Adult weight gain tied to prostate cancer risk
By Steven Reinberg,
Men who pack on excess pounds as young adults are at heightened risk of developing prostate cancer, although the risk varies by ethnic group, researchers from the University of Hawaii report.
Obesity is a risk factor for many common cancers, including colorectal cancer and breast cancer in postmenopausal women. However, whether obesity plays a role in prostate cancer risk has been unclear, researchers say.
The new study finds that "body mass in both younger and older adulthood, and weight gain between these periods of life, may influence prostate cancer risk," said study author Brenda Y. Hernandez, an assistant professor at the Cancer Research Center of Hawaii.
The report is published in the September online issue of Cancer Epidemiology, Biomarkers and amp; Prevention.
For the study, Hernandez's team looked at the relationship between weight and prostate cancer in a multiethnic population including blacks, Japanese, Hispanics, Native Hawaiians and whites, all of whom who participated in a long-term study called the Multiethnic Cohort.
The researchers collected data on almost 84,000 men who participated in the study. In all, more than 5,500 men were diagnosed with prostate cancer. Men who were overweight or obese at 21 had a lower risk of localized and low-grade prostate cancer, the researchers found.
When men put on weight seemed to matter, as did race and ethnicity. For example, "higher weight in older adulthood was associated with increased risk of prostate cancer among white and Native Hawaiian men and a decreased risk of prostate cancer among Japanese men," Hernandez said.
And excessive weight gain in young adulthood increased the risk of advanced and high-grade prostate cancers (the more dangerous kind) for white men, the report found. For black men, excessive weight gain as a young adult upped risks for less hazardous, localized and low-grade forms of the disease.
Genes and lifestyle may account for these differences in risk, Hernandez speculated. "The relationship of certain characteristics, such as body size, with cancer risk may vary across ethnic groups due to the combined influence of both genes and lifestyle," she said. "This study underscores the importance of investigating cancer etiology in diverse populations."
Victoria Stevens, strategic director of laboratory services at the American Cancer Society, said the study shows there are differences in ethnic groups, but these differences are not straightfoward.
"Their findings aren't definitive," Stevens said. "They are just not clear-cut, you don't see a simple linear relationship."
"The paper is very suggestive, but it is not clear in prostate cancer whether weight gain is as important" as it is for other malignancies, she said. "Exactly what that risk is, we still don't know."
More information
For more information on prostate cancer, visit the American Cancer Society.
SOURCES: Brenda Y. Hernandez, Ph.D., M.P.H., assistant professor, Cancer Research Center of Hawaii, University of Hawaii, Honolulu; Victoria Stevens, Ph.D., strategic director, laboratory services, American Cancer Society; September 2009 Cancer Epidemiology, Biomarkers & Prevention, online
| How Is Prostate Cancer Found? | |
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Screening refers to testing to find a disease such as cancer in people who do not have symptoms of that disease. Prostate cancer can often be found early by testing the amount of PSA (prostate-specific antigen) in your blood. Another way prostate cancer is found early is when the doctor does a digital rectal exam (DRE). This is when a doctor a puts a gloved finger into the rectum to feel the prostate gland. Because the prostate gland lies just in front of the rectum, during the DRE the doctor can feel if there are any bumps or hard places on the prostate. These might be cancer. If you have had routine yearly exams and either one of these test results is not normal, any cancer you might have has probably been found at an early, more treatable stage.
Since about 1990 it has become more common for men to have tests to find prostate cancer early. The prostate cancer death rate has dropped, too. But we do not yet know if this drop is the direct result of the tests.
These tests are not perfect, though. Uncertain or false test results could cause confusion and worry. There is no question that the PSA test can help spot prostate cancer early. But it can't tell how dangerous the cancer is. The problem is that some prostate cancers are slow-growing and may never cause problems. But because of a high PSA level, many men will be found to have prostate cancer that would never have led to their deaths. Often these men are being treated with either surgery or radiation, either because their doctor can't be sure how fast the cancer might spread or because they are uncomfortable not having treatment. Doctors and patients are still struggling to decide who should get treatment and who can be followed without treatment.
Until more is known, you should talk to your doctor about whether or not you want to be tested. Things to take into account are your age and your health. If you are young and you get prostate cancer, it will probably shorten your life if it is not caught early. But if you are older or in poor health, then prostate cancer may never become a major problem because it often grows so slowly.
