Can dogs detect human cancer?

Question

I heard several times that dogs could detect cancer before it was detected by humans.

Can Dogs Smell Cancer?

There are many published studies that prove dogs can detect cancer through breath samples, and scientists and doctors are trying to come up with a breathalyzer test that works as good as the dogs nose. So far, the only ones that can smell cancer in early stages, are the dogs.

Is it true? If so, how can it be explained and which types of cancers are concerned? Can they sniff it directly on people, and not only on human secretions samples (urine, blood…)?

Answer 1

Dogs 'sniff out prostate cancer with 98% accuracy,' study finds

A new study from Italian researchers, presented at the 109th Annual Scientific Meeting of the American Urological Association in Orlando, FL, found that specially trained dogs were able to detect prostate cancer from urine samples with 98% accuracy.

For their study, the team wanted to see whether two highly trained dogs were able to detect prostate cancer-specific VOCs in the urine samples of 677 participants. Of these, 320 had prostate cancer ranging from low-risk to metastatic and 357 were healthy controls.

UAMS Researchers Use Scent-Trained Dogs to Detect Thyroid Cancer

The dogs were then presented with urine samples from patients — some with thyroid cancer and some with benign nodules — and asked to indicate whether each sample had thyroid cancer or not. Their results were compared to a surgical pathology diagnosis and matched in 30 of 34 cases, or 88.2 percent accuracy.

At least for some types of cancer it seems to work. The cancers make chemicals the body doesn't make naturally, the dogs can smell them. Since it's an area of ongoing research a list of what types is going to be subject to change.

Answer 2

There are quite a number of published studies showing that dogs can be trained to do this with high accuracy.

For examples:

• Olfactory detection of prostate cancer by dogs sniffing urine: a step forward in early diagnosis

  The dog completed all the runs and correctly designated the cancer samples in 30 of 33 cases. Of the three cases wrongly classified as cancer, one patient was rebiopsied and a PCa was diagnosed. The sensitivity and specificity were both 91%.

• Diagnostic accuracy of canine scent detection in early- and late-stage lung and breast cancers.

  Among lung cancer patients and controls, overall sensitivity of canine scent detection compared to biopsy-confirmed conventional diagnosis was 0.99 (95% confidence interval [CI], 0.99, 1.00) and overall specificity 0.99 (95% CI, 0.96, 1.00). Among breast cancer patients and controls, sensitivity was 0.88 (95% CI, 0.75, 1.00) and specificity 0.98 (95% CI, 0.90, 0.99). Sensitivity and specificity were remarkably similar across all 4 stages of both diseases.

  Training was efficient and cancer identification was accurate; in a matter of weeks, ordinary household dogs with only basic behavioral "puppy training" were trained to accurately distinguish breath samples of lung and breast cancer patients from those of controls.

• Olfactory system of highly trained dogs detects prostate cancer in urine samples.

  For dog 1 sensitivity was 100% (95% CI 99.0-100.0) and specificity was 98.7% (95% CI 97.3-99.5). For dog 2 sensitivity was 98.6% (95% CI 96.8-99.6) and specificity was 97.6% (95% CI 95.9-98.7). When considering only men older than 45 years in the control group, dog 1 achieved 100% sensitivity and 98% specificity (95% CI 96-99.2), and dog 2 achieved 98.6% sensitivity (95% CI 96.8-99.6) and 96.4% specificity (95% CI 93.9-98.1). Analysis of false-positive cases revealed no consistent pattern in participant demographics or tumor characteristics.

• Can dogs smell lung cancer? First study using exhaled breath and urine screening in unselected patients with suspected lung cancer.

  With an intensified training procedure, the exhaled breath and urine tests showed sensitivity rates of 56-76% and specificity rates of 8.3-33.3%, respectively, in our heterogeneous study population.