INTRODUCTION:

Every year, across the world, billions of dollars are invested into curing and preventing cancer; the world’s leading cause of death. Advanced screening and detection methods are developed and new drugs and technologies are trialled to help fight the many forms of this disease. Yet still, the number of deaths caused by cancer continues to grow. Current figures show that approximately 8 million people die from cancer each year and the World Health Organisation predicts that this figure will increase 80% by 2030 (Centers for disease Contol and Prevention, 2014). Early detection may be man’s greatest from of defence. However, this is often difficult as screening techniques can be expensive and in some cases are not without their own health risks.

In order to encourage people to seek regular care, less invasive, and simpler methods would be advantageous, especially if they can prove to be more sensitive and accurate in detecting early stages of cancer. This demand has led to many alternative methods and technologies being explored. The theory that dogs may be able to detect human cancer using their superior olfactory system is one such alternative that has been widely researched in recent years. A dog’s sense of smell is said to be anywhere from 1000 to 10,000 times more sensitive than humans. Research has already shown that a dog can sense when an epileptic person is going to have a seizure or when a diabetic’s blood glucose level drops.

This is due to the dog’s ability to smell pheromones or chemical changes taking place in the body. Extensive training and tests have been carried out to discover if dogs can also be trained to identify and detect human cancers. Findings from these studies have prompted scientists to ask ‘what is it exactly that the dog can smell?’ ‘Does cancer have distinguishing odour signature made up of Volatile Organic Compounds (VOCs) which are emitted into the air?’ And if this chemical compound could be isolated and replicated then might it be possible to develop an electronic nose ‘which could potentially mimic the dog’s olfactory sense?’ It is hoped to explore these ideas and attempt to answer the questions posed. The scientific basis of the ability of dogs to detect the odour of cancer is believed to be linked to volatile organic compounds produced by malignant cells. It has been established that during tumour growth changes occur in some of the cellular proteins, leading to peroxidation of the cell membrane components, which then produces volatile organic compounds that can be detected in the headspace of the cells. There is strong indication from a number of studies that these cancer volatiles are excreted in urine or exhaled on the breath at an early stage in the disease process ^[1].

Brief history:

The first clinically robust investigation of cancer detection by dogs was reported by Willis and colleagues (British Medical Journal 2004). During this study, dogs were trained by individuals from Medical Detection Dogs (aka Cancer and Bio-detection Dogs) to detect bladder cancer (transitional cell carcinoma) by smelling urine samples from patients and healthy controls. Six dogs of varying breeds were used, none had been trained for previous scent work. Overall diagnostic accuracy was 41% (compared with the 14% success rate expected from chance alone). However there was considerable variation in the success rate between dogs, the best dog achieved 56%, but two dogs had no success at all.

The charity, in collaboration with Willis et al, published a further study in the journal Cancer Biomark 2011, ‘Volatile organic compounds as biomarkers of bladder cancer: Sensitivity and specificity using trained sniffer dogs’. Specificity ranged from 92% for urine samples obtained from young, healthy volunteers, decreasing to 56% for samples taken from older patients with non-cancerous urological disease.

Supporting evidence has been published around the world including a study by Cornu and colleagues, ‘Olfactory Detection of Prostate Cancer by Dogs Sniffing Urine: A Step Forward in Early Diagnosis’, indicated the possibilities of canine cancer detection (sensitivity 91%, specificity 91%). A second study published online in 2011 by Sonoda and colleagues investigated colorectal cancer screening using faecal samples, and demonstrated equally promising results (sensitivity 97%, specificity 99%). Ehmann et al (European Respiratory Journal, 2012) carried out the first published study showing that sniffer dogs can reliably detect lung cancer from a breath sample (sensitivity 71% specificity 93%) ^[2].

A recent study from Italy (Taverna et al, Journal of Urology 2014), reported the diagnostic accuracy of dogs trained to recognize specific volatile organic compounds of prostate cancer in urine samples (sensitivity 98–100%; specificity 98–99%) ^[3].

Procedure:

1. Detection of changes in Blood sugar level:-

Dogs have been shown to respond when their owners’ sugars are low or high, but as yet we cannot be sure as to what they are actually responding. Odour cues are the most plausible explanation especially as dogs show “alert” behaviours when their owners are asleep and presumably emitting few behavioural cues (although changes in breathing rate may occur).

In addition, owners frequently report their dogs responding when they are in another room and behavioural cues therefore implausible.

