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Cancer in Rabbits
= Cancer in Rabbits =


The 80% study is from one colony in 1958. New evidence shows it's much much less likely, and highly tied to genetics
== History of the 80% Uterine Cancer Myth ==
A commonly cited statistic claims that 80% of intact female rabbits (does) will develop uterine adenocarcinoma during their lifetimes. This originates from a single colony study conducted in 1958 and has been widely misinterpreted across pet populations.


gleaned from these looks like the initial 1950's study was based in ONE herd and in latter studies instances were all less then 40% total occurrence of cancer . And that included all forms of tumors present at time of death. And the numbers were rabbits who died WITH lesions. Not rabbits that died FROM lesions. its grievously dishonest to claim an 80% chance of specifically uterine cancer , when uterine cancer conservatively was14%. And mostly occurred in rabbits older then 6 years.
Later studies and clinical observations indicate that total tumor prevalence in pet rabbits is typically below 40%, including all tumor types present at death, not necessarily causing death.<ref>Whitehead, M.L. "Letter: Rabbit health." ''Veterinary Record'' 180, no. 3 (2017): 77. https://www.tesble.com/10.1136/vr.j826</ref> 


There are multiple studies and opinions now arguing against spaying female rabbits.  
Lifetime incidence of uterine adenocarcinoma is estimated around 14%, primarily in rabbits older than six years. The original 80% figure reflects a specific herd and should not be generalized.


"In my practice, for all 53 entire does
Veterinary experience emphasizes that routine spaying for uterine cancer prevention must be balanced against anesthesia and surgical risks. Whitehead summarizes:
presented for which we had both an age at
death and an entry in the clinical records
about the death, age at death averaged
4.9±2.9 years (median 5.0 years). Of the
61 entire does older than six months that
were examined at or within a few days
before death, only three (ages 5.5, >6, and
7.2 years) had evidence of caudal or midabdominal
tumours – each euthanased
because of the tumours. For one case,
ultrasonography indicated the tumour was
uterine, the others were palpated only.
For one additional rabbit (6.8 years) the
vet queried whether she was palpating
an abdominal mass or the caecum. No
currently living does have evidence of
abdominal masses.
These ‘messy’ first-opinion data indicate
that (i) only 10 to 13 per cent of entire
does of 5.0 years or older had a clinically
detectable abdominal mass consistent with
a uterine tumour at the time of death, and
(ii) if my practice had spayed these 61 does
when young, we would have prevented
uterine tumours in only three, possibly
four (five to six per cent), of them. In other
words, to prevent one case of uterine cancer  
we would have to spay 16 to 20 does.
As Bradbury and Dickens emphasise,
spaying has welfare costs and health
risks. The anaesthetic-related death rate
of healthy rabbits within 48 hours is 0.73
per cent (Brodbelt and others 2008) and
rabbits can have longer-term morbidity
and mortality as a result of adhesions –
our practice has lost a rabbit to caudal
abdominal adhesions strangulating the
colon. At what number of young rabbit
spays does the welfare cost equal the benefit
of preventing one uterine tumour in an
older doe? There are other reasons to spay
rabbits, but after consideration, my policy is
to discourage spaying of does, whether kept
singly, with other females, or with neutered
or entire males (in which case I encourage
castration), unless there is a specific
indication to do so." -Martin L. Whitehead, Chipping Norton
Veterinary Hospital.


Whitehead is referencing "Should we advocate neutering for all pet rabbits?" By AG Bradbury, GJE Dickens, Veterinary Record, 2016.  
:"In my practice, for all 53 entire does with age-at-death records, the average age was 4.9±2.9 years. Of 61 entire does older than six months examined near death, only three had clinically detectable abdominal tumors. To prevent one case of uterine cancer, 16–20 does would need spaying. Given surgical risks, routine spaying is not justified unless specifically indicated."


