The efficacy of intratumoural 5-fluorouracil for the treatment of equine sarcoids

OBJECTIVE: To document the efficacy of intratumoural injections of 5-fluorouracil for the treatment of equine sarcoids. DESIGN: A prospective study that included 13 horses and one donkey. PROCEDURE: Sarcoids were confirmed by histological examination and treated with intratumoural 5-fluorouracil every 2 weeks. If the sarcoids did not resolve after seven treatments, treatment was considered a failure. All cases were re-examined 6 months after treatment commenced and owners were telephoned 3 years after commencement of treatment to report on tumour recurrence. Outcome comparisons were performed to determine the effect of previous treatment, tumour size and tumour location on sarcoid resolution. The efficacy of intratumoural 5-fluorouracil was compared with other previously documented treatments of equine sarcoids. RESULTS: Sarcoids smaller than 13.5 cm3 were significantly (P = 0.032) more likely to resolve with treatment than larger sarcoids. Sarcoids that were not responsive to previous therapies were significantly (P = 0.007) more likely to recur after 3 years than sarcoids that had not been treated prior to this study. In this study, there were similar rates of resolution in cases with mutiple tumours (66.6%) when compared to cases with single tumours (60%). The numbers in this study were too small to properly evaluate the effect of tumour location on the success of treatment. Intratumoural 5-fluorouracil appeared to have resolved sarcoids in 9 of 13 cases (61.5%) as determined by follow up conversation with the owners 3 years after the initial treatment. CONCLUSION: The use of intratumoural 5-fluorouracil compares favourably with other treatment modalities for sarcoids, with a long term successful resolution rate of 61.5%. Owners should be warned that resistant sarcoids and sarcoids larger than 13.5 cm3 have a poorer prognosis for resolution and more aggressive therapeutic options should be considered.     

In vitro and in vivo evaluation of hypericin for photodynamic therapy of equine sarcoids

The therapeutic potential of the photodynamic compound, hypericin, in the treatment of equine sarcoids was evaluated. The in vitro cytotoxicity was assessed using three equine cell lines and the observed phototoxic effect was comparable to that on different highly sensitive human cell lines and significantly influenced by the energy density used although independent of the cell type. The in vivo antitumoural action of photodynamic therapy using hypericin was evaluated on three equine sarcoids in a donkey. Four intratumoural injections were given and the tumours were illuminated daily during 25 days. An 81% reduction in tumour volume was obtained at the end of therapy and 2 months later, a 90% reduction was observed. Further experimental work should be performed, but these results suggest that photodynamic therapy using hypericin has a potential for the non-invasive treatment of equine sarcoids.     

Successful treatment of equine sarcoids with cisplatin electrochemotherapy: a retrospective study of 48 cases

Reasons for performing study: Sarcoids are the commonest form of equine skin tumour. Several therapeutic measures have been described but none is considered to be universally effective. Electrochemotherapy (ECT) is a new anticancer therapy that utilises electrical field pulses to induce increased cell membrane permeability to antitumour hydrophilic drugs, such as cisplatin. The increased intracellular concentration of the drugs has a significant therapeutic benefit. The procedure has not been previously reported in a large number of horses. Objective: To validate ECT as a novel alternative treatment for equine sarcoids. Methods: A retrospective study evaluating the efficacy of cisplatin ECT in the treatment of equine sarcoids was performed. Electrochemotherapy treatments were applied under general anaesthesia at 2 week intervals with or without prior excision or debulking. Electric pulses were directly applied to the lesions following intra‐tumoural injections of an aqueous solution of cisplatin. Results: One‐hundred‐and‐ninety‐four sarcoids on 34 horses, 2 ponies, 11 donkeys and one mule were treated with ECT. The 4 year nonrecurrence rate was 97.9% for animals (47/48) and 99.5% (193/194) for tumours. When ECT was used as a single treatment, a significant influence of tumour size (ρ= 0.55) on the number of treatments required for cure was shown. When prior surgery was performed, there was a significant influence (P<0.001) of the excision quality (complete or incomplete) and the healing mode (closed or open wound) on the number of treatments. The most common adverse effect was a slight oedematous reaction for lesions located on thin skin regions. Conclusion and clinical relevance: Results demonstrate that ECT, with or without concurrent tumour debulking, is an effective alternative for treatment of equine sarcoids.     

