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Guest Post: Does Cancer Screening Cause “Overdiagnosis”?

The guest post below is written in response to Dr. Scot Aberegg’s blog post.  His and other recent blog posts and articles have claimed “overdiagnosis” of breast cancer and lung cancer due to screening.  Andrea Borondy Kitts, a former engineer and fellow Lung Cancer Social Media tweeter whose husband died of lung cancer last year, addresses Dr. Aberegg’s claims in her letter.

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Dr. Aberegg, thank you for your interesting post on overdiagnosis problems with breast and lung cancer screening. I would like to comment on many of your points.

Background:

I am a mechanical engineer.  I have a Master’s degree in Management and retired after a 32 year career in aerospace, 10 years as an executive. I am back in school getting a 2nd Masters degree, this time in Public Health. I advocate for lung cancer as a volunteer for the American Lung Association, for the National Lung Cancer Partnership, on twitter as @findlungcancer, and for several Hartford CT area hospitals with their lung cancer screening programs. I lost my husband, Dan, to lung cancer on April 12th, 2013 after an 18 month hard fought battle. Dan had all the risk factors for lung cancer. He was 69 years old at the time of his diagnosis, he had quit smoking 11 years prior to his diagnosis, he had an 80 pack year smoking history, his sister had died of lung cancer at age 62 and Dan had COPD. Unfortunately, at the time of his diagnosis, lung cancer screening was not recommended.

Comments on the BMJ paper about the Canadian National Breast Screening Trial:

We had a 3 hour discussion in my UConn Chronic Disease Control class last week about the recent British Medical Journal (BMJ) paper on the 25 year follow up to the Canadian National Breast Screening Study. In attendance were 2 cancer epidemiologists, one a breast cancer expert, and an oncologist with breast cancer expertise.  In conclusion, the consensus among the experts was the study did not provide enough credible evidence to change the recommendation for breast cancer screening in the US.

Key concerns raised with this study:

  • In the mammography group 2/3 of the breast cancers found were palpable. This is not consistent with clinical breast screening experience where most breast cancers found with mammography are too small to feel.
  • Screening was only for 5 years. Most breast cancers are slow growing so may not have screened long enough to capture the difference in mortality. The risk for breast cancer increases with age, so each passing year after the screening stopped the women had a higher risk of getting breast cancer. The number of breast cancers found in the mammography and non mammography arms were the same after the 5 year screening period was stopped.
  • Although mortality did not differ between the 2 groups, the cancers found in the mammography group were smaller and less were lymph node positive.
  • The study is predicated on universal access to adjuvant therapy. Canada has a National Health System so all women have access to care. This is not the case in the US.

Other discussion points:

  • There are 22 million women in the US between the ages of 40 – 49. Not screening this population would save a lot of money.
  • Need to have better genetic markers for who will develop breast cancer to risk stratify the population to screen

My “take-aways” from the discussion

  • Large screening clinical trials/studies are hard to do right especially with decades of follow-up; often new technology and new treatments can overtake results
  • Policy can be influenced by strong advocacy sometimes resulting in non-evidence based recommendations
  • Even the experts don’t fully understand the results and don’t know how to apply to population recommendations

Comments on lung cancer screening:

The most important point to consider when comparing lung cancer screening to Mammography or PSA screening is that lung cancer screening is different.  Screening is limited to the high risk population and the gold standard randomized trial, the National Lung Screening Trial (NLST), showed a 20% mortality reduction with LDCT screening versus chest x-ray.

I don’t understand the derivation of your NNS of 950. The original paper published in the NEJM calculates the NNS as 320 for the NLST study population.

One of your discussion points focused on all-cause mortality being biased lower in the LDCT group, not because of incidental findings, but because of changed behavior in the LDCT group with false positives; for example smoking cessation. I do not think this biases the results. The results are a real, albeit, an unintended benefit for LDCT screening. The public health and medical communities have been continuously searching for ways to influence people to adopt healthy behaviors.  It’s wonderful, if in fact, LDCT screening provides a “teachable moment” resulting in healthier behaviors and improved outcomes.

Your discussion about telling folks to quit smoking as a better alternative to lung cancer screening is flawed in that, more than 50% of lung cancer diagnoses are in former smokers. These are people who have already quit smoking. Their only hope for improved survival is for secondary prevention in the form of early diagnosis with LDCT screening.

Your discussion about older people not being screened due to overdiagnosis because of mortality due to other causes is disturbing. You seem to be advocating that when people reach a certain age, we should give up on any type of screening because they will probably die soon anyway. I was particularly shocked with your statement “What if, in essence, we save a lot of people from lung cancer who then die from a heart attack 6 months later?” This would imply we should not treat any disease with a 6 month or less prognosis; let’s just save the money, 6 months is not worth the expense to society. WOW. You criticize the USPSTF final recommendation to screen to age 80 as too old. However, you neglect to mention the USPSTF modifier that “screening should be discontinued once a person has not smoked for 15 years or develops a health problem that substantially limits life expectancy or the ability or willingness to have curative lung surgery”.

And finally you discuss how a physician patient discussion on lung cancer screening might go. I would like to add a few more scenarios to your hypothetical discussion.

  • There is now a recommended screening test for lung cancer for a high risk population. I think you might be in the recommended to screen group. I wanted to review your risk factors with you and discuss if screening might be right for you.
  • It’s great that you stopped smoking 11 years ago. However, your risk level is still elevated. Your heavy 80 pack year smoking history puts you at increased risk. We know there is a strong dose response relationship with smoking and lung cancer. In addition, knowing that your sister died at age 62 from lung cancer, puts you at increased risk as well. You also have COPD another known risk factor.  I have a risk calculator I use to help me stratify risk for my patients. http://www.brocku.ca/lung-cancer-risk-calculator
  •  There is a 25% chance you will have a finding from your screening. 95% of the time it will not be lung cancer. Most of the time, the follow up to the finding is another LDCT. There is a small possibility you would have a more invasive procedure. However, the benefit of finding lung cancer at an early stage is improved survival. At stage 1a there is an 85% chance you will be alive after 5 years. At stage 4 that is less than 10%.
  • Based on your risk profile, I think you should consider LDCT lung cancer screening.

The point is that each patient is unique and the discussion with the patient should be tailored to the risk profile for the patient. The discussion you portray would not be appropriate for my hypothetical patient, who yes, happens to fit the profile of my husband who died in April 2013 from lung cancer.

Lung cancer is the leading cause of cancer deaths in men and women in the US and worldwide. It is the second leading cause of all deaths in the US after cardiovascular disease. More people die of lung cancer than breast, colon, and prostate cancer combined. Five year survival at 16% is essentially unchanged since 1975. We finally have a screening test for lung cancer and if everybody would stop trying to discredit the test and just get out of the way we will save lives!

3 thoughts on “Guest Post: Does Cancer Screening Cause “Overdiagnosis”?

  1. I really would have been out of luck. I’m 47, quit smoking 18 years ago. I had a non smoking uncle who died from lung cancer at age 45. My cancer was found during a ct for another issue. Lucky for me I was stage 1a. I had a lobectomy and will now have quarterly ct scans which i never would have qualified for before my diagnosis.

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    • Glad your lung cancer was found at an early stage. Hope you never have to deal with it again.

      Lung cancer screening with LDCT is a start for early detection, but as you say, it won’t help everyone. As a never smoker, I wouldn’t be eligible for screening under the current guidelines either. Hopefully blood tests and/or breath test for lung cancer will someday provide affordable screening for everyone.

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