A variety of imaging techniques can be utilized for determining the extent of disease in patients with melanoma, including PET-CT scans and MRI. The exact patient population that is ideal for imaging can be guided by patient and tumor characteristics, such as tumor thickness and the presences of symptoms.

In asymptomatic patients, routine imaging by PET or CT scans may result in a higher rate of false positives than actual positives, believes Merrick I. Ross, MD. However, if a positive sentinel lymph node (SLN) is detected in a patient with a thick tumor, these approaches gain more value. Moreover, if the patient is a candidate for adjuvant therapy, an MRI or PET-CT scans could be useful for examining if CNS metastases are present, notes Ross.

In general, the imaging used should be risk adjusted, believes Jeffrey S. Weber, MD, PhD. Patients with stage IIIb/c or resected stage IV melanoma should be staged using a PET-CT scan and an MRI of the brain and spinal cord, since this could change the treatment administered. Discovering metastatic disease early may boost survival, Ross suggests. Making these types of imaging and SLN biopsy more important. However, Weber points out, the gains in survival with these techniques are modest, which begs the question of whether the additional costs of screening are justified in all patients.

At this point, a reliable biomarker does not exist for knowing which patients should receive SLN biopsy, PET-CT, or MRI. However, if a biopsy is conducted, a positive SLN can provide clues about the patient's outcome and risk, notes Jeffrey A. Sosman, MD. Additionally, a SLN biopsy that returns negative can be very reassuring to patients. To help further answer this question, the MSLT-II trial is comparing observation to surgery for patients with SLN-positive melanoma.