C. Kent Osborne, MD, Professor of Medicine and Molecular and Cellular Biology at Baylor College of Medicine and Director of the Lester and Sue Smith Breast Center at Baylor told The ASCO Post that this is “brand new” data that “looks very interesting.” He noted that groups for whom letrozole is the preferred antihormonal agent have already been established: those who are HER2-positive, have high proliferation rates, or have lower estrogen receptor levels. Published studies have shown that these factors predict for better outcomes with letrozole, he noted.

While the findings suggest yet another group might be added to this list, he cautioned, “This is an unplanned subset analysis, and there’s a hazard that you are getting the wrong answers. The findings should be confirmed in another dataset,” he maintained, “but do I believe the data? I think I do.”

Known Biology

Frankie A. Holmes, MD, of Texas Oncology in Houston, already foresees the information as “practice-changing,” she said. She also noted that the findings correlate with the known biology of this cancer subtype.

“We have always known that lobular patients are addicted to estrogen, especially the classic lobular type as in this study. They are not chemosensitive, and we know that letrozole is the superior means of reducing estrogen levels [among the antiestrogens]. It’s good to see some data, and it’s also good to see an orphan tumor type being addressed. Ten percent is a small proportion of patients with breast cancer, but it is a ‘significant small,’” she said. ■

Disclosure: Drs. Osborne and Holmes reported no potential conflicts of interest.