Found this article poking around the ASCO blog link that Brian had posted:
One interesting point (among many). A few weeks back I had posted that I've not had a PET scan since my Stage IV diagnosis. This could be why:
The first step in evaluating patients with known or suspected metastatic melanoma (stage IV) is to define the extent and sites of disease. A CT scan of the chest, abdomen, and pelvis is a good starting point. Some patients and physicians may be concerned about radiation exposure, in which case an abdominopelvic MRI can be substituted for the abdominopelvic CT. Although this adds expense, it decreases the overall radiation exposure from approximately 17 mSv to approximately 7 mSv. Given the risk and therapeutic significance of central nervous system metastases, it is also appropriate to obtain imaging of the brain with either MRI (preferred) or CT. Some oncologists rely on 18F-fluorodeoxyglucose (FDG) PET-CT scans to define the extent of disease and there are some studies to support this,8,9 especially in patients who are being evaluated for possible resection of oligometastatic disease.1018F-FDG PET-CT scans offer full body imaging with slightly decreased radiation exposure compared with CT scans of the chest/abdomen/pelvis. Clinicians should be aware, however, of certain drawbacks of 18F-FDG PET-CT scans. First, there is a substantial rate of false-negative in the lung,11 leading some clinicians to include a noncontrast lung CT scan with the PET scan. This results in total radiation exposures similar to that for a full body CT scan. Second, tumor dimension measurements generally cannot be made reliably from a PET scan, leading to the need to eventually perform a full body CT scan to monitor response to therapy, although newer PET-CT scanners can offer high-resolution CT images. Third, 18F-FDG PET-CT scan results do not correlate reliably with clinical effects in patients being treated with BRAF inhibitors;12 melanoma FDG uptake will nearly always decrease with BRAF inhibitor treatment whether or not there is substantial tumor shrinkage. Hence, PET scans should not be relied on to follow clinical response in these patients.