Estrogen Receptor Status May Determine Chemotherapy Use

The benefit of breast cancer chemotherapy may depend on the status of estrogen receptors lying on the surface of tumor cells, according to an analysis reported in the Journal of the American Medical Association (JAMA).

"Chemotherapy is helping [treat] estrogen receptor-negative tumors much more than estrogen receptor-positive," says study lead author Dr. Donald Berry, chairman of the department of biostatistics and applied mathematics at the M.D. Anderson Cancer Center.

That has been suspected for a long time, experts note, but this new analysis lends more credence to the theory.

Breast tumors are classified as either estrogen receptor-positive or negative, depending on cellular receptivity to the hormone.

"An estrogen receptor-positive tumor has lot of receptors for estrogen, and estrogen is the fuel that drives the breast cancer," explains Dr. Berry.

Typically, he says, women with cancers that have spread to nearby lymph nodes are given chemotherapy.

Those with estrogen receptor-positive tumors are also prescribed tamoxifen, which inhibits estrogen uptake by cancer cells.

Breast cancer is the most common cancer among women, except for nonmelanoma skin cancers, according to the American Cancer Society (ACS). The chance of developing invasive breast cancer at some time in a woman's life is about one in eight (13 percent of women).

It is estimated that in 2006, about 212,920 new cases of invasive breast cancer will be diagnosed among women in the US, states the ACS.

Carcinoma in situ (CIS) accounts for about 61,980 new cases each year. CIS is noninvasive and is the earliest form of breast cancer.

Breast cancer also occurs in men. Approximately 1,720 cases of invasive breast cancer were diagnosed in men in 2005. Breast cancer is the second leading cause of cancer death in women, exceeded only by lung cancer.

Chemotherapy a Plus for ER-Negative
Dr. Berry's team analyzed data from three clinical trials conducted over the past 20 years with a total of 6,644 patients.

The researchers found that 22.8 percent more estrogen receptor (ER)-negative patients were disease-free after five years if they got chemotherapy, compared with 7 percent of the ER-positive patients.

Improvements in survival were 16.7 percent for patients with ER-negative tumors, versus 4 percent for ER-positive.

Put another way, "one in six women with ER-negative are alive after five years because of the improvement in chemo," says Dr. Berry, whereas just "one in 25 women who are ER-positive are alive after five years because of the improvements."

Dr. Kent Osborne, director of the Cancer Center at the Baylor College of Medicine in Houston, calls the new analysis good news.

"This is a little bit stronger data than some of the earlier studies published a long time ago, which were sort of anecdotal series."

However, Dr. Osborne points out that, due to a lack of data, Dr. Berry's team "only looked at whether the tumor was ER-positive or ER-negative. There are degrees of being positive."

The new analysis should help women and their doctors make important treatment decisions, the experts say.

Benefit May Be Small for ER-Positive
"There is a growing body of evidence, and this is one, that suggests the chemotherapy benefit to patients in those with estrogen receptor-positive is much less," says Dr. Osborne .

"When patients are trying to decide whether to take chemotherapy or not, they need to be aware [that] yes, there may be a benefit, but it is likely to be very small if they are estrogen receptor-positive, particularly if they are strongly estrogen receptor-positive," he says.

Dr. Berry says, "It's a very clear decision to get more intensive chemotherapy for estrogen receptor-negative [tumors]. It is less clear for estrogen receptor-positive."

"About 60 to 65 percent of breast cancers are estrogen receptor-positive but it depends on age," says Dr. Berry. "The older the woman, the more likely she is to be ER-positive."

Always consult your physician for more information.