Frank P. Dawry LYMPHOSCINTIGRAPHY Sentinel node localization in Melanoma

Definition and Information Sentinel node is the first lymph node bed to receive lymphatic drainage from a tumor Useful in staging of primary melanomas that originate in the skin – Used only on patients with intact primary lesions or on patients who have had only excisional biopsies Lymphatic drainage pattern is identified eliminating the need for extensive lymph node dissection with it’s associated morbidity and cost – 80% of patients with intermediate (I and II) stage melanoma have tumor- negative lymph nodes

Injection

Majority of lymph nodes are anteriorly located

Procedure Patient preparation – no dietary or medication restrictions – Patients should follow pre-operative instructions if surgery the same day Precautions – if surgery is to be performed using an interoperative gamma probe, tracer must be injected within 3 hours of the surgery

Benefits of SLN Imaging The SLN biopsy method can accurately stage regional node fields and reduce operative and postoperative morbidity. It is a robust method that has been shown to be accurate in many different countries using many different radiocolloids and imaging and surgical protocols. Histologic examination of the SLN has led to unprecedented accuracy in nodal staging. The technique can be applied to any solid tumor that has the propensity to metastasize to regional lymph nodes. SLN biopsy is now the standard of care in patients with melanoma and breast cancer and is moving toward this in many other cancers.

Benefits of SLN Imaging - continued SLN biopsy allows the most aggressive clones of the tumor (those that have metastasized) to be examined. SLN biopsy is safe and does not increase the chance of local recurrence Disease-free survival does seem to be improved by SLN biopsy There may be some improvement in overall survival but this is yet to be definitively proved. Its use even in cancers that have no currently effective therapies for disseminated disease, can be justified on the basis of providing the most accurate prognostic information and staging for entry into therapeutic trials of new treatments.

Radiopharmaceuticals Tc-99m Sulfur Colloid – Filtered – 0.22 mm filtration Advantage in mapping the entire lymphatic drainage basin Disadvantage in progressing past the sentinel node – Unfiltered – mixed particle sizes up to 2.0 mm particle size Advantage in remaining in the sentinel lymph node(s) Disadvantage in not being able to map the lymphatic drainage basin – Antimony sulfur colloid Not available in this country – Tc-99m HSA Improved image quality over Sulfur Colloid but reduced sentinel node retention

Radiotracer Injection 0.1 ml volume in tuberculin syringe x uCi in each of 4 syringes Intradermal injection Body and Extremities – Inject at 12, 3, 6 and 9 o’clock location surrounding the lesion Head and Neck – Inject syringes superior to lesion in reference to the whole body Performed by an authorized user or delegate

Intradermal Injection is made directly under the epidermis similar to a tuberculin skin test

Precautions Pre-injection of 1.0% lidocaine hydrochloride before study to minimize injection pain Injections performed under semi-sterile conditions – site prepared with 70% alcohol or betadyne Use absorbent pad with small opening to prevent skin splash contamination Cover injection site with gauze to prevent leakage contamination

Imaging protocol LFOV camera LEHR collimator Cobalt sheet source for transmission imaging – Point source outlining as an alternative Views – Axillary and inguinal regions imaged for lesions on the trunk – Anterior and/or Posterior – depending on lesion location – Lateral and obliques views helpful to uncover multiple nodes overlying one another Skin marking – Triangulation in order to determine 3-D location of sentinel node – Patient may be marked using the patient’s position as it would be in the operating room

Acquisition parameters Sequential or continuous imaging beginning immediately following completion of injections for minutes or until sentinel node is identified – Continuous dynamic imaging at 30 seconds/frame – Sequential static imaging every 5 minutes/frame

Final Report In addition to routinely reported items (radiopharmaceutical, dose, injection method, etc.) – Location(s) of sentinel lymph node(s) – Presence of lymph channels if visualized on images An image should be available, with landmark locations, to the surgery team at time of surgery

Static imaging

Breast

Interoperative probe Sentinel node has at least 10x background counts

Surgery The 'hot' node(s) is(are) confirmed by the hand held gamma probe and then excised an ex-vivo count of radioactivity is obtained using the gamma probe