An interval cancer may be defined as a breast cancer diagnosed in a woman presenting with symptoms within one year of a negative screening mammogram. It is therefore crucial that interval cancers be reviewed by the radiologists responsible for a breast-screening programme. Based on a study of 231 false-negative screenings, Hofvind and colleagues characterized interval cancers as: “missed,” where cancer was clearly present in the screening mammogram (35%); “minimal sign,” where subtle or slowly developing signs were present (23%); and “true negative” in 42% of cases.
In an effort to reduce the incidence of false-negative findings during routine mammography screening, radiologists at the University of Münster in Germany employ a strategy of dual diagnosis: each mammogram must be separately read by at least two radiologists. As Dr Walter Heindel emphasized, “Two pairs of eyes are better than one, and this method gives at least a 15% increase in tumour detection rates compared with just one doctor.”
In an effort to explore strategies for increasing cancer detection rates, Dr Katrina Korhonen reviewed true-positive and false-negative results when employing digital breast tomosynthesis (DBT) as a screening modality. She and her colleagues at the University of Pennsylvania have just published their findings in RadioGraphics, in which they reported examples of cancers that were occult in full-field digital mammography (FFDM) but were diagnosed with DBT. However, there were occasions when both the DBT and FFDM images were initially interpreted as negative (see above right, © RSNA), and a patient-requested ultrasound (see above left) revealed an intermediate grade ductal carcinoma.
The authors acknowledged, “Although the false-negative rate of DBT screening is less than that of screening with FFDM alone, some cancers are still difficult to detect or nondetectable with DBT.” This begs the question: Would not the solution to the false-negative conundrum be addressed by combining FFDM with automated breast ultrasound (ABUS) – such as CapeRay’s Aceso system – or even combining DBT with ABUS?