Cancer: what you need to know.

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When it comes to cancer, we all know the basics.

Don't smoke. Don't get sunburned. Get recommended Pap smears and mammograms if you're a woman, PSA tests if you're a man, and colonoscopies no matter who you are.

But that's just the beginning. Which cancers are most likely to strike and which are most likely to kill? What are the warning signs? And how can you lower your risk?

According to the American Cancer Society, a third of the 565,650 cancer deaths expected to occur in 2008 are linked to what people eat and how much they move. Here's what you need to know to increase your odds of staying cancer-free.

What You Need to Know

Here's a snapshot of the key risk factors and warning signs for major cancers that are linked to diet, weight, or exercise.

Bear in mind that not all warning signs mean that you have cancer and that not all risk factors are equal. Smoking boosts your risk of lung cancer 20 times, for example, but most other risk factors barely double the odds of getting cancer.

Nevertheless, it's worth knowing what you can do to dodge a disease that strikes one out of two men and one out of three women during their lifetimes.

BREAST

An estimated 182,500 women in the United States will get a diagnosis of breast cancer in 2008. And roughly 41,000 women will die of the disease--more than any cancer other than lung. One in eight women will be diagnosed with breast cancer during her lifetime.

The incidence of postmenopausal breast cancer (the number of cancers diagnosed per 100,000 women) fell by 8.6 percent from 2001 to 2004.

The likely cause: Prescriptions for postmenopausal hormones plummeted from 61 million in 2001 to 21 million in 2004. In 2002, researchers reported that the hormones raise the risk of breast cancer, heart attacks, and stroke.

You have a higher risk:

Age: if you are a woman over 60.

Race: if you are non-Hispanic white.

Family history: if you have relatives--especially a mother, sister, or daughter--who had breast cancer.

Genes: if you have genes (like BRCA1 and BRCA2) that are found in families with high rates of breast cancer.

Weight: if you are overweight or obese (postmenopausal only).

Menstrual periods: if they started before age 12 or if you started menopause after age 55.

Age at childbirth: if you were older than 30 when you had your first child. Childbirth: if you never gave birth.

Hormones: if you took hormones (estrogen plus progestin) after menopause.

Breast density: if you have dense or fatty breast tissue (seen on a mammogram).

Abnormal breast cells: if a biopsy has found atypical hyperplasia or lobular carcinoma in situ (LCIS).

DIET, WEIGHT, EXERCISE

"The take-home message is that being overweight increases the risk of postmenopausal breast cancer," says Regina Ziegler, a researcher at the National Cancer Institute in Bethesda, Maryland, and a member of Nutrition Action's scientific advisory board.

And the risk rises steadily as you put on extra pounds. "There's no threshold where being a little overweight won't increase the risk," Ziegler explains.

In a study of 99,000 women, those who never used postmenopausal hormones and who gained at least 22 pounds since the age of 18 had a 30 percent higher risk than those who gained fewer than five pounds. (1) (Weight gain has less impact on women who take hormones because the estrogen they take dwarfs the extra estrogen produced by their fat cells.)

In some studies, women who are more physically active have a lower risk of breast cancer. (2) "But it's still unclear whether physical activity would lower your risk if it didn't keep your weight down," says Ziegler. "I don't think we've nailed that yet."

Alcohol also raises breast cancer risk, and it doesn't take much. "Alcohol increases the risk even if you compare women who have one drink a day to those who drink less," says Ziegler. But alcohol raises risk only slightly--9 percent for every daily drink--according to studies on roughly 300,000 women. (3)

While it's still uncertain if vitamin D, soy, or calcium protect the breast, other leads haven't panned out. "We don't have persuasive evidence that fruits and vegetables are protective," says Ziegler, "or that dietary fat--animal, saturated, or any other kind--raises risk."

Warning signs: a painless lump. Less common symptoms: thickening, swelling, distortion, tenderness, skin irritation, redness, scaliness, or nipple abnormalities (ulceration, retraction, or discharge).

