The topic has been floating around for quite a while, and hasn’t ceased to capture our attention: dogs can sniff out cancer - and not just lung cancer, but ovarian, colorectal, bladder, breast and skin cancers too. (1-5) The most recent publication by Ehmann et al. showed dogs could accurately detect 71/100 confirmed lung cancer cases. This well designed study also included control cases with COPD and the dogs were not fooled, correctly identifying 372 out of 400 cancer-free cases.
Are we investing in dogs, trainers, and handlers in every hospital? Not quite yet – there is still a bit of skepticism regarding implementing dogs as cancer-detectors. (And, who would foot the bill?) There isn’t a tremendous amount of published data, and those published studies weren’t all conducted the same way and have varying results. But, two German shepherds, one Australian shepherd and one Labrador retriever confirmed what scientists have been investigating for years – specific compounds in the breath resulting from cancer. (1, 6)
So, how does this fit into the current picture of cancer detection? In a perfect world, we’ll have a wide array of diagnostic tools that can help us detect lung cancer early:
- Imaging Tests: The results of the National Lung Screening Trial showed that low-dose spiral computed tomography (CT) screening can reduce mortality from lung cancer by 20%. (7) Patients at high risk are recommended to be screened. The National Comprehensive Cancer Network recommends screening for (A) heavy smokers (30 pack years or more), aged 55-74, who are current smokers or quit within the last 15 years, and (B) heavy smokers (20 pack years or more), aged 50 and over, with one additional risk factor other than second hand smoke (e.g. radon exposure).
- Blood Tests: Scientists are hard at work identifying specific proteins and cells in the blood (biomarkers) that can be used in a simple test to screen for lung cancer. There have been many publications of potential protein biomarkers, many of which still need to be validated in larger, costly trials. Additionally, circulating tumor cells (CTCs), cells shed from the tumor into the blood, are a hot topic in cancer early detection, and many academic groups and companies are developing technology to detect them.
- Breath Analysis: The ability of dogs to detect cancer gives a lot more support to exhaled breath analysis as a feasible means of lung cancer early detection. We might not be able to put dogs, trainers, and handlers in every hospital, but maybe we can develop an electronic method to mimic a dog’s nose. A number of groups are hard at work on this, finding ways to isolate and detect cancer-related compounds in exhaled breath. Check out a recent article on BusinessWeek about a new test being developed here: http://www.businessweek.com/articles/2012-03-01/a-machine-that-sniffs-out-cancer.
Taken together, these diagnostic tests will help a doctor decide a patient’s likelihood of having lung cancer, hopefully minimizing invasive examinations in negative cases, and enabling us to detect lung cancer at its earliest stages. Uniting Against Lung Cancer is currently funding a number of studies on this topic, collaborating with the Canary Foundation to identify and develop a test for non small cell lung cancer, and funding Dr. Julien Sage’s (Stanford) work in small cell lung cancer. Patients diagnosed with advanced disease have a very low five-year survival rate (<5%), but early detection can boost that to >70%.
With more research (and help from man’s best friend), we can get there.
- Ehmann et al. Canine scent detection in the diagnosis of lung cancer: Revisiting a puzzling phenomenon. European Respiratory Journal, 2011; DOI: 10.1183/09031936.00051711
- Horvath et al. Human Ovarian Carcinomas Detected by Specific Odor. Integrative Cancer Therapies, 2008; 7 (2): 76 DOI: 10.1177/1534735408319058
- McCulloch et al. Diagnostic accuracy of canine scent detection in early- and late-stage lung and breast cancers. Integr Cancer Ther 2006; 5:30e9.
- Sonoda et al. Colorectal cancer screening with odour material by canine scent detection. Gut, 31 January 2011 DOI: 10.1136/gut.2010.218305
- Willis et al. Olfactory detection of human bladder cancer by dogs: proof of principle study. BMJ 2004; 329:712.
- McCulloch et al. Lung cancer detection be canine scent: will there be a lab in the lab? Eur Respir J 2012; 39:511-512.
- National Lung Screening Trial Research Team, Aberle et al. Reduced lung-cancer mortality with low-dose computed tomographic screening. N Engl J Med. 2011 Aug 4;365(5):395-409.