Kidney Cancer
Weight Gain & Cancer Risk
Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: William C. Shiel Jr., MD, FACP, FACR
Excess weight is a known risk factor for many chronic diseases, such as
diabetes and heart disease. Obesity has also been linked an increased risk for
developing some cancers. To clarify the effects of weight gain on cancer risk,
researchers in 2007 conducted an analysis of many studies reported in medical
journals that describe 282,137 cases of cancer. The researchers wanted to see if
weight gain had an effect on the risk for certain cancer types.
In particular, the researchers looked at the risk of cancer associated with a
weight gain corresponding to an increase of 5 kg/m2 in body mass index (BMI). In
terms of actual pounds gained, a man with a normal-range BMI of 23 would need to
gain 15 kg (33 lbs.) of weight, while a woman with a BMI of 23 would need to
gain 13 kg (28.6 lbs.) to correspond to an increase of 5 in the BMI.
The results, published in the Lancet in February 2008, revealed that weight
gain is positively associated with the risk of developing a variety of types of
cancer as described below.
For women, a weight gain corresponding to an increase of 5 in the BMI
resulted in a significant increase in risk for developing four cancer types:
- esophageal adenocarcinoma (double the risk),
- endometrial cancer (slightly more
than double the risk),
- gallbladder cancer (slightly more than double the risk), and
- kidney (renal) cancer.
The kidneys
The kidneys are a
pair of organs on either side of the spine in the lower abdomen. Each kidney is
about the size of a fist. Attached to the top of each kidney is an adrenal gland.
A mass of fatty tissue and an outer layer of fibrous
tissue (Gerota's fascia) enclose the kidneys and adrenal glands.
The kidneys are part of the urinary tract. They make urine
by removing wastes and extra water from the blood. Urine collects in a hollow
space (renal pelvis) in the
middle of each kidney. It passes from the renal pelvis into the bladder through
a tube called a ureter.
Urine leaves the body through another tube (the
urethra).
The kidneys also make substances that help control blood pressure and the
production of red blood cells.
Understanding cancer
Cancer
begins in cells, the building blocks that make up tissues. Tissues
make up the organs of the body.
Normally, cells grow and divide to form new cells as the body needs them.
When cells grow old, they die, and new cells take their place.
Sometimes this orderly process goes wrong. New cells form when the body does
not need them, and old cells do not die when they should. These extra cells can
form a mass of tissue called a growth or tumor.
Tumors can be benign or malignant:
- Benign tumors are not
cancer:
- Benign tumors are rarely life threatening.
- Usually, benign tumors can be removed, and they
seldom grow back.
- Cells from
benign tumors do not invade tissues around them or spread to other parts of the
body.
- Malignant tumors are
cancer:
- Malignant tumors are generally more serious than
benign tumors. They may be life threatening.
- Malignant tumors often can be removed, but they can
grow back.
- Cells from malignant tumors can invade and damage
nearby tissues and organs. Also, cancer cells can break away from a
malignant tumor and enter the bloodstream or lymphatic system. That is how
cancer cells spread from the original cancer (primary tumor) to form new
tumors in other organs. The spread of cancer is called metastasis.
Several types of cancer can start in the kidney. This
booklet is about renal cell cancer, the most common type of kidney cancer in
adults. This type is sometimes called renal adenocarcinoma or hypernephroma.
Another type of cancer, transitional cell carcinoma,
affects the renal pelvis. It is similar to bladder
cancer and is often treated like bladder cancer. Wilms tumor is the most common
type of childhood kidney cancer. It is different from adult kidney cancer and
requires different treatment. Information about transitional cell carcinoma and
Wilms tumor is available from the Cancer Information Service at 1-800-4-CANCER
and at http://cancer.gov.
When kidney cancer spreads outside the kidney, cancer cells are often found
in nearby lymph nodes. Kidney cancer also may spread to the lungs, bones, or
liver. And it may spread from one kidney to the other.
When cancer spreads (metastasizes) from its original place to another part of
the body, the new tumor has the same kind of abnormal cells and the same name as
the primary tumor. For example, if kidney cancer spreads to the lungs, the
cancer cells in the lungs are actually kidney cancer cells. The disease is
metastatic kidney cancer, not lung cancer. It is treated as kidney cancer, not
lung cancer. Doctors sometimes call the new tumor metastatic or "distant"
disease.
Next: Who's at risk for kidney cancer? »
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