Dear Dr. Eva,

At the age of 58 my partner has been diagnosed with cancer. We are both stunned. Because we both have a family history of cancer, we have done everything we can to lower our risk. We have had colonoscopies on the recommended schedule, exercise regularly, eat cruciferous vegetables at least three times a week, and take antioxidant vitamins daily. We don’t use alcohol or tobacco. I didn’t think this could happen. Are all the precautions we took pointless?

Feeling Cheated

Dear Feeling,

Your precautions weren’t pointless. They have reduced your cancer risk and you should continue with the same precautions. However, it’s important to understand that only one out of three

cases of cancer (33%) is caused either by risk factors people can change (like smoking and diet) or by an inherited risk of cancer. The other two out of three cases (66%) are due to random mutations, which are spontaneous abnormalities in our genes that we have no way to control. These random mutations occur when DNA (genes) are copied incorrectly when cells divide to make new cells. Because these cancer-causing changes occur with cell division, tissues that shed many cells and make new cells, like the skin and the intestinal lining, are at high risk for cancer.

So, 33% is the most that people can decrease cancer risk by changing their behavior. This number varies depending on the specific type of cancer. In the case of lung cancer, avoiding smoking decreases the risk of lung cancer by more than 80%. Looking at all types of cancer together, if a group of ten people don’t take any precautions to prevent cancer, three people in the group will be diagnosed with cancer at some time in their lifetime. On the other hand, if a similar group of ten people follow all known recommendations for preventing cancer, only two people in the group will still be diagnosed with cancer.

The single most effective single preventive measure a person can take to avoid cancer is avoiding smoking. People who smoke have a five times greater risk of lung cancer compared to people who have never smoked. Even so, 15% of cases of lung cancer (about one in seven) are diagnosed in people who have never smoked. Smoking also increases the likelihood a person will have mouth, throat, bladder and pancreas cancer.

Dear Dr. Eva,

What are the most effective cancer prevention measures?

J.B.

Dear J.B.,

There are two kinds of cancer prevention: primary and secondary. Primary prevention methods prevent cancer from developing. Secondary prevention methods detect cancer early, so treatment can be given before the cancer becomes life-threatening.

These are the primary prevention methods with the best proof of effectiveness.

1) HPV (Human Papilloma Virus) vaccine – HPV vaccine prevents genital cancers, including cervical cancer and penis cancer, and nose and throat cancers. This vaccine was initially recommended recommended only for children age nine to 11, and that is still considered the best age to give it because at that age children have not yet been exposed to the HPV virus, which is sexually transmitted. Unfortunately, many parents refuse to have their children vaccinated out of a mistaken belief that vaccination encourages early sexual activity. Further research showed that the vaccine can be beneficial for people of any age who have more than one sexual partner, or whose partner has other partners. The vaccine has been approved up to age 45, and most insurance plans will pay for it up to age 45. For uninsured people and those over 45, the vaccine costs about $200 a dose. To become immune to HPV, three doses are necessary.

2) Hepatitis B vaccine prevents stomach cancer and liver cancer. Three doses of hepatitis B vaccine are included in the regular series of vaccines given to babies. The vaccine can be given at any age to people who are not immune.

3) Avoiding tobacco greatly reduces the risk of lung cancer, mouth and throat cancers, pancreas and bladder cancer.

4) Avoiding sunburn and limiting sun exposure by using covering clothing, hats, and sunblock. This prevents several forms of skin cancer: melanoma, squamous cell cancer, and basal cell cancer.

5) Avoiding alcohol use or drinking very little prevents esophageal cancer.

And the following are the secondary prevention methods with the best proof of effectiveness. These recommendations are from the United States Public Health Service Task Force (Uspreventiveservicestaskforce.org):

1) Cervical (uterus, womb) Pap smears (women) – start at age 21, then every three years until age 30. From age 30 to 65, Pap with HPV (human papilloma virus) test every three years. If Pap and HPV results are normal, screening can be stopped at age 65.

2) Colonoscopy – Start at age 50, then every ten years. Stop screening at age 75 unless the last colonoscopy showed abnormalities.

3) Mammogram (women) – Start at age 50, then every two years. Stop screening at age 74, unless a woman has a history of breast cancer.

4) Anal Pap smears: some authorities recommend anal Pap smears for early detection of anal cancer, especially for men who have sex with men, as this group has the highest risk of anal cancer. Long-term studies are in progress to find out whether screening with anal Pap smears can decrease the likelihood of anal cancer.5) Prostate specific antigen (PSA) (men) – Medical experts don’t agree on whether the PSA blood test should be routinely used to screen for prostate cancer, and the USPSTF recommends against it. The PSA level is often high in men who do not have prostate cancer, and the biopsies needed to determine if cancer is present are uncomfortable and can cause severe and lasting complications. PSA is most often recommended for men with a family history of prostate cancer. Physical exam of the prostate (digital-rectal exam, DRE) is no longer recommended for prostate cancer screening.

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