post SBRT SUV & CEA followup timeframes - 1251848

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post SBRT SUV & CEA followup timeframes - 1251848

My mother completed SBRT for a LUL stage 1B lung tumor, no confirmed biopsy, with 5 treatments of 10Gy on November 21, 2012 (5 wks ago). At time of diagnosis PET SUV was 10.5 and 1.5 for adjustcent nodule, with CEA > 20. I have the following questions and would greatly appreciate your opinion.

1. After how long post treatment would it be reasonable to expect the SUV/level off and repeat the PET scan?

2. When would treatment reflect in the blood CEA counts?

3. Can CT lung scan show increased size at this point (5wks post treatment) due to inflammation?

My mother's radiation oncologist did repeat CT last week, and wants to wait 12 weeks post SBRT to repeat PET scan.
On the other hand medical onc wants to repeat PET 6 wks post SBRT and expects CEA to go to 0 by then.
Which one of these would be the followup protocol? I've read her lung is probably a 'mess' right now. Just wondering if it's too soon to make a treatment decision should the CT scan show a larger mass or PET SUV not 0 or CEA not 0.

Thanks for your help and Happy Holidays!

Dr West
Reply To: post SBRT SUV & CEA followup timeframes

With the caveat that SBRT isn't so well established that there are any standards etched in stone, I would say that most experts would favor waiting at least 3-4 months after doing radiation to try to assess any results by PET, and that 6 weeks is definitely too early. Also, most experts don't advocate using CEA or any other tumor marker to define how well a cancer has been treated. I don't think there has ever been a single expert lung cancer doc here at GRACE, or that I've ever heard speak elsewhere, who has ever extolled the wisdom or any evidence to say we should use CEA as a critical result: the main debate is whether a CEA is bad idea to follow at all or perhaps of some ancillary value if used as a very secondary or tertiary factor. But a CEA has a normal low level, often up to about 6, so you don't expect to see it go to 0, ever. And I think it would be a terrifically awful idea to make a treatment decision for lung cancer on the basis of a CEA value alone.

I'd feel more reserved about my opinion except that there is no actual evidence to support using CEA for decision-making in lung cancer, nor do the experts actually debated whether it is a critical test. In fact, I think it has some arguable utility, but I see it often so over-interpreted and misused that I think it tends to often do more harm than good in managing lung cancer.

And yes, the findings on a scan could show enlargement or otherwise be essentially uninterpretable at this time point.

Good luck.

-Dr. West

Dr. Howard (Jack) West
Associate Clinical Professor
Medical Oncology
City of Hope Cancer Center
Duarte, CA

Founder & President
Global Resource for Advancing
Cancer Education