Glycolysis inhibition improves photodynamic therapy response rates for equine sarcoids

Photodynamic therapy (PDT) holds great promise in treating veterinary and human dermatological neoplasms, including equine sarcoids, but is currently hindered by the amount of photosensitiser and light that can be delivered to lesions thicker than around 2 mm, and by the intrinsic antioxidant defences of tumour cells. We have developed a new PDT technique that combines an efficient transdermal penetration enhancer solution, for topical delivery of 5‐aminolevulinic acid (ALA) photosensitiser, with acute topical post‐PDT application of the glycolysis inhibitor lonidamine. We show that the new PDT combination treatment selectively kills sarcoid cells in vitro, with repeated rounds of treatment increasing sarcoid sensitisation to PDT. In vivo, ALA PDT followed by 600 μM lonidamine substantially improves treatment outcomes for occult, verrucous, nodular and fibroblastic sarcoids after 1 month (93% treatment response in 27 sarcoids), compared with PDT using only ALA (14% treatment response in 7 sarcoids).     

Successful treatment of equine sarcoids by topical aciclovir application

Based on the anecdotally reported eradication of a sarcoid using aciclovir cream, the curative potential of this ointment was investigated in 22 sarcoid-affected horses referred to the Equine Clinic Tillysburg, Austria, between 2006 and 2009. Sarcoid disease was diagnosed by clinical examination and bovine papillomavirus types 1 and 2 from intact skin and tumour tissue. As nine horses had more than one lesion, a total of 47 sarcoids were treated by daily topical application of aciclovir 5 per cent cream for a period of two to six months; in four horses, surgical tumour ablation was performed before treatment. Disease parameters, including the tumour type, number, location and size, were recorded before and after aciclovir therapy. All 47 (100 per cent) of the sarcoids responded to treatment, with complete tumour regression observed for 32 (68 per cent) lesions and no recurrences reported thus far. Incomplete resolution was observed for 15 (32 per cent) lesions, probably due to their thickness. Aciclovir is proposed to be routinely used for the treatment of mild-type sarcoids and as an adjuvant therapeutic agent in combination with surgery.     

Bovine papillomaviruses: their role in the aetiology of cutaneous tumours of bovids and equids

Bovine papillomavirus (BPV) is perhaps the most extensively studied animal papillomavirus. In cattle BPVs induce benign tumours of cutaneous or mucosal epithelia, called papillomas or warts. Cattle papillomas are benign tumours and generally regress without eliciting any serious clinical problems in the host, but occasionally persist and provide the focus for malignant transformation to squamous cell carcinoma, as in the case of cancer of the urinary bladder and cancer of the upper alimentary canal. BPV is the only papillomavirus that jumps species: the virus also infects equids, and gives rise to fibroblastic tumours called sarcoids. Sarcoids very rarely regress, more often they persist and can be locally aggressive. These tumours are the most common dermatological tumour of equids worldwide. The purpose of this review is to discuss the biology of BPV, the biology of bovine tumours and equine sarcoids, and present the current understanding of BPV in tumour pathogenesis in its natural host, cattle, and in its heterologous host, equids. Finally, the use of anti-BPV vaccines as a therapy for equine sarcoids will be discussed. Only limited information on the clinical or pathological aspects of either bovine or equine tumours will be provided as this subject has been extensively addressed previously.     

Use of imiquimod 5% cream (Aldara™) in cats with multicentric squamous cell carcinoma in situ: 12 cases (2002–2005)*

Multicentric squamous cell carcinoma in situ (MSCCIS) is a variant of squamous cell carcinoma in cats, commonly referred to as Bowen’s‐like disease. Imiquimod 5% cream (Aldara?) is a novel immune response modifier (IRM) that has been reported as a successful treatment for Bowen’s disease in humans. The purpose of this study was to describe clinical findings, treatment protocols and survival in cats with MSCCIS treated with imiquimod 5% cream and to examine the effects of imiquimod 5% cream in cats with MSCCIS. The expression of papillomavirus group‐specific antigen in the study population was also determined. From review of medical records, 12 cats were identified with a histologic diagnosis of MSCCIS and treatment with imiquimod 5% cream. Initial lesions responded to imiquimod 5% cream in all cats. Most cats (75%) developed new lesions. New lesions also responded to imiquimod 5% cream in all cats treated. Five cats (41%) had side effects suspected to be associated with the use of imiquimod 5% cream, including local erythema (25%), increased liver enzymes and neutropenia (8%), and partial anorexia and vomiting (8%). Kaplan–Meier median treatment duration and median survival time probabilities for cats in this study were 1189 days, respectively. A time to failure model was generated as many cats were censored from analysis well before the aforementioned projected median. This model resulted in a shorter median survival time of 243 days. No patient‐related, tumour‐related or treatment‐related prognostic variables were identified. No expression for papilloma group‐specific antigen was found. Imiquimod 5% cream appears to be well tolerated in the majority of cats, and further studies are warranted to further examine its usefulness in cats with this disease.     