COLON & RECTUM

Colorectal cancer is the third most common cancer in both men and women. The incidence has dropped in the last two decades, partly because more people get polyps removed before they turn into cancers.

If colorectal cancer is diagnosed before it has spread to lymph nodes, patients have a 90 percent chance of surviving five years. But only 39 percent of cancers are caught at that early stage.

You have a higher risk:

Age: if you are over 50. (The average age at diagnosis is 72.)

Family history: if a parent, brother, sister, or child has had colon cancer.

Polyps: if you've ever had colon polyps (which are common in people over age 50, though they're mostly benign).

Other cancers: if you've had cancer of the ovary, uterus, or breast.

Inflammatory disease: if you have ulcerative colitis or Crohn's disease.

Tobacco: if you smoke cigarettes. Weight: if you are overweight or obese.

DIET, WEIGHT, EXERCISE

"We have convincing evidence that obesity is a risk factor for colorectal cancer," says David Hunter, professor of cancer prevention at the Harvard School of Public Health in Boston.

For example, in an American Cancer Society study, men with a waist measuring at least 47 inches had a 68 percent higher risk of colon cancer than men with a waist smaller than 37 inches. (4) Women who were at least 43 inches around the middle had a 75 percent higher risk than women with a waist smaller than 33 inches.

And the risk starts to climb long before you're shopping for plus sizes. "You see the risk increase all the way through the normal weight range, even before you reach overweight," says Eugenia Calle, director of analytic epidemiology at the American Cancer Society.

Getting up off the couch also matters. In the NIH-AARP study of nearly 500,000 Americans, men who engaged in sports or exercise at least five times a week had about a 20 percent lower risk of colon cancer than men who exercised rarely or never. (5) On the flip side, the risk was 20 percent higher for men who watched TV or videos for five or six hours a day than for men who watched for less than three hours. (The impact of exercise was less clear-cut for women.)

Eating less meat may also make a difference. (6) "Red and processed meats are associated with a higher risk of colorectal cancer," says Marji McCullough, strategic director of nutritional epidemiology at the American Cancer Society.

"That's one reason why the society's guidelines suggest limiting the consumption of red and processed meats, replacing them with fish, poultry, and legumes, and eating more vegetables, fruits, and whole grains."

Calcium-rich dairy foods may also protect the colon. When researchers pooled the results of 10 studies on a total of 500,000 people, they found a lower risk in people who consumed at least 1,000 milligrams a day of calcium from food and supplements. (7)

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"Calcium appears to be responsible, because supplements lowered the risk of recurrent colon polyps by about 20 percent in a clinical trial," notes McCullough. (8)

"Calcium is one of the few things that has had a significant impact in clinical trials." In contrast, fiber doesn't seem to play a role, and it's not clear that vegetables and fruits offer any protection. (9,10)

"The idea that you can lower colorectal cancer risk by supplementing with fiber is dubious," says David Hunter. "When we controlled for other risk factors, the association with fiber went away."

Of course, getting a colonoscopy or other test that finds polyps before they turn into cancer--and then removing the poyps--can slash your risk.

"For colorectal cancer, screening is really critical," says McCullough.

Warning signs: diarrhea or constipation, feeling that your bowel doesn't empty completely, blood (bright red or very dark) in your stool, narrow stools, gas pains or cramps, feeling full or bloated, weight loss, fatigue, nausea, vomiting.

ESOPHAGUS

Esophageal cancer is really two distinct cancers. Squamous cell cancer, which typically strikes the upper or middle esophagus, used to account for roughly 90 percent of all esophageal cancers.

Adenocarcinoma, which strikes the lower esophagus, now accounts for half of all esophageal cancers. "It's a rare but rapidly increasing cancer," says Christian Abner, a researcher at the National Cancer Institute. "And it's five to six times more common in men."

Survival rates are grim for both cancers because they're rarely found early. Only 16 percent of patients are alive five years after diagnosis.