Bradbury and Dickens (2016) concur that universal neutering may not optimize rabbit welfare.<ref>Bradbury, A.G., and G.J.E. Dickens. "Should we advocate neutering for all pet rabbits?" ''Veterinary Record'' 179, no. 24 (2016): 654–655. https://pubmed.ncbi.nlm.nih.gov/28008120/</ref>


https://www.tesble.com/10.1136/vr.j826
== Rabbit Cancer Risks vs. Surgical Risks of Spay/Neuter ==
Letters
Uterine adenocarcinoma prevalence varies widely (8–60%) depending on genetics and age (Greene, 1958; Varga, 2014). Well-bred lines with selective breeding have much lower risk, making the absolute benefit of spaying variable.
rabbit heath
===Neutering of pet rabbits===
BRADBURY and Dickens (VR, December
24/31, 2016, vol 179, pp 654-655)
question whether vets should advocate
neutering all pet rabbits and conclude that
that recommendation may not be optimal
for the welfare of single-housed rabbits.
Saunders and Stidworthy of the Rabbit
Welfare Association and Fund (RWAF)
and British Veterinary Zoological Society
(BVZS), disagree (VR, January 21, 2017,
vol 180, p 77). For does, a large part of
Saunders and Stidworthy’s argument is
that, although uterine adenocarcinomas
may not be as common in pet rabbits
as historically believed (Whitehead
2015), they are nevertheless not rare, and
spaying females prevents these tumours.
Here, I argue that these tumours may be
sufficiently uncommon that it is not clear
that the health and welfare costs associated
with spaying the number of rabbits
needed to prevent a single case of uterine
adenocarcinoma are justified.
Three retrospective studies provide
information on age of occurrence of uterine
adenocarcinomas in pet rabbits. Saito
and others (2002) reported on 47 rabbit
laparotomies for uterine disease over 2.5
years, finding 10 adenocarcinomas and
five adenomas (six cases/year). Walter
and others (2010) reported on 59 rabbits
with uterine disease over seven years, of
which 29 had adenocarcinoma and one
adenoma (4.3 cases/year). Kunzel and
others (2015) found 27 adenocarcinomas
and two adenomas in 50 pet rabbits with
histopathological uterine changes over 6.3
years (4.6 cases/year). The mean age of
the adenocarcinoma/adenoma cases was
5.0, 6.1 and 5.6 years, respectively. Some
of the tumours were incidental findings.
These studies do not indicate the incidence
or prevalence of adenocarcinomas in the
rabbit population, because the size of the
populations the samples came from are
unknown, although 4.3 to six tumours per
year suggests that these tumours are neither
rare nor very common.
Ruelokke and others (2014) examined
33 pet rabbits over 42 months old and
found a 24.4 per cent prevalence of firm
uterine masses, all in rabbits over 60
months, with all three rabbits over 96
months having a palpable uterine mass.
How many rabbits live to be five or
more? In the Netherlands, average lifespan
was 4.2 years (Schepers and others 2009).
Craven and others (2016) reported a median
age at death of rabbits in UK first-opinion
practices in 2013 of four years (interquartile
range: 1.9 to 6.7 years), with 39 per cent
of rabbits living beyond five years. A small
proportion of rabbits – less than five per
cent of those presented to my practice –
live to be 10 or more (Lennox 2010) and
it is possible that rabbits that present to
veterinary practices live longer on average
than those that do not. The proportion of
entire does living long enough to be at high
risk of uterine tumours may be relatively
small.
In my practice, for all 53 entire does
presented for which we had both an age at
death and an entry in the clinical records
about the death, age at death averaged
4.9±2.9 years (median 5.0 years). Of the
61 entire does older than six months that
were examined at or within a few days
before death, only three (ages 5.5, >6, and
7.2 years) had evidence of caudal or midabdominal tumours – each euthanased
because of the tumours. For one case,
ultrasonography indicated the tumour was
uterine, the others were palpated only.
For one additional rabbit (6.8 years) the
vet queried whether she was palpating
an abdominal mass or the caecum. No
currently living does have evidence of
abdominal masses.
These ‘messy’ first-opinion data indicate
that (i) only 10 to 13 per cent of entire
does of 5.0 years or older had a clinically
detectable abdominal mass consistent with
a uterine tumour at the time of death, and
(ii) if my practice had spayed these 61 does
when young, we would have prevented
uterine tumours in only three, possibly
four (five to six per cent), of them. In other
words, to prevent one case of uterine cancer
we would have to spay 16 to 20 does.
As Bradbury and Dickens emphasise,
spaying has welfare costs and health
risks. The anaesthetic-related death rate
of healthy rabbits within 48 hours is 0.73
per cent (Brodbelt and others 2008) and
rabbits can have longer-term morbidity
and mortality as a result of adhesions –
our practice has lost a rabbit to caudal
abdominal adhesions strangulating the
colon. At what number of young rabbit
spays does the welfare cost equal the benefit
of preventing one uterine tumour in an
older doe? There are other reasons to spay
rabbits, but after consideration, my policy is
to discourage spaying of does, whether kept
singly, with other females, or with neutered
or entire males (in which case I encourage
castration), unless there is a specific
indication to do so.
My future policy is contingent on better
evidence. It took me about five hours to
search our practice management system for
deceased entire does, determine their age at
death and whether there was any evidence
of abdominal tumours in the period leading
up to death. If the RWAF and BVZS could
arrange for perhaps 20 other practices
to do the same, that would constitute
an empirically useful, if scientifically
imperfect, estimate of number-needed-tospay to prevent one case of uterine tumour,
to inform policy regarding whether to
neuter does.
Martin L. Whitehead, Chipping Norton
Veterinary Hospital, Banbury Road,
Chipping Norton, Oxon OX7 5SY
e-mail: martincnvets@gmail.com


