Conference Coverage

PI3K inhibitor/fulvestrant has modest benefit, serious toxicity in breast cancer

 

Key clinical point: The PI3K inhibitor taselisib added to fulvestrant offered only modest benefit and significant toxicities in patients with advanced ER+/HER2- breast cancer.

Major finding: The combination of taselisib/fulvestrant extend median progression-free survival by two months.

Study details: Phase 3 randomized trial in 516 women with locally advanced or metastatic ER+/HER2- breast cancer.

Disclosures: The study was funded by F. Hoffman La-Roche. Dr. Baselga had disclosures related to GRAIL, Lilly, and Novartis, Infinity Pharmaceuticals, and Varian Medical Systems, PMV Pharma, and Juno Therapeutics. Dr. Burstein disclosed institutional research funding and speaker’s bureau activities for Novartis. Dr. Ma reported no relevant disclosures.

Source: Baselga et al. ASCO Abstract LBA1006.


 

REPORTING FROM ASCO 2018

CHICAGO – Is two months of progression-free survival worth it if those months mean living with serious side effects?

Dr. Jose Baselga of Memorial Sloan Kettering Cancer Center Neil Osterweil/ MDedge News

Dr. José Baselga

For women with advanced estrogen receptor-positive, HER2-negative breast cancer, the combination of the PI3K inhibitor taselisib and the selective estrogen receptor modifier fulvestrant (Faslodex) bought two additional months of PFS, compared with fulvestrant alone, but at the cost of serious toxicities in half the patients treated with the combination, results of the SANDPIPER trial show.

“These results are positive, but I think we all agree they are modest,” lead investigator José Baselga, MD, PhD from Memorial Sloan Kettering Cancer Center in New York, said at a briefing at the annual meeting of the American Society of Clinical Oncology.

The “challenging tolerability” of the combination led to frequent treatment discontinuations, and may have limited the clinical benefit of the combination, he said, but added that the study serves as proof of principle that PI3K may be a bona fide target in advanced breast cancer.


ASCO expert Harold Burstein, MD, from the Dana-Farber Cancer Institute in Boston agreed that PI3K “is a very appealing target. It’s a mutation that probably is the most common in breast cancer when you do genomic sequencing, and it arises in other tumors as well.”

He likened the study findings, however, to a key opening a locked door, only to find that there is a chain latch on the other side preventing entry.

In an interview, Dr. Burstein said that despite the best efforts of Dr. Baselga and others to find a suitable approach to targeting the PI3K pathway, the evidence to date suggests that it may not be an important driver of breast cancer.

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