SP263 and 22C3 Assays Show Similar Predictive Value for Atezolizumab in NSCLC
Two PD-L1 tests, SP263 and 22C3, show high agreement & effectively identify patients with early-stage non–small cell lung cancer who are likely to benefit from adjuvant atezolizumab.
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Findings from a phase 3 study (NCT02486718) suggest that both the VENTANA SP263 and Dako 22C3 (SP263 and 22C3) assays can be utilized to identify patients with early-stage non–small cell lung cancer (NSCLC) who are most likely to experience benefit from adjuvant atezolizumab (Tecentriq).1
According to results published in the Journal for Immunotherapy of Cancer, high concordance and a comparable clinical predictive value of atezolizumab at validated PD-L1 thresholds were observed using the SP263 and 22C3 assays. The study utilized tumor samples from the phase 3 IMpower010 study (NCT02486718) which evaluated the safety and efficacy of atezolizumab vs best supportive care (BSC) following adjuvant cisplatin-based chemotherapy in patients with completely resected stage IB-IIIA NSCLC. These samples were used to compare the 2 PD-L1 immunohistochemistry assays, SP263 and 22C3.
Investigators assessed the assays to see how they differentiated in regard to the identification of PD-L1 patient subgroups, as well as their predictive value for adjuvant atezolizumab vs BSC among patients with resectable early-stage NSCLC.
The SP263 assay evaluated PD-L1 expression by evaluating the percentage of tumor cells with any membranous PD-L1 staining, and the 22C3 assay assessed PD-L1 expression using the percentage of viable tumor cells which showed the partial or complete membranous PD-L1 staining.
This study was a global, multicenter, open-label, randomized, phase 3 trial. The safety and efficacy of 16 cycles of atezolizumab were compared with BSC in patients with stage IB-IIIA NSCLC following resection and adjuvant chemotherapy. One cycle lasted for a duration of 21 days. Once patients completed up to 4 cycles of adjuvant cisplatin-based chemotherapy, they were randomized 1:1 to receive either atezolizumab or BSC for up to 16 cycles.2
The primary end point of the study was disease-free survival (DFS) and secondary end points included overall survival, percentage of patients with adverse events, percentage of patients with anti-therapeutic antibodies to atezolizumab, and pharmacokinetics.
Looking at the concordance at the PD-L1-positive threshold, for which the SP263 assay tumor cell (TC) was ≥1% and the 22C3 assay tumor proportion score (TPS) was ≥ 1%, findings showed concordance between assays for 83% of the samples.1 Results were also concordant between assays at the PD-L1-high cut-off (SP263: TC ≥ 50%; 22C3: TPS ≥ 50%), for 92% of samples.
Regardless of which of 2 tests were used to measure PD-L1, the assays were comparable in regard to DFS for atezolizumab vs BSC for PD-L1-positive disease (TC ≥ 1% by SP263: HR, 0.58; 95% CI, 0.40-0.85; TPS ≥ 1% by 22C3: HR, 0.65; 95% CI, 0.45-0.95) and PD-L1-high (TC ≥ 50% by SP263: HR, 0.27; 95% CI, 0.14-0.53; TPS ≥ 50% by 22C3: HR, 0.31; 95% CI, 0.16-0.60) subgroups.
Overall, researchers concluded that these 2 assays for PD-L1 in early-stage NSCLC can both be used to choose patients who are likely to do well with atezolizumab.
