The Walls St. Journal published a story this morning, â€œBad Cancer Tests Drawing Scrutinyâ€ that detailed how â€œthousands of breast-cancer patients may be getting the wrong treatment because of errors in two laboratory tests widely used to determine which drugs are prescribed.â€
The reporter was referring to the tests pathologists use to determine a tumorâ€™s HER2 and hormone receptor status. These tests are important because only tumors that are HER2-positive will respond to the drug trastuzumab (brand name Herceptin) while only those that are estrogen receptor (ER) and/or progesterone receptor (PR) positive will respond to hormone therapy.
The article mentions â€œrecent studiesâ€ that found that these tests are not always accurate. However, none of the studies are really that new. In fact, none of this is really â€œnewsâ€ at all. Oncologists have known about this problem for years.
Iâ€™m not really sure why this story is coming out now. I find it more of a scare story to alert people to the standard of care. It is true that, as the article says, these laboratory tests are not always accurate. Weâ€™ve known for some time that these tests are accurate about 80 percent of the time. This is also true about x-rays, doctor’s diagnoses, recommendations for surgery, pathological diagnosis, etc. Medicine is rarely about 100 percent certainty. Not only are all medical tests wrong sometimes, but there is no quality control on most procedures, other than mammography
Having said that, it is true that, as the article points out, there is no external quality control for these tests, and that any lab can start doing them, regardless of how much experience they have. Moreover, as we increase our understanding of the different types of breast cancer and begin to develop treatments for each of them, we are undoubtedly going to rely more and more on the use of complicated tests to determine which targeted therapies are needed to treat each tumor type. This means it will probably be necessary to develop some controls and standards for these tests that address who performs them and how.
Until then, I would encourage women to ask for second opinions on their pathology and test results if there is any question about their tumor type. Most likely, this will be women whose tumors are found to be ER, PR and/ HER2-negative. For them, re-testing may be important as it could mean they have another treatment option.