You have a higher risk:

Age: if you are over 60.

Gender: if you are male.

Tobacco: if you smoke cigarettes.

For adenocarcinoma:

Barrett's esophagus: if stomach acid backs up into your esophagus (gastric reflux) often enough to irritate cells in your esophagus, making them resemble cells that line the stomach.

Weight: if you are overweight or obese.

For squamous cell cancer:

Alcohol: if you drink heavily.

DIET, WEIGHT, EXERCISE

In the NIH-AARP study, extra pounds boosted the risk of adenocarcinoma. (11) "We saw the risk increase even within the normal weight range." says Abnet.

Extra weight may cause damage by causing stomach acid to back up into the esophagus. "People who are overweight have more reflux because there's more pressure on their esophageal sphincter," says Abnet. But so far, it's not clear whether extra weight boosts the risk if it doesn't cause reflux.

"Heavy alcohol intake is a risk factor for squamous cell cancer," notes Abnet, and fruits and vegetables are linked to a lower risk of squamous cell. (12)

"Cigarette smoking is a consistent risk factor for both cancers," he adds, "but it's stronger for squamous cell."

Warning signs: difficult or painful swallowing, severe weight loss, hoarseness, chronic cough, vomiting, coughing up blood, pain in the throat or back, pain behind the breastbone or between the shoulder blades.

KIDNEY

In 2008, an estimated 54,400 Americans will be diagnosed with kidney cancer, and 13,000 will die. Incidence rates have been climbing since the 1970s, but death rates haven't changed much since the mid-1980s.

Nine out of ten kidney cancers strike the renal cell. Fortunately, most renal cell cancers are found before they spread to distant organs in the body.

You have a higher risk:

Gender: if you are male. (Men have double the risk.)

Weight: if you are overweight or obese.

High blood pressure: if you have hypertension.

Tobacco: if you smoke cigarettes.

DIET, WEIGHT, EXERCISE

In the NIH-AARP study, the risk of renal cell cancer was higher in people who were either overweight or obese. (13)

"The argument has been whether obesity increases kidney cancer because it increases the risk of hypertension," says Harvard's David Hunter. "But the data seems to suggest that obesity is still a risk factor if you have normal blood pressure."

How might extra pounds lead to cancer in a kidney cell? "People speculate that in the obese, the kidney is working harder," says Hunter. "But the mechanism is not yet clear."

Warning signs: blood in the urine (slightly rusty to deep red color), pain in the side, a lump or mass in the side or the abdomen, weight loss, fever, tiredness.

OVARY

If you catch ovarian cancer early, the five-year survival rate is 92 percent. Unfortunately, that only happens in about one out of five cases, because the cancer has no clear warning signs or reliable screening tests.

If the cancer has spread to lymph nodes, five-year survival drops to 71 percent, and if cancer cells are found elsewhere, the odds of living five years are only 30 percent.

You have a higher risk:

Other cancers: if you or your mother, daughter, or sister has had cancer of the ovary, breast, uterus, colon, or rectum.

Genes: if you have genes (like BRCA1 and BRCA2) that are usually found in families with high rates of ovarian cancer.

Age: if you are over 55. (Most women are diagnosed in their 70s.)

Childbirth: if you never gave birth.

Estrogen: if you took estrogen (without progesterone) for at least 10 years.

DIET, WEIGHT, EXERCISE

Are overweight women more likely to get ovarian cancer? "The data are not really consistent," says the American Cancer Society's Eugenia Calle.

For years, some scientists have suggested that milk or other dairy foods raise the risk of ovarian cancer. Lactose, the naturally occurring sugar in milk, gets broken down into another sugar called galactose, explains the cancer society's Marji McCullough. "And galactose could be toxic to ovarian cells."

But when researchers pooled the results of 12 studies that tracked more than 550,000 women, they didn't find much. (14) "The lactose equal to three glasses of milk a day may weakly raise risk," says McCullough. "There might be something there," she adds, but it would take further studies to know.

