How science can help dogs and cats with can­cer

Wicklow People (West Edition) - - LIFESTYLE - PETE WEDDERBURN

CAN­CER is the big­gest killer of dogs over the age of ten, with one in four dogs de­vel­op­ing can­cer. And it’s com­mon in cats too. Vet­eri­nary re­searchers have been work­ing hard to find out how to pre­vent and treat this chal­leng­ing is­sue.

Can­cer re­search has four main ar­eas of fo­cus: di­ag­no­sis, pre­ven­tion, treat­ment and pal­lia­tive care.

Di­ag­no­sis gen­er­ally in­volves tak­ing a biopsy from a suspicious area and hav­ing it an­a­lysed by a lab­o­ra­tory: tech­niques for do­ing this are now eas­ier, cheaper and less in­va­sive.

Pre­ven­tion is easy in the­ory: you need to know the cause, and then re­move the cause. The chal­lenge is that the cause is not al­ways easy to iden­tify. Broadly, can­cer is caused by dam­age to

DNA which then leads to un­con­trolled di­vi­sion of ab­nor­mal cells. This dam­aged DNA can be in­her­ited (breed-re­lated) and or ac­quired.

In­her­ited cancers are com­mon in some breeds of dog. Flat-Coated Retriev­ers, Golden Retriev­ers, Ir­ish Wolfhounds and Labrador Retriev­ers are af­fected, with can­cer dra­mat­i­cally short­en­ing the av­er­age life­span of some breeds e.g. over 50% of Flat-Coated Retriev­ers die of can­cer, and the av­er­age age of this breed is only eight years. For re­searchers, iden­ti­fy­ing the spe­cific ge­netic causes of in­her­ited types of can­cer is a key goal. If the spe­cific genes linked to the cancers can be iden­ti­fied, these can be re­moved by screen­ing the pop­u­la­tion be­fore breed­ing from dogs, only breed­ing from those that do not have the of­fend­ing gene. This is a very ac­tive area of cur­rent re­search.

Ac­quired can­cer is more dif­fi­cult to pre­vent: there’s a long, long list of known and pos­si­ble causes of can­cer but there are some spe­cific ones that pet own­ers should know about.

Ul­travi­o­let ra­di­a­tion from sun­light causes ma­lig­nant squa­mous cell car­ci­noma of the ear tips and nose of white cats, be­cause they have no pig­ment to pro­tect them from the sun. Reg­u­lar ap­pli­ca­tion of sun block to white cats’ ears and nose tips pre­vents this type of can­cer.

Viruses can cause can­cer and vac­cines can some­times pro­tect against these, pre­vent­ing spe­cific cancers. Fe­line Leukaemia Virus, caus­ing leukaemia in cats, is the best ex­am­ple in pets.

Hor­mones can have a strong ef­fect on can­cer. Re­peated ex­po­sure of mam­mary tis­sue to high lev­els of oe­stro­gen pre­dis­poses to can­cer: if a bitch is spayed be­fore her first sea­son, the risk of can­cer is re­duced by 99.5%. In cats, spay­ing at any age re­duces the risk of mam­mary tu­mors by 40% to 60%.

In con­trast, early spay/neu­ter­ing of gi­ant breeds of dog is linked to an in­creased in­ci­dence of os­teosar­coma (bone can­cer), so it is now rec­om­mended to leave these breeds un­til sex­ual ma­tu­rity be­fore do­ing the op­er­a­tions (e.g. 18 months of age).

Nowa­days, vets say that a de­ci­sion on spay/neuter should be done on an in­di­vid­ual ba­sis, de­pend­ing on the specifics of the pet, to op­ti­mise tim­ing.

Chronic in­flam­ma­tion caused by some dis­eases can lead to can­cer e.g. in­testi­nal can­cer in pets can fol­low long term in­flam­ma­tory bowel dis­ease in some cases. Prompt and ef­fec­tive treat­ment of such ill­nesses may re­duce the risk of can­cer

Fi­nally, in­hala­tion of to­bacco smoke is linked to can­cer in pets: many pets spend al­most 24 hours a day in the house where chem­i­cals and tox­ins can linger in the air or fur­ni­ture. So if peo­ple stop smok­ing in their own homes, they re­duce the risk of this type of can­cer in their pet.

There are four main forms of treat­ment of can­cer.

First, surgery: early ex­ci­sion of can­cer­ous tis­sue, as well as a wide mar­gin of nor­mal tis­sue around it, is still the most ef­fec­tive way of treat­ing many cancers.

Sec­ond, chemo­ther­apy, with in­jec­tions and oral med­i­ca­tion, has been used for many years to treat can­cer. Es­sen­tially, these are poi­sons that se­lec­tively act on cells that are di­vid­ing rapidly, and since in adult an­i­mals, can­cer cells are of­ten the main ones that are di­vid­ing rapidly, chemo­ther­apy se­lec­tively acts on can­cer cells. More re­cent types of chemo­ther­apy in­clude tar­get­ted can­cer drugs, such as drugs that specif­i­cally in­hibit can­cer growth fac­tors. These are more ef­fec­tive, with fewer side ef­fects com­pared to tra­di­tional chemo­ther­a­pies. They are al­ready avail­able for spe­cific cancers in dogs such as mast cell tu­mours and melanomas.

Ion­is­ing ra­di­a­tion also kills cells, and ir­ra­di­a­tion is now used as a care­fully fo­cussed, com­puter-mapped beam to treat cer­tain spe­cific cancers in pets, as in peo­ple. This does re­quire ex­pen­sive fa­cil­i­ties, and it is not yet avail­able for pets in Ire­land.

Im­mune based ther­a­pies are the most re­cent and promis­ing type of treat­ment for cancers are: this in­cludes in­fu­sions with spe­cial im­mune cells, ther­a­peu­tic can­cer vac­cines against spe­cific can­cer anti­gens and gene ther­apy, where the dam­aged genes in can­cer cells are re­placed by healthy genes

Treat­ment of can­cer is rapidly de­vel­op­ing, led by re­search at univer­si­ties and other in­sti­tu­tions.

For pet own­ers, the main mes­sage is that much more can be done now than in the past. Can­cer may be a se­ri­ous chal­lenge, but science is tack­ling that chal­lenge in new and ex­cit­ing ways.

Half of all flat coated retriev­ers die from hered­i­tary can­cer.

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