Understanding PET scan results - 1265755

Thu, 09/04/2014 - 19:39

My mother, 76 years old,has metastatic breast cancer to the bone. We are trying to understand the PET scan. Peak SUV Values ranging from 4.0 to 8.5 are noted some of which are new lesions and some are old lesions that show an increase from previous scans 2 years prior. The report states multiple hypermetabolic bone lesions consistent with bone metastasis with interval progression. What does interval progression mean ? What is the significance of the SUV numbers and what does their value indicate relative to staging, progression and prognosis generally speaking. Also some lesions are sized as for ex. 1.7 cm while others are listed as 2.7 x 4.6 cm. Why is that and once again does the size of them give any indications to progression and prognosis. I am only looking for general information as to what the numbers represent.

Thank you for your time.

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Hello mstewart,

"Interval progression" means that when the radiologist compares the current scan images to the most recent previous scan, he/she sees that there has been progression in that "interval" of time.

Although SUV numbers are not always a reliable indication of progression, rising values combined with lesions which have increased in size is a pretty clear indication of progression.

When a lesion size is only stated as one number (e.g. 1.7 cm) that tends to indicate a more or less round lesion, while two numbers (2.7 x 4.6) indicates a lesion which is oblong or irregular in shape. Comparing those sizes to those seen on the previous scan and taking into account the length of time between scans, gives an indication of how aggressive the progression has been. If it is only a small change over several months, that is less concerning than a large change over a similar or shorter interval.

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Dr West

I have little to add to Jim's great summary. Just wanted to mention that "SUV" stands for standard uptake value, which is an arbitrary unit of metabolic activity on a PET scan. a number below about 4 or 5 is relatively low, 5 to 10 is more intermediate in terms of rate of cell growth and progression (and overall visible change in the bulk of cancer on scans), and more than 10 is on the faster, more aggressive side. I've seen SUVs go up to a little over 50, and this metabolic activity does correlate with overall pace of the cancer and prognosis.

The size of the individual lesions has very little correlation with prognosis.

Good luck.

-Dr. West