Warning signs: enlarged abdomen (caused by fluid accumulation). Some women may experience persistent, vague symptoms like bloating, pelvic or abdominal pain, difficulty eating, feeling full quickly, or urinary urgency or frequency.

PANCREAS

You know it's one of the worst cancers when statisticians report one-year survival rates (which are 24 percent). Only S percent of patients make it to five years.

That's why pancreatic cancer causes more deaths than any cancer other than lung, colorectal, breast, and prostate, even though it's the tenth most common cancer among men and the eleventh most common among women.

You have a higher risk:

Age: if you are over 60.

Race: if you are African-American.

Family history: if a close family member had pancreatic, ovarian, or colon cancer.

Diabetes: if you have diabetes.

Tobacco: if you smoke cigarettes. (It doubles or triples the risk.)

Inflammation: if you get chronic pancreatitis.

Weight: if you are overweight or obese.

DIET, WEIGHT, EXERCISE

"Pancreatic cancer is the most recent addition to the list of cancers that are related to obesity," says Eugenia Calle. Because the cancer is fairly rare, researchers didn't see much of a link until huge studies looked.

Now several large studies have seen a higher risk in people who have excess weight or excess waist. (15-17)

For example, in the NIH-AARP study of nearly 500,000 people, the risk of pancreatic cancer was higher in women with a waist of at least 36 inches than in women with a waist under 30 inches. (15) "Some of the data shows a higher risk for a large waist independent of obesity," says Calle.

Red meat may also put the pancreas in jeopardy. In men (but not women), red meat--especially if it's cooked at high temperature--was linked to a 40 percent increased risk of pancreatic cancer. (18) In the Multiethnic Cohort, which tracks 190,000 Hawaiians, the link was strongest with processed meats (like bacon, sausage, hot dogs, and bologna). (19)

Warning signs; pain in the upper abdomen or upper back, yellow skin and eyes, dark urine, weakness, loss of appetite, nausea and vomiting, weight loss.

PROSTATE

In 2008, prostate cancer will strike more men (186,300) than any other cancer, and will kill more men (28,700) than any cancer other than lung. One in six men will be diagnosed with prostate cancer during his lifetime.

The good news is that more than 90 percent of prostate cancers are found in the local or regional stages, which means the five-year survival rate is close to 100 percent. In fact, 91 percent of those patients survive 10 years and 76 percent live for 15 years.

You have a higher risk:

Age: if you are over 65.

Race: if you are African-American.

Family history: if your father or brother had prostate cancer.

Cell changes: if a biopsy has found high-grade protastic intraepithelial neoplasia (PIN).

DIET, WEIGHT, EXERCISE

Many men get prostate cancer. Only a fraction get the kind that kills.

"It's particularly important to look at aggressive cases because many men die with--not of--prostate cancer," says researcher Ulrike Peters of the Fred Hutchinson Cancer Research Center in Seattle.

That's why scientists are going beyond earlier studies that linked diet or lifestyle to any prostate cancer diagnosis. "The shift is to focus on aggressive disease," says Peters. And that has made obesity stand out as a risk factor. (20)

"Dozens of studies have found no relation with total prostate cancer," notes Calle. "But obesity is related to aggressive prostate cancers that go on to kill you."

That fits with research looking at men who already have the disease. "Those studies show that once you have prostate cancer, survival is lower if you are obese," says Calle.

Other possible links with prostate cancer are now muddier. For example, a European study found a 60 percent lower risk of advanced prostate cancer in men with the highest lycopene levels in their blood. (21) But an equally large U.S. study didn't see a lower risk of aggressive prostate cancer in men with higher blood levels of lycopene. (22) "We didn't find anything," says Peters. "I don't have a good explanation."

It's still unclear whether vitamin E and selenium can protect the prostate. The ongoing SELECT trial is giving both or a placebo to more than 35,000 men. "But the trial isn't closing until 2012," says Peters. "And so far, the evidence for vitamin E comes mostly from smokers."

