Scans

Some patients, after being diagnosed with melanoma, will have scans performed by their physician(s).

What do I mean by “scans”?

Scans are radiologic tests done specifically to look for metastatic disease. They may include CT or computed tomography scans, MRI (magnetic resonance imaging) scans, bone scans and PET/CT scans. They provide more information than standard chest xrays, which I would not include as “scans.”

Computed tomographic scans are three-dimensional computer reconstructions of multiple simultaneous xray beams. The most common CT scans done for melanoma are of the chest, abdomen, and pelvis. This gives a snapshot of the lungs, heart, liver, spleen, adrenal glands, ovaries, and all the lymph nodes throughout those areas. It can detect metastatic disease in those sites that cannot be discovered by physical examination. CT scans are particularly good (relatively speaking) at looking at the lungs, lymph nodes, and abdominal organs.

Magnetic resonance imaging scans (MRI) do not involve xray beams or any radioactivity. They evaluate the different levels of water in tissue and how those tissues respond to concentrated magnetic fields. For that reason, patients with pacemakers and certain types of metal implants cannot have MRI scans. MRI’s are particularly good for looking at the brain, particularly when you are looking for tiny sites of metastatic disease. For the lung and abdomen, CT scans are generally better and more informative, except in exceptional circumstances that can only be identified on the CT scan.

PET/CT scans are computerized combinations of two technologies: PET (positron emission scans, looking at glucose uptake as an indicator of metabolic activity, because tumor cells in general are growing more rapidly than normal cells) and regular CT scans. The first generation of PET scans were limited by (among other things) difficulty localizing where any hot spots might be in the body beyond general location (ie upper abdomen). Computerized combination of the two technologies improves localization while giving information on metabolic rate that would not be available from CT scans. The downside of PET/CT scans are limited utility in the brain (hopefully, everybody’s brain would light up from some thoughts during the scan) and limited resolution of the CT portion of the scan, unless “diagnostic quality” CT scans are simultaneously done. Generally, insurance companies hesitate to approve diagnostic quality scans. With the standard PET/CT scans, lesions below about 1 cm in size may not be detected. This is particularly relevant in the lungs, where very small, 2-3 mm, lesions will be readily seen on standard CT scans but often missed on PET/CT images.

Bone scans involve the injection of a radioactive agent that localizes to bones and is used to detect bony metastases. In general, it is rarely performed in melanoma patients unless there are specific symptoms (usually pain) that suggest bone involvement. It would definitely not be used as “screening” scans in melanoma, although it is in other cancers that are more likely to spread to bones.

What are the indications for scans?

This is somewhat of a controversial point in the medical literature and varies widely among practitioners, even those who see a high volume of melanoma patients. At the time of initial diagnosis, I believe that scans should be done on patients at signficiant risk for distant systemic disease, which in my practice include anybody with a Breslow thickness 4 mm or greater (T4 in the staging system) and/or with ulcerated melanomas, both of which have been suggested to have a greater risk of systemic disease beyond the lymph nodes. For most patients, scans are not necessary initially in my opinion.

However, I do recommend scans in patients after their definitive surgery, depending on the constellation of data from the intial biopsy and subsequent surgery. I use PET/CT scans alternating with CT scans of the chest, abdomen and pelvis with a brain MRI (patients with head and neck melanomas would also get neck CT scans). The reason for alternating the scans is because (as noted above) the strengths and weaknesses of the types of scans are somewhat complementary and therefore I feel you get more overall information by alternating them. The frequency and timing of scans is very controversial and the insurance companies have recently become very picky, often denying the requested studies. In general, for patients at some significant risk for recurrence, I get scans about once a year, increasing the frequency if they have already had metastatic disease at some point. The frequency of scans can be diminished as the time without a recurrence increases.

What if I already had scans before my surgery?

If so, the best thing to do is to get a copy of your scans from the hospital or imaging center where the scans were done, along with the scan interpretation. Then, your physician can review both the report and the actual scans if necessary. In today’s world, it is best to get the scans on a computer CD, NOT the films themselves.

Eric D. Whitman, MD

Senior Editor, TheMelanomaCenter.com

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