PET, CT Scans for the Staging of Malignant Melanoma

CAT scan PET equipment
Person undergoing a CAT scan in hospital. PET scan equipment. Medical CT scan of patient.
Findings suggest that PET/CT imaging should be included in the malignant melanoma treatment algorithm starting with T2 patients.

Positron emission tomography and computed tomography (PET/CT) imaging could reduce the need for sentinel lymph node biopsy and lymph node dissection for staging patients with diagnosed malignant melanoma, according to study data published in Dermatologic Therapy.

In the retrospective study, the investigators used images from pretreatment PET/CT scans to assess the effectiveness of PET/CT imaging in diagnosing lymph node and distant metastases in patients with malignant melanoma. The investigators also evaluated factors that affect patient prognosis, including tumor location, Breslow thickness, Clark’s level, number of mitoses, and the presence of ulceration and metastases.

Of the 139 patients included in this study, 79 were women. The mean Breslow thickness was 3.20 mm, Clark’s level was Grade 4 or lower, the mean number of mitoses was 9/mm². Ulcers were present in 59% of the lesions. In additionally, 29.5% of patients had lymph node uptake and 27.3% had distant metastases.

The PET/CT scans were more likely to detect distant metastases in lesions with Breslow thickness >2.85 mm (56.1% detection rate), and regional lymph node metastases in lesions with Breslow thickness >3.4 mm (64.7% detection rate). Clark’s level (odds ratio [OR], 2.421; 95% CI, 1.118-5.244; P =.025) and the number of mitoses (OR, 1.052; 95% CI, 1.015-1.090; P =.006) were significantly different between patients who had lymph node uptake compared with those who did not.

One limitation of this study was that the researchers did not assess the cost-effectiveness of avoiding surgery.

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The researchers concluded that “PET/CT imaging for metastasis scanning starting from T2 patients may be used in the [malignant melanoma] staging and may reduce the need for [sentinel lymph node] biopsy and lymph node dissection.”

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Yılmaz H, Orhan E, Şahin E, Olguner AA, Arpacı E. Efficacy of positron emission tomography and computed tomography in clinical staging of cutaneous malignant melanoma [published online March 11, 2020]. Dermatol Ther. doi: 10.1111/dth.13304