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D. Zander
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P1.08 - Poster Session/ Thymoma, Mesothelioma and Other Thoracic Malignancies (ID 224)
- Event: WCLC 2015
- Type: Poster
- Track: Thymoma, Mesothelioma and Other Thoracic Malignancies
- Presentations: 1
- Moderators:
- Coordinates: 9/07/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)
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P1.08-038 - The Effect of the WHO Histologic Classification on Thymic Specific Survival and Overall Survival (ID 2616)
09:30 - 17:00 | Author(s): D. Zander
- Abstract
Background:
In 1999 the World Health Organization published a histologic classification system for thymoma that divided it into 5 categories (A, AB, B1-B3). We investigated the effect that this classification has on outcomes and determined if there was a role for radiotherapy in patients undergoing resection.
Methods:
The SEER database was used to retrospectively analyze thymomas from 2000-2011. Only those patients having first primary thymic neoplasia and undergoing resection were included in the analysis. Overall survival (OS) and thymic-specific survival(TSS) were evaluated by Kaplan-Meier Methods. Propensity Score was used to determine the role of radiotherapy.
Results:
1047 patients had median follow-up of 53 months. In patients not receiving radiation (N=428), multivariate analysis found that worse OS was associated with older age, unmarried status, advanced stage, and partial resection. Better TSS was associated with white race and early stage. Histologic classification did not have any effect on OS or TSS. In patients with stage I and II disease (N=541), the 5-year OS and cumulative incidence rates of thymic death were 87.5% and 3.0%. In 483 stage III/IVA patients, propensity match of 153 patients treated with or without radiation demonstrated that radiation was associated with a significantly better OS (HR=0.400, p= 0.001) and TSS (HR=0.473, p=0.034), and that the effect of radiation did not depend upon histologic subtype. Selection factors for radiation included younger age and tumor size. Radiation was not associated with an increase in cardiopulmonary deaths or deaths due to second malignancies. Only 36.6% of patients had any lymph nodes explored, and 12.0% were positive. WHO Histology B3 was most likely to have involved lymph nodes (20%), while histology A (0%) and B2 (2%) were least likely. 125 (11.9%) patients have developed secondary malignancies.
Conclusion:
Radiation may be beneficial for surgically-resected advanced-stage thymoma. Neither OS or TSS was affected nodal involvement or histology. The lack of correlation of histology with outcomes may demonstrate that the current histologic system is not predictive of outcomes or that it does not translate to the broad spectrum of pathologists in SEER registry areas.
