It has now become accepted that the cancers which affect our canine companions have similarities to some of the same cancers that afflict humans. This has been shown most clearly in canine osteosarcoma and has prompted joint research ventures that will benefit both human and veterinary patients. What could be more appropriate than cementing the bond between humanity and dogs than by studying the diseases that affect them both to their mutual benefit!

The sequencing of the canine genome and the advances in canine cytogenetics offer a unique opportunity to explore the genetic basis for many canine cancers that primarily affect certain breeds (e.g. osteosarcomas and Rottweilers, sarcomas and Flat-Coat Retrievers, gliomas and mast cell tumours and Boxers, etc.) (Breen 2008). Identifying genes in these breeds may ultimately allow identification of similar genes in humans, but in the meantime will hopefully enable these genetic weaknesses to be bred out of our pure-breed dogs.

Dysregulation of many oncogenes has been associated with the development of many human cancers. The recent identification of one of these, the MET proto-oncogene in a large percentage of Rottweilers compared to other breeds, supports the belief that germline mutations contribute to the high rates of cancer in a similar manner to inheritable cancer in humans (Liao et al 2006). Modiano et al (2005) evaluated breed predisposition in the development of B- and T-cell lymphomas and were able to demonstrate that certain breeds were more likely to develop T-cell rather than B-cell disease.

Telomere length and the rate of telomere loss are similar in both humans and dogs, which means that drugs targeted at telomerase, one of the main mechanisms by which cancer cells achieve immortality, can be developed using naturally occurring tumours in dogs to define new strategies that will benefit both species (Cadile et al 2007).

The early diagnosis of cancer is vital to successful treatment and throughout this book we have emphasized how important it is to recognize signs early and set up the appropriate diagnostics and treatments. In veterinary medicine there is much we can improve on by the simple process of thorough physical examination, simple diagnostics such as fine needle aspirates and biopsies, and talking with specialists as to the best approach for patient management. One spectacular improvement is the enhanced availability of advanced imaging in the form of CT/MRI that facilitates improved staging, treatment planning and prognostic evaluation, etc. for our patients. These tools have been available to our human colleagues for a number of years and all contribute to improved survival time for patients.

The hunt for ‘serum markers’ of malignancy that are specific for individual cancers continues to be an active area of research that has come a long way since the identification of CA-125 and its association with ovarian cancer in women (Nossov et al 2008). The hope is that a simple blood test can be developed to screen for cancer and therefore facilitate early diagnosis. Such tests would also be potentially valuable in monitoring response to treatment and tumour recurrence. In humans, prostate-specific antigen has been a valuable tool in the early detection of prostatic carcinoma in men (Diamandis 1998), but a similar test in male dogs did not show the same specificity (Bell et al 1995).

Proteomics research does have the potential in the future to provide new screening methods for veterinary cancers; the major problem with the technology presently is determining the specificity of the tests (Jackson et al 2007, McCaw et al 2007) and further investigations are required (Gaines et al 2007). Currently, one serum marker that is routinely used to assess response to treatment in veterinary patients is hypercalcaemia, a common paraneoplastic syndrome, that when present is, in many cases, a valuable marker of tumour burden in patients with lymphoma and anal sac adenocarcinoma. Interestingly, in some patients, treatment selects tumour cells that no longer produce parathormone-like factors, making this method of monitoring these patients not always reliable.

Enhancing the immune system in the fight against cancer has always seemed to make intellectual sense; however, it has proved to be much more difficult than was previously thought. There have been a few tantalising breakthroughs in human oncology that have been sufficient to continue research in this area. Active research has certainly led to a more in-depth understanding of the complexity of how the immune system works, with the anticipation that an immunological approach, in conjunction with standard treatments (multimodality treatment), will result in improved survival times for patients with cancer.

In veterinary medicine the development of the melanoma vaccine (Bergman et al 2006) has been the most promising development in the treatment of canine melanoma since the availability of radiation to control local disease. Other interesting developments along the lines of tumour vaccine include the recent report on the development of an allogeneic haemangiosarcoma tumour lysate vaccine (U’Ren et al 2007). Although the vaccine elicited a good humoral response in dogs with haemangiosarcoma, further trials are required to determine a survival benefit to the vaccine. This vaccine was given concurrently with doxorubicin and as such was not intended as sole treatment, but rather worked in a complementary fashion to chemotherapy.

Cytokines are a further arm of the immune system that potentially can be utilized in the treatment of cancer patients. Interleukin-2 (IL-2) has been used in human patients with renal carcinoma (Klapper et al 2008), and inhalant IL-2 showed some promise for canine patients with pulmonary metastases (Dow et al 2005). Jourdier et al (2003) looked at the effect of IL-2 on feline fibrosarcomas. In this study patients were given intratumoral injections of a recombinant poxvirus expressing IL-2. Sixty-one per cent of cats treated with surgery and iridium radiotherapy had recurrence over a 12-month period, whereas only 28% of cats given immunotherapy as part of treatment had local recurrence. Interferons (IFNs) are also currently under investigation in the management of feline sarcomas (Hampel et al 2007).