It is likely that dogs detect changes in the chemical composition of their owners’ sweat, or breath (including products of ketosis), using their acute sense of smell. This is supported by the fact that MDD are increasingly training new dogs using remote odour samples collected from clients during times of hypoglycaemia, before they introduce dog and owner. Unlike the training of seizure alert dogs, MDD do not intentionally train dogs to respond to behavioural cues.

However, once placed some dogs may learn to utilise additional predictive cues as well as odour, including subtle changes in their owners’ mood or behaviour (e.g. trembling, becoming disorientated). Research is now required to determine the precise cues used and to identify any odour signature involved.

This study is the first to examine the effectiveness of trained glycaemia alert dogs and has demonstrated that most clients are willing and able to collect data, although some improvement in recording methods is recommended. Although based mainly on owner-recorded data, multiple findings point consistently to the potential value of trained alert dogs, but for conclusive proof, longitudinal studies are now required, examining matched clients pre- and post-dog allocation ^[4].

Such studies can never be truly randomised, as the population willing to use a dog as an intervention will by necessity be self-selected. However, comparison of waiting list applicants to those who have acquired a trained dog, will help to determine the full value of this intervention.

2. Cancer detection:-

Fig no 1:- Shows Dog detecting Cancer

In Cancer detection some patients gave a urine sample at their first visit to the thyroid clinic before they went on to have a biopsy of suspicious thyroid nodules and surgery.

The surgical pathology result was diagnosed as cancer in some patients and benign thyroid disease in rest of the patients.

These urine samples were presented, by a gloved dog handler, one at a time to Frankie to sniff. Neither the dog handler nor the study coordinator, who recorded the dog's responses after the handler announced them, knew the cancer status of those subjected patients with urine samples.

The handler interspersed some urine samples that had a known cancer status so he could reward the dog for correct answers: alerting to a cancer sample by lying down, and turning away from a benign sample to alert the absence of cancer ^[5].

Training of the dogs:

Six dogs of varying breeds and ages completed a seven month period of training. All were familiar with obedience commands, but none had been previously trained for search or scent discrimination tasks. We made no attempt to include dogs with a particular suitability for scent discrimination.

The training objective was to enable the dogs to discriminate between urine from patients with bladder cancer and urine from diseased and healthy people, using samples entirely new to them, so as to preclude simple memory recognition of participants' unique odour signatures. Dogs were trained to detect (“alert to” or “indicate”) one urine sample from a patient with bladder cancer placed among six control specimens. We selected this task format (of being able to select one urine from seven) with reference to data on dogs' behaviour. Training was by operant conditioning, using the clicker training method; the dogs were taught to indicate the appropriate sample by lying beside it. Early recognition of the tumor scent was achieved by using search and find games, which were gradually replaced by discrimination phases of increasing complexity. Urine from patients with bladder cancer was presented sequentially against water, diluted urine from healthy people, undiluted urine from healthy controls, urine (containing blood) from menstruating women, and urine from patients with non-malignant active or recent urological disease or other disease. Samples were not pooled at any stage.

Participant selection:

Patients presenting with new or recurrent transitional cell carcinoma of the bladder gave urine before surgical intervention.

Then male controls aged over 50 only if recent prostate histology had been negative for cancer was included. And then patients with premalignant urological disease or a history of urological carcinoma was excluded.

A history of other malignancy was acceptable providing the patient was now considered disease-free. All other past or current medical conditions were permissible and made no exclusions on the basis of drugs, menstrual cycle, ethnicity, diet, alcohol consumption, smoking habits, exposure to chemicals, or findings on urinalysis.

After all details of all of these factors for each participant, in case needed to consider their influence on the composition and odour of the urine at any stage was recorded.

Analysis and processing of urine samples:-

After urinalysis refrigeration of fresh urine specimens within 45 minutes and froze them 2-32 hours later as 0.5 ml aliquots in glass vials.

Then stored them at -40°C for up to five months. For presentation to the dogs, samples were defrosted and pipetted on to filter paper in Petri dishes (58 x 15 mm) and used either immediately in a wet state or within four weeks after overnight air drying and storage at room temperature^[4].

Dog training:

A Belgian Malinois shepherd was trained by a professional and dedicated team of two people from the beginning to the end of the detection process. The first objective was to teach the dog to discriminate between urine from individuals with PCa and urine from controls. The dog was trained by the clicker training method (a kind of operant conditioning). The dog was given his ball as a reward for alerting to a cancer urine. The dog was taught to sit in front of the sample of urine recognized as cancer.

