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Deaths From Cancer Surgery Must Be Properly Counted

In judging the progress against cancer, deaths from treatment and diagnosis must also be accounted for, report Dartmouth Medical School physicians in a new study.

The overall cancer mortality rate could increase by about one percent if all deaths within one month of cancer-related surgery were correctly attributed to the underlying cancer rather than the surgical procedure, suggest H. Gilbert Welch, M.D., and William C. Black, M.D. Their research appears in the July 17 issue of the Journal of the National Cancer Institute.

The calculation of cancer mortality depends on accurate determination of the underlying cause of death. The Dartmouth professors argue that cancer mortality should include deaths from treatment for cancer as well as deaths from the disease. They note, however, that clear guidelines for classifying treatment-related deaths in cancer do not exist.

"The more we look for cancer and the more we treat people with the diagnosis, the more important it will be to properly assign diagnostic and treatment-related deaths. Otherwise, observed mortality trends may make harmful interventions appear beneficial," say Welch and Black.

As a rule, researchers consider deaths within 30 days of a surgical procedure to be treatment-related when calculating mortality from the underlying disease. To determine if this rule is being applied uniformly to cancer patients, Welch and Black used national cancer registry data to find the reported cause of death in patients who, between 1994 and 1998, died within one month of cancer-related surgery to remove a solid tumor. Among the 4,135 deaths within one month of diagnosis and cancer-related surgery, 41percent were attributed to a cause other than the cancer.

The proportion of cases not attributed to cancer ranged from 13 percent for cervical cancer to 81 percent for laryngeal cancer. There is a trend toward increasing misclassification among those cancers, such as breast and prostate, for which early detection has increased substantially, the authors note.

If all deaths within one month of cancer-directed surgery were attributed to cancer, cancer mortality would rise by about one percent over current estimates in national trends, the authors say. They note that the proportion of deaths not attributed to cancer was highest during the period immediately following surgery. If all deaths in the year following cancer-directed surgery were attributed to cancer, then, according to the authors, the reported cancer mortality would increase from two to four percent.

Some deaths resulting from cancer-related surgery are not being properly attributed to cancer. "Although the estimated effect of this misclassification on overall cancer mortality is modest, it may be indicative of more widespread confusion about how to code treatment-related deaths of patients with cancer," the authors conclude.

They advocate steps to assure that cancer mortality remains a valid indicator of cancer progress and propose developing some rules, such as that all deaths within one month of surgery, radiation therapy or chemotherapy be attributed to the cancer for which the treatments were initiated.

Welch, DMS professor of medicine and of community and family medicine is with the Veterans Affairs Outcomes Group in White River Junction, VT. Black, DMS professor of radiology and of community and family medicine, is with the Norris Cotton Cancer Center at Dartmouth-Hitchcock Medical Center. Both are also affiliated with Dartmouth's Center for the Evaluative Clinical Sciences.

For more information, contact William Black at William.Black@dartmouth.edu.

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