Megan Brooks

April 21, 2015

PHILADELPHIA — The number of breast cancer cases in American women is expected to jump 50% by 2030, according to a study by researchers from the National Cancer Institute (NCI).

The increase is driven mostly by a marked increase in estrogen receptor (ER)-positive tumors and in the number of cases in women older than 70 years.

"The one silver lining is that we expect fewer ER-negative tumors, which include the most difficult-to-treat HER2-positive and triple-negative subtypes," Philip S. Rosenberg, PhD, a senior investigator in the division of cancer epidemiology and genetics at the Biostatistics Branch of the NCI, noted in a news release.

Nonetheless, managing this clinical burden will present a "huge challenge," he said.

Dr Rosenberg presented the findings here at the American Association for Cancer Research 2015 Annual Meeting.

The NCI team used data from the Surveillance, Epidemiology, and End Results (SEER) Program, population projections from the US Census Bureau, and mathematical models to forecast the number of breast cancer cases in the United States from 2011 to 2030. Such forecasts "could help the oncology community develop a proactive roadmap to optimize prevention and treatment strategies," they note in a meeting abstract.

After adjustment for potential confounding factors, they forecast that the number of new invasive and in situ breast cancer cases will increase from 283,000 in 2011 to 441,000 in 2030. "That's an increase of 50%," Dr Rosenberg noted during the press briefing. But he cautioned not to get "hung up" on this number. "There is a lot of uncertainty, and if you run some different models, you can get a range from 25% to 55%." The increase reflects, in part, the increasing population and better life expectancy of women.

Although the proportion of new breast cancer cases in women 50 to 69 years of age is expected to decrease from 55% in 2011 to 44% in 2030, the proportion of cases in women 70 to 84 years is expected to increase from 24% to 35%, the analysis shows.

It also suggests that the proportion of ER-positive invasive cancers will remain at about 63%, whereas the proportion of early ER-positive in situ cancers, most of which are detected through screening mammography, will increase from 19% to 29%.

"Important Predictions"

The increasing shift toward earlier-stage breast cancers being detected "creates major challenges for how we deal with in situ breast cancer. Are they all going to need to be treated? What will the criteria for treatment be?" asked Louis M. Weiner, MD, director of the Georgetown Lombardi Comprehensive Cancer Center in Washington, DC, who moderated the press briefing during which the data were presented.

In contrast, the researchers forecast that the proportion of ER-negative cancers, both invasive and in situ, will drop from 17% of all tumors in 2011 to 9% in 2030.

The reasons for this decline remain unclear, but there are "intriguing clues," Dr Rosenberg said. "For example, early age at first delivery in the absence of breast-feeding is a particularly strong risk factor for the early onset of ER-negative tumors. We know that in recent years, women have been delaying births and breast-feeding more often, both of which might partly explain the decline in this type of breast cancer," he explained in a news release.

Overall, this analysis provides a "powerful and important set of observations and predictions," said Dr Weiner.

"I think it is intuitively obvious that, as our population expands and our population ages, certain kinds of cancers would be more prevalent; that is sensible. We'd like to see a reduced incidence because we've developed more effective prevention strategies, but those have remained very difficult to identify in this population," he added.

This research was supported by the Intramural Research Program of the National Institutes of Health. Dr Rosenberg has disclosed no relevant financial relationships.

American Association for Cancer Research (AACR) 2015 Annual Meeting: Abstract 1850. Presented April 20, 2015.

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