PTEN loss, PIK3CA mutation predicted resistance to cetuximab in HNSCC

June 2, 2013

Source: Helio.com

 

CHICAGO — PTEN loss or PIK3CA mutation predicted resistance to treatment with cisplatin plus cetuximab in a cohort of patients with head and neck squamous cell carcinoma, according to phase 3 study results presented at the ASCO Annual Meeting.

“Cetuximab is the only targeted therapy in use in head and neck cancer, and although it prolongs survival, the effects are modest. For patients who receive [cetuximab] in the setting of metastatic or recurrent disease, median survival remains less than 1 year,” Barbara Burtness, MD, a medical oncologist at Fox Chase Cancer Center who specializes in head and neck cancers and a HemOnc Today Editorial Board member, said in an interview. “In colon cancer, patients are tested for KRAS mutations to detect patients with upfront resistance to cetuximab, but KRAS mutation is rare in head and neck cancer, and we haven’t had a biomarker to separate the sensitive from resistant patients.”

Burtness and colleagues compared cisplatin plus placebo vs. cisplatin plus cetuximab (Erbitux, Eli Lilly) in 117 patients. The researchers also assessed PIK3CA mutations and loss of PTEN expression in the cohort.

Results indicated that 34% of tumors studied had a loss of PTEN expression and 4% had PIK3CA mutations in the three hotspots studied.

Researchers did not observe any statistically significant differences in OS, PFS or overall response rates.

However, among patients with PIK3CA and PTEN expression, median PFS was 4.2 months for those assigned to cetuximab vs. 2.9 months for those assigned to placebo (adjusted P value=.07). Among patients with PIK3CA mutations but without PTEN expression, median survival was 4.6 months for those assigned to cetuximab and 3.5 months for those assigned to placebo.

“This study was limited by the small size of the original clinical trial, as well as by the fact that specimens were not available for all the patients, so the results are of borderline statistical significance,” Burtness said. “But if these data are corroborated in larger cohorts of cetuximab-treated patients, they would suggest that PTEN loss together with PIK3CA mutation could serve as a signature to identify patients who will not benefit from cetuximab therapy as it is currently given. The advent of PIK3 inhibitors could give us a new treatment strategy for these patients, potentially in combination with cetuximab.”