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PD-L1 expression influences DFS, therapy response in papillary thyroid cancer
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LAKE BUENA VISTA, Fla. — Programmed death-ligand 1 expression in tumor cells and the adjacent microenvironment correlated with poor DFS and aggressive metastatic disease in patients with papillary thyroid cancer, according to retrospective study results presented at the International Thyroid Congress.
These findings may justify the potential application of anti–PD-1/PD-L1 immunotherapy for patients with refractory disease, according to the researchers.
“Monoclonal blockade of the PD-1/PD-L1 receptor has been recently recognized as a promising immunotherapy for several metastatic cancers,” Paul G. Walfish, CM, O.Ont, MD, FRCPC, Alex and Simona Schnaider research chair in thyroid oncology at Mount Sinai Hospital in Toronto, said during a presentation. “Overexpression of PD-L1 in some human cancer cells is associated with a poor prognosis and may correlate with anti–PD-1/PD-L1 monoclonal drug blockade. When PD-L1 is overexpressed in a cancer cell, the T cells are inhibited by this checkpoint, and consequently inactivated.”
Walfish and colleagues sought to evaluate PD-L1 expression in papillary thyroid cancer with varying aggressiveness. Researchers also evaluated whether PD-L1 expression correlated with clinical outcomes to determine whether PD-L1 serves as a therapeutic target in refractory aggressive or metastatic papillary thyroid cancer.
The researchers performed a retrospective immunehistochemical analysis of PD-L1 in 200 patients with variant papillary thyroid cancers. They correlated protein expression with available relevant long-term clinical data and disease outcomes.
The study included data on PD-L1 expression in 161 patients. The researchers considered 74 patients to have nonaggressive papillary thyroid cancer (stage I or stage IIA) and 87 patients to have aggressive disease (stage IIB, III or IV).
The researchers found that patients with PD-L1 membrane-positive tumor cells had significantly shorter median DFS compared with patients with PD-L1–negative tumor cells (9.75 months vs. 166.5 months; P < .001). Further, PD-L1 immunopositivity in tumor infiltrating lymphocytes correlated with poor DFS (median, 33 months; P = .023).
Patients with PD-L1–positive tumor cells and microenvironment had shorter DFS compared with patients who had no detectable expression (33.9 months vs. 166.5 months; P = .017).
“In summary, high PD-L1 expression could identify patients who would require more aggressive follow-up and therapy,” Walfish said. “The highest PD-L1 levels were observed in patients with stage III or IV disease.” – by Cameron Kelsall
Reference:
Ralhan R, et al. Oral Abstract 463. Presented at: International Thyroid Congress; Oct. 18-23, 2015; Lake Buena Vista, Fla.
Disclosure: Walfish reports a consultant role with Genzyme Canada. Further, Walfish and one other study researcher report ownership interests in Proteocyte Diagnostics, Inc. The other researchers report no relevant financial disclosures.