Patients and samples:

Urine samples were obtained from Caucasian patients recruited in tertiary reference who had given written consent for analysis of their urine for detection, including genetic analysis. All men included were referred to an urologist because they had an elevated PSA level or abnormal findings on Digital Rectal Examination (DRE).

Data collected at the visit were age, height, weight, PSA level, and DRE data. Urine was collected during the first consultation after DRE.

Then all patients underwent prostate biopsies according to a standard procedure (12 cores) and were classified as cases or controls after pathologic examination of the specimens. Patients were not selected in case of history of urothelial carcinoma or other malignant disease. There were no exclusion criteria regarding other medical history, alcohol consumption, drugs, food, tobacco consumption, or other habits.

Study design:

The double-blind testing phase consisted of consecutive runs. For each run, the dog was presented six samples (five controls and one cancer). During each run, the cancer urine was one of the selected cancer samples and the 5 control urines were samples randomly selected among controls. Samples were anonymised and numbered so that people conducting the test were not able to discriminate cancer from control samples. The samples were frozen at 4 8C from the time of urine collection to the time of testing. Each urine sample was slowly heated to 37 8C with the same material immediately before examination in a dedicated area outside the testing room.

During each run, the dog had to scent successively the six samples that were hidden in boxes. Each box had a hole so that the dog could not access the urine itself, but only its odor. After a mean time of 30 sec, the dog had to sit in front of a box to designate the cancer sample. In case of success (dog sitting in front of PCa urine sample), the result was classified as a true positive and the controls as true negatives, and the next cancer sample was tested. In case of mistake (dog sitting in front of control urine sample), the control sample was classified as false positive and the cancer sample as a false negative. The false-positive sample was excluded from the pool of controls used for the future runs, and the cancer sample was retested in association with other controls. A new prostate biopsy was proposed to the patient who provided the false-positive sample ^[6].

3. Seizure detection:-

Over the last decade a new kind of service animal has emerged. Seizure alert dogs warn people with epilepsy of an oncoming attack minutes—sometimes hours—before it occurs. This allows the person time to take seizure blocking medication, get to a safe place, or call for assistance.

How dogs detect an oncoming seizure in a human is a mystery. Some trainers and researchers think they detect subtle changes in human behaviour or scent before an episode occurs. There are no scientific studies, however, to prove these theories. Trainers also believe the behaviour is not breed, age or gender specific in dogs.

Dogs can be trained to stay with the person during a seizure. When selecting a potential seizure alert dog to work with, she performs a trainability test ^[7].

Understanding dog's senses

A big part of understanding a dog is understanding its senses and accepting that they are indeed different than humans. Both humans and dogs have the same three senses: sight, hearing and smelling, however while most humans communicate by hearing, seeing, and then smelling, dogs primarily communicate by smelling, seeing and lastly hearing. Dogs also have a universal sense which humans do not have, where they can feel the energy (emotions) of the other beings around them. The statistics below will vary slightly with different types of breeds, for example a sight hound may have slightly better vision and a coonhound type of dog may have a slightly better sense of smell than other types.

Properties of each of senses

The Nose: A dog interprets the world predominantly by smell, whereas a human interprets it by sight. As a human I cannot even imagine what that would be like to get most of my information from what I smell. This is why a blind or deaf dog can get along just fine if allowed to be a dog, given the proper leadership and exercise and their sensory whiskers are not cut off when they are groomed. While a dog's brain is only one-tenth the size of a human brain, the part that controls smell is 40 times larger than in humans. A dog’s sense of smell is about 1,000 to 10,000,000 times more sensitive than a human’s (depending on the breed). A human has about 5 million scent glands, compared to a dog, who has anywhere from 125 million to 300 million (depending on the breed).

Ever wonder why your dog's nose is wet? The mucus on a dog's nose actually helps it smell by capturing scent particles. When a dog’s nose is dry they may lick it to aid them in scent.

