XRAYS - Making Sense of Cancer Headlines

FORCE’s eXamining the Relevance of Articles for Young Survivors (XRAYS) program is a reliable resource for breast cancer research-related news and information. XRAYS reviews new breast cancer research, provides plain-language summaries, and rates how the media covered the topic. XRAYS is funded by the CDC.

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Dogs: Companions, hunters, and cancer detectors?

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XRAYS:  Making Sense of Cancer Headlines

In August 2016, many news outlets published stories about how actress Shannen Doherty’s dog was able to sniff out her cancer before she was diagnosed. Is there scientific validity to that claim? (9/616)


“Shannen Doherty Opens Up About Chemo Struggles Through Picture of Her Beloved Dog That Sniffed Out Her Cancer.” This title appeared with an article that People magazine published this past August about the Beverly Hills, 90210 actress Shannen Doherty and her dog. The Huffington Post, US Magazine, and Entertainment Tonight also ran similar stories about how her dog was able to smell her cancer.


Has research been done on dogs smelling cancer?

“The notion that animals, especially those with a highly sensitive sense of smell, such as dogs, can sniff malignant tumors is nothing but awkward,” writes Giuseppe Lippi and Gianfranco Cervellin in their scientific review of canine olfaction (smell) detection of cancer. Shannen Doherty claims that her dog obsessively sniffed at her right side, where her breast cancer was subsequently discovered. Other similar cases dating back to 1989 have been published in the literature as case reports, which are scientific publications based on observations of a single patient.

Other studies have tried to determine whether dogs that are trained to recognize the “scent” of a cancer can correctly sniff out the cancer samples from noncancer samples. There are not many of these studies, and the success of the findings differs by cancer type, but some of the results suggest that dogs, with their extremely sensitive sense of smell, are picking up on something that is being emitted from some of the cancer samples.

Does this mean dogs can reliably sniff out cancer?

Not at all.

This is an interesting field of study that has potential to aid in developing new technologies for cancer detection—the dogs may smell odors that humans can’t detect. These odors might be new biomarkers for a particular cancer, and once they are identified, humans can try to develop technologies that are specific for that biomarker. However, there is not sufficient data to definitively say that dogs are able to sniff out cancers. Because of this, headlines like the one about Shannen Doherty’s dog are more of an interesting story than a medical finding.

While a few published case studies that sound similar to Shannen Doherty’s story have been published, there is a tendency in academic science to only publish positive results. What this means is that positive things such as a dog sniffing out a cancer are more likely to be published than dogs sniffing at something that is not cancer.

People can look for established signs if they are concerned about breast cancer. Women should be familiar with the look and feel of their breasts, and notice any changes. The Susan G. Komen website notes the following symptoms:

  • A lump, hard knot or thickening inside the breast or armpit
  • Any swelling, warmth, redness or darkening of the breast
  • Any changes in size or shape of the breast
  • Any dimpling or puckering of the breast skin
  • itchiness, or a scaly sore or rash on the nipple
  • A nipple pulling inwards
  • Nipple discharge that suddenly appears
  • Any new pains in the breast that don’t go away

While these changes do not indicate that a person has breast cancer, they indicate the need to see a health care provider to get it checked out.  Men also get breast cancer, although at far lower rates than women. They may notice similar changes and should take similar action if they do.

Breast cancer screening

Additionally, all women should be up to date on their breast cancer screenings. National Comprehensive Cancer Network guidelines for breast cancer screening and diagnosis were recently released. Guidelines are as follows:

Women at average risk for breast cancer

  • Clinical breast exam every 1-3 years for women 25-40
  • Annual clinical breast exam every year after age 40
  • Annual screening mammogram beginning at age 40
  • Consider 3D mammography

Women at high risk for breast cancer due to either a mutation in a gene that increases breast cancer risk or a strong family history of breast cancer

  • Clinical breast exam every 6 months to 1 year
  • Annual mammogram beginning at age 30 or 10 years prior to youngest age of diagnosis in the family (whichever is older)
  • Annual breast MRI at age 25 or 10 years prior to youngest age of diagnosis in the family (whichever is older)
  • Consider 3D mammography

Men with mutations in BRCA1 or BRCA2

  • Annual clinical breast exams beginning at age 35 and
  • Discussion with health care provider about the possibility of additional screening.

Breast cancer survivors

  • Physical exam 1-4 times per year for 5 years, then annually
  • Annual mammogram for survivors who did not have mastectomy


Stories about cancer-sniffing dogs are interesting and could lead to some really cool biological discoveries. But they are not clinically applicable for human patients—people can look to their furry friends for companionship, but not for cancer screening.

Questions to ask your doctor:

  • What are things I can do to lower my breast cancer risk?
  • Can you help me assess my breast cancer risk?
  • What factors would put me at high risk of breast cancer?
  • What types of changes in my breast should I be concerned about?
  • How often should I have regular breast cancer screening?

Posted 9/6/16


Lippi G. and Cervellin G. “Canine olfactory detection of cancer versus laboratory testing: myth or opportunity?” Clin Chem Lab Med, 2012; 50(3): 435-439.

NCCN Clinical Practice Guidelines in Oncology: Breast Cancer Screening and Diagnosis Version 1.2016, July 27, 2016.  

NCCN Clinical Practice Guidelines in Oncology:  Genetic/Familial High-Risk Assessment: Breast and Ovarian Version 2.2016, March 15, 2016. 

Warning Signs of Breast Cancer” from Susan G Komen.

Related Information and Resources

FORCE Information:  Breast Cancer Screening 

FORCE Information: Risk Management Guidelines 

Be Empowered Webinar: High-risk Surveillance for Breast Cancer 

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