Reduced Tumour Proportion Scores for Programmed Cell Death Ligand 1 in Stored Paraffin Tissue Sections.
Author(s): Sato Y, Fujimoto D, Uehara K, Kawachi H, Nagata K, Nakagawa A, Otsuka K, Sakanoue I, Hamakawa H, Takahashi Y, Imai Y, Tomii K
Publication: Anticancer Res, 2018, Vol. 38, Page 1401-1405
PubMed ID: 29491064 PubMed Review Paper? No
Purpose of Paper
This paper investigated whether the extent or intensity of PD-L1 immunostaining is adversely affected by the storage of formalin-fixed, paraffin-embedded (FFPE) slides at 4°C for 2 to 8 weeks prior to immunohistochemical staining compared to those stained immediately.
Conclusion of Paper
PD-L1 immunostaining was adversely affected when unstained FFPE slides were stored at 4°C for 2 weeks or longer. The prevalence of a weakly positive tumor proportional score (TPS) for PD-L1 increased from 0% for slides stained immediately (100% of slides were strongly positive) to a weakly positive score in 41%, 33%, 58%, and 76% of slides stored for 2, 4, 6, and 8 weeks at 4°C prior to immunostaining, respectively. Slides with PD-L1 results affected by storage had similar FFPE block storage durations and clinical characteristics than slides that remained stable, with the exception of non-small cell lung cancer (NSCLC) stage I.
Studies
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Study Purpose
This paper investigated whether the extent or intensity of PD-L1 immunostaining is adversely affected by the storage of formalin-fixed, paraffin-embedded (FFPE) slides at 4°C for 2 to 8 weeks prior to immunohistochemical staining compared to those stained immediately as part of a retrospective study. FFPE non-small cell lung cancer (NSCLC) specimens collected from 12 patients that had a tumor proportion score (TPS) for PD-L1 of ≥50% were investigated as part of a retrospective study. NSCLC specimens were fixed in formalin for 24-72 h and stored as blocks for 22.3-91.9 months prior to sectioning. Five serial sections (4 µm thick) from each case were stored for 2, 4, 6, or 8 weeks at 4°C prior to immunohistochemical staining with the anti-PD-L1 clone 28-8 or immunostained immediately after sectioning. Immunostained slides were evaluated by two pathologists using a blind design. Specimens were denoted as PD-L1 positive if the cell membrane was partially or completely immunostained, regardless of staining intensity. Tumor proportional score (TPS) was recorded as strongly positive (TPS ≥ 50%), weakly positive (TPS 10-49%), or negative (0-10%).
Summary of Findings:
Tumor proportional scores (TPS) for PD-L1 were severely affected by FFPE slide storage prior to immunohistochemistry. After 8 weeks of FFPE slide storage the TPS The prevalence of a weakly positive TPS score for PD-L1 increased from 0% for slides stained immediately (100% of slides were strongly positive) to a weakly positive score in 41%, 33%, 58%, and 76% of slides stored for 2, 4, 6, and 8 weeks at 4°C prior to immunostaining, respectively. The only difference among patients that whose samples were susceptible to effects of FFPE slide storage and those that remained stable was NSCLC stage ,with stable PD-L1 immunostaining after storage at 4°C for up to 8 weeks observed in patients with stage I KSCLC. Storage durations and clinical characteristics were similar in slides from NSCLC stage I and II specimens.
Biospecimens
Preservative Types
- Formalin
Diagnoses:
- Neoplastic - Carcinoma
Platform:
Analyte Technology Platform Protein Immunohistochemistry Pre-analytical Factors:
Classification Pre-analytical Factor Value(s) Immunohistochemistry Specific Targeted peptide/protein PD-L1
Storage Storage duration 0 d
2 weeks at 4°C
4 weeks at 4°C
6 weeks at 4°C
8 weeks at 4°C