• Cancer Journal: The PET Scan

    In December, I got a computerized tomography (CT) scan to determine whether the radiation treatment I had received had destroyed the tumour in my throat. The report from that scan misinformed me that I now had not just a throat tumour but also a lung tumour. This was an error: a radiologist didn’t proofread his dictated report before he saved it to my electronic health record. When contacted he corrected the report: the CT scan showed no evidence of lung cancer. The CT scan showed, however, that there were residual tumour masses in my throat and in the lymph nodes in my neck. My radiation oncologist thought that these tumours were likely dead, but you can’t confirm this from a CT scan. So he ordered a positron emission tomography (PET) scan.

    You might imagine that when your physician writes an order for a diagnostic procedure, you get the procedure. This has not been my experience. When I first developed cancer symptoms, my family doctor ordered some imaging. All this got me was a place on a waitlist. I was only diagnosed after I went to the Emergency Department, coughing blood. Similarly, weeks passed without a response from Nuclear Medicine, the people who do PET scans. I stopped by their office one afternoon to ask why. No one was there and the person in the next office said that everyone left at 3:30. Finally, I got someone on the phone who was able to find an opening due to a cancellation.

    I wonder what Nuclear Medicine did with my oncologist’s order. I imagine a meeting like the one in the last scene of Raiders of the Lost Ark.

    Indy and Dr. Brody are trying to convey to a bureaucrat the urgency of researching the Ark. The bureaucrat tells Indy that “Top men” are working on it.

    Indy (acid skepticism); Who?

    Bureaucrat: Top. Men.

    In reality, the crate containing the Ark has been lost in the warehouse. Perhaps my oncologist’s order was stacked on top of that crate.

    In any event, on February 26th I got the procedure. In a PET scan, you are first injected with a radioactive sugar solution. Cells eat sugar and in doing so they absorb the radioactive material. Cancer cells have crazy high metabolisms and eat voraciously. This means that they pick up more radiation than other cells. In a PET scan, therefore, cancer cells glow brightly in the image against the background of healthy cells.

    I do not see that image; it goes to a nuclear medicine fellow, who interprets it and writes a report. But in the new world of electronic health records open to patients, I was the first person on my care team to read the report.

    What my PET scan showed was that a portion of my throat tumour has survived my radiation treatment. Similarly, the metastatic lymph nodes in my neck still have active cancerous cells.

    Me: Uh. Oh.

    I wrote my radiation oncologist with QUESTIONS. Impressively, he got back to me in less than 24 hours, and I’d summarize his reaction as, “Our first attempt to treat this didn’t work.”

    So what now?

    Radiation is no longer an option: apparently, I’ve had all I can tolerate. My radiation oncologist has referred me back to the surgeon who biopsied me back in July. The journey isn’t over. I will let you know what my options are after I have spoken to him.

    The PET scan was BAD NEWS, but it was far from the WORST NEWS.* Surgery can work in these circumstances. I feel healthy, I’m hopeful, and I am prepared for whatever comes next. Writing about this experience is helping me get through it. Unfortunately, I still have more to say about being a cancer patient in the COVID pandemic. But there it is.


    *There was actually GOOD NEWS, which was that the scan revealed no new metastases. Or maybe goodish news, because there are limits to what you can see in a PET scan. The problem is that, like case numbers in epidemics, cell counts in tumours grow exponentially. Suppose that a cell from my original tumours had escaped into my lymphatic system and migrated to a new site. At the new site, it might start growing, with cell counts doubling every so often. While those counts are small, the new tumour would be too small to register in a PET scan. By the time it became large enough to be imaged, each doubling would manifest as a rapid, aggressive expansion. In short, the absence of evidence of new metastases in a PET scan is only weak evidence that they are absent.


    • To read the Cancer Journal from the start, please begin here.
    • The next post is here.
    • A table of contents for the Cancer Journal is here.
    • To get the Cancer Journal in email, go here.

    @Bill_Gardner

     
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