Inside a mystery of oncoscience: The cancer-sniffing pets

Abstract

Worldwide, sick people are daily enjoying the benefits of pet-therapy [1-6]. Next to this scientific evidence, the media report cases of patients who claim to have been saved by their cancer-sniffing pets through an early diagnosis of malignancy. By virtue of this, the concept of ‘canine cancer detection’ has been advanced, on the basis of the presumed olfactory ability of pets, in particular dogs, to smell very low concentrations of aromatic and/or alkanes compounds generated and released by malignant tumors in the patient’s breath, urine or watery stool and into adsorbent materials [7-15]. It is well known that the brain of a domestic dog (Canis lupus familiaris from the Latin) is dominated by a wide olfactory cortex unlike the humans, where a visual cortex predominates. More in detail, dogs are equipped up to 56 times more smellsensitive receptors than the human beings, reaching the number of 280 million in selected breeds, spread over an olfactory surface about the size of a pendrive (9.76 cm2), if compared to 5 million over an area about the size of a postage stamp (3.08 cm2) for the humans [16, 17]. This is thought to render its sense of smell up to 56 times more sensitive than human’s. The domestic cat (Felis silvestris catus from the Latin) also possesses an acute sense of smell, due to its well-developed olfactory bulb and, in addition, to a large surface of olfactory mucosa (about 5.8 cm2), which is almost twice that of the human beings [16]. In oncological medicine, among the diagnostic hallmarks of malignancy there are: lymphovascular and perineural invasion; infiltrative neoplastic growth; immune evasion; a high cytoproliferative index; an elevated mitotic cell count; and tumor necrosis [18, 19]. More in detail, tumor necrosis (νέκρωσις – death from the Greek) is a form of hypoxic death related to the high metabolic demand of cancer cells. It does not follow the apoptotic cascade, but the uncontrolled release of cell death products evokes in the surrounding space an inflammatory response Research Perspective