Radiology's role grows in biopsy decisions, procedures

December 3, 2004

In the not-too-distant future, a woman might undergo a screening mammogram, an image-guided biopsy, and percutaneous treatment of cancer, all in the same day. Breast imaging experts are moving toward such a scenario with incremental improvements in the accuracy and efficiency of image-guided biopsy. In the past decade, the less invasive, more cost- and time-effective procedure has proved to be just as accurate as surgical biopsy.

In the not-too-distant future, a woman might undergo a screening mammogram, an image-guided biopsy, and percutaneous treatment of cancer, all in the same day. Breast imaging experts are moving toward such a scenario with incremental improvements in the accuracy and efficiency of image-guided biopsy. In the past decade, the less invasive, more cost- and time-effective procedure has proved to be just as accurate as surgical biopsy.

"Our patients accept the option of having a needle biopsy versus surgery almost all the time when the two are discussed," said Dr. Frederick Margolin, director of the breast health center at California Pacific Medical Center in San Francisco. "Our clinicians believe that the data and results are so good that we now just schedule patients ourselves for the biopsy without going through the clinician."

The choice of image-guided biopsy over surgical biopsy may be relatively easy, but practitioners must also choose the modality to be used. MR is gaining ground in image guidance, thanks to the advent of MR-compatible vacuum-assisted biopsy devices.

"This technology continues to develop and is becoming available to many more centers," said Dr. Alexis Nees, a clinical assistant professor of radiology at the University of Michigan. "As the number of screening and diagnostic breast MRIs performed increases, lesions will be identified that can only be seen on MRI."

Dr. Laura Liberman, an attending radiologist at Memorial Sloan-Kettering Cancer Center, was the lead author of a study presented at the American Roentgen Ray Society meeting in May. Her group found MR-guided vacuum-assisted biopsy successful in 87% of 38 lesions biopsied.

In another study presented at the ARRS meeting, Dr. Constance Lehman, director of breast imaging at the University of Washington, Seattle, reported a 100% successful biopsy rate of 38 lesions, using MR-guided vacuum-assisted biopsy.

And in a study published in the September issue of Radiology Clinics of North America, Dr. Wendie Berg, a breast imaging consultant, compared the success rate for MR-guided biopsies with those of ultrasound and stereotactic biopsy. She reported success rates across several series of 95% to 99% for MR-guided percutaneous biopsy.

"With any new imaging technique, the site offering the imaging should be prepared to perform a biopsy guided by that technique. Every center that performs breast MRI should have a formal arrangement with a radiology practice capable of performing MR-guided biopsies," Berg said.

Despite the interest in MR-guided biopsy, ultrasound and stereotactic imaging continue to be used in hospitals across the nation. Community clinics may find the cost of MR prohibitively expensive for routine imaging and biopsy procedures.

Ultrasound remains the most useful and cost-effective imaging modality, provided the lesion can be seen sonographically, said Dr. Laurie L. Fajardo, chair of radiology at the University of Iowa. Improvements in ultrasound equipment and growing experience with the modality have made more lesions amenable to ultrasound biopsy.

"High-volume MR scanning is not done in our facility. There are cost limitations; many of our patients are underinsured," said Dr. Tommy E. Cupples, director of breast imaging at the South Carolina Comprehensive Breast Center. "The MR scanner is not in the breast center at our facility; it's in the main hospital, where the schedule is cramped. We've found that with careful use of mammography, digital mammography, and ultrasound, we haven't had to resort to MR."

Biopsy equipment that can be used with all three imaging modalities has great potential, according to Dr. David Dershaw, director of breast imaging at Sloan-Kettering.

"Being able to use the same piece for stereotactic, sonographic, and MR-guided biopsy would be cost-effective for facilities and easier for training people," he said.

HITTING THE BULL'S-EYE

Regardless of the imaging modality used, the ongoing quest is to improve accuracy and determine the best way to biopsy particular lesions.

One method for boosting accuracy is to x-ray tissue taken in a stereotactic core biopsy to ensure that it contains the previously targeted calcifications. Using cores without such calcifications increases the chance of missing malignant lesions, according to a report published in Radiology (2004 Oct;233[1]:251-254).

"Our study indicates that you haven't done the biopsy satisfactorily if you have retrieved cores without calcifications," Margolin said.

In a retrospective study, Margolin and colleagues examined 113 patients who had undergone vacuum-assisted 11- or 14-gauge-needle stereotactic core biopsy for calcifications. They sent cores with and without calcifications to pathologists. Eighty-four percent of the cores with calcifications led to final diagnoses of malignancy, compared with 71% of the cores without calcifications. Furthermore, 11% of cores without calcifications led to missed cancers, compared with only 1% for cores with calcifications.

Dense breast tissue can also be a barrier to accurate biopsies. The use of radio-frequency energy enables physicians to easily penetrate dense connective tissue and better target lesions, according to another study in Radiology (2004 Jul;232[1]:205-210).

Instead of "cooking" cancer tissue, as it does in ablation mode, RF can be used to cut through dense breast tissue. This provides better access to the lesions, said lead author Dr. Nathalie Duchesne, head of breast imaging and intervention at the Ottawa Regional Women's Breast Health Center in Montreal.

