The majority of breast cancers diagnosed in the United States are early stage tumors. Often, this results in breast cancers that are only detected on imaging and are not able to be felt by hand (nonpalpable breast cancers). Surgery will require localization of the tumor prior to removing the cancer in the operating room. This process is facilitated by placing a “clip” in the breast cancer at the time of the initial biopsy. On the day of surgery, a marker of some kind is used to identify this “clip” which allows the surgeon to determine the exact location of the cancer.
The most common method of localization has been the wire guided localization method; it is estimated that 80% of lumpectomies for nonpalpable breast lesions (breast lesions which cannot be felt by hand) use this technique. With this technique, the localizing wire is placed in the breast the morning of surgery under local anesthesia while the patient is awake. The patient is then taken to the operating room where the wire, clip and tumor are removed. There are some limitations to wire guided localization. These include the wire being displaced or cutting across the wire during surgery. Also, the wire may interfere with the surgical approach and can cause patient distress and discomfort.
Recently, newer techniques for localization have been developed. Most of these methods utilize a “seed” to localize the tumor in preparation for surgery. There are different types of seed technology and these are:
- Radioactive seed localization
- Radioguided seed localization
- Magnetic seed localization
Radioactive seed localization
Utilizes a seed that contains radioactive material inside the sealed seed. This seed is very small usually the size of a grain of rice. At the time of surgery, a hand-held gamma probe (geiger counter) is used to detect the low levels of radiation emitted by the seed. This type of localization is under nuclear medicine regulations which vary from state to state.
Radioguided seed localization
Utilizes radar which has been used for decades to help localize the lesion. A small reflector seed is placed in the breast; it may be placed up to 30 days before surgery. At the time of surgery a handheld locator is used to identify the unique radar signal emitted by the reflector in the breast. This technique does not utilize any radioactive material.
Magnetic seed localization
Utilizes magnetic field emission to identify the breast lesion. A magnetic seed marker is placed in the breast. At the time of surgery, a handheld locator comprised of a strong magnet is used to localize the tumor. As with other radioguided techniques it does not involve radiation and can be placed up to 30 days before surgery.
A significant advantage to the seed technology is that most of these can be placed before the day of surgery. This decreases the amount of time spent at the hospital on the day of surgery. The seed localization techniques are all usually well tolerated by patients and are less cumbersome than wire localizations..
There are few randomized clinical controlled trials comparing the various techniques to each other. While wire guided localization is the most common methods all these newer techniques are just as successful in localizing the tumor. The complication rates are similar and the need for additional surgery is comparable. Which technique is used will be dependent on which techniques are available at a patient’s medical institution of choice.