Joe is a 60–year old male who began smoking cigarettes in high school at age 18. While his smoking habits have fluctuated over the years, for the most part Joe has consistently smoked a pack a day for 42 years and continues to do so.
When Joe reviewed the Male 5-Year Risk Table he needed to identify how many pack years he had smoked. To do that, Joe followed the following formula:
| |
Number of packs smoked per day |
1 pack |
| X |
Number of years he smoked |
42 years (Age 18 to current age of 60) |
|
|
| = |
Total Pack Years |
42 Pack Years |
Joe’s Current Age 60
Joe’s Pack Years 42
Joe’s Current Status Still smoking
Joe then consulted the Male 5–Year Risk Table (see below) to identify his own 5-year risk for lung cancer. He found his age in Column 1 (60) and since he is still smoking, found his pack years under the blue column (42-57.4 Pack Years). The chart shows Joe has a 4.3% risk of having lung cancer over the next 5 years.
References:
A Risk Model for the Prediction of Lung Cancer, Margaret R. Spitz, Waun Ki Hong, Christopher I. Amos, Xifeng Wu, Matthew B. Schabath, Qiong D ong, Sanjay Shete, Carol J. Etzel. J Natl Cancer Inst 2007;99: 715 – 26
Identifying Individuals at High Risk of Melanoma: A Practical Predictor of Absolute Risk, Thomas R. Fears, DuPont Guerry IV, Ruth M. Pfeiffer, Richard W. Sagebiel, David E. Elder, Allan Halpern, Elizabeth A. Holly, Patricia Hartge, and Margaret A. Tucker. J Clin Oncol 24:3590-3596
Joe first thought that a 4.3% risk was no big deal; in fact it seemed low. Then Joe looked at the risk associated with a non-smoker his same age and realized that it was only .12%, meaning Joe was 35 times more likely to develop lung cancer in the next 5 years than someone 60 years old that had not smoked. That put his own risk in the proper perspective. Joe became even more concerned about the increased risk to his health and decided to take the EarlyCDT-Lung test immediately.
References:
A Risk Model for the Prediction of Lung Cancer, Margaret R. Spitz, Waun Ki Hong, Christopher I. Amos, Xifeng Wu, Matthew B. Schabath, Qiong D ong, Sanjay Shete, Carol J. Etzel. J Natl Cancer Inst 2007;99: 715 – 26
Identifying Individuals at High Risk of Melanoma: A Practical Predictor of Absolute Risk, Thomas R. Fears, DuPont Guerry IV, Ruth M. Pfeiffer, Richard W. Sagebiel, David E. Elder, Allan Halpern, Elizabeth A. Holly, Patricia Hartge, and Margaret A. Tucker. J Clin Oncol 24:3590-3596
What Does a Positive Result Mean?
After Joe took the test and was waiting for his results, he wanted to learn more about what impact a “positive” result might have on the possibility of actually having lung cancer. Joe decided to consult the Positive Predictive Value (PPV) Table on the EarlyCDT-Lung Educational Brochure to identify the impact of a positive result for EarlyCDT-Lung.
The PPV* is a statistically derived calculation that provides an assessment for your risk group (defined by age and smoking history) for EarlyCDT-Lung or CT (computed tomography) Scan positives separately and the PPV for EarlyCDT-Lung and CT diagnostic imaging scan positives in combination.
Joe learned that since this was a statistically derived calculation for his risk group it didn’t specifically apply to a singe test result but instead this was the PPV for his risk group.
In Joe’s case with a 4.3% (4%) risk for his age and smoking history group a positive result indicated:
1 out of 21 people who test positive from a CT diagnostic imaging scan will truly have the presence of lung cancer.
1 out of 7 people with positive results from the EarlyCDT-Lung test test will truly have the presence of lung cancer.
1 out of 4.3 people who test positive from both the EarlyCDT-Lung test and a CT scan will truly have the presence of lung cancer.
References:*Positive Predictive Value (PPV) is a way of stating how many “true cancers” will result from the number of tests that show a “positive” result. As an example, if a positive EarlyCDT-Lung test has a PPV of 1 in 7, this means that for every 7 people testing positive from EarlyCDT-Lung, one person will have a true lung cancer.
How Does a Positive for my Risk Group compare to a Low Risk Group?
When Joe compared his Risk Group or 4.3% to a lower Risk Group of .2% he clearly understood the difference in PPV between the two risk groups.
Low Risk Group of 0.2%
PPV for CT Scan only of 1 in 278.2
PPV for EarlyCDT-Lung only of 1 in 125.8
PPV for EarlyCDT-Lung and CT Scan of 1 in 70.3
Joe’s Risk Group of 4.3%
PPV for CT Scan only of 1 in 21
PPV for EarlyCDT-Lung only of 1 in 7
PPV for EarlyCDT-Lung and CT Scan of 1 in 4.3
The combination of determining his risk and the PPV for his risk group helped Joe clearly understand his risk for lung cancer and the potential impact of a positive result for EarlyCDT-Lung.
Risk Factors
The Male and Female Risk Calculations are based on algorithms created by clinicians at the MD Anderson Cancer Center that were developed from extensive data that took into account age, smoking history and consumption levels to establish an estimated risk for smokers and ex-smokers. In this simplified version of the model below we do not take into account a number of additional risk factors, such as first degree relatives and we have adjusted the calculation to give 5 year risk. In order to better understand this data, we will use “Joe” as an example of a typical male smoker. A Risk Calculator is available on this Web site that may be helpful in advising your patients of the importance of early detection.
Are you at Increased Risk of Lung Cancer?
