CHICAGO – Is two months of progression-free survival worth it if those months mean living with serious side effects?
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 theshow.
“These results are positive, but I think we all agree they are modest,” lead investigator 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.