{"id":2414,"date":"2013-02-20T11:04:35","date_gmt":"2013-02-20T00:34:35","guid":{"rendered":"http:\/\/leemakennels.com\/blog\/?p=2414"},"modified":"2013-03-26T11:03:52","modified_gmt":"2013-03-26T00:33:52","slug":"golden-retrievers-cancer-if-you-do-cancer-if-you-dont","status":"publish","type":"post","link":"http:\/\/leemakennels.com\/blog\/research-dogs-and-politics\/golden-retrievers-cancer-if-you-do-cancer-if-you-dont\/","title":{"rendered":"Golden Retrievers: Cancer If You Do, Cancer If You Don’t"},"content":{"rendered":"

You don’t need to be in the dog world for very long before you hear about desexing\u00a0benefiting\u00a0the health of dogs. These claims talk about reducing cancer (testicular, mammary, prostate, ovarian, uterine, cervix), reducing prostate disease (in boys), and preventing pyometra (in bitches).<\/p>\n

What we don’t hear about is the undesirable side effects of desexing, and how desexing is linked to increased risks of some cancers, and an increased likelihood of joint disorders.<\/p>\n

Torres de la Riva et al, in their research published just this month, decided to look into the health effects of desexing in golden retrievers;\u00a0Neutering Dogs: Effects on Joint Disorders and Cancers in Golden Retrievers<\/a>.<\/p>\n

They, indeed, hit back at these spruced ‘health benefits’ in the introduction of their piece, saying:<\/p>\n

“In contrast to the rather strong evidence for neutering males and\/or females as a risk factor for osteosarcoma, hemangiosarcoma, lymphosarcoma, mast cell tumours and prostate cancer, evidence for neutering as protection against a dog acquiring one or more cancers is weak.”<\/p><\/blockquote>\n

\"Golden<\/a><\/p>\n

This research set out to investigate spay and neuter in Golden Retrievers from 1-8 years. \u00a0They chose goldens because they are commonly used as assistance animals, and so they hoped the implications of this study may have consequences for related assistance organisations (of course, dog science only happens when it helps people!<\/a>). It makes sense: it’s ‘wasteful’ to invest in a dog becomes invalid for the work they were trained in, especially if that invalidity could’ve been prevented by more-appropriate timing of desexing.<\/p>\n

While other research has pooled many breeds and health affects together, this is the first study to look at desexing in just one particular breed. \u00a0Prior-analysis determined several conditions to look at: hip dysplasia, cranial cruciate ligament tear, lymphosarcoma, hemangiosarcoma, mast cell tumours, osterosarcoma, and elbow dysplasia.<\/p>\n

Dogs were included in the study if they were between 1-8 years of age. \u00a0They were put into categories of either ‘early neuter’ (before 1 year of age), ‘late neuter’ (after 1 year of age), and ‘intact’. \u00a0Data regarding their health was retrospective, gained from veterinary records. \u00a0Any dogs where a health diagnosis was ‘grey’ (non-conclusive), they were excluded from the study.<\/p>\n

<\/p>\n

Results<\/strong><\/p>\n

Hip Dysplasia<\/em><\/p>\n

Males who were desexed early had twice (10.3%) the incidence of hip dysplasia than intact males (5.1%). \u00a0Males that were late-neutered had a hip dysplasia rate of approximately 3%.<\/p>\n

In bitches, approximately 5% of early-spayed bitches got hip dysplasia. \u00a0Intact and late-neutered bitches had hip dysplasia rates of approximately 3%. This difference was not statistically significant.<\/p>\n

This is in keeping with research (quoted within this research) that indicated that desexing increases the likelihood of hip dysplasia by 17%.<\/p>\n

 <\/p>\n

Cranial Crucial Ligament Tear<\/em><\/p>\n

No intact dogs, males or females, got cranial crucial ligament tears. \u00a0Animals that were neutered early were more likely to get tears (5.1% of boys and 7.7% of bitches). \u00a0No late-spayed bitches developed a tear, and only 1 dog developed a tear (1%).<\/p>\n

This is consistent with research that showed a 3-fold increase in excessive tibial plateau angle in desexed dogs (of both sexes, across all breeds). This excessive tibial plateau angle is a risk factor for crucial ligament tears.<\/p>\n

 <\/p>\n

Lymphosarcoma<\/em><\/p>\n

Approximately 3% of intact males got lymphosarcoma, compared to 9% of early-neutered males, and 0% of late-neutered males. \u00a0In bitches, approximately 1.5% of intact bitches got lymphosarcoma, compared to 6% of early-spayed bitches, and 1% of late-spayed bitches. \u00a0The research states,\u00a0“Although the rates of\u00a0occurrence\u00a0of this disease were lower in both male and female intact dogs, than in the early-neutered\u00a0dogs, the difference was statistically significant only in males. Early-neutered males had nearly 3 times the occurence of [lymphosarcoma] as intact males and no cases of [lymphosarcoma] were observed in the late-neutered males”.<\/p>\n

