Elsevier

Annals of Oncology

Volume 26, Issue 3, March 2015, Pages 556-561
Annals of Oncology

original articles
head and neck tumors
A randomized, phase II trial of cetuximab with or without PX-866, an irreversible oral phosphatidylinositol 3-kinase inhibitor, in patients with relapsed or metastatic head and neck squamous cell cancer

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ABSTRACT

This manuscript reports on a prospective, randomized study of cetuximab plus/minus a small molecule PI3K inhibitor (PX-866) targeting the protein product of PIK3CA, the gene with the highest rate of activating mutations in head and neck squamous cell cancer (HNSCC). The combination of PX-866 and cetuximab failed to improve outcomes compared with cetuximab alone in patients with advanced HNSCC.

Background

The phosphotidylinositol-3 kinase (PI3K)/serine–threonine kinase/mammalian target of rapamycin signaling pathway is frequently altered in head and neck squamous cell cancer (HNSCC). PX-866 is an oral, irreversible, pan-isoform inhibitor of PI3K. A phase I trial demonstrated tolerability of this combination. This randomized phase II study evaluated PX-866 combined with cetuximab in patients with advanced, refractory HNSCC.

Methods

Patients with recurrent or metastatic HNSCC who had received at least one and no more than two prior systemic treatment regimens were randomized (1 : 1) to cetuximab with or without PX-866 (8 mg p.o. daily; arms A and B, respectively). The primary end point was progression-free survival (PFS). Secondary end points included objective response rate (ORR), overall survival (OS), toxicity, and correlation of key biomarkers with efficacy outcomes.

Results

Eighty-three patients were enrolled. There was a similar response rate between arms (10% versus 7%). Of patients for whom tissue was assessable, 57% were human papillomavirus (HPV) positive. Median PFS was 80 days in both arms and there was no difference in OS between the two arms (211 versus 256 days). Overall toxicity was higher in arm A compared with arm B, especially in terms of nausea (53% versus 23%), vomiting (45% versus 15%), fatigue (43% versus 23%), diarrhea (40% versus 21%), and hypokalemia (25% versus 10%). Grade 3 or higher adverse events were infrequent, but more common in the combination arm although without a specific pattern.PIK3CA mutations were observed in 17% of the cases assessed, andPTEN loss was infrequently observed.

Conclusion

The addition of PX-866 to cetuximab did not improve PFS, RR, or OS in patients with advanced, refractory HNSCC enrolled without molecular preselection. In this contemporary cohort, HPV-positive patients comprised the majority, and neither HPV-positive nor HPV-negative patients derived clinical benefit for the addition of cetuximab plus PX-866.

Key words

PI3K
cetuximab
combination therapy
head and neck squamous cell cancer
PIK3CA

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