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Survival improved in HER-2–positive breast cancer patients treated with drug combination

Issue: January 25, 2012

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San Antonio Breast Cancer Symposium

SAN ANTONIO — Treatment with lapatinib plus paclitaxel improved survival in patients with HER-2–positive metastatic breast cancer, despite the presence of PTEN seromutations, data presented here suggest.

“The relevance of PTEN loss and PIK3CA on efficacy of lapatinib have been studied in both preclinical and clinical studies, but the results are not consistent across these studies,” Bing-he Xu, MD, of the Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College in Beijing, said during a presentation. “Further study of the relevance of these biomarkers is warranted.”

To evaluate the prognostic and predictive value of these markers in patients with HER-2–positive metastatic breast cancer receiving first-line treatment paclitaxel alone or in combination with lapatinib (Tykerb, GlaxoSmithKline), Xu and colleagues conducted an exploratory study of data from EGF104535, a randomized, double blind, placebo-controlled phase 3 clinical trial. They examined tissue samples from primary breast tumors in 274 patients who were randomly assigned to receive one of the two treatments.

Results indicated that 58% of all patients had PTEN loss, which also was well balanced between the two treatment arms. Sixteen percent of patients in the combination group and 10% of those in the paclitaxel-alone group had absence of PTEN expression, Xu said, whereas 28% and 34%, respectively, had PIK3CA seromutations.

Although data showed that survival outcome was independent of PTEN expression, PIK3CA seromutations were significantly associated with worse OS. Nevertheless, the researchers detected a chance of benefit for these patients in favor of combination therapy in terms of OS (HR=0.79) and PFS (HR=0.71). However, there was no significant difference between treatment arms, which may be attributed to the limited sample size of patients with PIK3CA mutations (n=35), according to Xu.

Lapatinib plus paclitaxel appeared to significantly improve PFS in both patients with PTEN loss or PTEN expression compared with paclitaxel alone. Patients with PIK3CA seromutations, however, did not significantly benefit from combination therapy vs. paclitaxel alone in terms of PFS.

“Our study demonstrates that PIK3CA seromutations were an adverse prognostic factor in this HER-2–positive metastatic breast cancer study population,” Xu said. “PI3K inhibitors combined with lapatinib should be considered in future studies in this population.”

Disclosure: Dr. Xu reports no relevant financial disclosures.

Earn CME this spring at the HemOnc Today Breast Cancer Review & Perspective meeting to be held March 23-24, 2012 at the Hilton San Diego Bayfront. See details at HemOncTodayBreastCancer.com.

For more information:

• Xu BH. #S3-3. Presented at: the 2011 CTRC-AACR San Antonio Breast Cancer Symposium; Dec. 6-10, 2011; San Antonio.

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