Balancing Harms and Benefits of Cancer Screening: The Debate Continues

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Barnett S. Kramer, MD, MPH

Barnett S. Kramer, MD, MPH

Over the past several decades, widespread cancer screening has saved lives from various cancer types. However, despite advances in early-detection technologies, many cancers still remain undetected until they become symptomatic, conferring poor prognoses and outcomes. Moreover, some methods of screening that have garnered mainstream acceptance have come under scrutiny by health-care experts who question the balance of benefits vs harms. To shed light on this continuing debate, The ASCO Post recently spoke with medical oncologist Barnett S. Kramer, MD, MPH, Director of the Division of Cancer Prevention at the National Cancer Institute. 

Challenges of Lung Cancer Screening 

Despite the National Lung Screening Trial results and the grade B recommendation from the U.S. Preventive Services Task Force (USPSTF), rolling out population-based lung cancer screening remains challenging. Why do you think that is so? 

The situation points out the difference between proving efficacy in a controlled clinical trial environment and translating that finding into the general population, beyond academic and major medical centers. This was part of our discussion early on in the National Lung Screening Trial. Chest x-ray and sputum cytology have been tested in the past without success, but nevertheless the National Lung Screening Trial showed the value of considering each new screening test on its own merit, not on past screening endeavors with different technologies. 

There was a benefit shown in the National Lung Screening Trial, which is the largest reported mature screening trial in lung cancer to date. We’re still waiting for data from some of the trials across Europe to see whether they replicate the results of the National Lung Screening Trial. However, the National Lung Screening Trial gave impetus to the discussion of whether lung cancer screening should become public policy. And, if so, how screening in high-risk populations should be implemented. 

To that end, when the Centers for Medicare & Medicaid Services (CMS)’s MEDCAC panel convened to advise the Agency on the pros and cons of coverage for lung cancer screening in the Medicare population, panel members expressed concerns that despite the fact that a randomized trial had shown a benefit, the benefit was modest and the balance of benefits and harms might differ with general usage. There was a reduction of about 3 deaths from lung cancer per 1,000 people screened over 7 years of follow-up. It was a statistically significant and medically important finding. However, 3 lives saved per 1,000 screened does not leave much wiggle room for error. Therefore, if the benefits are slightly less outside of the controlled clinical trial environment, or if the harms are more, it can reverse the benefit-to-harms ratio. 

Based on the National Lung Screening Trial, the USPSTF gave National Lung Screening Trial lung screening a grade B recommendation, which means the Task Force was confident that screening conferred a net benefit and should be routinely offered in populations at sufficiently high risk of lung cancer. But that was only the first step. The CMS wanted to be sure screening centers could replicate the results of the National Lung Screening Trial, so the Agency required a screening register—which the College of Radiology has since launched—so patient recall rates could be tracked and also ensure smoking cessation tools are provided for current smokers. It is clear that despite the benefits of National Lung Screening Trial screening of current and former heavy smokers, the benefits of stopping smoking are substantially larger than screening. 

A legitimate concern of the CMS panel was that current smokers would use lung screening as an excuse for not stopping smoking. So, as part of the CMS-funding decision, the Agency wanted evidence that smoking cessation was linked to the roll-out of screening programs. There are many challenges ahead in the effort to implement widespread lung cancer screening, one of which is to ensure that screening programs are uniform and effective. 

Understanding PSA Screening 

The USPSTF recently shifted its [draft] prostate-specific antigen (PSA) screening recommendation from grade D to C, which now advises general practitioners to have an informed decision-making conversation with their male patients between the ages of 55 and 69. What effect do you think this change in recommendation will have? 

PSA screening represents an issue parallel to our previous discussion about National Lung Screening Trial lung cancer screening, since the benefits-to-harms ratio is closely matched. In fact, although the Task Force changed its PSA recommendation from grade D to C, it didn’t change it to B, indicating that the possible harms-to-benefits ratio may be more closely matched than in lung screening. Therefore, the doctor-patient conversation becomes all the more complex and nuanced. And that has been a concern, especially among generalists. 

Men who have been shown printed materials have a better understanding of PSA screening.
— Barnett S. Kramer, MD, MPH

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I recently gave grand rounds at the Mayo Clinic, and there were a lot of internists in the audience. One of the first questions was about the time needed to have an informed decision-making conversation with a patient in a busy practice. It’s been referred to in the past as the “crowding out” phenomenon in the clinical setting. In other words, if there is a list of issues a doctor is supposed to bring up and discuss, certain things may get pushed aside given the time constraints in a busy clinical setting. There are ways, however, to maximize discussions by using printed materials and videos, which are not generally available in many practices. Perhaps this will change things. It has been demonstrated that men who have been shown printed materials have a better understanding of PSA screening. 

Benefits of HPV Vaccine 

The Pap test along with the human papillomavirus (HPV) vaccine is arguably the most successful screening and prevention scenario in public health. However, we still lag behind other countries in HPV vaccination, such as the UK and Australia. What are your thoughts about the small but vocal antivaccine sentiment in the United States? 

The magnitude of benefits in HPV vaccine as a preventive measure against cancer of the cervix is very clear. The potential harms associated with the vaccine are as close to nil as statistically possible. It’s also clear that in countries such as Australia, which have widespread cervical screening and vaccination programs, there is a sizable reduction in preneoplastic cervical lesions and fewer genital warts; this will no doubt lead to a substantial reduction in invasive cervical cancers and mortality. 

The potential harms associated with the HPV vaccine are as close to nil as statistically possible.
— Barnett S. Kramer, MD, MPH

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We haven’t been able to match that success for a variety of reasons, one of which was the problem with our early messaging; it was noted this vaccine was developed to prevent a sexually transmitted disease, which gave pause to some parents. Whereas in other countries such as Australia and the UK, it was promoted as an anticancer vaccine. 

Cancer Prevention Messaging 

We know that a majority of cancers are preventable, so why are we failing in our messaging efforts on the prevention side of cancer care? 

First of all, the common notion that most cancers are preventable is associated with a very wide “conceptual confidence interval” of about 30% to 60%. One major problem in the cancer prevention messaging is the public’s understanding or appreciation on how firm the message is. 

Tobacco prevention messaging is relatively easy in that it is a scientifically black and white issue. All tobacco products are linked with disease; there is no way to nuance the issue about smoking. Along with a host of deadly diseases, it causes lung cancer, the number one cancer killer in the world. But people wake up in the morning and hear on the news that a food product that was considered unhealthy a year ago is now considered beneficial in some way (or vice versa). 

Weight and cancer is another issue that has flip-flopped in its messaging. Also, it’s very clear what the dose of tobacco should be if you want to avoid lung cancer: zero. Whereas the dose for specific elements in diet and exercise is a lot less clear, differing in the particular guidelines you use. 

That said, it is clear that obesity leads to poor health and is at least associated with greater risk of some cancers. But nobody knows the secret of sustained weight loss (short of surgery in the setting of extreme obesity). If you quit smoking, you know you cannot have another cigarette without risking starting up again. But everyone has to eat, and therein lies the complexity of the issue. Obesity remains a major public health challenge, one that needs more research and effort. 

DISCLOSURE: Dr. Kramer reported no conflicts of interest.