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Some Asians Fare Better with Prostate Cancer in US

Prostate Cancer Statistics and Risk Factors

Prostate cancer is the most common cancer among men, excluding skin cancer. The American Cancer Society (ACS)  estimates for 2007 include 218,890 new cases of prostate cancer in the US.

Year 2007 estimates include 27,050 deaths occurring from prostate cancer in the US alone, making it the second leading cause of cancer death in men.

What is a risk factor?  A risk factor is anything that may increase a person's chance of developing a disease. It may be an activity, such as smoking, diet, family history, or many other things. Different diseases, including cancers, have different risk factors.

Although these factors can increase a person's risk, they do not necessarily cause the disease. Some people with one or more risk factors never develop cancer, while others develop cancer and have no known risk factors.

Knowing your risk factors to any disease can help to guide you into the appropriate actions, including changing behaviors and being clinically monitored for the disease.

What are risk factors for prostate cancer?  In general, all men are at risk for prostate cancer. However, there are specific risk factors that increase the likelihood that certain men will develop the disease, including the following:

  • Age is a risk factor for prostate cancer, especially men age 50 and older. More than 70 percent of all prostate cancers are diagnosed in men over the age of 65.
  • Prostate cancer is nearly 60 percent more common among African-American men than it is among Caucasian-American men. Japanese and Chinese men native to their country have the lowest rates of prostate cancer.
  • Data suggests that the diet consumed in Western industrialized countries may be one of the most important contributory factors for developing prostate cancer. 
  • Dietary fiber intake may influence circulating levels of testosterone and estradiol, which, in turn, may decrease the progression of prostate cancer.
  • Besides lower fat intake, another major difference between Asian and American diets is the consumption of soy, averaging 35 g a day per capita. Soy contains isoflavones which, in several studies, have been found to inhibit the growth of prostate cancer.
  • Carotenoids containing lycopenes have been shown to inhibit the growth of human prostate cancer cells in tissue cultures (cells grown in the laboratory). The primary source of lycopenes is processed tomatoes in tomato juice and tomato paste.
  • Having a father or brother with prostate cancer more than doubles or triples a man's risk of developing this disease. The risk is even higher for men with several affected relatives, particularly if the relatives were young at the time of diagnosis.

Always consult your physician for more information.

[August, 2007] Your outlook for surviving prostate cancer may depend on your racial and ethnic background, a new study suggests.

Picture of an older Asian couple

Published in the medical journal, Cancer, the study shows that compared to Caucasian men, most Asian ethnic groups - except South Asians - have better outcomes at the time of diagnosis. The study is the first to report prostate cancer survival data for Korean, South Asian, and Vietnamese men living in the US.

"Nearly all Asians do far better when they get prostate cancer," says study lead author Dr. Anthony Robbins, of the California Cancer Registry in Sacramento. "But Indian men didn't do as well as other Asian men, and they did worse than all other men, including blacks and Caucasians," he adds.

Puzzling and Paradoxical

The reasons for these racial and ethnic differences in prostate cancer survival are not known, Dr. Robbins says, adding, "We just couldn't explain it."

Not only can the researchers not explain the finding, they note an apparent paradox. The Asian men were usually older and had more advanced disease at the time of diagnosis, Dr. Robbins states. "Based on their risk factors, you would think they were going to do worse," he says.

Comparing Prognostic Factors

In the study, Dr. Robbins and his co-researchers collected data on 116,916 men (108,076 Caucasians and 8,840 Asians from the six largest represented Asian ethnicities - Chinese, Filipino, Japanese, Korean, South Asian, and Vietnamese) diagnosed with prostate cancer. The researchers compared prognostic factors (which help predict the course of disease) and survival rates among the men.

They found that for Asians, risk profiles were worse compared with Caucasians. For example, Asians were more likely to have more advanced disease and use non-curative therapies. But, for Asians - except for South Asians - survival rates were still equal to or better than rates for Caucasians.

Japanese-American men were 34 percent less likely to die from prostate cancer compared with Caucasians. But South Asian men - those from India, Pakistan, Bangladesh, Sri Lanka, Nepal, and Bhutan - were 40 percent more likely to die from the disease, Dr. Robbins says.

Researcher Considers Why

Some of the factors that may influence the findings include diet, exercise, and genetics, Dr. Robbins speculates.

"Doctors that are seeing patients for prostate cancer need to be aware that these differences can be used as factors in planning the patient's treatment and telling the patient what their survival might be," Dr. Robbins says.

The risk among different Asian ethnicities is poorly understood partly because most studies have grouped all Asians into a single racial category, ignoring the diverse ethnicities that make up Asia.

Interestingly, the most current data has shown that compared to non-Hispanic Caucasian Americans, some Asian ethnicities, such as Japanese-Americans, have higher survival rates, despite worse clinical disease, whereas others, such as Filipino-Americans, have worse survival rates. However, South Asians - e.g., Indians, Pakistanis, Bangladesh, etc. - who represent the third largest Asian subgroup in the US, have never been studied for prostate cancer before.

More Research Needed for Specific Ethnic Groups

Dr. Durado Brooks, director of prostate and colorectal cancer at the American Cancer Society (ACS), thinks this study confirms the need to better understand how different racial and ethnic groups respond to diseases.

"This study points out the potential misleading conclusions we can come to when we use these large groups to lump different subpopulations into," he says.

"If you lump in the South Asian subgroup with other Asians, as is traditionally done, you totally miss the fact that these folks have a strikingly higher chance of dying from prostate cancer," Dr. Brooks says.

Dr. Brooks says the study finding can provide a basis for research to try to understand why these differences exist between populations.

The study should help physicians more accurately apply prognostic factors to their prostate cancer patients.

In conclusion, the study authors say these results argue that traditional prognostic factors for survival from prostate cancer such as stage, grade, treatment, age, year of diagnosis, and socioeconomic status, do not explain why most Asian men have better survival compared to Caucasians. But they do explain the poorer survival of South Asian men compared to Caucasians.

Always consult your physician for more information.

  
 
Yale School of Medicine