Cancer Sniffers Perform Better with Some Cancers than Others, but Testing Parameters Need More Standardization

Two scientists, one from the New College of Florida and one from the Pine Street Foundation in San Anselmo, reviewed the current state of canine cancer detection research, finding 531 potentially relevant articles, but focusing their analysis on five articles and one unpublished manuscript. The studies looked at canine detection of the following cancers:

1. Bladder cancer detection from smelling urine of patients, with 41% success rate (compared with 14% expected by chance).1
2. Melanoma detection by smelling lesions on patients, with a success rate between 75 and 85.7%.2
3. Lung and breast cancer by smelling samples of a patient’s exhaled breath,3 with a specificity of 99% and a sensitivity of 99%. The authors of the survey article explain that sensitivity is the proportion of cancer samples which the canines correctly identify, and specificity is the proportion of control samples which the canines correctly indicate as controls.
4. Ovarian cancer by smelling ovarian tumor samples, with a sensitivity of 100% and a specificity of 97.5%.4 The researchers noted that the accuracy was remarkable given that some of the control tissues had been removed from areas adjacent to the tumor within the same patients.
5. Breast and prostate cancer by smelling urine samples in test tubes, with overall success rates that were not statistically significant.5 Another study, not analyzed because as yet unpublished, also failed to find significant results from dogs smelling urine of prostrate cancer patients.
6. Ovarian cancer by smelling exhaled breath condensate, with results not yet available.

The experiment involving breast and prostrate cancer was criticized by the authors of the review study for having different trainers using different methods, so that “inconsistencies in training may have made it nearly impossible for the dogs to perform well.” Storage conditions in the bladder cancer study varied, and dogs did considerably better when the urine sample was relatively fresh. The authors note that this study might have had insufficient controls, which might also have been true of the ovarian, breast, and prostrate cancer studies. The authors suggest also that there may be more cancer biomarkers at the source of the tumor and in exhaled breath than there are in urine.

The authors reaffirm their faith in using dogs as a diagnostic tool, but they emphasize the importance of additional research, as well as repeating studies already done. Mary Elizabeth Thurston suggested many years ago that cancer sniffers might be useful in poor countries (Lost History of the Canine Race).6 Much more research will be needed, however, before regular clinical use of cancer sniffers will become a reality. E. Moser and M. McCulloch (2010), Canine Scent Detection of Human Cancers: A Review of Methods and Accuracy. Journal of Veterinary Behavior, 5, 145-152.

1. Willis, C. M., Church, S. M., Guest, C. M., Cook, W. A., McCarthy, N., Bransbury, A. J., Church, M. R. T., & Church, J. C. T. (2004). Olfactory Detection of Human Bladder Cancer by Dogs: Proof of Principle Study. BMJ [British Medical Journal], 329, 712–715.
2. Pickel, D. P., Manucy, G. P., Walker, B. B., Hall S. B., & Walker, J. C. (2004). Evidence for Canine Olfactory Detection of Melanoma. Applied Animal Behaviour Science, 89, 107–116.
3. McCulloch, M., Jezierski, T., Broffman, M., Hubbard, A., Turner, K., & Janecki, T. (2006). Diagnostic Accuracy of Canine Scent Detection in Early- and Late-Stage Lung and Breast Cancers. Integrative Cancer Therapies, 5(1), 30–9.
4. Horvath, G., Jarverud, G.A., Jarverud, S., Horvath, I., 2008. Human Ovarian Carcinomas Detected by Specific Odor. Integrative Cancer Therapies, 7, 76-80.
5. Gordon, R.T., Schatz, C.B., Myers, L.J., Kosty, M., Gonczy, C., Kroener, J., Tran, M., Kurtzhals, P., Heath, S., Koziol, J.A., Arthur, N., Gabriel, M., Hemping, J., Hemping, G., Nesbitt, S., Tucker-Clark, L., Zaayer, J., 2008. The Use of Canines in the Detection of Human Cancers. Journal of Alternative and Complementary Medicine, 14, 61-67.
6. See my chapter on the Cancer Sniffers in Service and Therapy Dogs in American Society, 112.