What the American Cancer Society recommends
The American Cancer Society (ACS) does not recommend routine prostate cancer screening for all men at this time. ACS believes that doctors should discuss the pros and cons of testing with men so each man can decide if testing is right for him. If a man chooses to be tested, the tests should include a PSA blood test and DRE (digital rectal exam) yearly, beginning at age 50, for men at average risk who can be expected to live at least 10 more years.
For men at higher risk, this discussion should take place starting at age 45. Men at high risk include African American men and men who have a close relative (father, brother, or son) who had prostate cancer before age 65.
This discussion should take place at age 40 for men at even higher risk (those with several close relatives with prostate cancer at an early age).
After this talk, if a man asks his doctor to make the decision about testing for him, he should be tested, unless there is a specific reason not to test.
The PSA blood test
PSA (prostate-specific antigen) is a substance made by the prostate gland. Although PSA is mostly found in semen, a small amount is also found in the blood. Most healthy men have levels under 4 ng/mL (nanograms per milliliter) of blood. The chance of having prostate cancer goes up as the PSA level goes up. If your level is between 4 and 10, you have about a 1 in 4 chance of having prostate cancer. If it is above 10, your chance is over 50%. But some men with a PSA below 4 can also have prostate cancer.
Factors other than cancer can also cause the PSA level to go up, including:
- BPH (benign prostatic hyperplasia), a non-cancerous swelling of the prostate that many men get as they grow older.
- Age: PSA levels go up slowly as you get older, even if you have no prostate changes.
- Prostatitis: an infection or inflammation of the prostate gland.
- Ejaculation can cause the PSA to go up for a short time, and then go down again.
Some things can cause PSA levels to go down, even when cancer is present:
- Certain medicines used to treat BPH or urinary symptoms. You should tell your doctor if you are taking medicines for these problems, because the doctor may need to adjust the reading.
- Some herbal mixtures that are sold as dietary supplements "for prostate health" may also hide a high PSA level. This is why it is important to let your doctor know if you are taking any type of supplement. Saw palmetto (an herb used by some men to treat BPH) does not seem to affect the measurement of PSA.
- Obesity: Very overweight men tend to have lower PSA levels.
There are a number of new types of PSA tests that might help to show whether or not you need more testing. Not all doctors agree on how to use these new PSA tests. You should talk to your doctor about your cancer risk and any tests that you are having.
Use of the PSA blood test after prostate cancer diagnosis
Although the PSA test is used mainly to find prostate cancer early, it has other uses, too.
- In men diagnosed with prostate cancer, it can be used along with other results to help decide which types of testing or treatment might be helpful.
- A very high PSA level might mean that the cancer has spread beyond the prostate. This also helps determine treatment because some forms of treatment are not as helpful for cancer that has spread to the lymph nodes or other organs.
- The PSA test can also be used to help show if treatment is working, how well it is working, or whether the cancer has come back after treatment.
- If you choose a "watchful waiting" approach, the PSA level can be used to help decide whether the cancer is growing and whether you should think about starting treatment.
If prostate cancer has come back (recurred) after treatment, or if it has spread outside of the prostate (metastatic disease), the actual PSA number may not be as important as whether it changes. The PSA number does not tell whether or not a man will have symptoms or how long he will live. Many people have very high PSA values and feel just fine. Other men have low values and have symptoms. With advanced disease, it also may be more important to look at the way the PSA level is changing rather than the actual number.
Signs of prostate cancer
Early prostate cancer often causes no symptoms. It may be found by a PSA test or DRE. Problems with urinating could be a sign of advanced prostate cancer, but more often this problem is caused by a less serious disease known as BPH (benign prostatic hyperplasia).
Symptoms of advanced prostate cancer are:
- trouble having or keeping an erection (impotence)
- blood in the urine
- pain in the spine, hips, ribs, or other bones
- weakness or numbness in the legs or feet
- loss of bladder or bowel control
Once again, other diseases also can cause these symptoms.
If certain symptoms or the results of early tests suggest you might have prostate cancer, your doctor will do a prostate biopsy to find out whether the disease is present.
