CONTENTS:

1.7.The Benefits of Screening for lung cancer
1.8 Potential Harm from Screening
1.8.1 Over Diagnosis of Lung Abnormalities
1.8.2 Patient Anxiety
1.8.3 False-Positive Diagnosis
1.8.4 Radiation from CT X-ray Imaging

Forward to 1G More Lung Cancer Trials.   Back to 1E Evidence to Support Screening.

Not a shred of evidence exists in favour of the idea that life is serious.

1.7 The Benefits of Screening for Lung Cancer

 
The following characteristics of lung cancer suggest that screening should be effective:

• High morbidity and mortality of lung cancer
• Significant prevalence of lung cancer ( between 0.5 to 2.2 % of the population). Identifiable risk factors that allow targeted screening for high-risk individuals
• A lengthy pre-clinical phase for some types of lung cancer; and
• Evidence that therapy is more effective in early-stage disease.

It is known that the outcome for patients who are diagnosed with non-small cell lung cancer (NSCLC) relates to the stage of the tumor at the time of diagnosis. The five-year survival of lung cancer ranges from > 60 % for stage I lung cancer to < 5 % for stage IV lung cancer.  For early-stage, (stage I) lung cancers, there is a relationship between tumor size and survival.

The success of any lung cancer screening program can be evaluated using several outcome measures. These include:

• cancer detection rates,
• stage at detection,
• survival,
• disease-specific mortality and
• overall mortality.

The most important clinical outcomes to assess in any screening program are cancer-related mortality and overall mortality.

For my New Year’s Resolution I have decided only to smoke after sex. If last year is anything to go by, I’ve quit.

1.8 Possible Harm from screening for Lung Cancer

 
While screening has the potential benefits of decreased morbidity and mortality from lung cancer, it also has potential risks:

1.8.1 ‘Over Diagnosis’ of Lung Abnormalities

 
Individuals who have smoked for many years are more likely to have chronic, life-threatening diseases including ischemic heart disease, other cancers and chronic obstructive pulmonary disease (COPD). So, there are some lung cancers that may be identified by screening that if never detected, would not have caused morbidity or mortality during the patient’s lifetime.

The identification of such cancers is referred to as over diagnosis. Lung cancer screening  with low-dose CT have estimated that the extent of over diagnosis ranges from 13% to 27 % of cases.

After 6.5 years of follow-up in the National Lung Screening Trial (NLST) trial, there were 119 more lung cancers identified in the LDCT group when compared with the chest X-ray group (1060 versus 941). The true estimate of over diagnosis will only result from long-term follow-up in future lung cancer screening programs.

So just over 18 extra cases of lung cancer a year were identified by CT screening.

All extra cases of lung cancer that are detected are good news. Even better if they are Stage 1 (very early) of the disease and treatable.

Every life counts.

1.8.2 Patient Anxiety

 
There are few clinical trials to evaluate patient anxiety caused by low-dose CT screening. In 2014, in a systematic review by Slatore and colleagues, five randomized trials, and one cohort study found that LDCT screening was associated with short-term psychological distress, but this did not affect health-related quality of life.

There is anxiety for patients who undergo prolonged follow-up of benign lung nodules detected on imaging. This follow-up can last for several years.

I’ve been part on an online social anxiety support forum for about a year now. I haven’t posted anything yet.

1.8.3 False-Positive Diagnosis

 
A false-positive diagnosis after screening for lung cancer is one that does not lead to a definitive diagnosis of lung cancer. In most screening programs, some degree of false-positive diagnosis from first-line screening (using imaging) is regarded as inevitable in order to keep the levels of false-negative diagnoses as low as possible.

The definitive diagnosis of a CT-detected lung abnormality will depend on lung cytology or histopathology (see Section 6).

Lots of percentages and statistics coming up.

Five out of four people have trouble with fractions, you know?

Yes, and you know what else seem odd? Numbers that aren’t divisible by two.

In the National Lung Screening Trial (NLST), more than 53,000 high-risk individuals were randomly assigned to LDCT scan or chest X-ray screening (24.2 % LDCT scans and 6.9 % radiographs), 6 % were false-positive diagnoses; 11 % of the positive results led to an invasive second-line investigation (cytology or biopsy). False-positive results were also associated with short-term increase in patient anxiety.

If you’re anxious and you know it, clasp your hands.

1.8.4 Radiation from CT X-ray Imaging

 
In a lung cancer screening program, the radiation given during serial CT imaging may add an independent risk of cancers, including lung cancer.

The radiation given with spiral CT imaging is estimated to be in the range of 0.61 to 1.50 mSv.  Since screening occurs over several rounds and positive findings may require further imaging, the cumulative radiation dose is important. For comparison, most mammograms emit radiation doses on the order of 0.7 mSv.

Don’t forget though, a day without radiation, is a day without sunshine.

References:

Jaklitsch MT1, Jacobson FL, Austin JH, et al. (2012). The American Association for Thoracic Surgery guidelines for lung cancer screening using low-dose computed tomography scans for lung cancer survivors and other high-risk groups. Journal of Thoracic and Cardiovascular Surgery 144(1), 33–38. (Retrieved 22^nd Jan 2015): http://www.ncbi.nlm.nih.gov/pubmed/22710039

Slatore CG, Sullivan DR, Pappas M, Humphrey LL. (2014). Patient-centered outcomes among lung cancer screening recipients with computed tomography: a systematic review. J Thorac Oncol. 9(7), 927. (Retrieved 23^rd Jan 2015): http://www.ncbi.nlm.nih.gov/pubmed?term=24922011
 

More references for this section are on this page.

Patient Information:

Radiology Info. Org Lung Cancer Screening. (Retrieved 1^st April 2015): http://www.radiologyinfo.org/en/info.cfm?pg=screening-lung

NHS Choices CT Scan – Risks (Retrieved 1^st April 2015): http://www.nhs.uk/conditions/ct-scan/pages/risks.aspx
 

More patient information for this section is on this page.

Forward to 1G More Lung Cancer Trials.   Back to 1E Evidence to Support Screening.