When dogs smell something they are not just registering a smell, they get an entire story. They can smell pheromone, which is not only found in the urine and fecal, but on the skin and fur. From this they can tell a lot about another dog or human including if they are male or female, what they ate, where they have been, what they have touched, if they are ready to mate, if they have recently given birth, or had a false pregnancy, and what mood they are in. They have even been known to smell cancer on people, alerting them to it and saving their lives. This means when your dog smells another person, tree that another dog has peed on, pant leg that another dog has rubbed up against, or chair that someone has sat in, they are actually reading a story, not just smelling an interesting scent. While a human will smell something like spaghetti sauce as one smell, a dog smells each individual ingredient. Unlike humans, dogs can move their nostrils independently, allowing them to know what direction a smell is coming from.

A dog can both sniff and breathe. These are two different functions. Breathing is for air, but when they sniff with short breaths they actually save some scent that does not get exhaled. When a dog is overheated and actively panting, its sense of smell is reduced by as much as 40 percent as it uses the air to cool itself rather than for smelling. Puppies have heat sensors in their noses to help find their mother during the time when their eyes and ears are closed. These sensors disappear by the time they are adults.

The Eyes:

Since dogs do not have a spoken language, their thoughts are more like a sequence of images, much like a child before it learns to speak.

A common question among humans is, "Are dogs colour blind?" The answer is no, not exactly, meaning they do not only see in shades of only black and white. Studies have shown that dogs see in colours of various shades of blue and yellow. For example, a rainbow to a dog would be as follows: dark blue, light blue, light gray, light yellow, dark brownish yellow, and dark gray.

Purple and blue are both seen as shades of blue. Greenish-blue is viewed as a shade of gray. Red is seen as a black or dark gray. Orange, yellow and green all are seen to a dog as various shades of yellow. This means that, to a dog, bright orange toys are the same yellowish shade as the green grass. If you want your dog to clearly see his toys in the green grass you are better off giving the dog blue toys; if you have orange, yellow or green toys, the dog will be able to find them with his nose.

Dogs can see best at dusk and dawn. Their low-light vision is much better than a human’s, but their overall vision is not better. While a human’s vision is considered perfect at 20/20, a dog's vision is on average 20/75. Dogs cannot see as well at a distance as a human with normal eyes. Humans can also see things close up better than a dog can. On average, a human can see something clearly as close as 7 cm away, compared to a dog that sees things burry if they are closer than 33 cm away. Dogs can recognize objects better when they are moving and sometimes overlook the same object when it is still. Dogs see images on a TV screen, but most likely also see a rapidly flickering light, almost like a strobe light, in the picture; a human’s flicker resolution ability is about 55 Hz and a dog's is about 75 Hz.

Puppies are born deaf and cannot hear until they are about 21 days old. Their eyes are also closed. During this time they rely solely on scent to interpret their world. By the time their sense of hearing is completely developed they can hear about 4 times the distance of a human who has normal hearing. Dogs can hear higher pitched sounds that humans cannot hear. They often bark at vacuums because they hear a very loud annoying pitch to their motors.

Dogs detect sounds in the frequency range of approximately 67 - 45,000 Hz (varies with different breeds), compared to humans with the approximate range of 64 - 23,000 Hz. As humans and dogs get older they both lose the ability to hear certain frequencies.

Dogs have 18 or more muscles in their ears allowing them to be mobile, whereas a human has only 6 and can only move their ears slightly, if at all. Dogs with perked ears can usually hear better than dogs with hanging ears, especially if they can move their ears in the direction of the sound.

Animals can feel energy. If you break it down to simple science, the kinetic energy a dog detects might simply be a frequency. Light, sound and heat are all frequencies. This energy is a universal animal language. Have you ever been watching a group of wild animals out in the yard, perhaps a squirrel, rabbit and a deer all eating peacefully? Clearly these animals are not speaking words to one another asking if they all come in peace; somehow they all know that they are not going to harm one another. Or perhaps you know a dog that other dogs do not tend to like, or a cat that likes one dog but not another. Or perhaps you know of a person who dogs are prone to bark at. Dogs can sense fear. It is believe they can smell the pheromone and perhaps they can even feel it radiating from a being. Some dogs can tell a few minutes before a human is about to have a seizure even before the person knows. When I was a kid growing up I had a Lab mix who loved everyone. There was not a single person he didn't like, except for my uncle. When my uncle would come around he would bark at him. I later discovered that many dogs tended to bark at my uncle and as I got older I realized my uncle was a very tense, nervous person. Another example was a time when my husband and I were driving down the road with our two dogs in a van that did not have any windows in the back. The dogs were sleeping on the van floor. Suddenly our Pit Bull stood up and started growling. I was in the passenger seat and didn’t see or hear anything. My husband, on the other hand, was amazed. He had just passed a cop and for a split second thought he may have been speeding and at the exact moment he felt a chill of fear run down his spine, his dog had popped up from his curled up sleep and growled, not at us but toward the walls of the moving van. The dog had felt his fear and was jumping up in protection mode.