The results of this study are not dissimilar to others quoted, where intact females were at a significantly lower risk of developing lymphosarcoma than neutered females, or males (entire or desexed).<\/p>\n

 <\/p>\n

Hemangiosarcoma<\/em><\/p>\n

Intact males and early-neutered males had an incidence of hemangiosarcoma\u00a0of around 3%, while only 1% of late neutered dogs got hemangiosarcoma. This difference was not statistically significant.<\/p>\n

In bitches, the difference was more significant (statistically and otherwise!): 7.4% of late-neutered bitches were diagnosed with hemangiosarcoma, which was over 4 times the frequency seen in intact (1.6%) and early-spayed (1.8%) bitches. \u00a0Late neutered bitches also got hemangiosarcoma\u00a0early (3.2 years old), while intact and late-spayed bitches got the cancer later (at 6.4 years and 7.6 years respectively).<\/p>\n

This is in keeping with existing research that shows that hemangiosarcoma\u00a0occurs 4 times more in spayed females than those intact, and spayed females had more than 2 times the risk of developing splenic hemangiosarcoma\u00a0than intact bitches.<\/p>\n

 <\/p>\n

Mast Cell Tumours (MCT)<\/em><\/p>\n

This research found that approximately 3% of the intact males got MCT, approximately 2% of neutered early males got MCT, and about 4% of late neutered males got MCT. \u00a0Clearly, these results were not statistically significant.<\/p>\n

However, while no intact bitches got MCT, 2.3% of early-desexed bitches did, and 5.7% of late-neutered bitches developed tumours.<\/p>\n

This is consistent with other research that showed cutaneous mast cell tumours had a 4 times greater frequency in neutered females than intact females.<\/p>\n

 <\/p>\n

Osterosarcoma<\/em><\/p>\n

The incidence of osterosarcoma was so small in this study that it was excluded from analysis. \u00a0Other studies (quoted in this research) showed that osteosarcoma\u00a0occurred\u00a02-times as often in neutered relative to intact dogs, while another study showed that neutering prior to 1 year of age increased the\u00a0occurrence\u00a0of osteosarcoma 3-4 times.<\/p>\n

 <\/p>\n

Other health implications (elbow dyplasia and mammary cancer)<\/em><\/p>\n

Body condition scores were used to control for extra weight in neutered dogs, but the scores were similar between groups (neutered and entire).<\/p>\n

In regard to Mammary Cancer (MC), the study says, “No cases of MC were diagnosed in intact females in this study. This finding is partially explained by the relatively low frequency in which MC is diagnosed in Golden Retrievers. While this finding contrasts with the general concern expressed about the risk of MC in gonadally intact females, it is consistent with recent findings from a systematic meta-analysis finding a weak link, if any, between neutering and a reduce risk of MC.”<\/p>\n

This study also quoted other research, that found that prostate cancer occurred four times as frequently in neutered males as intact males.<\/p>\n

 <\/p>\n

Results In Graphs<\/strong><\/p>\n

If you’re a visual person, you may appreciate the graphs to illustrate the results of this study.\"Disease<\/p>\n

HD: Hip dyplasia; CCL: Cranial crucial ligament tear; LSA: Lymphosarcoma; HSA: hemangiosarcoma; MCT: Mass cell tumours.<\/p>\n

\"DesexingHD: Hip dyplasia; CCL: Cranial crucial ligament tear; LSA: Lymphosarcoma; HSA:\u00a0hemangiosarcoma; MCT: Mass cell tumours.<\/p>\n

 <\/p>\n

Why would desexed dogs get joint problems?<\/strong><\/p>\n

It is likely that the joint problems (hip dyplasia and cranial crucial ligament tears) investigated in this study are more likely to occur due to neutering’s affects on growth plate closure. Other factors include breed related\u00a0vulnerabilities, and sex related closure speeds (i.e. the growth plate closes more quickly in males than females). \u00a0This may be why the\u00a0occurrence\u00a0of hip dyplasia in early-neutered males is double that of hip dyplasia in intact males.<\/p>\n

 <\/p>\n

Why would desexed dogs get cancer?<\/strong><\/p>\n

This is a harder question to answer. \u00a0It’s believed that estrogen acts on “microsatellite<\/a> instability” – or the likelihood of parts of DNA to change, which is linked to cancer. \u00a0Estrogen effectively stops microsatellites for being ‘so changing’. \u00a0When sex organs of bitches are removed, estrogen is also reduced, and so it can no longer act upon microsatellites and so cancer is more likely. \u00a0However, it is also hypothesised that bitches need to have a heat cycle for estrogen to have this protective affect. \u00a0This is why late neutering is perhaps associated with higher rates of hemangiosarcoma\u00a0and mass cell tumours in\u00a0entire\u00a0and early-neutered bitches. \u00a0There is a lot to learn in this area, and a lot more research needs to take place to understand the affects of hormones on cancer.<\/p>\n

 <\/p>\n

Conclusions from this Research<\/strong><\/p>\n

This research concludes that:<\/p>\n