Types of Detection Dogs--How Many Can You Name?

When I began working on Service and Therapy Dogs in American Society, I was soon struck by the proliferation of service dog types, including the fairly recent category of hypoglycemia alert dogs and the still anecdotal migraine-alert dog category. This is nothing compared to the list of scenting dogs that were assembled by a group of chemists in 2004. They came up with 30 scent detection dog categories. Some of these categories probably only represent a few dozen dogs, but many of them are essential to law enforcement and are found throughout the world. The categories are:

1. Abalone (endangered mollusk poaching) detector dog
2. Agricultural product (importation) detector dog
3. Arson (accelerant) detector dog
4. Brown tree snake (pest species) detector dog
5. Airport/runway detector dog
6. Cadaver (human remains) detector dog
7. Chemical weapon detector dog
8. Citrus canker detector dog
9. Concealed person detector dog
10. Currency detector dog
11. Drug (narcotic) detector dog
12. Explosives (bomb) detector dog
13. Gas leak detector dog
14. Gold ore detector dog
15. Gun/ammunition detector dog
16. GYPSY moth larvae detector dog
17. Land mine trip wire detector dog
18. Melanoma detector dog
19. Missing person detector dog
20. Rotten power pole detector dog
21. Scent line-up detector dog
22. Screw worm detector dog
23. Seal detector dog
24. Search and rescue (warm blood) detector dog
25. Syringe needle (dried blood) detector dog
26. Termite detector dog
27. Tracking (fleeing suspect) detector dog
28. Truffles detector dog
29. Water search detector dog
30. Wildlife detector dog

The list was compiled for an article in the Journal of Analytical and Bioanalytical Chemistry. Lorenzo, N., Wan, T.L., Harper, R.J., Hsu, Y.L., Chow, M., Rose, S., and Furton, K.G. (2004). Laboratory and Field Experiments Used to Identify Canis lupus var. familiaris Active Odor Signature Chemicals from Drugs, Explosives, and Humans. Analytical and Bioanalytical Chemistry, 376: 1212-1224.

For more on the use of detection dogs in conservation projects, see Brown, C., Stafford, K., and Fordham, R. (2006). The Use of Scent-Detection Dogs. Irish Veterinary Journal, 59(2), 97-104. dogs have been used to find dead bats at wind farms. Arnett, E.B. (2006). A Preliminary Evaluation on the Use of Dogs to Recover Bat Fatalities at Wind Energy Facilities. Wildlife Society Bulletin, 34(5), 1440-1445. They have also been trained to detect microbial growth in buildings, which can cause respiratory and other symptoms in occupants. Kauhanen, E., Harri, M., Nevalainen, A., and Nevalainen, T. (2002). Validity of Detection of Microbial Growth in Buildings by Trained Dogs. Environmental International, 28, 153-7. A master's thesis filed with South Dakota State University studied dogs trained to find ferrets. The thesis was adapted into an article Reindl, S.A. et al. (2006). Efficacy of Scent Dogs in Detecting Black-Footed Ferrets at a Reintroduction Site in South Dakota. USDA National Wildlife Research Center Staff Publications; Kerley, L.L. and Salkina, G.P. (2006). Using Scent-Matching Dogs to Identify Individual Amur Tigers from Scats. Journal of Wildlife Management, 71(4), 1349-1356 (a unique study in that the dogs were not trained just to recognize tigers, but also to identify individual tigers).

In the Federal Register of October 2, 2013, the Fish and Wildlife Service reported that dogs had been used in an attempt to identify and locate potential natural roosts of the bonneted bat in Florida. 78 Fed. Reg. 61004 (October 2, 2013), at 61007 and 61018.  The dogs were obtained from Auburn University's EcoDogs.