Radiofrequency Ablation of a Stereotactically Localized Nonpalpable Breast Carcinoma

Robert L. Elliott, M.D., Ph.D.,* Pamela B. Rice,* L.R.T.R.M, Joe A. Suits, R.N., O.C.N,* Alan J. Ostrowe, M.D.^, Jonathan F. Head, Ph.D.*

From *The Elliott-Elliott-Head Breast Cancer Research and Treatment Center ^and Pain Management Services, Baton Rouge, LA

Minimally invasive diagnostic techniques are well accepted for breast masses and mammographically detected nonpalpable lesions. Core biopsy under local anesthesia of palpable masses and image-guided stereo-tactic or ultrasound biopsy of nonpalpable masses or calcifications seen on mammograms are now routine diagnostic procedures. Increased use of mammography has resulted in more cancers being detected earlier at a much smaller size; thus less invasive therapeutic surgical procedures are being done. Lumpectomy with or without postoperative radiation is now common practice, and with the evolution of sentinel node biopsy even less violation of the axilla for staging may be done in the future. Recently Jeffrey et al. have reported on ultrasound-guided radiofrequency ablation of locally advanced breast cancer under general anesthesia, and Dowlatshahi et al. have reported on stereotactically guided laser therapy of occult breast tumors. In the present communication we report a case of stereotactic localization and radiofrequency ablation of a nonpalpable invasive ducal carcinoma under local anesthesia. The mass was detected by screening mammography and its pathology was confirmed by stereotactic core needle biopsy. This is the first reported case of radiofrequency ablation of a nonpalpable breast cancer by stereotactic technique. This case is the first in a prospective study under the protocol presented in this communication.

Case Report

The patient is a 71-year-old woman who has been coming to the Elliott Mastology Center Breast clinic for breast screening since January 20, 1976. On October 31, 2000 she came for her routine annual mammogram, and there had been an interval change showing a small spiculated and irregular density (1.6 cm) inferiorly in the left breast (Fig. 1). That same day a stereotactic core needle breast biopsy was performed at our office (Fig. 2). Histologic examination revealed invasive ductal carcinoma (Fig. 3). Immunohistocytochemistry was done on the core specimens for estrogen receptors, progesterone receptors, and HER2/neu protein, and they were reported as positive, negative, and negative respectively. The patient’s physical examination was unremarkable, there was no local regional lymphadenopathy, and routine staging revealed no evidence of systemic disease. After numerous consultations about her options for therapy the patient elected and signed an Informed Consent Form to have radiofrequency ablation of her lesion before excision of her tumor (protocol MRI 200002; see Table 1). On November 15, 2000 the patient was placed on a Lorad stereotactic table (LORAD, Danbury, CT), and under local anesthesia and intravenous sedation she had a 12-guage 16-cm-long RITA StarBurst WL radiofrequency ablation probe (RITA Medical Systems, Mountain View, CA) was inserted through the Bard cannula and the nine arrays were deployed to 3cm through the tumor. After the position of the electrode was confirmed by X-ray (Fig. 5) the tumor was ablated with a RITA model 1500 generator at an average temperature of 75 degree C for approximately 20 minuets with the maximum power set at 25 W (Table 2). After a 30-second cooldown the peripheral temperature of the four peripheral thermocouples ranged from 58 degree C to 70 degree C. The patient experienced no pain of discomfort. She was observed in the office for one hour after the procedure and was discharged with a small dressing, surgical bra, and ice pack. When she was examined on week later there was a slight swelling of that area. The patient’s mediolateral mammographic view of the breast showed the tumor to be much smaller with very little reaction mammographically (Fig. 6). A week later she was examined and her left breast had a little more induration and tenderness in the lower quadrant, which was the area of radiofrequency ablation. There were no skin changes. On December 13, 2000 the patient came to our clinic and had needle localization of the surgical area that had previously undergone radiofrequency ablation and placement of a surgical clip (Fig. 7). She then had a segmental mastectomy for this lesion as an outpatient at the hospital. The specimen was inked by the pathologist and specimen radiography performed (Fig. 8).
Then the specimen was sectioned and photographs were taken of the gross specimen sections (Fig. 9). Multiple sections were taken for histology and no viable tumor was identified (Fig. 10). The margins were clear. The patient’s postoperative course was uneventful. She was placed on anti-estrogen therapy. Annual follow up is planned.

