The PET Food Diet; Scanning for PETs and C(A)Ts

It’s Thursday, 63 days ATN and 23 days since the start of chemo.

At long last it’s time for the PET/C(A)T scan. Because, of course, it’s quite important to know if there are any dogs, fish, mice, or squirrels running around or in me. Cats apparently need a dedicated scan since they’re sneaky creatures and might not be detected in a normal PET scan.

The medical oncologist ordered the PET scan about a month ago. “Numerous small foci” in my liver were detected in the initial CT, which the radiologist indicated were likely cysts or hemangiomas. But metastases couldn’t be ruled out and a follow-up MRI failed to completely resolve what they were. So the tumor board decided a PET was warranted. According to the oncologist’s nurse PET scans are generally authorized (or I suppose rejected) in two or three days. For whatever reason Anthem Blue Cross took its sweet time in authorizing it. Had they met the usual timeline the scan would have happened just before the first chemotherapy infusion. I suspect Anthem was hoping I’d die first and they’d be off the hook for the ~$10k the scan costs.

As an amusing side-note, in the last pre-infusion visit I asked my oncologist if it was OK to adopt a pet, since during the infusion teaching session the nurse seemed to be quite interested in whether I had any. I thought the concern might be with having the port IV pulled out (Caper certainly would’ve done that), chewed up (that’d be Jasper’s domain), or just that I’d be toxic to a small pup (I’m not allowed to share any bodily fluids with any human and dogs are notorious for licking you…) The oncologist’s first reaction was “A cat?!” She then explained that cats shed something in their feces which can be problematic for the immunocompromised (which I may end up being at various times during chemotherapy), so I would need to be cautious. And definitely stay away from litter boxes. (Actually there seems to be several potential problems with cats as outlined in this article.) I told her no, I was thinking of a puppy. She seemed a bit thrilled (and relieved) and said “No problem!” She did caution me to make sure I’d be able to keep up with a little four legged ball of energy.

So all cleared on the oncology front to adopt a pet. As I was walking out of the building my phone rang with the Palo Alto Medical Foundation caller ID. It turned out to be nuclear medicine. They wanted to schedule a PET scan. I guess the oncologist had sent them an urgent note to help me find a suitable pet and to scan for one ASAP! As we started talking about dates for the scan and (as I was fumbling with my phone trying to bring up my calendar as well as talk to the scheduler) I mentioned I was about ten yards from nuclear medicine and maybe I should just drop in? She was a bit surprised but said come on by (as I walked through the door), and we managed to get everything scheduled and the paperwork sorted out in a couple minutes.

The PET Food Diet

Since it seems everyone is most interested in the food posts I’ll start off with the PET food diet. Basically in a PET scan you’re injected with F-18 FDG, which is glucose (sugar) tagged with a radioactive tracer. Cancer cells consume up to 30 times more glucose than normal cells, so should light up light a Christmas tree, Menorah, or brightly lit holiday season object of your choice during the scan. This article from the Simms/Mann UCLA Center for Integrative Oncology provides a good discussion about PET/CT scans.

For those of you too lazy to click on the link, basically back in 1921 (wow, 100 years ago!) the metabolism of cancerous cells was found to be different than normal cells. Normal cells get their energy via respiration of oxygen, while cancer cells get their energy by fermenting sugar. (Hmm. So cancer cells ferment sugary liquids, have a wild party, engage in uncontrolled reproductive activities, and wreak havoc on their surroundings in the process? Sounds a lot like college life.) While both normal and cancer cells consume glucose, fermentation is much less efficient than respiration so cancer cells are much more glucose-hungry.

To ensure that the FDG is taken up by cancer cells, you basically want a low glucose level so that insulin levels remain low. If insulin levels are high then the FDG (along with other glucose floating around in your blood) will be taken up and stored by muscles. In addition to depriving the cancer cells (which really want that FDG) it makes the scan difficult to interpret. For the same reason you shouldn’t exercise or perform any strenuous activities the day before a PET scan.

