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detection research, finding 531 potentially relevant articles, but focusing their analysis on five articles and one unpublished manuscript.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tubes, with overall success rates that were not statistically significant.5 Another study, not analyzed because as yet unpublished, also failed to find significant results from dogs smelling urine of prostrate cancer patients.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.