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S. Suehiro
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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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P1.08-034 - The Clinicopathological Significance of PD-L1 Expression in Thymoma (ID 1572)
09:30 - 09:30 | Author(s): S. Suehiro
- Abstract
Background:
Programmed Death Ligand 1 (PD-L1) is an immune checkpoint molecule that binds to the PD-1 receptor, thereby suppressing the activity of tumor infiltrating cytotoxic T cells. On the other hand, the immune checkpoint inhibitors (PD-L1, PD-1, CTLA-4) are notorious for causing autoimmune disorders. Ipilimab, an anti-CTLA-4 antibody, and nivolumab, an anti-PD-1 antibody, have been shown to induce myasthenia gravis (MG) in clinical trials. Although it has been hypothesized that the binding of PD-L1 to PD-1 is essential for T cell maturation, the role of PD-L1 in thymoma and autoimmune disorders remains unclear.
Methods:
We studied 52 consecutive patients who underwent resection for thymoma in our institution from 1995 to 2013. The median age of the 52 patients was 59 years (range: 21-77), 46% were male, and 31%, 52% and 15% corresponded to the WHO types of A or AB, B1 or B2, and B3, respectively. Thirty-five percent of the patients had MG, and 23% had advanced disease (Masaoka stage IV). Formalin-fixed paraffin embedded tissue sections were stained with PD-L1 rabbit monoclonal antibody (Cell Signaling Technology). The PD-L1 staining scores were calculated by multiplying the staining intensity (0: negative to 3: strong) of the membrane / cytoplasm in the tumor cell by the proportion of stained tumor cells. The staining score, WHO classification, Masaoka stage and the coexistence of MG were compared using the Mann-Whitney U -test.
Results:
The mean PD-L1 score was 45 (range: 0-300). The PD-L1 scores were higher in patients with more advanced disease (Masaoka stage IV; median 60, range 10-300) than in those with localized disease (Masaoka stage I-III; median, 20; range 0-160; p=0.047). Furthermore, the score was also related with the WHO classification; it was high in WHO type B3 patients (median, 60; range, 10-300), despite the fact that it remained low among types A, AB, B1 and B2 (median 20, range 0-160, p=0.033). There was no statistically significant association between the presence of MG and a high PD-L1 score.
Conclusion:
PD-L1 was highly expressed in more aggressive and advanced stages of thymoma. No prior studies have so far reported the significance of the PD-L1 expression on thymoma. Further studies are warranted to utilize immune checkpoint targeting therapies for thymoma.
