What Body Fat Can Tell Us About Kidney Cancer

A new tool to predict the aggressiveness of kidney tumors has been recently described by Doctors in Shanghai:  the amount of visceral fat in the abdomen.  You can’t see visceral fat when you look at a person – it’s all on the inside, surrounding the internal organs.  Some people carry more fat on the outside, some on the inside.  This is determined by genetics – which we can’t control.  Its fair to say, though, that the more fat we have overall, the more fat we have inside of our bodies.

CT scans showing visceral and sub-cutaneous fat

Three views of the abdomen at the level of the belly button. Image A: the fat is black. Image B: the visceral fat is white. Image C: the fat of the abdominal wall is white.

How does this help predict the behavior of kidney cancer?  All kidney cancers are not the same – they can differ in how aggressive they are.  One measure of aggressiveness is the “Grade” of the cancer.  High grade kidney cancer grows faster than low grade cancer, and has a greater likelihood of invading other organs and spreading to distant marts of the body.

Since many tumors are now discovered when they are small, many doctors and patients have the dilemma of deciding to watch a kidney tumor or treat it.  Biopsy can offer some guidance.  It’s becoming better at differentiating between cancer and non-cancerous tumors.  Biopsy still falls short when it comes to predicting the grade of a tumor.

The Chinese study used the same CAT scans that were used to diagnose the kidney tumors.  Radiologists calculated the percentage of visceral fat in relation to total abdominal fat by measuring fat both inside and outside the body.  The study showed a 6% greater chance of a high grade tumor for each increase in visceral fat of 1%.  The percentage of visceral fat varied tremendously among patients in the study from 17 to 83%.  When these patients were divided up into four groups based upon the percentage of visceral fat, the lowest two groups had 19% and 21% high grade tumors, and the highest two groups had 28% and 31% high grade tumors.  The study also confirmed a previously known finding that the larger tumors were more likely to be high grade.

Why does the visceral fat predict high grade tumors?  This is not known, but this type of fat is known to effect cholesterol, and is associated with atherosclerosis that causes hert disease and strokes.  The lates finding adds yet another reason to follow a healthy diet and perform aerobic exercise on a regular basis.

It is helpful to know about the relationship if visceral fat and the aggressiveness of kidney cancer.  Interest in identifying patients with kidney tumors who can be watched has relied on biopsy.  Measurements of fat inside the abdomen case add to our ability to predict which tumors by filling in some of the gaps where biopsy falls short.

Visceral Obesity and Risk of High Grade Disease in Clinical T1a Renal Cell Carcinoma. Yao Zhu et al. J Urology 1 February 2013 (volume 189 issue 2 Pages 447-453

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