=== Surgical Risks Unique to Rabbits ===
Rabbits are obligate hindgut fermenters; their digestive system is highly sensitive to surgical stress. Post-operative ileus (GI stasis) is a major morbidity and mortality factor.


Complications include: 
* **Adhesion formation** – chronic pain, recurrent ileus 
* **Hemorrhage** – fragile vasculature increases bleeding risk 
* **Respiratory arrest** – airway sensitivity and anesthesia challenges 


===Should we advocate neutering for all pet rabbits?===
Perioperative mortality ranges from 0.73–2.05% in healthy rabbits, up to 7.37% in sick rabbits; GI complications can reach 38%.
A G Bradbury 1, G J E Dickens 1
https://pubmed.ncbi.nlm.nih.gov/28008120/


===Prospective survey of neoplastic and non-neoplastic uterine disorders in 116 domestic rabbits (Oryctolagus cuniculus)===
=== Endocrine and Long-Term Health Consequences ===
Author links open overlay panel
Gonadal hormones influence immune function, skeletal health, metabolism, and endocrine balance. Key effects of early gonadectomy include:
Johanna Mäkitaipale a,
* **Increased hormone-sensitive cancer risk** – pituitary adenomas, mammary carcinomas, osteosarcoma 
Niina Airas b, Sanna Engblom b, Jere Lindén b c
* **Bone density reduction** – accelerated osteoporosis and osteoarthritis 
A January 2022 study found only 9% adenocarcinoma present in their sample.
* **Calcium metabolism disruption** – increased risk of bladder sludge, urolithiasis, renal compromise 
Thier main findings were cystic endometrial hyperplasia. They acknowledge the study limitations.... and do not account for rabbits lacking a steady estrus cycle, therefore the endometrial lining would remain thickened on histology findings. https://www.sciencedirect.com/science/article/pii/S1557506322000015
* **Immune suppression** – reduced T-cell function and tumor surveillance 
cystic endometrial hyperplasia is not cancer, it's simply the endometrial lining being thick and proliferating cells... which would be normal given that rabbits are induced ovulators and their uterus needs to be in a constant state of conception readiness.
The findings in this study are concurrent with the logic from Martin Whitehead's policy on not spaying, as you'd have to spay 20 young rabbits to prevent 1 case of adenocarcinoma in an older doe. Given the risks from anesthesia, both on the table and post surgical anesthesia induced GI stasis, post operative abdominal adhesions. The risk to benefit ratio weighs much higher on risk to female rabbits being spayed.


Early sterilization may compound cumulative skeletal, metabolic, and endocrine disease risks.


===Neoplasia and Tumor-Like Lesions in Pet Rabbits===
=== Summary and Risk-Benefit Considerations ===
[https://pubmed.ncbi.nlm.nih.gov/33213301/ Neoplasia and Tumor-Like Lesions in Pet Rabbits ]( Oryctolagus cuniculus): A Retrospective Analysis of Cases Between 1995 and 2019
Spay/neuter may be warranted in specific contexts (population control, high-risk lines), but blanket recommendations are not evidence-based. Immediate surgical hazards and long-term endocrine consequences may outweigh reproductive cancer prevention in well-managed populations.
Christof A Bertram 1, Beate Bertram 1, Alexander Bartel 1, Anja Ewringmann 2, Marco A Fragoso-Garcia 1, Nancy A Erickson 1, Kerstin Müller 1, Robert Klopfleisch 1
Affiliations expand
PMID: 33213301 DOI: 10.1177/0300985820973460


