Study queries ultrasound's role in breast cancer screening

Enthusiasm about ultrasound as a complementary tool for screening women with dense breasts may be exaggerated or even unfounded, according to an Italian radiologist speaking at the European Congress of Radiology.

Dr. Stefano Ciatto of the Centro per lo Studio e la Prevenzione Oncologica in Florence struck a pessimistic note with results from a new study of over 20,000 women.

The study concluded that ultrasound does help in finding some cancers missed by mammography in women with dense breasts but perhaps not enough to justify the exorbitant cost of routine use. Based on its results, researchers estimated the cost of routine complementary screening with ultrasound in dense breasts at more than Euro 25,000 per cancer detected.

Despite enthusiasm about ultrasound, evidence about the modality's value in terms of reducing mortality rates is lacking, pending the results of ongoing randomized controlled trials, Ciatto said.

"With ultrasound, it is possible to detect a few [additional] cancers at a very high cost. If you use ultrasound as a complement to mammography in your clinical practice, that is your personal decision, but it is not based on efficacy. There is no evidence to suggest that doing ultrasound in a woman with dense breasts will save her life," he said.

Ciatto's group studied 20,478 women who underwent mammography screening from 2000 to 2005. Of those, 7615 had dense breasts, per BI-RADS definitions, and were followed up with ultrasound. Many of the women with dense breasts were in their fifties, Ciatto said.

In the dense breast group, 35 additional cancers were detected by ultrasound following a negative mammogram. This figure was equivalent to about 18% of all cancers detected in the study. Most of the cancers detected with ultrasound were small and low grade, suggesting that ultrasound has value as a complementary tool in finding cancers at earlier stages, when potential for treatment is theoretically greater.

Radiologists blinded to the original mammography results then reviewed the mammograms in the 35 cancer cases, most of which were available. They found many cancers that had gone undetected in mammography due to errors in radiologists' interpretations.

The total number of cases found by ultrasound when the cancer was not visible in retrospect by experts on the screening mammogram was adjusted downward to 17, equivalent to just 9.3% of all cancers.

One downside of breast ultrasound is its false-positive rate of 2% to 3%. The biopsy ratio of benign to malignant findings is 10:1, which is incredibly high in comparison with the mammography benign to malignant screening biopsy ratio of 1:1, Ciatto said.

"With ultrasound, there is a lower threshold. You pick up a lot of things that may be nothing, and you still have to biopsy," he said.

Although ultrasound adds value, it comes at a high cost. It would be necessary to do 1300 ultrasound exams to find one cancer, according to the study. The cost per patient was Euro 22.95, but the cost per cancer detected was more than Euro 25,000.

"The cost is incredible. To the woman it is not very high, but the cost per cancer detected is five times the cost with mammography screening," Ciatto said.

The study demonstrated that many cancers picked up by ultrasound could actually have been detected on the original mammogram. This finding suggests the necessity for routine review of radiologists' interpretations, Ciatto said.

It also shows that ultrasound may not have value in all settings. It may prove to be more useful for following up mammograms done by radiologists who are less skilled in breast imaging. Clinical studies must account for skill level, he said.

"We should not use poorly experienced radiologists in mammography and help them with ultrasound. We should start with very experienced radiologists, which we don't do at the moment, and see whether ultrasound helps," Ciatto said. "I am not saying that ultrasound does not help at all, but we should not be too enthusiastic about the results."