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Breast Cancer Survival Rate Tied to Tumor Size

Posted on: Monday, 8 August 2005, 18:00 CDT

Much of the improvement in breast cancer survival in recent years is because the average tumor is smaller, not just because treatments are so much better, a huge new study has found.

Examining 25 years of cancer records nationwide, researchers concluded that smaller tumor size accounted for 61 percent of the improvement in survival when cancer had not spread beyond the breast, and 28 percent when it had spread just a little.

For women 65 and older with early stage tumors the most common scenario the shift in size accounted for virtually all of the improvement in survival.

"We don't in any way want to diminish the benefits we've seen from advances in treatment because they've been enormous," said lead researcher Elena Elkin. "But not all of the improvement in survival is due to treatment when important characteristics like size have also changed over time."

The study wasn't designed to determine the value of mammograms or treatments. But it implies much about the value of early detection. Mammograms have increased dramatically in recent years and are the chief reason that cancers today are detected sooner and smaller than they were in years past.

"This really helps to show the importance of screening," said Debbie Saslow, who heads breast cancer research at the American Cancer Society. "In addition to finding more small tumors, we're also finding less big tumors."

Saslow had no role in the study, which was being published Monday online by the society's journal Cancer and will be in its Sept. 15 print edition.

It was conducted by doctors at Memorial Sloan-Kettering Cancer Center in New York and used a federal government's database that includes cancer registries covering 10 percent of the U.S. population. More than 265,000 breast tumors were analyzed.

Survival has increased, but experts have argued over how much of that is because of better drugs or tumors being found at earlier stages. Two-thirds of breast cancers today are diagnosed at the local stage, when they're still confined to the breast; in the 1970s, only half were.

"Even within the same stage category, the average tumor size is smaller today than it was 25 years ago," Elkin said.

For example, the number of local-stage breast cancers that were smaller than 1 centimeter rose from less than 10 percent from 1975 through 1979 to 25 percent from 1995 through 1999. An inch is about 2.5 centimeters.

Of regional-stage cancers those that spread to nearby tissue or lymph nodes the portion that were smaller than 2 centimeters rose from one-fifth to one-third.

Next, researchers compared five-year survival rates for these time periods, taking into account the shift in tumor size.

For women with local-stage breast cancers, survival rose from nearly 91 percent to more than 97 percent, but was only 93 percent after adjusting for smaller tumors. Looked at another way, the shift in size accounted for 61 percent of the improvement in survival.

For regional cancers, survival rose from about 68 percent to about 80 percent, but was only 76 percent once tumor size was factored in.

On the Web

For more information, visit

New England journal: www.nejm.org

Cancer Society: www.cancer.org

National Cancer Institute: www.cancer.gov

Source: Columbian

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