Laser Photocoagulation of Breast Cancer Shows Promise

OB/GYN News,  July 1, 2000  by Bruce Jancin

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DENVER -- The future looks bright for percutaneous laser photocoagulation of breast cancer, Dr. Steven B. Harms reported at the annual meeting of the International Society for Magnetic Resonance in Medicine.

The laser procedure is expected to offer a minimally invasive alternative to conventional surgical lumpectomy Instead of narcotics, the outpatient procedure requires only oral Xanax (alprazolam), local anesthesia, and post-treatment acetaminophen. Cosmetic deformity is rare, and patients can go back to work the next day, according to Dr. Harms, professor of radiology at the University of Arkansas, Little Rock.

The modality hinges on a type of high-resolution MRI called Rotating Delivery of Excitation Off-resonance (RODEO) to accurately show lesion margins before and during the procedure. This permits accurate tissue ablation, which spares the time and expense involved with conventional surgery in sending tissue specimens to a pathologist for determination of margin status.

During laser photocoagulation, the lesion is identified and localized. Then utilizing an MRI stereotactic system, as many as four 18-gauge needles are placed in the tumor. A laser fiber is inserted through each needle. The low-energy diode laser operating at 805 nm is applied for 10 minutes, gradually heating a section of tumor to the point of cell death. Serial RODEO MRI images are obtained every 1-2 minutes so the operator can see whether the ablation zone has extended beyond the tumor margins.

Dr. Harms and his coworkers have performed more than 3,000 RODEO breast MRIs, obtaining pathologic correlations via serial section mastectomy in more than 400 cases.

"We know RODEO MRI is accurate. We have about twice the sensitivity of mammography and about three times the specificity of mammography in the same cases," said Dr. Harms, adding that the negative predictive value is close to 100%.

In a pilot study, Dr. Harms reported on 30 patients with infiltrating breast cancers of 0.8-6.0 cm who underwent laser photocoagulation therapy The women subsequently had a lumpectomy or mastectomy permitting pathologic correlation between MRI indications of ablation success and cell death as determined by tissue staining with hematoxylin and eosin and proliferating cell nuclear antigen.

The average ablation zone was about 1 cm. Successfully treated zones marked by complete cell death closely matched MRI images in all cases. The only side effect was a minor skin burn due to photocoagulation of a rumor near the breast surface.

This treatment causes few or no cosmetic defects, Dr. Harms said, based on extensive experience using the same method to treat benign breast fibroadenomas.

One problem with the lasers is their potential to heat adjacent interstitial fat, which then flows to unwanted areas causing injury an outcome that can occur when too much laser power is applied, one meeting attendee noted.

The development of an interactive temperature control system would enable the operator to main tam a temperature of about 60[degrees] C in the ablation zone; at this temperature, laser interactions with adjacent tissue are minimized, Dr. Harms responded.

Others challenged the wisdom of developing a technique for treating malignancy that doesn't provide any information on margins.

Dr. Harms responded that even though pathologic studies indicate subclinical residual disease exists in roughly 40% of patients undergoing breast conservation therapy, the 20-year disease-free survival for patients with infiltrating breast cancer of 1 cm or less is greater than 90%. If laser photocoagulation proves about as effective as conventional surgery but with less morbidity, no deformity, lower cost, and less time missed from work, it will be much in demand.

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