Discussion

The ablation of nonpalpable breast cancer lesions without surgical removal is an idea that has previously been unobtainable. Two techniques had to be developed and united for this procedure to be successful. One technology that has been developed over the last decade is stereotactic localization of a breast lesion followed by exact (i.e., within 1 mm) placement of a biopsy needle. The second required method is the ability to ablate a tumor by using either cooling or heating, or laser. Jeffrey et al. have reported on five women with advanced invasive breast cancer whose tumors were treated with radiofrequency energy, and this resulted in cancer cell death. Dowlatshahi et al. have reported on laser ablation of stereotactic localized mammographically detected breast cancers. The conditions for laser ablation are still being evaluated as the present procedure only achieves complete necrosis of tumors in 66% of patients.

In the present case report we have combined what we think are the best aspects of the two recently reported studies: stereotactic localization of the breast lesion and radiofrequency ablation. The stereotactic method allows a very quick and accurate localization of the nonpalpable breast lesion under local anesthesia in an outpatient/officer setting, which was not done in the previously reported radiofrequency ablation technique. The radiofrequency method as presently developed seems superior to the laser ablation method because radiofrequency ablation destroyed all of the cancer cells in the ablated area in 80 per cent (four of five patients) of tumors as measured by NADH (nicotinamide adenine dinucleotide, reduced from)-diaphorase cell viability staining. Furthermore this occurred in tumors of greater size/volume than the tumors in the laser study.

The better tumor cell destruction rate that occurred with radiofrequency ablation as compared with the laser probe probably results from more even heating by the nine elongated heat sources of the extended radiofrequency probe compared with the focal heat source of the laser probe. The radiofrequency probe would result in more even heating of the tumor and especially radiation and convection of heat to the margins and beyond the margins of the tumor. Thermal damage to the cells of tissue begins around 41 degree C and when the tissue reaches 46 degree C the mechanism of cell and tissue death changes from apoptosis to necrosis. It is well accepted that 54 degree C is acutely lethal to cells; in the two previous studies a maximum temperature of 70 degree C was achieved in the previous radiofrequency ablation procedure and a temperature of 60 degree C was sustained in the laser procedure. In the present study using stereotactic radiofrequency ablation the temperature within and surrounding the lesion was sustained at between 58 degree C and 70 degree C.

There are further advantages to the present procedure. The procedure reduces the morbidity associated with open biopsy as it only resulted in two needle scars and minor induration after 4 weeks. Also there were no major side effects with little pain during or after the procedure and no drainage. This procedure is also suitable for small nonpalpable tumors that cannot be visualized by ultrasound, which was a shortcoming of the Jeffery et al. procedure. Additionally this is a very cost-effective procedure in that it is done without general anesthesia in an outpatient/office setting.

The future of stereotactic localization followed by radiofrequency ablation of nonpalpable breast cancers is very promising. Further studies need to be done to work out the many details of the procedure and to determine the maximum size of the lesion that can be completely ablated by radiofrequency. The minimum temperature and for what maximum period of time-which we believe to be 60 degree C for 20 minutes-must be confirmed or adjusted higher if viable residual tumor is later demonstrated. Also we believe there is a limit to the maximum temperature that the patient will tolerate under local anesthesia, and sedation must also be determined. However, we believe that when these details are worked out stereotactic radiofrequency ablation will be a viable curative procedure for minimal breast cancer.

Acknowledgement

This work was supported by funds from The Breast Foundation (Baton Rouge, LA).

References

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