NEW YORK (Reuters Health) - Some breast-cancer screening guidelines suggest that women who get certain abnormal results return early for their next screening, rather than immediately undergo additional testing. That practice, according a study by a Canadian research team, can lead to dangerous delays in diagnosing cancer.

The researchers found that women diagnosed with breast cancer more than 20 weeks after receiving their first suspicious screening results were more likely to have large cancers, or cancers that had spread, if the delay since their initial screening had been longer.

The finding indicates that putting off diagnosis, in addition to increasing patients' anxiety by prolonging their uncertainty, can result in cancer being more advanced by the time it's identified, according to the report in the in the April 15 issue of the journal Cancer.

"We confirmed that if [physicians and patients] wait on it, the cancer does grow enough that it may alter the prognosis," study coauthor Lisa Kan of the British Columbia Cancer Agency-Vancouver Island Centre, in Victoria, told Reuters Health.

Kan and colleagues from seven Canadian medical institutions pooled data from breast-cancer screening programs to identify several thousand women who had been diagnosed with breast cancer between 1990 and 1998 after getting suspicious screening results.

The researchers classified women according to how much time had elapsed between their suspicious screening and their cancer diagnosis.

They also noted which women had received abnormal, highly suspicious screening results and which had been diagnosed after getting results that were abnormal but less suspicious.

Different screening programs had recorded different types of information, so the researchers used various criteria to identify highly suspicious results. In some cases, for example, they counted screenings as highly suspicious if abnormalities cropped up on both a mammogram and a physical examination. In other cases, they deemed a screening highly suspicious if it was followed directly by biopsy.

Diagnosis of cancer in the group with low-suspicion abnormal screening results took 47 days on average--50% longer than in the group with more suspicious results. Because screenings that raise more red flags might be more likely to reflect advanced cancers, the researchers adjusted their data to take level of suspicion, or "suspicion bias," into account.

After this adjustment, delays longer than 20 weeks were associated with increasingly serious cancer. Compared with cancers diagnosed 4 to 12 weeks after screening, those identified 20 to 52 weeks later were 20% more likely to have spread beyond the breast, or metastasized. Those caught one to two years after screening were 2.2 times more likely--and those found two to three years later were 3.2 times more likely to have metastasized.

The chance that a diagnosed tumor was larger than 0.4 inches (10 millimeters) across also increased with the length of time between screening and diagnosis for delays longer than 20 weeks.

Suspicion bias made it impossible for the researchers to demonstrate whether delays shorter than 20 weeks also increased the risk that the cancer had grown or metastasized, but Kan told Reuters Health there is probably no "magic effect" that kicks in only after 20 weeks. Any delay, she said, could result in worse prognosis once the cancer is identified.

The current practice of proposing early follow-up screening after low-suspicion abnormal results is popular, in part, because giving biopsies to all women with suspicious mammogram results would result in many unnecessary procedures. Several available procedures that are minimally invasive would be good alternatives in low-suspicion cases, the study's authors write.

SOURCE: Cancer 2002;94.

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