On the plus side, recent studies have questioned--but not put to rest--earlier concerns that calcium, dairy foods, or the alpha-linolenic acid in vegetable oils might promote prostate cancer. (23-25)

Vitamin D is far more confusing. In animals, it seems to protect against prostate cancer, but in humans, most research has shown no link. However, a recent study--which was large enough to look at aggressive cancers--found a higher risk in men unless they had the lowest vitamin D levels in their blood. (26) But the risk didn't rise as vitamin D levels rose.

"It may be worrisome, but we have to see if it's reproducible in other studies," says co-author Richard Hayes of the National Cancer Institute.

Warning signs: weak or interrupted urine flow, difficulty starting or stopping urine flow, the need to urinate frequently, blood in the urine, pain or burning with urination.

UTERUS

Roughly 40,000 U.S. women will be diagnosed with cancer of the uterus in 2008. Most of the cancers will be in the uterine lining, or endometrium. After five years, 83 percent of patients are still alive, since most cases are caught before they spread to distant sites.

You have a higher risk:

Age: if you are over 50.

Race: if you are white.

Weight: if you are overweight or obese.

Blood sugar: if you have diabetes.

Blood pressure: if it's high.

Childbirth: if you never gave birth.

Menstrual periods: if they started before age 12 or if you started menopause after age 55.

Hormones: if you take estrogen without progesterone.

Hyperplasia: if you have endometrial hyperplasia (extra cells lining the uterus). Symptoms include heavy menstrual periods, bleeding between periods, and bleeding after menopause.

DIET, WEIGHT, EXERCISE

"The relationship between obesity and endometrial cancer is well-established," says the American Cancer Society's Eugenia Calle. That's because it's so powerful.

Among women who don't take postmenopausal hormones, the risk is twice as high if they have gained 11 to 44 pounds since the age of 18. (27) (Extra fat may boost risk because fat cells make estrogen. But the extra estrogen from fat cells has little impact on women who have higher estrogen levels because they take hormone pills.)

"The risk of endometrial cancer increases even within the normal weight range," says Calle. One encouraging note: If you're overweight or obese, even light or moderate exercise can help lower your risk. (28)

Warning signs: abnormal uterine bleeding or spotting, pain during urination or intercourse, pain in the pelvic area.

(1) J. Am. Med. Assoc. 296: 193, 2006.

(2) J. Am. Med. Assoc. 290: 1331, 2003.

(3) J. Am. Med. Assoc. 279: 535, 1998.

(4) Cancer Causes Control 19: 783, 2008.

(5) Cancer Causes Control 19: 939, 2008.

(6) J. Am. Med. Assoc. 293: 172, 2005.

(7) J. Natl. Cancer Inst. 96: 1015, 2004.

(8) N. Engl. J. Med. 340: 101, 1999.

(9) J. Am. Med. Assoc. 294: 2849, 2005.

(10) J. Natl. Cancer Inst. 99: 1471, 2007.

(11) Eur. J. Cancer 44: 465, 2008.

(12) Int. J. Cancer 121: 2753, 2007.

(13) Am. J. Epidemiol. 168: 268, 2008.

(14) Cancer Epidemiol. Biomarkers Prev. 15: 364, 2006.

(15) Am. J. Epidemiol. 167: 586, 2008.

(16) Cancer Epidemiol. Biomarkers Prev. 15: 879, 2006.

(17) Cancer Epidemiol. Biomarkers Prev. 14: 459, 2005.

(18) Cancer Epidemiol. Biomarkers Prev. 16: 2664, 2007.

(19) J. Natl. Cancer Inst. 97: 1458, 2005.

(20) Cancer Epidemiol. Biomarkers Prev. 16: 63, 2007.

(21) Am. J. Clin. Nutr. 86: 672, 2007.

(22) Cancer Epidemiol. Biomarkers Prev. 16: 962, 2007.

