test.
Thymoma was associated with MG in 75 patients (34 male/ 41 female), with a mean age at thymomectomy of 52 years (range 1570); thymoma was not associated with MG in 32 subjects (19 male/13 female), mean age 56 years (range 1878). Mean follow-up was 45 (range 885) and 43 months (range 688) in MG and non-MG patients, respectively. All thymoma histological subtypes were found in non-MG patients; type C thymic tumors were absent in the MG series. Adjuvant treatment consisted of radiotherapy (25 MG and five non-MG patients), cisplatin-based chemotherapy (eight MG and three non-MG patients) and both radio- and chemotherapy (five MG and three non-MG patients). Other autoimmune disorders were diagnosed in 12 of 75 (16%) MG patients and in 6 of 32 (19%) non-MG subjects. Sixty-three MG patients received immunosuppressive therapy (in most cases prednisone plus azathioprine); three non-MG subjects were treated with steroids because of their autoimmune diseases (polymyositis, systemic lupus erythematosus, pemphigus).
Additional tumors were noted in six of 75 MG (8%) and in eight of 32 non-MG subjects (25%) (P = 0.038). One patient in each group had two extra-thymic malignancies. These data are shown in Table 1. Eight cancers were diagnosed at the same time as thymoma, three occurred before and five after thymomectomy. No preferential association with any thymoma subtype was observed. Of those patients with extrathymic tumors, three non-MG cases were also affected by autoimmune diseases, four MG and two non-MG subjects were receiving immunosuppressive therapy; adjuvant treatment had been administered to three MG and one non-MG individuals who developed malignancy after thymomectomy.
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In summary, we compared thymoma patients with and without myasthenia gravis (MG) for the incidence of extrathymic malignancies. We found a significantly higher rate of additional tumors in non-MG patients. These findings could be related to an apparent protective effect of MG.
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