US-Guided Mammotome Biopsy Allows Complete Excision

SEATTLE—Ultrasound (US)-guided Mammotome biopsy is both effective and safe for sampling breast lesions, Nathalie Duchesne, MD, a staff radiologist at the Hôpital du Saint-Sacrement, Quebec, said at the 101st Annual Meeting of the American Roentgen Ray Society (abstract 19). In fact, for most small lesions, the Mammotome permits complete excision of the lesion.

The low but persisting false-negative rate of core biopsy for small breast masses was a key impetus for the development of the Mammotome Breast Biopsy System (Biopsys Medical, Inc, Irvine, California), Dr. Duchesne said.

She and her colleagues prospectively studied the accuracy, feasibility, and reproducibility of the 11-gauge handheld Mammotome with ultrasound guidance for the sampling and removal of breast lesions. The Mammotome is inserted beneath breast lesions, whenever possible, and removes tissue by vacuum.

Eight Indications

The researchers chose eight indications for the use of the Mammotome: small lesions (less than 1.5 cm); lesions that were close to the pectoralis muscle or implants; lesions that would have been difficult to sample by core biopsy because of features such as fibrosis; heterogeneous lesions; intracystic solid masses; lesions suspected of being recurrent in situ carcinoma; lesions with discordant core biopsy results; and lesions for which the patient expressed a preference for Mammotome biopsy.

The Mammotome obtains impressively large tissue specimens that patients may find distressing, Dr. Duchesne cautioned. "We offer the patients virtual reality glasses for use during the biopsy," she said. "About half of the patients choose to watch the ultrasound procedure, and the other half choose to see a movie showing a panoramic view of Canada."

The 61 ultrasound-guided Mammotome biopsies done in the initial 1-year study period (August 6, 1999, through August 6, 2000) comprised 34% of all ultrasound-guided biopsies performed at the institution. The lesions ranged in size from 4 mm to 50 mm. Complete excision was achieved in 55% of all cases and in 77% of cases with lesions measuring 10 mm or less. A marker clip was successfully positioned within 1 cm of the biopsy cavity in 70% of cases.

When an additional 50 cases performed through January 2001 were included in the analysis, the complete excision rate increased to 59% overall and to 80% for lesions measuring 10 mm or less. Dr. Duchesne attributed these increasing rates to greater experience with the procedure.

"In the beginning, Mammotome biopsy was used mainly for diagnostic purposes," she said. "We just wanted to get a good sample of the lesion and did not aim to remove the whole lesion. As we started to become more comfortable with the procedure, we felt that we could remove the whole thing."

Immediate complications occurred in 10% of patients; these complications included skin defects and arterial bleeding, which was related to the nature of the lesion and not to the biopsy. Delayed complications occurred in 11% of patients; these included pain that was relieved with acetaminophen and hematomas measuring less than 2 cm that resolved without intervention.

The malignancy rate determined by Mammotome biopsy for the initial group of patients was 7%, but this rate increased to 13% by January 2001. "In the beginning, we weren’t very confident in biopsying the BI-RADS 5 lesions with the Mammotome," Dr. Duchesne explained. "But as we were getting better and better, we started biopsying them."

During the study, there was only one upgrade between the diagnosis on ultrasound-guided Mammotome biopsy (in situ carcinoma) and the subsequent diagnosis on surgery (invasive carcinoma).

Mammotome biopsy has several advantages over other breast biopsy techniques, Dr. Duchesne noted. Patients have less anxiety, and follow-up is simpler because the lesion has been completely removed. Physicians have greater certainty about the diagnosis because the entire lesion has been sampled. The procedure requires only a single needle insertion, and, because the Mammotome is positioned beneath the lesion, there is less concern that any cancer cells will be displaced during the biopsy.

Time is one disadvantage, she noted. Mammotome biopsy takes about 15 minutes, whereas core biopsy takes about 5 minutes. Greater cost is also a consideration at this point.

"I think the indications for Mammotome biopsy will have to be defined, compared with those for core biopsy," Dr. Duchesne said. Researchers in Canada have started a prospective, randomized, controlled study—the Multicenter Mammotome Ultrasound-Guided (MMUG) study—that will compare the indications for core biopsy and ultrasound-guided Mammotome biopsy.