Discussion
There is currently no universal treatment for equine sarcoids. The
ultimate goal in treatment is to remove all tumour cells. It is
imperative to take into account all factors when choosing a suitable
regimen for each case, however finances and compliance of the client and
horse may become the most influential factors.
A variety of topical chemotherapy agents are used such as acyclovir and
5% fluorouracil. However, one study suggested that the former drug has
little benefit (Haspeslagh et al. 2017), but the latter has produced
good results as an adjunct to surgery or cryotherapy (Knottenbelt and
Kelly 2000).
AW5-LUDES cream is a compounded medication available for veterinary
surgeon application only from Equine Medical Solutions as a special
product, produced and prescribed to an individual horse as per the
United Kingdom licensing Cascade (GOV.UK, 2022). It was previously
referred to as AW3 or AW4 in older preparations and has been widely used
in this country. A protocol is created for each case, determined by the
appearance/type of sarcoid, location and response to previous treatments
(Knottenbelt and Walker 1994). The cream contains 5-fluorouracil,
thiouracil, heavy metal salts and steroid, and is produced in several
different concentrations. Initially a single application of AW3-LUDES
cream was reported to be successful in 80% of cases when 50,000 lesions
were studied in 100 horses (Knottenbelt and Walker 1994). However, a
later study of AW4-LUDES cream reported only 35% success rate when it
was used as the primary treatment in periocular sarcoid cases
(Knottenbelt and Kelly 2000). It is worth noting, however, that
periocular sarcoids are characteristically different and potentially
more difficult to treat than sarcoids in other areas of the body.
Localised pain and swelling are expected from 24 hours after application
of AW5-LUDES cream, and horses may be dull and reluctant to ambulate for
a period of 4-6 days. These signs are usually resolved by oral
phenylbutazone treatment. The tumour mass is noted to blacken and
develop a well-defined border with the surrounding healthy tissue.
Histological findings support preferential penetration of the abnormal
tissue, although it is suggested that stronger preparations may have
deeper and less specific effects. Scarring has been recorded, usually
causing solely cosmetic issues, and delayed wound healing can present in
more mobile areas (Knottenbelt and Walker, 1994). Collateral damage to
adjacent healthy tissues due to runoff or misapplication, and poor
results due to non-compliance of application may also occur. Prior to
application, it is important to consider the underlying anatomy and,
therefore, potential complications. These may include haemorrhage,
neuropathies and associated paralysis, necrosis of healthy tissues and
associated infection, or in more severe cases, loss of sight
(Knottenbelt and Kelly, 2000). Extensive eyelid necrosis and loss of the
underlying globe has been reported in one case, however the horse had
undergone previous home treatments unbeknown to the treating
veterinarian (Knottenbelt and Kelly, 2000). The use of AW5-LUDES cream
is now contraindicated around the eye or overlying the facial nerve
(Knottenbelt 2019), and alternative treatment methods are recommended
where complications encountered are likely to be severe and life
changing. The authors have also encountered a horse that developed
septic arthritis of a metacarpophalangeal joint following the
application of AW5-LUDES to a sarcoid located on the dorsal fetlock; the
treatment had resulted in widespread necrosis of the skin, subcutaneous
and dorsal joint capsule (unpublished observation).
Following the presentation of this horse, an internal review was
conducted which found 1595 similar lesions treated in the 3 years prior,
of which this was the only case of evisceration. Since use of the cream
started, the manufacturer has had no other evisceration cases reported
(Knottenbelt, personal communication, 2021).
Evisceration of the abdominal contents can be a fatal event in horses
and has been recorded following castration (Moll et al. 1995), due to
acute abdominal dehiscence of a ventral laparotomy incision (Hann et al.
2022) or subsequent to penetrating abdominal wounds (Netto et al. 2006).
Prognosis for survival decreases with increasing time, deteriorating
condition of the horse, length of intestine eviscerated, intestinal
damage or contamination, and the requirement for intestinal resection
anastomosis (Van der Velden 1988; Thomas et al. 1998). Survival rates of
young horses undergoing surgical repair for evisceration post castration
is reported to vary from 36.4% (Hutchins and Rawlings 1972) to 87.5%
(Hunt and Boles 1989), although rapid surgical intervention was
instigated in those cases with better outcomes. Following dehiscence of
the linea alba post laparotomy, secondary closure is usually performed
rather than mesh placement due to infection in the tissues. This
technique however requires suture placement 5cm from the edge of the
wound (Tulleners et al. 1983; Freeman et al, 2002), which due to the
extent of the tissue devitalisation in this case was not possible
It is possible that the lesion being treated in this horse was a
different neoplasm. Most suspected sarcoids are not confirmed
histologically prior to treatment as tissue biopsy can be
contraindicated (Ragland et al. 1970). Similar-looking lesions can
include fibrosarcoma, fibroma or neurofibroma (Knottenbelt and Kelly
2000). It is worth noting that the response of these other tumours to
AW5-LUDES cream is unknown. Verrucous or fibroblastic sarcoids and
similar appearing neoplasms seem to be most commonly contained within
the epidermis and dermis (Murray et al. 1978). Around the eye however,
deeper invasion into the subcutis and musculature is a frequent finding
and is associated with a negative prognosis as the muscles become
distorted and weakened (Knottenbelt and Kelly 2000). It is possible that
sarcoids in other locations may invade in a similar way, but
unfortunately samples of the tissue were not submitted for
histopathology in this case. More information is required on the
invasive nature of sarcoids in different locations and hallmarks of this
kind of tumour behaviour.
This case report describes a serious complication following treatment
with AW5-LUDES cream. It is worth noting that there is minimal recently
published evidence surrounding the use of AW5-LUDES cream in a variety
of locations. The evidence surrounding periocular sarcoids should be
interpreted with caution, although it may guide decision making where
sarcoids are suspected to have invaded more extensively. Referral of the
horse was carried out in a timely manner with minimal damage to the
intestines and did not contribute to the decision to euthanase the
horse. Severe necrosis of apparently previously healthy surrounding
tissues was the precluding factor for difficulty in defect closure and
guarded prognosis.