Local Recurrence and Satellite or InTransit Metastases

There are no studies that specifically examine the efficacy of FDG-PET in the evaluation of patients with locally recurrent primary melanoma tumors, and there are only two studies that evaluated satellite and in-transit metastases. Acland et al.362 studied 9 patients with satellite metastases adjacent to the primary tumor excision site and found a sensitivity of 93% and a specificity of 50% for the ability of FDG-PET to detect locoregional metastatic disease. Stas et al.363 described a change in clinical management in patients with varying types of recurrent melanoma with adjacent metastases or distant in-transit lesions. These findings suggest a possible role for PET in this population, but very small tumor volume of disease will not be detected.

The sensitivity of FDG-PET may be low in patients with small metastases in adjacent lymph nodes,379,380 but patients with suspected regional metastases based on physical examination or other imaging modalities may have greater detectability with PET. The majority of patients (80% or greater) with clinically localized tumors never develop distant disease. Blessing et al.364 found a sensitivity of 74% and a specificity of 93% for the evaluation of 20 clinically suspicious lymph node basins imaged with FDG-PET.

Crippa et al.,365 in a study of 38 patients, found the accuracy of FDG PET to be 91% for clinically or radiographically enlarged lymph nodes. Sensitivity dropped off rapidly for lymph nodes less than 5 mm, but was 100% and 83% for nodes that were greater than or equal to 10 mm and 6 to 10 mm, respectively.

Tyler et al.366 attempted to show the utility of FDG-PET in a study of 95 patients with clinically evident stage III lymph node and/or in-transit melanoma. The sensitivity was 87%, the PPV (with the integration of pertinent clinical information) was 91%, the specificity was 44% (although few prophylactic lymph node dissections were performed), and the findings led to a change in clinical management in 15% of the patients. These findings argue that FDG-PET has a useful role in the patient with suspected regional lymph node metastases (Table 33.16).

In the case of confirmed lymph node metastases beyond the SLN, the value of FDG-PET is to localize occult distant metastases that might be amenable to surgical resection or to exclude metastatic disease in patients with equivocal findings on conventional anatomic images. Wagner et al.367 and Acland et al.362 showed that in this group of patients it was unknown distant disease that may have altered patient management.

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