Duchesne and colleagues examined the utility of an RF introducer developed by SenoRx, along with a handheld ultrasound-guided breast biopsy system, in three institutions between September 2000 and June 2001. (Duchesne is a shareholder of SenoRx.) Of 99 patients, 50 were randomly assigned for breast biopsy with the handheld system only, while 49 were scheduled for the RF introducer. The researchers found no significant differences in procedure time for the two groups, and average pain was comparable for both.

In terms of penetration, however, the RF group had a mean score of 1.6 on a 5-point scale (with 5 being extremely difficult), compared with 2.4 in the control group. The ease of penetration with RF increased in patients with dense breast tissue, with a mean score of 1, compared with 2.9 for the control group.

RIGHT TOOL FOR THE JOB

Selecting the right needle size for the appropriate lesion type is essential for accuracy and efficiency in image-guided breast biopsy. Doctors at Sloan-Kettering, where about 300 MR biopsies are performed every year, do not use 14-gauge MR biopsy needles because of problems with lesion sampling, accuracy of sampling, and underestimation, said Dr. Elizabeth Morris, director of breast MRI.

Imagers at the center do use 14-gauge needles for ultrasound, although ultrasound vacuum devices are available if needed. For stereotactic biopsy, they uniformly use the vacuum-assisted device and primarily use 11-gauge needles, although they are moving toward the 8-gauge system.

"My algorithm is you don't shoot ducks with a rifle, you use a shotgun," Cupples said. "But if you have a large, discrete lesion, then you can be a minimalist and take a couple of true cut cores."

Fourteen-gauge needles are needed for ultrasound biopsies of masses because they can generate enough tissue to produce a pathology result. Many radiologists, Morris said, do not see the need for vacuum-assisted ultrasound biopsy unless the goal is lesion removal or increased assurance that the right area was biopsied.

"In my own experiences, sometimes up to 20 procedures a day, most of us are using 14-gauge needles for small masses. We do very little fine-needle aspiration, as we don't have the pathology support," said Dr. Ellen Mendelson, chief of breast imaging at Northwestern University.

CLIPPING THE ISSUE

Clipping is a topic that does not often come up in the medical literature, according to breast imaging experts, but many of them do it on a regular basis.

"We tend to be very liberal using clips. If there has been a problem related to placing a clip, it's because we didn't place a clip and wish we had," Cupples said.

Placing a clip in the biopsied area is important when chemotherapy is to be administered before excisional surgery, because the breast mass may disappear and the clip will serve to remind imagers where the biopsy was done.

Clipping has no real downside, and it may even become standard, Cupples said.

"Imagine a scenario where a biopsy comes back benign. You've placed a clip in during the biopsy. A year or two later, somebody sees a nodule during a screening. If they see a clip in there, they will immediately know it's been biopsied. Women are fairly mobile and sometimes they don't remember their imaging history. A clip serves as a permanent record that a biopsy was performed," he said.

According to Dershaw, it would be helpful to have a localizing clip that is usable with all three kinds of imaging modalities. A variety of materials could be used.

Clips used to be primarily made of stainless steel but are now often made of titanium, according to Mendelson. Manufacturers made the change because steel causes susceptibility artifacts on MR imaging.

"This has been a function of robbing Peter to pay Paul," Dershaw said. "When you increase the advantage you have under one modality, you reach a compromise under the other one. If you could get one that you could nicely see and accurately place, it would be great. Accuracy is not too bad under sonography, but it's more chancy under MR and stereotactic."

COMPLETING THE PICTURE

Image guidance methods, clipping, and increased accuracy are steps toward providing breast cancer care as efficiently and accurately as possible. But the picture isn't complete without consideration of lymph node biopsy, Dershaw said.

While physicians can aspirate and even core lymph nodes, biopsying them requires that the entire node be excised.

"Once we get the technology done for this safely, we can make it possible to totally treat the patient for breast cancer percutaneously. That has been the progression of the research. It would be nice to have the capability to start with screening mammography and end the day with a complete treatment of cancer. But to do this, we need to treat the axilla and the breast," Dershaw said.

In a study presented at the ARRS meeting, researchers from the University of Michigan and the University of Vermont/Fletcher Allen Health Care reported on sonographic evaluation and ultrasound-guided fine-needle aspiration of axillary lymph nodes in patients with newly diagnosed cancer. In the retrospective study, they examined 113 axillae in 110 patients over a 24-month period from 2000 to 2001.

"Our study demonstrated that the sensitivity of USFNA is 92% and the specificity is 100%. Abnormal axillary ultrasound and USFNA positive for metastatic disease may identify patients who can proceed with full axillary dissection. This could obviate initial sentinel lymph node sampling in these patients and possibly spare the patient a surgical procedure," Nees said.

Nees was scheduled to present new material on the subject at the RSNA meeting in November.

"The integration of multiple imaging and diagnostic modalities is critical for optimal patient care. It is a very exciting time in the field of breast imaging, as we have so many sophisticated tools to bring to bear on the problems of both screening and diagnosis," Berg said.