The prostate biopsy
A biopsy is the only way to know for sure if you have prostate cancer. During a biopsy, tissue from the prostate is removed so it can be sent to the lab to see if it contains cancer cells. A core needle biopsy is type used most often. Here is how it's done:
A small probe is placed in the rectum. The probe gives off sound waves which make a picture of the prostate on a video screen. This technique is called TRUS (transrectal ultrasound). Guided by TRUS, the doctor puts a thin needle through the wall of the rectum into the prostate gland. When the needle is pulled out, it takes out a piece of tissue, usually about ½ inch long and 1/16 inch across. Some doctors do the biopsy through the skin between the rectum and the scrotum.
Although the test sounds painful, it usually causes little discomfort because it is done very quickly. The doctor can numb the area ahead of time. You might want to ask your doctor about numbing the area. Samples are often taken from different parts of the prostate. Ask your doctor how many samples will be taken.
The biopsy takes about 15 minutes and is usually done in the doctor's office. You will likely be given antibiotics to take ahead of time and afterwards to reduce the chance of infection. For a few days afterwards you may notice some soreness, blood in your semen, rust-colored urine, or light bleeding from the rectum. Some men have blood in their semen for up to a month or 2 after the biopsy.
Cancer may only be present in a small area of the prostate. Because of this, sometimes the biopsy will miss the cancer even when it is there. This is known as a "false negative." If your biopsy doesn't show cancer, but your doctor still strongly suspects cancer, a repeat biopsy may be needed.
Grading the prostate cancer
The biopsy sample will be sent to a lab. A doctor there will look for cancer cells in the sample. If cancer is present, the sample will be graded. Grading the cancer helps to predict how fast the cancer is likely to grow and spread.
Prostate cancers are graded on the basis of how closely the cells in the sample look like normal prostate cells. Those that look very different from normal cells are likely to mean a cancer that grows faster. The system used most often for grading prostate cancer is called the Gleason system.
Samples from 2 areas of the prostate are each graded from 1 to 5, and the number grades are added to give a Gleason score or sum of between 2 and 10. The lower the number, the more the cells in the sample look like normal prostate cells. A higher score means the cells look less normal and the cancer is likely to grow more quickly. Ask your doctor to explain the grade of your cancer because it is an important factor in making treatment decisions.
Sometimes the cells don't look like cancer but they don't look really normal either. In these cases, more biopsies may be done later.
Other things you may see on a biopsy report
The biopsy report tells you the grade of the cancer (if it is present), but it also often gives you other information that may give a better idea of the scope of the cancer. These can include:
- the number of biopsy samples that contain cancer (for example, "7 out of 12")
- the amount of cancer in each of the cores (given as a percentage)
- whether the cancer is on one side (left or right) of the prostate or both sides (bilateral)
Brawley was referring to the fact that the entire annual budget for the National Cancer Institute is less than the budget for two weeks in Iraq.
That’s part of the reason the treatment of metastatic cancer has been a “disappointment” over the last 40 years, according to Brawley.
New cancer drugs may be marketed by drug companies, but a lot of them get their start in academic labs funded by NCI grants. As of now, the NCI can only afford to fund 10 percent of the grants it approves, Brawley said. The money tends to go to conservative choices because “nobody wants to fund an idea that might fail and get accused of wasting grant money,” he added.
An example: Brian Druker’s early research on Gleevec (imatinib) was turned down by the NIH as too risky and “darn near didn’t get funded by the ACS either,” Brawley said. Gleevec, now marketed by Novartis for chronic myeloid leukemia and certain stomach cancers, has been hailed as one of the greatest breakthrough cancer drugs and generated $3.7 billion in sales last year.
Not all cancer drugs have been as successful as Gleevec – either financially or in terms of efficacy. In fact, not many have. Brawley argued that decreased smoking and increased screening for breast and colorectal cancer have had a lot more impact on cancer death rates than new drugs.
The survival benefit of drugs for metastatic cancers is often measured in “a few days to a few months,” Brawley complained. When Tarceva (erlotinib, OSI Pharmaceuticals and Genentech/Roche) was approved for pancreatic cancer based on a survival benefit of less than two weeks, someone mailed Brawley a stopwatch.
That said, biotech drugs are still important, in Brawley’s opinion, because developing drugs that improve survival by two or three weeks is a “step toward getting three years.” And there are always patients who exceed the averages, achieving results nothing short of miraculous.
With venture capital tough to come by, angel investors seeing their pocketbooks pummeled by the market, and nonprofits struggling to keep their own doors open, that government grant funding is more important than ever. Let’s hope somebody besides the folks already in the choir hears Brawley preaching.
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