Now back to food…basically for the day before a scan you need to go on a low glycemic index diet. This is actually similar to a keto diet and also what you’d want if you’re diabetic. So fish, chicken, and beef are good as are non-root vegetables such as broccoli and cauliflower. Hard cheeses and eggs are also allowed. Off the list are pastas, breads, desserts and root vegetables such as potatoes and carrots.

I’m already on a reduced sugar and refined carbs diet Just In Case it proves beneficial in slowing tumor growth (and also because I’ve been watching my fasting glucose level creep up over the years, and don’t want to end up classified as pre-diabetic). So the challenge of going ultra low sugar/carb for a day while still enjoying meals was intriguing.

Here’s what I ended up with:

  • Breakfast: broccoli (steamed until tender), mushroom and sharp cheddar cheese omelet. I was trying for the folding method demonstrated in this folded kimbap video, and it sort of worked…
  • Dinner: Filet mignon (medium well) and sautéed asparagus. (No, I don’t normally buy filet mignon, in fact I don’t think I’ve ever bought it at a grocery before and spent a good half hour scouring the web for the best way to cook it. But I figured I’d treat myself…)
  • Snack: Celery and no-sugar-added 100% natural peanut butter. I’m not a fan of stringy celery but came across this method to de-string it. Why doesn’t someone create a variant of celery that isn’t so stringy?
  • Snack: Costco rotisserie chicken. Yes rotisserie chicken isn’t exactly your typical snack but it was in the refrigerator and you have to admit – it’s tasty.
  • Drink (morning): Trader Joe’s Mango Black Tea (note that you’re not allowed teas and other caffeinated drinks for some scans, particularly cardiac PET scans).
  • Drink (evening): Trader Joe’s Ginger Turmeric Tea.

Scanning for PETs and C(A)Ts

On the day of the scan I arrived at the Nuclear Medicine clinic, which happens to be one door down the hall from the PAMF oncology clinic, my home away from home these days.

I was brought into a room where they inserted, I think, a peripheral venous catheter. A small amount of blood was drawn for a rapid glucose test to ensure I was in range for a scan (apparently 98 was, since I believe that’s what the nurse mentioned), then two syringes encased in what I assume was a radiation-shielded box appeared. The two syringes were injected via the PVC, the PVC was removed, and then I had to wait around for an hour for the FDG to circulate and be consumed by any dogs, cats, or mice that happened to be sharing my body. Frankly if they wanted to attract a dog injecting some of the aforementioned filet mignon would have been a better idea, but I assume the nuclear medicine people know what they’re doing.

The nurse said not to worry I wouldn’t glow or anything (But why not? And no, apparently they don’t have a special glow-in-the dark formulation if your scan is on Halloween. I asked. They probably do a special Black CAT scan though.) Nor would I gain any super powers (in other words, don’t try to fly. The landing could be painful.) However, the nurse thought if I happened to have a Geiger counter at home it’d be cool to turn it on myself. (For the record I don’t have a Geiger counter at home. It looks like you can get one for $90 on Amazon so maybe if I have another PET scan….)

After spending an hour draining my phone’s battery reading emails and trekking the far reaches of the ‘net, the nurse came back and led me to the scan room. The whole experience was similar to the CT and MRI, but I didn’t need to do breath/hold exercises and the machine didn’t make the obnoxious buzzing sounds of the MRI. And for whatever reason I didn’t have to change into a gown – just lower my pants below my knees. Then lie still and relax. I almost dozed off a couple times. The scan was over in fifteen minutes.

The instructions I got when scheduling the PET were very clear on what to do afterwards: Go home. Go directly home. Do not pass Go. Do not linger in the building. Do not go to any other appointments. (The instructions also said to avoid close or prolonged contact with pregnant women and children under 18. I assume I should also avoid anyone who happens to be carrying a Geiger counter. The former could be harmed by my radioactive non-super powers. As for the latter…anyone who wanders around with a Geiger counter is probably best avoided under any circumstance.) Actually you’re not terribly radioactive and if you sit across the table from someone they’re sufficiently far away (~3 feet) that they’re unlikely to be harmed. You might want to keep your dog off your lap though. In any case the tracer has a short half-life so you’re safe to annoy people without irradiating them after about six hours.

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