Obese patients with various types of cancer are known to have a poorer prognosis (see: Obesity Linked to Poor Colon Cancer Prognosis). However, I was not familiar with any theories explaining this phenomenon until I came across a recent article (see: Why obese patients with cancer often have a poorer prognosis). Here's some information from the author of a recent study on this topic:
"Our earlier studies led us to hypothesize that fat tissue called white adipose tissue, which is the fat tissue that expands in individuals who are obese, is itself directly involved and that it is not just diet and lifestyle that are important,” he said....In obese and lean mice that ate the same diet, tumors grew much faster in obese mice than they did in lean mice....Detailed analyses indicated cancer induced mobilization of adipose stromal cells into the circulation. Once in the tumors, some of these [white adipose tissue] cells developed into fat cells, while others were incorporated into tumor-associated blood vessels. Tumor-associated blood vessels support tumor growth by bringing in oxygen and nutrients vital for cancer cell survival and proliferation. [He] noted that the ability of adipose stromal cells to contribute to the formation of tumor-associated blood vessels is likely one of the main reasons that the excess of these cells in tumors was associated with increased malignant cell proliferation and tumor growth.....“The fact that these cells are present in tumors is still an emerging concept. We have shown that not only are they present, but they are also functional and affect tumor growth. Identifying the signals that cause these cells to be recruited to tumors and finding ways to block them might provide a new avenue of cancer treatment.”
Here's a definition for white adipose tissue (see: White adipose tissue):
White adipose tissue (WAT) or white fat is one of the two types of adipose tissue found in mammals. The other kind of adipose tissue is brown adipose tissue. In healthy, non-overweight humans, white adipose tissue composes as much as 20% of the body weight in men and 25% of the body weight in women. Its cells contain a single large fat droplet, which forces the nucleus to be squeezed into a thin rim at the periphery. They have receptors for insulin, growth hormones, norepinephrine and glucocorticoids.
All of this makes perfect sense. Many malignant tumors can only grow rapidly if they can stimulate the proliferation of blood vessels in and around the tumor for nutrition. As noted above, white adipose tissue, also called adipose stromal cells, contribute to the formation of tumor-associated blood vessels and accelerate tumor growth. This research prompts a question in my mind whether it's a good idea for patients with the diagnosis of, say, colonic cancer to try to lose weight to improve their prognosis. Here some advice from one physician on this topic (see: Colon cancer prognosis worse for the obese, type 2 diabetics):
Obesity, elevated body-mass index and diabetes are associated with worse [colonic cancer] disease states across the board," said Dr. David Bernstein, chief of gastroenterology at North Shore University Hospital in Manhasset, N.Y. "But, we don't know if you lose weight [whether the] risk will go down. I don't counsel patients who've been diagnosed with colorectal cancer to lose weight, because weight loss tends to be a worry in people undergoing cancer treatment anyway. I do counsel my patients that haven't been diagnosed with cancer to lose weight. The medical community needs to spend more time counseling prevention."