The study included patients treated at Houston's M.D. Anderson Cancer Center between 1985 and 2001 who were cancer-free five years after initial treatment with surgery or surgery and radiation.
All had additional drug treatments, including chemotherapy and/or up to five years of therapy with the anti-estrogen drug tamoxifen.
Over the next decade after drug treatment, one in five of the women experienced a recurrence of her breast cancer.
"The risk of relapse was still small, but certainly not insignificant," M.D. Anderson breast oncologist and study researcher Abenaa M. Brewster, MD, tells WebMD. "I think these numbers are somewhat reassuring, but they also highlight the need for new [therapeutic] options for women who have completed five years of treatment."
Breast Cancer: Many Treatment Options
This year in the United States, roughly 180,000 women with a new diagnosis of breast cancer will face a myriad of choices about how to best treat their disease.
For most, that will include some form of drug treatment after surgery or surgery and radiation.
Prior to 2000, this often included five years of treatment with tamoxifen for postmenopausal patients with tumors that respond to hormone treatments.
These days, however, a newer class of estrogen-targeting drugs , known as aromatase inhibitors, is often recommended instead of tamoxifen for the treatment of hormone-sensitive breast cancers.
The newly published study included only a small number of patients treated with aromatase inhibitors, so the relevance of the findings for the majority of patients being treated today are not clear.
But they have obvious relevance for the millions of breast cancer survivors who did take tamoxifen -- usually for five years after initial treatment.
The study included 2,838 patients with stage I to III breast cancers treated with chemotherapy, tamoxifen, or both after their initial treatment.
Five years after all treatment ended, the risk of relapse was 7% in women treated for stage I disease, 11% in women treated for stage II disease, and 13% in women treated for stage III disease.
Among breast cancer patients who were still free of cancer five years after beginning drug treatment, 89% remained cancer-free five years after that and 80% remained cancer-free 10 years after ending treatment - 15 years after their diagnosis.
The study was made public Tuesday in the online issue of the Journal of the National Cancer Institute.
Good News for Some Patients
There was some good news in the study results for women who have breast cancers that do not rely on estrogen to grow.
These estrogen-receptor (ER) negative tumors are less common than hormone-sensitive tumors, and they are considered more deadly.
But the study showed that some women with ER-negative tumors who survived for five years after initial treatment actually had a better prognosis than women with hormone-sensitive tumors.
"These tumors are certainly more aggressive early on, but the outlook is good for women with these tumors who survive for five years," Brewster says. "We can now tell these women that their risk for developing a recurrence is lower than for women with ER-positive tumors."
American Cancer Society deputy chief medical officer Len Lichtenfeld, MD, tells WebMD that the findings highlight the benefits of treating ER-negative women with intensive chemotherapy.
"There has been some discussion about whether aggressive treatment makes a difference, and this study supports the view that it does," he says.
Lichtenfeld agrees that additional treatment options are needed for all cancer survivors, including those treated for estrogen-sensitive tumors who compete five years of hormone-targeting therapy.
"The jury is still out on what we need to be offering women who have finished five years of adjuvant treatment," he says. "What this study tells us is that these women still have a residual risk of recurrence that is significant."
By Salynn Boyles
Reviewed by Louise Chang
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