Dogs “interpret human emotions” such as worry, anxiety, fear, anger, pity and nervousness, as weaknesses and they do not listen to these emotions. Dogs listen best to someone who is calm but firm in their approach. They use their sense of energy to determine who should be the leader of their pack. The being with the strongest and most stable energy is the one they look to, be it themselves or another being around them. While you can hide your emotions from another human, you cannot hide them from a dog ^[8].

Advantages

1. As compared to other conventional detection method, this method is much more accurate.

2. Less time consuming method.

3. Sensitivity is much better.

4. Future scope is very promising.

Disadvantages

1. More expensive.

2. Need a well trained dog.

3. Need a perfect trainer to trained the dogs .

4. Needs more research.

5. Low awareness.

Applications of Medical Detection of Dogs

§ Medical Alert Assistance Dogs (Shirley).

§ The most prominent application of MDD is lies in the field of cancer detection. Various type of cancer like breast cancer, bladder cancer, prostate cancer, ovarian cancer, lungs cancer can be detected by this advance screening and early detection method of MDD.

§ Assists individual in reducing hyperglycaemic associated conditions.

Future Scope:

Through the research & development of electronic systems (E noses) is introduced recently that will assist in the early detection of cancer through cheap non-invasive tests. In the short term the cancer dogs can provide second line screening for cancers that are currently very difficult to diagnose reliably, such as prostate cancer. Trained dog can be used to assist an individual with severe narcolepsy. Plans for the future include the training of dogs to detect substances that result in severe allergic response in atopic clients.

CONCLUSION:

Approach to training was vindicated by the results achieved when the dogs were formally evaluated. Despite the fact, that do not use dogs without proved scenting abilities, and despite the inclusion of age matched diseased controls statistically significant success rate was achieved by scientists. Great deal of learning was achieved during the study, and it was certain that improvements in the success rate can be achieved by modifications to the training regimen. Suitable reward mechanisms for the trainers those who are blinded to the samples, so as not to confuse the dogs. Also, for this approach in cancer detection to have more clinical relevance, need to train the dogs for respond to more than one positive sample at a time, and to have a signal for “no positive sample present.” Future of medical detection is very bright if new & latest techniques are incorporated time to time. Some other types of detection may be possible in future if proper research is done on this project.

REFERENCE:

1. Available at: http://medicaldetectiondogs.org.uk, collected on 21/10/2015.

2. Ehmann R, Boedeker E, Friedrich U, Sagert J, Dippon J, Friedel G, Walles T, Canine scent detection in the diagnosis of lung cancer: revisiting a puzzling phenomenon, Eur Respir J., 2012 Mar; 39 (3): 669-76.

3. Gianluigi Taverna, Lorenzo Tidu, Fabio Grizzi, Valter Torri, Alberto Mandressi, Paolo Sardella, Giuseppe La Torre, Giampiero Cocciolone, Mauro Seveso, Guido Giusti, Rodolfo Hurle, Armando Santoro, Pierpaolo Graziotti, Presented at annual meeting of American Urological Association, Orlando, Florida, May 16-21, 2014.

4. Available at: http://news-medical.net, collected on 7/11/2015.

5. Willis CM, Church SM, Guest CM, Cook WA, McCarthy N, Bransbury AJ, Olfactory detection of human bladder cancer by dogs: a proof of principle study. BMJ 329:712-4, 2004.

6. Jean-Nicolas Cornu, Geraldine Cancel-Tassin, Valeria Ondet, Caroline Giradet, Olivier Cussevot; Olfactory detection of Prostate cancer by dogs sniffing urine : A Step Forward In Early Diagnosis, European Association Of Urology, Elsevier B.V, 198, 2011.

7. Available at: news.nationageographic.com/news/2003/04/0416_030416_seizuredogs.html, collected on 7/11/2015.

8. Available at: http://dogbreedinfo.com/articles/dogsense.htm, collected on 7/11/2015.

Received on 09.02.2016 Accepted on 28.02.2016

Asian J. Pharm. Ana. 6(1): January- March, 2016; Page 47-52