Radio-isotope guided surgery

Radio-isotope guided surgeryI wish to share a few lessons learned at a course on “minimally invasive radio-isotope guided surgery”- at the Moffit Cancer Center/USF, Tampa, Florida. For the sake of brevity the topics covered will be divided into four:

  • malignant melanoma
  • carcinoma of the breast
  • parathyroid adenoma
  • colonic cancer

Malignant melanoma

The aim is to reach a low morbidity and low cost compromise between routine lymphnode dissection (LND) and observation in patients with clinical stage II disease (non palpable nodes).

Patients with lesions of less than 0.76 mm may be sparred the procedure as their chance to have involved nodes are remote; patients with lesions thicker than 4 mm are known to harbor disseminated disease-and therefor may not benefit from the procedure.

At a certain time prior to the operation-depending on one’s local facilities-the melanoma site or the site of its previous excision are injected with the radioisotope and the potential lymphnode basins are scanned to locate the position of the first node taking the radioisotope-called the SENTINEL NODE. Lesion of the trunk and head and neck may drain to LN basins remote from the lesion or to more than a one basin. Thus, we were showed patients with melanoma of the back draining to both axillas and one groin, and lesion on the left chest draining to the right axilla!

The approximate location of the “hot” LN is then tattooed on the corresponding skin. On the morning of surgery the original injection site is re-injected with the radioisotope. In the OR before the surgeon scrubs he injects the primary tumor site or its scar with a blue dye.

At the sentinel node biopsy the surgeon is guided by the tattoo on the skin, the blue dye which stains the lymphatics converging on the sentinel node, and by a hand-hold radioisotope counter (probe) which guides the surgeon onto the hottest spot. Best results are obtained by using together all 3 modalities.

Finding a negative sentinel node means that in 99% there are no other involved “skip lesions” at the dissected LN basin.

The procedure is performed under local anesthesia and is relatively easy-less so, however, in fat patients. It saves the patient the morbidity of “full’ LND which at the groin situation is relatively severe- i.e. limb edema and wound complications. Obviously, in cases with multiple sentinel nodes ;i.e. a scalp lesion with “hot” nodes on both sides of the neck-both nodes are dissected.

If the sentinel LN is positive the patient is subjected to a full LND at another day. Currently, positive LN in melanoma means systemic therapy with interferon- which has been showed to improve survival.

Having seen the relative ease of the procedure at the animal lab and OR , its role in malignant melanoma is convincing to me.

Carcinoma of breast

The technique is the same as in melanoma. Let us take for example a T1b lesion at the LLQ. The patient comes to the OR with her axilla tattooed over the assumed sentinel LN. You inject 5 ml of blue dye around the palpable lump. In cases of a non-palpable lump you inject the dye around the localizing needle -that is if you believe that such patients need axillary staging (see below). After the lumpectomy you go and search for the sentinel node through a small axillary incision (local anesthesia) again guiding yourself using the blue dye and radioisotope sensing probe.

Should the LN turn positive the patient will require formal LND. The Tampa guys use “touch cytology” technique to immediately evaluate the adequacy of the lumpectomy margins and assess whether the sentinel node is positive. The excised lump in divided and marked into 5-6 “surfaces” -each “touched” with a slide. their results show that negative cytology for malignant cells excludes positive margins and secure a local recurrence rate of 2 % after radiotherapy). When malignant cells are seen on the slide the corresponding lumpectomy field is immediately re-excised. But obviously you must have a well trained cytologist.

I was impressed by the easiness of this technique and am convinced that sentinel node biopsy may spare formal axillary LND in numerous women. I was concerned however with the rather wide indications as practiced in Tampa.

We were shown a pre-menopausal lady with a scar following a needle guided biopsy of an in situ ductal carcinoma. The scar was injected and the sentinel node dissected. Many would argue that in such a case the axilla needs no attention at all.

Then a 70 yo lady with a 1cm’ lesion; in many places such a patient would receive a lumpectomy, radiotherapy +/- tamoxifen. Dissection of the axilla has no staging and surely no therapeutic benefits here.

And, in view of the recent studies of radiotherapy we all heard about, perhaps in 5 years or so from now most patients will be managed by local excision of the lesion and wide -field radiotherapy+/- chemotherapy and “to hell with the axilla”.

Parathyroid adenoma

The Tampa guys argue against the conventional credo that localization tests are not necessary prior to parathyroid surgery for primary adenoma. They claim that it is indicated to permit a minimally invasive surgery.

The Sestamibi scan permits a very precise localization of the adenoma; in fact -one “hot” site means that there is ONE adenoma in almost 99% of the cases. At operation, the surgeon places the incision over the tattoo, previously placed by the isotope-guys. The surgeon then zooms directly on the adenoma guided by the isotope probe. After the adenoma is removed the field becomes “radioactively silent”. While conventional parathyroid surgery requires bilateral anatomical dissection averaging 2.2 hours the Tampa team does it under local anesthesia in the average of 40 minutes. The patient diagnosed as having hyperparathyroidism (based on elevated PTH levels) comes to the surgeon’s office, undergoes the scan and the operation – all in the same day. Makes sense.

Colonic cancer

RIGS or radio-isotope guided surgery in colonic ca is not new but has never really caught on. Only a few centers in this country continue evaluating this technique. During this course we were not exposed to such cases but the topic has been mentioned. As I understand it now- perhaps the only practical indication for RIGS would be prior to a planned hepatectomy for colonic met’s. A day before operation the patient is injected with anti-CEA radio-tagged antibodies. During laparotomy the abdomen is explored with the isotope sensing probe and any “hot” spots are biopsied- when positive- hepatectomy is FUTILE. “Hot” spots are commonly present along the duodenohepatic ligament.

In conclusion:

it appears that sentinel node biopsy guided by radioisotopes and blue dye has a real role in patients with melanoma and breast ca. Radioisotope scan guided “minimal’ surgery may proof the ideal way to deal with parathyroid adenomas RIGS in colonic ca has a limited but still under evaluation role.

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