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Developed as a way to sample mammographic abnormalities in a potentially less invasive way, stereotactic technology has generated significant controversy. Speaking at the 11th International Breast Cancer Meeting in San Antonio earlier this year,
Developed as a way to sample mammographic abnormalities in a potentiallyless invasive way, stereotactic technology has generated significantcontroversy. Speaking at the 11th International Breast CancerMeeting in San Antonio earlier this year, Monica Morrow, MD, ofNorthwestern University Medical School said that some overly-enthusiasticradiologists consider stereotactic biopsy to be the techniqueof choice for almost all mammographic abnormalities, whereas sometotally disinterested surgeons believe there is no real role forthis technique. Dr. Morrow believes that the appropriate positionlies somewhere between these two extremes--"stereotacticbiopsy is an appropriate technique for a selected group of mammographicabnormalities."
The purported advantages of stereotactic biopsy include:
It can be performed rapidly
It is relatively painless
It avoids scarring, both externally (preserving the cosmetic appearanceof the breast), and internally (minimizing distortion at biopsysites on a mammogram).
Some maintain it is significantly less costly, but this may notbe completely accurate, Dr. Morrow said. In the larger contextof the treatment of breast cancer, some of the apparent cost savingsare lost, especially in cases where the stereotactic biopsy representsan additional step.
Opponents of stereotactic biopsy say that it is often not usefulfor treatment planning due to insufficient specimens, and false-negative/false-positiveresults.
The Beginnings: Fine Needle Aspiration
Fine-needle aspiration cytology was the initial stereotactic techniqueavailable. In the literature, typical results of this procedureyielded a sensitivity of 91%. Unfortunately, for a variety ofreasons, not the least of which is a lack of trained cytopathologists,the use of aspiration cytology never became widespread. One problemis the fact that aspiration cytology can identify a mammographicabnormality as benign, but can't specify the type of lesion. Furthermore,this procedure does not reliably distinguish invasive from insitu carcinoma, a major difficulty in planning treatment. Finally,any atypia on cytology requires biopsy, although only approximately20% will actually be cancer.
Core Needle Breakthrough
With the development of core needles that fit into the stereotacticbiopsy holder, the technique became much more appealing, Dr. Morrowsaid. As opposed to collecting a cytologic specimen, a core oftissue for histopathologic examination was obtained. The resultsof a core biopsy (confirmed by open surgical biopsy) generallyindicate a sensitivity in the upper 90% range.
One of the technical factors affecting the outcome of a core biopsyis needle size, with larger needles (commonly 14 gauge) providingbetter results. The number of specimens taken also influencesthe results. Many investigators are obtaining 10 cores as a samplingprocedure. To confirm the presence of calcification when thisis the indication for biopsy, the core specimen should undergox-ray. Also, whether or not lobular carcinoma in situ is classifiedas a malignancy will influence sensitivity.
Proponents of stereotactic core biopsy claim that it renders adefinitive diagnosis of benign abnormalities, eliminates the false-positiveresults seen with cytology due to atypia, distinguishes invasivefrom in situ carcinoma, and enables surgeons to perform a definitiveoperation armed with a diagnosis of cancer. However, many of theseclaims are debatable, Dr. Morrow said.
A review of the literature indicates that a core biopsy correctlydiagnosed ductal carcinoma in situ in only 70% of cases. (Allof the core biopsies were confirmed surgically.) Based on thislimited information, it appears that a core biopsy's ability toreliably identify ductal carcinoma in situ may be considerablyless than that reported for invasive carcinoma.
Furthermore, the information obtained from a core biopsy doesnot necessarily correlate with intraoperative findings. Althoughductal carcinoma in situ was detected using optimal core technique(a mean number of core samplings of seven per case with a large-gaugeneedle) in a study of 82 cases of cancer, 10% of the time invasivecancer that was not found by the biopsy core was identified onopen biopsy. In another 6% of cases, when simple invasive cancerwas identified on the biopsy core, an extensive intraductal componentwas found intraoperatively. In essence, there have been some difficultieswith the pathologic information obtained from the core biopsyand the ability to sample certain breast lesions.
Although one of the apparent advantages of a core biopsy is theavoidance of sampling the atypias seen with cytology, many ofthe atypical hyperplasias found on core biopsies actually werefound to be cancer on open biopsy.
The claim that being armed with a diagnosis of cancer somehowhelps a surgeon perform a lumpectomy more effectively has notbeen substantiated, according to Dr. Morrow. In a series of 239lumpectomies, 173 were performed as diagnostic procedures, and66 were performed with a cancer diagnosis obtained via fine-needleaspiration. The total positive margin rate was 5%. Therefore,regardless of whether or not there was prior knowledge of cancer,conservative lumpectomy as a single operation was effective 95%of the time.
Although many of the alleged benefits of the core biopsy havenot been confirmed, it is a useful procedure in certaincases. For example, to avoid open biopsy, Dr. Morrow may use corebiopsy for mammographic abnormalities that are suspicious butdeemed unlikely to be cancerous--lesions that, on mammography,have perhaps a 2 to 20% risk of being malignant.
In summary, Dr. Morrow recommends stereotactic core needle biopsybe considered for:
Relatively nonsuspicious breast lesions that are not clearly benign.
Women who are candidates for breast-conserving surgery but arefound to have other benign-appearing lesions elsewhere in thebreast.
Women who are candidates for mastectomy only.
As an alternative for women with significant co-morbidities suchthat open biopsy would be more hazardous than usual.