Women who have seemingly beaten breast cancer may still be at risk for the cancer’s unceremonious return decades later, according to a new study.
This year, an estimated 246,660 women in the US will be diagnosed with breast cancer, which currently ranks as one of the most common causes of cancer deaths in American women. Breast cancer takes on different forms, and estrogen receptor-positive is the most common type in which estrogen hormone fuels the growth of the cancer cells. Standard treatment for this type of breast cancer involves tamoxifen or aromatase inhibitors, which block the effects of estrogen.
But can breast cancer return after treatments have proven successful? For a long time, doctors knew that breast cancer was prone to coming back. That’s why the standard protocol for estrogen receptor-positive breast cancer puts patients on five years of treatment. Although five years seems to be a long time for breast cancer treatment, the new study suggests it isn’t nearly enough.
The research team analyzed data from nearly 63,000 women with estrogen receptor-positive breast cancer, from 88 clinical trials. All the patients had received tamoxifen or aromatase inhibitors therapy, and were clear of breast cancer at the five year point. But the cancer wasn’t gone for good.
Over the next 15 years, the cancer resurfaced. "Even though these women remained free of recurrence in the first five years, the risk of having their cancer recur elsewhere (for example in the bone, liver or lung) from years five to 20 remained constant," said Daniel F. Hayes, a Stuart B. Padnos Professor of Breast Cancer Research at the University of Michigan Comprehensive Cancer Center, and the study’s senior author.
The team could correlate the risk of recurrence with the original tumor size and severity. That is, those with large tumors that had spread to the lymph nodes had the highest risk (40 percent) of seeing the cancer again. Those with small, confined tumors had the lowest risk (10 percent) of recurrence.
"It is remarkable that breast cancer can remain dormant for so long and then spread many years later, with this risk remaining the same year after year and still strongly related to the size of the original cancer and whether it had spread to the (lymph) nodes,” said Hongchao Pan, the study’s lead author, from University of Oxford.
Should breast cancer patients continue taking medications for an additional five years, ten years? While some studies have found longer remission associated with longer therapy length, the answer will likely be complicated and dependent upon each patient’s profile.
"As we look at extending endocrine therapy for 10 years, we wanted to determine whether there were certain subgroups of women whose risk of recurrence was so low they might not need to continue endocrine therapy after five years," said Hayes.
Furthermore, patients and physicians must also weigh the risks of side effects with extending the duration of treatment. Aromatase inhibitors and tamoxifen are associated with severe side effects, such as nausea, vomiting, pain and weakness. In addition, because the drugs affect the estrogen, women may experience hormonal changes, such as hot flashes, weight change, and hair loss.
Additional sources: BBC