You may want to read the Mayo Clinic article on carbs feeding cancer. One of those internet myths that will not die.
https://www.mayoclinic.org/diseases-conditions/cancer/in-depth/cancer-causes/art-20044714
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Myth: People with cancer shouldn't eat sugar, since it can cause cancer to grow faster.
Fact: Sugar doesn't make cancer grow faster. All cells, including cancer cells, depend on blood sugar (glucose) for energy. But giving more sugar to cancer cells doesn't speed their growth. Likewise, depriving cancer cells of sugar doesn't slow their growth.
This misconception may be based in part on a misunderstanding of positron emission tomography (PET) scans, which use a small amount of radioactive tracer — typically a form of glucose. All tissues in your body absorb some of this tracer, but tissues that are using more energy — including cancer cells — absorb greater amounts. For this reason, some people have concluded that cancer cells grow faster on sugar. But this isn't true.
However, there is some evidence that consuming large amounts of sugar is associated with an increased risk of certain cancers, including esophageal cancer. It can also lead to weight gain and increase the risk of obesity and diabetes, which may increase the risk of cancer."
2nd article for you to review.
https://scienceblog.cancerresearchuk.org/2017/05/15/sugar-and-cancer-what-you-need-to-know/
You could also try some of the freeze dried foods like Ziwipeak or Stella and Chewy's. Not necessarily for the lower carb percentages, but for higher quality food. I do not know the carb percentages on either of those foods.
Although, ran a couple of the Stella and Chewy's through a basic carb calculator using the GA (guaranteed analysis) percentages on the label. Came out at around 20-21% carbs. Anything with organ meats (liver, heart, gizzard) are going to have some carbs in the food, due to the organ meats.
Ziwipeak has TNA info (typical analysis) you can download directly from their website.
https://www.ziwipets.com/cat-food/air-dried/free-range-chicken-recipe No idea how they got these figures. It looks to me like they may have reversed the Ash and Carb percentages. But I could be wrong.