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Dartmouth Cancer Investigators Help National Cancer Institute Present Statistics in More Understandable Ways

February 03, 2015
Lebanon, NH

The difference between survival and mortality is important to patients and policy-makers

Three papers in the survival monograph published by the Journal of the National Cancer Institute, co-authored by Dartmouth's Norris Cotton Cancer Center investigators Steven Woloshin, MD, MS, and Lisa Schwartz, MD, MS, aim to help doctors, patients, and policymakers better understand cancer prognosis and survival.

"Survival statistics are deceptively simple – explaining the concepts clearly for the general public is the big challenge," said Drs. Woloshin and Schwartz.

In the first paper, "When Do Changes in Cancer Survival Mean Progress? Insight From Population Incidence and Mortality," first author Hyunsoon Cho, PhD, explained that the statistics most people see about cancer, such as those used to judge whether we are making progress against cancer, are easily misunderstood. "Increasing survival sounds like good news, decreasing survival sounds like bad news. But the story is more complicated," Cho said. Improved survival represents progress when it is accompanied by a decreased burden of disease: fewer people being diagnosed or dying from cancer. But improved survival can also occur even when disease burden is increased. Cho's paper is written to help people know how to use and interpret survival statistics.

To explain another area of common misunderstanding, Nadia Howlander, PhD, wrote "Providing Clinicians and Patients with Actual Prognosis: Cancer in the Context of Competing Causes of Death," . The paper differentiated between "cancer prognosis," which isolates the effect of cancer on the chance of surviving, and "actual prognosis," which is a person's chance of dying from cancer, from other causes, or surviving.

"We encourage registries to report both kinds of prognosis," said Howlander. "Cancer prognosis statistics are useful for researchers and policy makers because they clarify whether increased survival among cancer patients reflects improvements in the prevention or treatment of cancer versus the prevention or treatment of competing causes of death, such as cardiovascular disease.  Actual prognosis is useful because it estimates what is likely to happen to individuals diagnosed with cancer."

In the third paper, "Cancer Survival: An Overview of Measures, Uses, and Interpretation," Angela Mariotto, PhD wrote that, "In common usage, survival and mortality are two sides of the same coin: a person is either alive or dead. But in cancer statistics, survival and mortality are two sides of different coins." Early diagnosis, over diagnosis, and genuinely longer survival may all have an effect on cancer statistics.

Cancer and actual prognosis can differ a lot, especially as people get older and have other serious health problems that may cause death before the cancer. The Dartmouth team, led by Woloshin and Schwartz, says it is important for clinicians, patients, and communicators to understand how to use and interpret common cancer survival statistics to help guide both individual and policy-level decision making.

The National Cancer Institute is adopting the formats developed by Woloshin and Schwartz for use in presenting survival statistics on their website.

The Woloshin and Schwartz team research cancer at Dartmouth's Norris Cotton Cancer Center and the Dartmouth Institute; both are in Lebanon, New Hampshire. The work to prepare these papers was funded by the National Cancer Institute.

About Norris Cotton Cancer Center at Dartmouth-Hitchcock

Norris Cotton Cancer Center combines advanced cancer research at Dartmouth and the Geisel School of Medicine with patient-centered cancer care provided at Dartmouth-Hitchcock Medical Center in Lebanon, NH, at Dartmouth-Hitchcock regional locations in Manchester, Nashua, and Keene, NH, and St. Johnsbury, VT, and at 12 partner hospitals throughout New Hampshire and Vermont. It is one of 41 centers nationwide to earn the National Cancer Institute's "Comprehensive Cancer Center" designation. Learn more about Norris Cotton Cancer Center research, programs, and clinical trials online at cancer.dartmouth.edu.

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