Breast cancer receptor change may predict outcomes

Technical artifacts when testing receptor status in breast cancer complicate assessments of their potential ramifications on outcomes.

Dr. Lajos Pusztai

ER and PR status can change if you repeat the testing on the same specimen without any change in the actual marker status. In one "classic" study, the HER2 or ER status changed in 23% of samples after they were air-mailed from one center to another. You can’t conclude that it was the airplane flight that changed receptor status.

Similarly, in the current study, you can’t conclude that it was the chemotherapy that changed the receptor status, because part of this discordance is from the technical imprecision of the test. If a test is 90% accurate, for example, 10% of results on first testing will be "noise" and approximately 20% of results on repeat testing will be discordant.

The study also did not report the proportion of cases in which initial receptor status tests were conducted in one laboratory and the second test was conducted at a different center, as is often the case in the real world. That also introduces a very large, obvious cause for receptor discordance independent of therapy.

Dr. Lajos Pusztai is a professor of medicine and director of the Breast Medical Oncology Section at Yale University, New Haven, Conn. He made his remarks during a question-and-answer session at the meeting. Dr. Pusztai reported financial associations with BiPar Sciences/Sanofi, Bristol-Myers Squibb, Pfizer, AstraZeneca, Roche/Genentech, and Foundation Medicine.