VeriStrat, a serum-based protein assay, can help select which patients with non–small cell lung cancer (NSCLC) not known to have epidermal growth factor receptor (EGFR) mutations might benefit from an ­EGFR-targeted agent, according to a study presented at the ASCO Annual Meeting by Vanesa Gregorc, MD, on behalf of Chiara Lazzari, MD,¹ and described at the Best of ASCO 2013 meeting in Los Angeles by ­Heather A. Wakelee, MD, Associate Professor of Medicine, Stanford University, Palo Alto, California.

Second-line therapy for advanced NSCLC patients after disease progression on platinum-based regimens typically employs chemotherapy or erlotinib (Tarceva). Improved progression-free survival in patients treated with erlotinib is associated with EGFR-sensitizing mutations, but there is little means of optimizing treatment in patients with wild-type or unknown EGFR mutation status or squamous histology, she noted.

VeriStrat is a commercially available serum-based protein test designed to identify which patients are likely to benefit from an oral EGFR tyrosine kinase inhibitor such as erlotinib or gefitinib (Iressa). The test evaluates pretreatment serum using matrix-assisted laser desorption ionization mass spectrometry to classify a patient as having a “good” or “poor” profile for treatment benefit. In retrospective studies, VeriStrat has demonstrated prognostic and predictive utility. 

At the Best of ASCO meeting, Dr. Wakelee presented the results of the current PROSE study, which she said is the first completed prospective biomarker-stratified validation study in oncology to test the treatment/biomarker interaction.

Details of PROSE

The study included 285 patients stratified by ECOG performance status, smoking, and blinded pretreatment VeriStrat classification (“good” or “poor”). Patients were randomly assigned to receive erlotinib or chemotherapy at standard doses. The primary endpoint was overall survival, and the primary hypothesis was that there would be a significant interaction between test status and treatment.

In the per-protocol primary analysis, 68% of the chemotherapy arm and 72% of the erlotinib arm were classified as VeriStrat good, while 32% and 28%, respectively, were classified as VeriStrat poor. EGFR and KRAS analysis was performed in about two-thirds of patients.

VeriStrat Profile Predicted Treatment Outcome

The trial reached its primary objective of significant interaction between treatment and VeriStrat classification, with an interaction P value of .037. Patients in the VeriStrat poor group performed worse on erlotinib than on chemotherapy (hazard ratio [HR] = 1.72, 95% confidence interval [CI] = 1.08–2.74) but for the VeriStrat good group, treatment assignment made no significant difference in overall survival (HR = 1.09, 95% CI = 0.79–1.50).

Median overall survival by treatment arm was 9.0 months with chemotherapy and 7.7 with erlotinib (a nonsignificant difference). At progression, about half the patients received a third-line regimen.

Differences did emerge, however, according to pretreatment VeriStrat results. Median overall survival was about 11 months for all patients with the VeriStrat good profile, whether they received erlotinib or chemotherapy, but for VeriStrat poor patients, overall survival was doubled with chemotherapy—6.4 months vs 3 months with erlotinib—Dr. Wakelee reported.

The results suggested that VeriStrat status is predictive of a differential overall survival benefit for erlotinib vs chemotherapy in the second-line setting, the authors maintained. ■

Disclosure: Dr. Wakelee reported no potential conflicts of interest.

Reference

1. Lazzari C, Novello S, Barni S, et al: Randomized proteomic stratified phase III study of second-line erlotinib versus chemotherapy in patients with inoperable non-small cell lung cancer (PROSE). 2013 ASCO Annual Meeting. Abstract LBA8005. Presented June 3, 2013.