(23) Cancer Epidemiol. Biomarkers Prev. 16: 1364, 2007.

(24) Cancer Epidemiol. Biomarkers Prev. 16: 2623, 2007.

(25) Am. J. Epidemiol. 166: 1270, 2007.

(26) J. Natl. Cancer Inst. 100:. 796, 2008.

(27) Cancer Epidemiol. Biomarkers Prev. 16: 723, 2007.

(28) Int. J. Cancer 123: 1877, 2008.

FIVE-YEAR SURVIVAL RATES

                  All Stages   Local   Regional   Distant
Site                  %          %        %          %

Breast (female)       89        98        84        27
Colon & Rectum        64        90        68        10
Esophagus             16        34        17         3
Kidney                66        90        61        10
Larynx                63        81        50        24
Liver                 11        22        7          3
Lung                  15        49        15         3
Skin (Melanoma)       91        99        65        15
Oral                  59        82        52        27

                  All Stages   Local   Regional   Distant
Site                  %          %        %          %

Ovary                 45        92        71        30
Pancreas              5         20        8          2
Prostate              98        100       --        32
Stomach               24        61        24         3
Testicle              95        99        96        70
Thyroid               97        100       97        56
Bladder               80        92        45         6
Cervix                72        92        56        17
Uterus                83        95        67        23

The odds of surviving for at least five years depend on the type
of cancer and whether the tumor is local or whether it has spread
to regional lymph nodes or to distant sites in the body. Individual
odds vary. These percentages are based on patients who were
diagnosed at least five years ago, so they don't reflect recent
advances in treatment.

Source: Cancer Facts & Figures 2008, American Cancer Society.

CATCHING CANCER EARLY

If you have no symptoms, these are the screening tests that
the American Cancer Society recommends for the major cancers.

SITE             SCREENING

Breast           Mammogram: Yearly if 40 or older.

                 Clinical breast exam: Yearly if 40 or older;
                 every 3 years if 20-39.

                 Breast self-exam: Monthly for all.

Colon & Rectum   If 50 or older, choose one:

                 1. Fecal occult blood test every year

                 2. Flexible sigmoidoscopy every 5 years

                 3. Both 1 and 2 (preferred over either 1 or 2)

                 4. Double-contrast barium enema every 5 years

                 5. Colonoscopy every 10 years

                 If at high risk (family history of polyps or colon
                 cancer, etc.), consult doctor.

Prostate         Digital rectal exam and PSA test: Yearly if 50 or
                 older and life expectancy is at least 10 years.

                 If at high risk (African-American, family history,
                 etc.), start at age 45.

Cervix           Pap test & pelvic exam: Yearly if 21 or older
                 (or younger if sexually active for at least 3 years).
                 Less frequently after 3 or more normal exams.

Source: Adapted from "Screening Guidelines For the Early Detection
of Cancer in Asymptomatic People," Cancer Facts & Figures 2008,
American Cancer Society.

LEADING CANCER KILLERS

Female

Lung                             71,030
Breast                           40,480
Colon & Rectum                   25,700
Pancreas                         16,790
Ovary                            15,520
Non-Hodgkin Lymphoma              9,370
Leukemia                          9,250
Uterus                            7,470
Liver                             5,840
Brain                             5,650
Myeloma                           5,050
Kidney                            4,910
Stomach                           4,430
Bladder                           4,150
Cervix                            3,870

Male

Lung                             90,810
Prostate                         28,660
Colon & Rectum                   24,260
Pancreas                         17,500
Liver                            12,570
Leukemia                         12,460
Esophagus                        11,250
Bladder                           9,950
Non-Hodgkin Lymphoma              9,790
Kidney                            8,100
Brain                             7,420
Myeloma                           5,640
Skin (Melamona)                   5,400
Oral Cavity & Pharynx             5,210
Larynx                            2,910

Estimated number of cancer deaths for 2008.

Source: Cancer Facts & Figures 2008, American Cancer Society.

Note: Table made from bar graph.