Rates of breast cancer recurrence fell by half or more between the 1980s and the early 2000s - likely due to improved treatments and increased screenings, according to a new study from Canada.
The analysis of data on Canadian breast cancer patients offers reassurance that breast cancer survival is improving and also provides updated data to researchers, said the study’s lead author, Dr. Karen Gelmon from the BC Cancer Agency in Vancouver, British Columbia.
“It gives some contemporary numbers to people designing trials testing adjuvant treatments,” she said.
An earlier study, published in the 1990s and based on data from 1978 to 1988, found that women whose breast cancers fed off the hormone estrogen (so-called estrogen-receptor positive breast cancers) had a consistent risk of the cancer recurring over time. For breast cancers not driven by estrogen, recurrence risk was high for five years after successful treatment, but then dropped below the risk of those with estrogen-receptor (ER)-positive cancers.
In the new study, published in the Journal of Clinical Oncology, Gelmon's team compared data on 7,178 women treated for early to moderately-advanced breast cancer during two different periods: 1986 to 1992, and 2004 to 2008.
The researchers matched the cancer characteristics of each patient from the first period to a patient from the second period, including estrogen-receptor status as well as the presence of another protein on cancer cells, HER2.
The HER2 molecule helps drive cancer-cell growth. Tumors with HER2 tend to be more aggressive than HER2-negative ones, the researchers note.
Starting in the 1990s, drugs targeting molecules on cancer cells like HER2 became available. Together with improved early detection of less-advanced cancers, which gives such drugs a better chance of working, the targeted therapies have been credited with improving overall cancer survival
In the new study, the overall risk of breast cancer recurrence for women in the later group was about 50 percent lower than for women in the earlier group, for each year after being cancer-free.
Like the 1990s study, the new analysis found a high risk of recurrence within the first five years among women with cancers that were not driven by estrogen. Among women treated in the 2000s, that early increased risk was less dramatic, however.
Specifically, the risk of recurrence after one year was about 11 percent among women from the earlier period with cancers not driven by estrogen, compared to about a 6 percent risk among women with the same type of cancer in the later period.
“It showed we were doing better, but the peaks are still there,” Gelmon said.
The researchers also found that HER2-positive cancers saw some of the greatest reductions in recurrence risk.
For example, the risk of recurrence in the second year of being cancer-free among women whose tumors were HER2-positive and ER-negative fell from about 23 percent in the earlier period to about 9 percent in the most recent period.
The new study can't show why recurrence rates improved, but the researchers say it’s most likely a result of screening leading to early detection and more “comprehensive and appropriate” treatments targeting specific cancer types.
For example, they also saw large increases in the use of chemotherapy, and of drugs targeting estrogen-driven cancers, among the most recent patients.
Drugs targeting HER2-positive cancers were not available in the earlier time period.
“I think the most important thing is (the study) validates all these things we’ve been doing all these years,” said Dr. Marleen Meyers, an oncologist and breast cancer expert at the NYU Langone Medical Center’s Perlmutter Cancer Center in New York City.
Meyers, who wasn’t involved in the new study, also called the findings reassuring.
“I think we continue to learn,” she said. “I think this is very good, very positive information for women.”
SOURCE: bit.ly/1vOlzpm Journal of Clinical Oncology, online November 24, 2014.
