Lung cancer is a fearsome disease. Despite decades of progress in its treatment, it remains the number one cancer killer. In the United States alone, some 132,000 people die every year –– killing more people than prostate, colon, and breast cancers combined. Across the globe, the World Health Organization estimates that some 2.2 million cases of lung cancer are diagnosed each year, with 1.8 million succumbing to the disease.
The oft-celebrated decline in the percentage of adults who smoke was partly driven by the justified fear many people have of contracting this usually fatal disease. Yet one significant fact is often ignored. As many as one out of five people who die from lung cancer in the U.S. have never smoked or used any other form of tobacco. This is a huge number, which is made worse because nonsmokers have traditionally been excluded from the type of screenings that can detect early-stage lung cancer –– when the prognosis is the most favorable and treatment is the most successful. At New York University’s Langone’s Perlmutter Cancer Center, a novel screening program aims to find out why lung cancer strikes non-smokers, too. Here’s how this and similar research may affect people who don’t smoke.
Shifting Cancer Risks
When genetically damaged cells continue to divide and thrive, passing along their DNA in the process, they can form cancerous tumors. These tumors may spread –– or metastasize, killing healthy cells. With the most common form of lung cancer, non-small cell, the risk of it spreading is huge. Despite advances like precisely targeted robotic thoracic surgery that can cure early-stage cancer by removing a tiny portion of the diseased lung rather than the entire organ, the five-year survival rate after diagnosis of non-small cell lung cancer remains a grim 25%.
It’s important not to overstate the risk. Lung cancer patients are overwhelmingly current or ex-smokers. The sharp decline in lung cancer diagnoses during the second half of the 20th century was driven almost entirely by a mirroring decline in smoking rates. According to the Centers for Disease Control and Prevention, less than 14% of adults in the U.S. smoke — a decline of approximately two-thirds in the past 50 years. Unfortunately, although there are conflicting reasons behind the cause, it can’t be ignored that even as smoking rates declined there was a marked increase in Americans who are overweight or obese. Studies have demonstrated that current smokers “have a lower mean body mass index (BMI) than never and former smokers, with former smokers having the highest mean BMI.” This is significant since both never-smokers and former smokers with BMIs over 25 face an elevated risk for numerous cancers .
Nonsmokers and Lung Cancer
Nonsmokers who get lung cancer are markedly different from smokers who get the disease. They tend to be younger –– often in their 40s or 50s. The disease manifests differently. For one thing, they rarely get the more frequently fatal small-cell. Instead, they often have adenocarcinomas and large-cell anaplastic carcinomas which are less likely to spread. This means discovering the cancer can more readily lead to a cure.
Non-smokers who develop lung cancer are also more likely to be female and more likely to be Asian. Indeed, while the cost-benefit analysis for screening among nonsmokers is somewhat uncertain, there seems to be advantages in predominantly Asian populations. A screening trial focused on never-smokers in the country of Taiwan, for example, had a very high 2.34% lung cancer detection rate.
For lower risk groups, there are always downsides to testing. A recent study pointed out that using CT scans (a reliable method for detecting early-stage lung cancer) in a nonsmoking population may be ineffective. There will also be false-positives along with “overtreatment of indolent lesions” –– cancers that are so slow growing they pose less of a risk to the patient than the surgery used to remove them. As the study noted, success shouldn’t be measured by detection alone but by a “reduced mortality rate in the screened population.”
Of course even a “slow-growing” cancer presents risks to someone in their 40s with an expected two or three decades of life left to be lived. This is the narrow needle a pair of screening initiatives at NYU Langone hope to thread. The first expanded a lung cancer screening program across multiple New York boroughs and Long Island. Over 250 patients are now receiving annual low-dose CT scans in hopes of detecting early-stage lung cancer before it spreads.
The second initiative hopes to uncover why some 40% of Asian women diagnosed with lung cancer never smoked. Enrolling a cohort of Asian American female nonsmokers, the three-year study will not only provide annual low-dose CT scans but will also collect blood samples. Utilizing a revolutionary screening tool that leverages machine learning to uncover the genetic markers for seven types of cancer, this portion of the study will create a database that can hopefully uncover risk factors besides smoking tobacco. Risks for lung cancer include nonsmokers who live with smokers, radon gas, and air pollution (perhaps explaining why Asian non-smokers in some of the world’s most polluted cities are getting the disease). Identifying these factors can help reduce the mortality rate of nonsmoking lung cancer patients. Those at an elevated risk will be screened just like smokers.
The important thing for nonsmokers and former smokers to remember is that not smoking doesn’t create an impenetrable force field. Diet and exercise play an outsized role in whether or not someone will get a fatal disease. Regular screenings can help as well –– if you feel you’re in a high-risk group it’s important to have a conversation with your health provider that goes beyond the smoking question. You’ll be glad you did.
Written by John Bankston
References
- Key Statistics for Lung Cancer
- World Health Organization: Cancer
- Lung Cancer Risks for People Who Don’t Smoke
- DNA damage and gene mutations
- Neoplasm (Tumor)
- Lung Cancer – Non-Small Cell: Statistics
- Adult Obesity Facts
- Unraveling the Relationship between Smoking and Weight: The Role of Sedentary Behavior
- Obesity and Cancer Fact Sheet
- National lung screening program in Taiwan
- Lung cancer screening in never-smokers: facts and remaining issues
- Lung Cancer Strikes Non-Smokers, Too. This Novel Screening Program Aims to Find Out Why