Joint Program in Nuclear Medicine

Lymphoscintigraphy and Melanoma : "Expected Drainage"

Pritinder K. Thind, MD
Kevin J. Donohoe, MD

January 4, 2000

Presentation

Imaging Findings

A lateral static image from another patient who had a left cheek melanoma (arrowhead shows sites of injection) demonstrates tracer uptake in the submandibular and posterior cervical lymph nodes (shown by arrows).

Discussion

History

• first node to receive drainage from the tumour
• visualization of an afferent lymphatic vessel from the tumour site to the node

Implications of the sentinel node in malignant melanoma:

The presence of regional nodal involvement lowers the 5 year survival rate to ~ 50% (Yudd et al). The sentinel node is the best tissue to sample for histopathologic examination.

Characteristic of ideal imaging agents:

• rapid clearance from the interstitial space into the lymphatic channels
• produce high quality images
• deliver low radiation dose to the patient
• good tracer retention in the lymph nodes to insure gamma probe localization at surgery

Types of radiopharmaceuticals that have been used:

• gold-198: first agent (45 years ago), small size, long half-life (2.7 days), beta emission, 412 keV gamma emission
• Tc-99m antimony trisulfide colloid: favourable energy, uniform size, moderate retention
• Tc-99m human serum albumin: 4.5 nm in diameter, poor retention

Procedure and imaging (Alazraki et al):

• inject 400 uCi of Tc-sc (0.1ml each) intradermally at four points around the tumour site
• early dynamic images: 10 seconds per frame for 10 minutes
• static images every 5 minutes for 30 to 40 minutes
• late imaging at up to 2 hours
• transmission images-cobalt 57 flood source: improves localization of channels and nodes relative to body contour and skin surfaces

Melanoma technique (Yudd et al):

• intradermal injection of 0.1 ml of filtered tc sc at 4 to 8 points around the lesion/scar
• prior to injection, remove air from the syringe to avoid aerosolization of the tracer and surface contamination
• 30 sets of dynamic images are acquired at 30 seconds/frame
• 2 to 3 sets of dynamic images are obtained
• at ~ 30 minutes, localize lymph nodes with respect to anatomic landmarks
• static images of 3-5 minute duration are obatined with cobalt 57 source transmission images
• final set of images at 1.5-2 hours

Following imaging:

• cobalt 57 source is used to assist in marking the skin surface
• in the or, the gamma probe is placed over the marked skin surface for 10 seconds to obtain a reading
• after the incision, the probe is placed over the node for 10 seconds
• following excision, count readings of the lymph node bed and excised node are obtained

Comments about the technique:

• reproducibility: 85-88%
• causes of non-reproducibility
  • particle size
  • label efficiency tecniques
  • injection dose and volume
  • location of tumour
  • camera acquisition and display parameters
  • timing of imaging
  • lymphatic disruption due to prior biopsy

Malignant melanoma classification/staging:

• Breslow classification: 4 groups based on tumour depth of invasion [<. 75mm, .76-1.5 mm, 1.51-2.25 mm, 2.26-3.0 mm, >3 mm]
• Clarke scheme: 5 levels on the basis of dermal invasion
• american joint committee on cancer (1988): tumour thickness, level of dermal invasion, +/- regional or distant metastases

Difficulties in evaluation:

• variability of drainage basins: frequently occurs with trunk melanoma
• reproducibility in 2 series varied from 85-88%
• Yudd et al: 17% discrepency between the scintigraphic demonstration of sentinal nodes and the number of sentinel nodes found during gamma probe and blue dye-assisted surgery

Variable drainage patterns:

• extremities: inguinal and axillary regions
• head, neck and trunk: drainage to more than 1 adjacent predictable group varies from 40-75%
• Berman et al: 135 patients with melanoma of the head, neck, shoulder and trunk
  • 41% discordancy rate between expected drainage and imaging
  • discordancy rate highest for head (64%) and neck (73%)
  • altered surgical management in 33%

Effects On Elective Lymph Node Dissection:

• intermediate thickness and/or stage i/ii melanoma: no evidence of tumour spread
• 80% don’t have nodal metastases by elnd
• of the 20% with metastases, elnd can offer more accurate staging
• with the sentinel node concept, invasive surgery can be avoided in 80%
• in the remaining 20%, sln biopsies and lymphatic mapping can direct the lymphatic dissection

Results For Melanoma

• >95% sensitivity for localizing sentinal lymph nodes and lymph node basins (yudd et al)
• berger et al: primary axial cutaneous melanoma- scintigraphy predicted >98% of basins with positive metastases
• 209 patients with high risk melanoma of the trunk: 94% sensitivity in detecting metastases

References

Bonges V, Borel Rinkes H, Barneveld P, et al: Towards quality assurance of the sentinel node procedure in malignant melanoma patients: a single institution evaluation and a european survey. European Journal of Nuclear Medicine 26 (2): 84-90, 1999.

Valdes Olmos R, Hoefnagel C, Nieweg O, et al: Lymphoscintigraphy in oncology: a rediscovered challenge. European Journal of Nuclear Medicine 26 (4), Suppl.: S2-s10, 1999.

Wilhelm A, Mijnhout G, Fransenn E: Radiopharmaceuticals in sentinel lymph-node detection- an overview. European Journal of Nuclear Medicine 26 (4), Suppl.: S36-s42, 1999.

Yudd A, Kempf J, Goydos J, et al: Use of sentinel node lymphoscintigraphy in malignant melanoma. Radiographics 19: 343-353, 1999.

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