How to interpret SUV

[Stephanie2024]

Just completed 6-month PET and MRI scans. Compared to 3 months ago, there are no new legions and tumor size is slightly smaller, but SUV is higher, and bone mets SUV are higher in some places and lower in others, relative to liver mean. I have been taking Tagrisso for 6 months and completed 4 rounds of chemo February through April. Does this mean that Tagrisso is not effective any more? Should I consider radiation for the spots with higher SUV?

[Tom Galli]

Stephanie,

No new lesions and small sizes are good and may be evidence that your Tagrisso is effective. Interpreting SUVs is an art form, especially an increase over a previously lower value. The standard uptake value (SVU) measures metastatic activity and this can vary from test to test. Some survivors report their physician attributes increased SUV to the effect treatment is having on the tumor, that is killing tumor cells and the cancer's attempt to replace them increases the metabolic activity and increases glucose uptake.

I am not a physician and don't know for certain why your SUV increase occurred. As regards your question about precision radiation, I think it is always appropriate to consult with a radiation oncologist. They have different tools and their therapy can often complement that of a medical oncologist.

Stay the course.

Tom

 

[Stephanie2024]

Thank you so much, Tom!

[Stephanie2024]

Tom,

My CEA in blood went up slightly from last month, and I think that correlates with higher cancer activity. Did you ever experience ups and downs in metabolic activity during treatment? Also the places that showed higher activity are places where I sometimes feel a dull pain. I wonder if that's the cancer activity in my bones causing the pain. Did you ever experience pain in places that had cancer activity?

[edivebuddy]

The standard in Standard uptake value only applies to you. And then it only applies to that one imaging study.  So many things can affect SUV values.  What you are the day before.  Room temperature, how many minutes it's been since the tracer injection. They even vary from machine to machine. 

Now beyond that higher SUV values can just be different parts of a tumor. As the tumor dies, different parts can metabolize glucose at different rates.  Tumors treated with radiation can also show higher SUV as they're dying. This can happen months after treatment.  

There are other benign causes of high SUV uptake like inflammation, infection, injury. 

SUV values above 2.5 are worrisome for malignancy . But   my last 12 PET scans have had multiple skin lesions with High SUVs  as high a 6.  These are not cancer but eosinophilic dermatoses caused by a Avastin. 

Relative to liver is just a comparison of the SUV values.  An SUV value that's higher than that of your liver May mean increased metabolism or worrisome for malignancy.  It can also be compared to blood pool which is blood in the aorta or other major blood pool. Interesting tidbit.  The average SUV of the liver according to Zincirkeser, E S ¸ahin, M Halac et al. Is 3.2.  so if an SUV lower than the liver is indicative of normal metabolism how is 2.5 worrisome for malignancy?  

With the Positron Emission Tomography Response Criteria in Solid Tumors. PERCIST  SUV values of less than 30% more or less are not considered a response or progressive metabolic disease.  Most likely reported as a slight decrease or increase in uptake.

They will also use the Response Evaluation Criteria in Solid Tumors guidelines to help judge your response to treatment.  30% smaller sums of the  dimensions is a partial response. A 20% increase would be progressive disease.  Even there it would have to be judge as not pseudoprogression.

I hope I didn't get you even more confused. Your doctor will go over the results with you. You can ask him about radiation but at stage IV it's generally not an option unless it's palliative. But you can definitely ask. Even if your scan is actually clear.  There are limited circumstances where they will do it.  

 

Good luck to you.

[Stephanie2024]

Thank you so much for your response! This is super helpful! Do you think dull pain in certain spots are correlated with cancer activity?

[Tom Galli]

Stephanie,

My oncologist never seemed to be concerned with blood CEA variances. I had nearly 4 years of constant chemo and my CEA values moved a lot from test to test. I experienced no dull pain, except for pain caused within the plane of thoracic incision scars and taxol toes from too much Taxol chemotherapy. The incision pain was validated by increased SUVs in PET results.

My oncologist always asked if I felt any dull pain in my long bones (legs and arms) as this might be an indicator of bone mets but I never had that sensation.

Stay the course.

Tom

[Stephanie2024]

Thank you!

[edivebuddy]

I don't believe there is no correlation to pain and cancer.  Pain is never good and tumors can cause pain when they press other nerves or organs.  While tumors can grow nerves I believe they do so only to stimulate chemical production or it was encoded in their original DNA .  Any pain felt from these can be hard to pinpoint.  My skin met had no sensation whatsoever.

New pains are probably not new tumors. But even the smallest tumors in a bone scan cause pain. Sometimes extreme. 

We are getting older and it can be hard to tell if it's the cancer or just age causing or symptoms.  But don't let that stop you from telling your care team.