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Margaret Redpath
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P2.09 - Pathology (Not CME Accredited Session) (ID 958)
- Event: WCLC 2018
- Type: Poster Viewing in the Exhibit Hall
- Track:
- Presentations: 1
- Moderators:
- Coordinates: 9/25/2018, 16:45 - 18:00, Exhibit Hall
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P2.09-07 - Does Metastatic Site Matter for PD-L1 Testing in Stage IV NSCLC? (ID 13385)
16:45 - 18:00 | Author(s): Margaret Redpath
- Abstract
Background
Stage IV non-small cell lung cancer (NSCLC) often presents with metastasis to multiple distant sites. Currently PD-L1 expression by immunohistochemistry (IHC) testing with Tumor Proportion Score (TPS) ≥ 50% and ≥1% is required for first- and second-line Pembrolizumab treatment respectively. However, it is not well known if PD-L1 expression differs in NSCLC specimens sampled from different distant metastatic sites. In this study, we evaluate PD-L1 expression in distant metastatic sites.
a9ded1e5ce5d75814730bb4caaf49419 Method
A total of 400 NSCLC specimens from distant metastatic sites are included in this study. The metastatic sites include brain, bone, non-regional lymph nodes, serous membranes (pleura, pericardium and peritoneum) and organs outside the chest (liver, adrenal gland, skin, soft tissue). The samples are either cytology cell blocks, small biopsies or surgical resections. IHC was performed using Dako PD-L1 IHC 22C3 pharmDx. A total of 100 viable tumor cells is required for adequacy. TPS≥ 50% and 1-49% are defined as high and low PD-L1 expression respectively.
4c3880bb027f159e801041b1021e88e8 Result
Overall, the rate of TPS >50% ranges from 36-47% in different metastatic organ sites (Table 1). The prevalence of PD-L1 high and low expression is similar for all distant metastatic sites (P=0.91). Brain metastases have a slightly lower rate of high PD-L1 expression but the difference is not statistically significant.
Table 1. PD-L1 expression in different metastatic sites
Metastatic sites
Tumor Proportion Score (TPS)
Total
≥50%
n (%)
1-49%
n (%)
0%
n (%)
n (%)
Brain
13(36%)
9 (25%)
14(39%)
36 (100%)
Bone
21(44%)
11(23%)
16(33%)
48 (100%)
Nonregional lymph nodes
6(40%)
3(20%)
6 (40%)
15 (100%)
Serous membranes
91(40%)
62(27%)
74(33%)
227 (100%)
Organ outside chest
35(47%)
20(27%)
19(26%)
74 (100%)
Total
166(42%)
105(26%)
129(32%)
400 (100%)
P=0.91
8eea62084ca7e541d918e823422bd82e Conclusion
Our results suggest that the specimens for PD-L1 IHC testing can be sampled from any accessible distant metastatic site.
6f8b794f3246b0c1e1780bb4d4d5dc53
