As a rule, patients with stage III B and III C melanoma groin metastases are treated with a combination of superficial (inguinal) and deep (iliac and obturator) groin dissection (CGD). In addition, iliac lymphadenectomy may be performed, but the value of this procedure is still not well understood, report researchers from the Netherlands Cancer Institute in Amsterdam. To help clarify the situation, the authors evaluated the diagnostic value of positron emission tomography/computed tomography (PET/CT) in detecting iliac lymph node metastases, and compared it with the pathological analysis after CGD.
Result: While PET/CT imaging could well be a valuable addition for the preoperative work-up, neither specificity nor sensitivity were good enough to recommend it as sole tool to determine the extent of surgery.
The study included 70 melanoma patients with stage IIIB or IIIC melanoma and an indication for therapeutic CGD; median disease-free survival (DFS) was nine months, median follow-up time was 16 months.
For superficial melanoma groin metastases the results were:
- Sensitivity PET/CT: 97 %
- Specificity: 50 %
- Positive predictive value (PPV): 90 %
- Negative predictive value (NPV): 71 %
For iliac lymph node metastases the results were:
- Sensitivity of PET/CT: 67 %
- Specificity: 91 %
- PPV: 73 %
- NPV: 81 %,
- False negative rate: 33 %
This means that one-third of patients with iliac lymph node involvement will be missed on PET/CT, stress the authors.
Their conclusion: While there might be some added value of this imaging method, it should not be used as sole instrument to define the extent of surgery.