Malignant Thymoma: Longterm Outcomes with Radiotherapy MingYii Huang1,2 ShiLong Lian1, ChihJen Huang

1
Malignant Thymoma Long-term Outcomes with
Radiotherapy Ming-Yii Huang1,2 Shi-Long
Lian1, Chih-Jen Huang1,2 Shah-Hwa Chou3
Pei-Chien Tsai4 Sheau-Fang Yang5 1Department
of Radiation Oncology, 3Division of Thoracic
Surgery, Department of Surgery, 4Department of
Public Health, 5Department of Pathology,
Kaohsiung Medical University Hospital, 2Graduate
Institute of Medicine, Kaohsiung Medical
University, Kaohsiung, Taiwan, ROC

• Purpose/Objective The aim of this study is to
  analyze survival and the significance of
  prognostic factors in patients with malignant
  thymoma. The patients had been treated by
  subtotal, total resection of tumors or by biopsy.
  Subsequently they received radiotherapy.
• Materials/Methods We performed a retrospective
  study of clinical and histopathological data on
  60 patients underwent biopsy or resection of
  thymic tumors from 1990 through 2004. Treatment
  combined surgery and radiation therapy (/-
  chemotherapy), with curative intent. Histological
  diagnosis based on the new WHO classification
  system. Univariate and multivariate analysis of
  prognostic factors predicting survival were
  carried out.
• Results Surgery consisted of complete resection
  in 31 patients (51.7), partial resection in 9
  patients (15), and biopsy in 20 patients
  (33.3), as show in Tab. 1. The median radiation
  dose to the tumor was 52 Gy (40-62.2Gy).
  Chemotherapy, combined with radiation in 14
  patients, consisted of multidrug regimens, mainly
  platinum based. The median follow-up is 3.7 years
  (2.0614.66 years)(Fig.1). The Masaoka staging
  system showed 19 stage II, 17 stage III and 24
  stage IV. Histological results were 4 subtype A,
  12AB, 6B1, 5B2, 8B3 and 25 C. The frequency of
  invasion to neighboring organs according to tumor
  subtype were A (50), AB (50), B1 (67), B2
  (60), B3 (75), and C (96)(Tab.2). Mediastinum
  RT was administered in 33 patients (33/60, 55),
  and mediastinum with supraclavicular RT
  administered in 27 patients (27/60, 45). For
  tumors at stage IV, additional mediastinum RT
  (33/60, 55) was given (Tab.3). There is a great
  impact of the extent of surgery on survival the
  3-, 5- and 10-year survival rates were 93.5,
  66.7 and 16.1 , respectively, after radical
  resection, compared to 31, 10.3 and 6.9
  after partial resection or biopsy (p 0.0001).
  Local control at 5 years was obtained in 18 of 25
  patients (72 ) 11 Stage II, 6 Stage III, 1
  Stage IV. There is a significant relationship
  between the extent of surgery and the local
  control (19.4 of relapse after complete
  resection vs. 41.2 of relapse after partial
  resection or biopsy, p 0.0001)(Tab. 4). Eight
  prognostic factors were statistically
  significant WHO histologic subtype, Masaoka
  clinical staging, Karnofsky score, surgery way,
  respectability, radiation field, radiation dose
  and radiation fraction. Mediastinum radiation
  dose (? 50 Gy) was significant in decreasing
  recurrence (p 0.0001) and distant metastasis (p
  0.011). Mediastinum and supraclavicular fossa
  irradiation was significant in decreasing distant
  metastasis (p 0.0149), but not statistically
  significant in recurrence (p 0.1492).
• Conclusions In this retrospective study of
  malignant thymoma (Stage II-IV) treated by
  surgery and radiation, results show the
  importance of loco-regional treatments, such as
  surgery and radiation therapy (/- chemotherapy).
  There is also a great impact of supraclavicular
  fossa irradiation on distant metastasis. However,
  the rates of local recurrence (30) and distant
  metastasis (25) justify recommending a higher
  dose of mediastinum radiation (? 50 Gy) and
  essential elective supraclavicular fossa
  irradiation for malignant thymoma patients.

Figure 1. Survival curves of malignant thymoma
patients