Doctors have long assumed that, if a woman’s breast cancer recurred, it would return with the same receptor status. New research presented at the American Society of Clinical Oncology’s 44th Annual Meeting, shows that a fairly high proportion of recurrences—28 percent—had changes in receptor status: estrogen, progesterone, or HER2.

Interestingly, doctors said that most women do not get additional biopsies for relapsed or metastatic breast cancer. This new information, though, suggests that all new cancers should be biopsied, as changes in receptor status can mean significantly different treatment. For example, if you had been estrogen and progesterone negative, doctors would not treat you with hormone therapy such as tamoxifen. If cancer returns as positive for either estrogen or progesterone, such therapy could be beneficial. Likewise, if you were originally estrogen and progesterone positive and your cancer returned as negative, hormone therapy would not help.

The research was done on tissue samples of women in British Columnia who had relapses between 1986 and 1992.

Forty-five of the original 160 samples showed some type of change. Of these, 11 were local recurrences—at the site of the original tumor—and 34 were regional or distant relapses—in other parts of the body. Of the 34 regional or distant relapses:

11 changed from ER/PR positive to ER/PR negative
14 changed from ER/PR negative to ER/PR positive
3 changed from HER2 negative to HER2 positive
6 changed from HER2 positive to HER2 negative.

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