Cancer Screening
On May 19, 2015 The American College of Physicians released a new set of cancer screening guidelines in an effort to clarify some of the confusion surrounding cancer screening recommendations. These guidelines address 5 types of cancer including Breast Cancer, Colon Cancer, Cervical Cancer, Prostate Cancer, and Ovarian Cancer.

In developing these recommendations the authors used the most current studies and literature to determine what screening tests offered the best benefit to risk ratio. In other words which tests were most likely to have a positive health impact with a minimum of risk to the patient.

Screening tests are obviously done in an effort to detect illnesses at an earlier stage so that we can improve outcomes. While it would seem to make sense to screen whenever possible there can be shortcomings to certain screening methods and reasons to be selective about what tests we do and in whom we do them.

First, no screening test is perfect. There is always some level of false positives and false negatives in any screening test no matter how perfectly it is done. These false results can have negative consequences for patients.

A false negative would be a test that came back negative even though the disease is present. Some false negatives will always occur because no test can ever be 100% sensitive. A breast tumor may be too small or not dense enough to show up on a mammogram. A prostate tumor may produce little or no PSA and therefor may not elevate a mans PSA to a level that would be considered abnormal. False negatives give us a false sense of security that everything is OK when its not. Although all screening tests have some false negatives, tests with a high rate of false negatives will miss so many cancers they are not worth doing.

The polar opposite of the false negative is the false positive. A false positive is a test that implies the patient has a disease when in fact there is nothing wrong. Just as with false negatives, every screening test will have some level of false positives. A dark spot on a mammogram for example may look like cancer until a biopsy is done and it turns out to be old scar tissue or a benign growth. An elevated CA125 would be interpreted as indicating the presence of ovarian cancer but more often than not when a CA125 is elevated there is nothing wrong at all. The problem with false negatives is that you miss an important diagnosis, but the problem with false positives is that you expose an otherwise healthy person to unnecessary discomfort, inconvenience, cost, and even risk as a result of further testing which is usually more invasive.

False positives and false negatives are not the only problems we need to concerned ourselves with when we discuss screening tests. There is also the question of whether the detection of cancer at an earlier stage will result in a better outcome. Our gut (and lots of public service announcements) would lead us to believe that early detection can only improve our chances but that may not always be the case. Sometimes early detection may not change anything and in some cases early detection can actually be harmful. We need to know which of these is the case for a particular cancer before we recommend for or against screening.

Right now some of you are thinking “How in the world could early detection ever be a bad thing”? I can understand how crazy that would sound so let me explain. Cancer is not one disease. Its many different diseases and while these diseases have some similarities they also have many differences. Even within a single organ there are often many types of cancer. There is not just one type of lung cancer or breast cancer. There are many different cell types within each organ that can become cancerous and each behaves differently. Some grow slowly and others fast. Some metastasize early and others never do.  It may come as surprise to many people that at least some prostate cancers and even certain types of breast cancers may be relatively harmless. Many prostate cancers grow very slowly and remain dormant even into old age. Studies have shown that nearly 90% of men over the age of 80 have prostate cancer but the vast majority will die of cardiovascular disease of some other illness in old age without ever succumbing to the cancer.  There is also evidence that some breast cancers as well as other types of cancer may be eliminated by the immune system without ever coming to our attention. In these cases had we not been screening for them we would have lived out our normal lifespans and never even known we ever had cancer, but early detection changes that. With early detection we will unavoidably end up treating some of these cases that would have never caused the patient any trouble and some of those patients will have complications and a very small but not zero number may die as a result of the treatment.

At the other end of the spectrum are cancers for which there is no available effective treatment, or the treatments which are available result in very minimal benefits, extending life only a few weeks on average. For these patients early detection may have little to no benefit and may ultimately result in a decrease in the quality of the short time they have left.

This is not to say that early detection isn't helpful, far from it. Screening tests which are done at the right time in the right people can make a big impact and even save lives. The key is to know when and in whom to do these tests so that we maximize the benefits and minimize the harm. This in essence is the purpose of the ACP publication. This group of expert physicians has taken the time to analyze the best information currently available so that we can make smart decisions about the right tests to do for each patient.

The complete ACP document can be downloaded from the link at the bottom of the page, but I will summarize the recommendations below. Please keep in mind that as we learn more, as treatments change, and as diagnostic tools improve these recommendations will obviously need to be updated and changed over time to reflect those things.

New Cancer Screening Guidelines

Please be aware that the following recommendations are for average risk individuals. Everyone's risk is different, so discuss the recommendations with your physician to determine what the best approach is for your situation.