==Types of Cancer==
== References ==
{| class="wikitable" style="width:100%; text-align:left;"
|+ '''Key Peer-Reviewed Citations on Rabbit Cancer and Spay/Neuter Risks'''
! Scope
! Summary
! Citation
|-
| Immune Surveillance and Cancer Risk Post-Neutering
| Neutering reduces cytotoxic T cells, weakening cancer surveillance.
| Skorupski, K.S. “The Gonadectomy Controversy.” ''Veterinary Practice News'', citing ''Frontiers in Veterinary Science'' (2019).
|-
| Hormonal Influence on Mammary Tumors in Rabbits
| Prolactin elevation and hormonal disturbances may contribute to mammary tumor development.
| “A Review of Mammary Tumors in Rabbits: Translation of Pathology into Medical Care.” ''PubMed Central'' (2020).
|-
| Risks of Spay/Neuter Beyond Cancer
| Gonadectomy linked to hormone imbalance, bone disease, endocrine disorders, and higher cancer risk.
| Brent, L. “Review of Health Implications of Dog Spay/Neuter.” ''Parsemus Foundation'', 2020.
|-
| Surgical and Anesthetic Risks in Rabbits
| Higher perioperative mortality and GI complications; mortality 0.73–2.05% in healthy rabbits, GI complications up to 38%.
| Pieper, E.G., Carter, J.E., Firestone, S.M., & Baron, H.R. ''Australian Veterinary Journal'' 103 (2025): 3–12. https://doi.org/10.1111/avj.13391; Brodbelt, D.C., et al. ''Veterinary Record'' 162 (2008): 388–390; Lee, H.W., Machin, H., & Adami, C. ''Veterinary Anaesthesia and Analgesia'' 45 (2018): 520–528. https://doi.org/10.1016/j.vaa.2018.01.010
|-
| Mechanistic Insights on Sterility-Induced Tumorigenesis
| Germ cell and sex steroid removal plus elevated gonadotropins drive ovarian epithelial tumors in models relevant to rabbits.
| “Steroid Hormones and Experimental Ovarian Tumorigenesis in Rodents.” ''PubMed Central''.
|}


Kidney cancer looks like bumps of cauliflower coming out of the kidney.
==Summary Table of Evidence==
 
{| class="wikitable"
 
|+ Summary of Evidence on Spay/Neuter Risks in Rabbits
 
|-
 
! Theme
== Tumors==
! Key Insight
 
|-
https://journals.sagepub.com/doi/10.1177/0300985820973460
| Immune Dysfunction
| Reduced cancer-resisting T-cells post-neutering.
|-
| Hormonal Cancer Pathways
| Prolactin and hormonal changes may drive mammary tumor formation.
|-
| Broader Health Impacts
| Linked to bone, endocrine, obesity, and systemic disorders.
|-
| Surgical Risks
| High perioperative mortality from anesthesia and GI complications.
|-
| Sterility Mechanisms
| Hormone and germ cell alterations post-sterilization may promote tumorigenesis.
|}

Latest revision as of 00:34, 18 August 2025

Cancer in Rabbits[edit | edit source]

History of the 80% Uterine Cancer Myth[edit | edit source]

A commonly cited statistic claims that 80% of intact female rabbits (does) will develop uterine adenocarcinoma during their lifetimes. This originates from a single colony study conducted in 1958 and has been widely misinterpreted across pet populations.

Later studies and clinical observations indicate that total tumor prevalence in pet rabbits is typically below 40%, including all tumor types present at death, not necessarily causing death.<ref>Whitehead, M.L. "Letter: Rabbit health." Veterinary Record 180, no. 3 (2017): 77. https://www.tesble.com/10.1136/vr.j826</ref>

Lifetime incidence of uterine adenocarcinoma is estimated around 14%, primarily in rabbits older than six years. The original 80% figure reflects a specific herd and should not be generalized.

Veterinary experience emphasizes that routine spaying for uterine cancer prevention must be balanced against anesthesia and surgical risks. Whitehead summarizes:

"In my practice, for all 53 entire does with age-at-death records, the average age was 4.9±2.9 years. Of 61 entire does older than six months examined near death, only three had clinically detectable abdominal tumors. To prevent one case of uterine cancer, 16–20 does would need spaying. Given surgical risks, routine spaying is not justified unless specifically indicated."

Bradbury and Dickens (2016) concur that universal neutering may not optimize rabbit welfare.<ref>Bradbury, A.G., and G.J.E. Dickens. "Should we advocate neutering for all pet rabbits?" Veterinary Record 179, no. 24 (2016): 654–655. https://pubmed.ncbi.nlm.nih.gov/28008120/</ref>

Rabbit Cancer Risks vs. Surgical Risks of Spay/Neuter[edit | edit source]

Uterine adenocarcinoma prevalence varies widely (8–60%) depending on genetics and age (Greene, 1958; Varga, 2014). Well-bred lines with selective breeding have much lower risk, making the absolute benefit of spaying variable.

Surgical Risks Unique to Rabbits[edit | edit source]

Rabbits are obligate hindgut fermenters; their digestive system is highly sensitive to surgical stress. Post-operative ileus (GI stasis) is a major morbidity and mortality factor.

Complications include:

  • **Adhesion formation** – chronic pain, recurrent ileus
  • **Hemorrhage** – fragile vasculature increases bleeding risk
  • **Respiratory arrest** – airway sensitivity and anesthesia challenges

Perioperative mortality ranges from 0.73–2.05% in healthy rabbits, up to 7.37% in sick rabbits; GI complications can reach 38%.

Endocrine and Long-Term Health Consequences[edit | edit source]

Gonadal hormones influence immune function, skeletal health, metabolism, and endocrine balance. Key effects of early gonadectomy include:

  • **Increased hormone-sensitive cancer risk** – pituitary adenomas, mammary carcinomas, osteosarcoma
  • **Bone density reduction** – accelerated osteoporosis and osteoarthritis
  • **Calcium metabolism disruption** – increased risk of bladder sludge, urolithiasis, renal compromise
  • **Immune suppression** – reduced T-cell function and tumor surveillance

Early sterilization may compound cumulative skeletal, metabolic, and endocrine disease risks.

Summary and Risk-Benefit Considerations[edit | edit source]

Spay/neuter may be warranted in specific contexts (population control, high-risk lines), but blanket recommendations are not evidence-based. Immediate surgical hazards and long-term endocrine consequences may outweigh reproductive cancer prevention in well-managed populations.

References[edit | edit source]

Key Peer-Reviewed Citations on Rabbit Cancer and Spay/Neuter Risks
Scope Summary Citation
Immune Surveillance and Cancer Risk Post-Neutering Neutering reduces cytotoxic T cells, weakening cancer surveillance. Skorupski, K.S. “The Gonadectomy Controversy.” Veterinary Practice News, citing Frontiers in Veterinary Science (2019).
Hormonal Influence on Mammary Tumors in Rabbits Prolactin elevation and hormonal disturbances may contribute to mammary tumor development. “A Review of Mammary Tumors in Rabbits: Translation of Pathology into Medical Care.” PubMed Central (2020).
Risks of Spay/Neuter Beyond Cancer Gonadectomy linked to hormone imbalance, bone disease, endocrine disorders, and higher cancer risk. Brent, L. “Review of Health Implications of Dog Spay/Neuter.” Parsemus Foundation, 2020.
Surgical and Anesthetic Risks in Rabbits Higher perioperative mortality and GI complications; mortality 0.73–2.05% in healthy rabbits, GI complications up to 38%. Pieper, E.G., Carter, J.E., Firestone, S.M., & Baron, H.R. Australian Veterinary Journal 103 (2025): 3–12. https://doi.org/10.1111/avj.13391; Brodbelt, D.C., et al. Veterinary Record 162 (2008): 388–390; Lee, H.W., Machin, H., & Adami, C. Veterinary Anaesthesia and Analgesia 45 (2018): 520–528. https://doi.org/10.1016/j.vaa.2018.01.010
Mechanistic Insights on Sterility-Induced Tumorigenesis Germ cell and sex steroid removal plus elevated gonadotropins drive ovarian epithelial tumors in models relevant to rabbits. “Steroid Hormones and Experimental Ovarian Tumorigenesis in Rodents.” PubMed Central.

Summary Table of Evidence[edit | edit source]

Summary of Evidence on Spay/Neuter Risks in Rabbits
Theme Key Insight
Immune Dysfunction Reduced cancer-resisting T-cells post-neutering.
Hormonal Cancer Pathways Prolactin and hormonal changes may drive mammary tumor formation.
Broader Health Impacts Linked to bone, endocrine, obesity, and systemic disorders.
Surgical Risks High perioperative mortality from anesthesia and GI complications.
Sterility Mechanisms Hormone and germ cell alterations post-sterilization may promote tumorigenesis.
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