Breast Cancer

  • Women aged 40–49 yr:    For women in this age group mammogram is not routinely recommended unless a full discussion of the risks and benefits is undertaken and the woman feels she wants to have the test done. The reason for this approach is that studies have not shown a consistent benefit from routine mammography in women under 50. There are risks to mammography including unnecessary biopsies, pain, anxiety,  and possibly treatments that may or may not alter the outcome. In addition there is some very small risk from additional radiation exposure. All of these issues should be reviewed along with family history and other individual risk factors before deciding whether mammography is appropriate for each woman.
  • Women aged 50–74 yr in good health: The benefits of mammography in this age group have been demonstrated sufficiently to warrant the recommendation of routine mammography every other year.

Colon Cancer

Colon cancer screening is recommended for average risk individuals who are age 50 to 75.  Several screening options are available including the following:
  • High Sensitivity Fecal Occult Blood testing every year
  • Sigmoidoscopy every 5 years
  • Combined High Sensitivity Fecal Occult Blood every 3 years plus Sigmoidoscopy every 5 years
  • Colonoscopy every 10 years
Each screening option has advantages and disadvantages. The optimal choice will be decided by the patient in consultation with their physician.

Note: Virtual colonoscopy was not mentioned as an option. While no explanation was given I have often advised against this procedure for my patients for several reasons. Most patients who have had a colonoscopy do not mind the procedure. What they don't like is the laxatives they need to take to prepare for the procedure. Since a virtual colonoscopy requires the same preparation there is no advantage from a comfort standpoint. Additionally if something is found on the virtual colonoscopy the patient will have to have a traditional colonoscopy to find and biopsy the lesion which will require them to go through the preparation a second time. Finally a virtual colonoscopy is a special type of CT scan procedure and as such it involves a significant dose of xrays which a traditional colonoscopy does not expose patients to. There seem to be very few situations in which a virtual colonoscopy would offer an advantage over other testing options.
 

Cervical Cancer

The majority of cervical cancers are thought to be caused by an infection with the Human Papilloma Virus (HPV). Since screening for this disease began several decades ago deaths from cervical cancer have dropped dramatically. Previously PAP smears were done on an annual basis but the current evidence seems to indicate that we can achieve the same benefits with screening every three years. In addition to the traditional PAP smear, HPV testing is sometimes also performed. HPV testing is not recommended however for women under 30 yrs old unless their PAP smear is positive because HPV is likely to resolve on its own in this age group without leading to long term medical complications while women 30 and older have a higher risk of developing precancerous and cancerous changes due to an HPV infection. The current recommendation for cervical cancer screening is as follows.
  • Women age 21-29 - PAP smear (cytology testing) is recommended on an every 3 year schedule
  • Women age 30-65 - PAP smear every 3 years or PAP smear along with HPV  testing every 5 years

Prostate Cancer

The blood test for prostate cancer is known as the PSA test. This is a blood test that measures the level of a protein called Prostate Specific Antigen ( hence the PSA). Some prostate cancers produce increased amounts of PSA so the idea was that an elevated level would help us detect prostate cancer at an earlier stage. The problem is that some prostate cancers produce no PSA and some enlarged but healthy prostates produce lots of PSA. This as you can imagine leads to more false positives and false negatives than we would like. For a more in depth discussion of the issues related to the PSA test follow this link to my blog post on this subject: PSA Blog Post

The new guidelines make the following recommendation:
  • PSA should only be done on men from 50-69 and only if the man expresses a clear preference to have this test done after a complete review of the risks and benefits. They also recommend that PSA's be done no more frequently than every 2-4 years if a man decides to proceed with this testing

Ovarian Cancer

No screening test for ovarian cancer has been shown to improve survival. Both sonograms and CA125 have been studied in this regard and neither has resulted in improved outcomes. Both screening tests add costs and expose the patient to risks including unnecessary surgery and even death. At this time there is no effective recommended screening test for this disease. High risk individuals ( ie. strong family history of breast or ovarian cancer or history of BRCA positive test in self or family member) May want to speak to their physician about other options.
  • No Screening recommended

Summary of New Recommendations

A  Final Word on Cancer Screening

Upon reviewing these recommendations it is not uncommon for a patient to ask me why we would recommend against a particular screening test when there is no alternative test that is better? That's a good question until you realize that a bad test that causes more harm than good is worse than no test at all. If a test causes pain, discomfort or puts the patient at risk and does not improve survival then sometimes it really is better to do nothing, especially if your only other option is to make things worse.

We do have some tests that make a difference. Mammograms in women over 50 have improved survival from breast cancer, colonoscopies have lowered colon cancer deaths and PAP smears have reduced cervical cancer deaths. Hopefully with time and more research our tests will get better and we will have more tools to work with. For now these are the best recommendations for the tools we already have

For more information consult with your physician. You may also download the full ACP document at the link below.

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