Bovine papillomavirus infection in equine sarcoids and in bovine bladder cancers

Bovine papillomavirus (BPV) type 2 is involved in carcinogenesis of the urinary bladder in cattle, while BPV-1 is commonly associated with equine sarcoid tumours. In both cases the early viral proteins are expressed, but virion is not produced. Given the similarities in BPV biology between the tumours in cattle and horses, bovine bladder cancers and equine sarcoids were compared with respect to physical status, load of viral DNA and variability of the E5 open reading frame (ORF). Rolling circle amplification demonstrated that BPV-1 and BPV-2 genomes exist as double stranded, episomal, circular forms in the two tumours. Realtime quantitative PCR revealed that equine sarcoids contained higher viral DNA loads compared to bovine bladder cancers. The BPV-1 E5 ORF showed sequence variation but BPV-2 ORF did not. The presence of BPV-1 E5 variations or their absence in the BPV-2 E5 ORF does not appear to have an effect on viral DNA load in either tumour type.     

A pilot study on the use of ultra-deformable liposomes containing bleomycin in the treatment of equine sarcoid

The efficacy of a novel topical liposome-encapsulated preparation of bleomycin (Bleosome) was studied in 118 clinical cases of equine sarcoid and efficacy was compared with two other standard conventional treatments, tazarotene and 5-fluorouracil (5-FU) as well as with the Bleosome in combination with each of these two conventional treatments. Treatments were arbitrarily assigned. Fifty-two of the 118 sarcoids (44%) were resolved after 12 months but there were significant differences between treatment groups with the combinations of either 5-FU and bleomycin, or tazarotene and bleomycin resulting in significantly superior resolution of 77 and 78% of the lesions, respectively. The preliminary results suggest that bleomycin in a liposomal carrier may be a useful treatment modality for superficial, diffuse and verrucose sarcoids. The treatment process was simple, and outcomes were functionally and cosmetically excellent. Liposome-encapsulated bleomycin is economic compared to radiation and other treatment options and can be applied effectively by the owner under guidance. Further studies with different administration protocols and higher concentrations of bleomycin are warranted.     

Apparent clinical resolution of pinnal actinic keratoses and squamous cell carcinoma in a cat using topical imiquimod 5% cream

Imiquimod is a topical immune response modifier and stimulator used in humans to treat a number of cutaneous neoplasms. This case report describes a cat with actinic keratoses and squamous cell carcinoma of the pinnae. The pinnal lesions were treated with topical 5% imiquimod three times per week. Treatment was discontinued after 82 days of therapy. Twelve weeks of topical imiquimod application resulted in clinical resolution of the pinnal lesions. Although no post-treatment biopsies were performed, there was no relapse of the pinnal lesions in 5 months of clinical follow-up. Expected side effects were limited to erythema, crusting, alopecia, and mild discomfort at the sites of application during the first 3 weeks of application. These results suggest that topical imiquimod, although unproven, might be a therapeutic option or adjunct to therapy for cats with actinic keratoses and squamous cell carcinoma, especially those cats for whom surgery and radiation therapy are not an option.     

Pathomorphological and immunohistochemical study of selected markers of tumour cell proliferation in equine sarcoids

The purpose of the study was a pathomorphological and immunohistochemical analysis of tumour cells and connective tissue in equine sarcoids. Investigations were performed using histopathological, ultrastructural, immunohistochemical (PCNA, p53, cytokeratin, vimentin) and histochemical (Ag-NORs) methods. The study was conducted on 50 sarcoids originating from 36 horses and classified as occult, verrucous, fibroblastic and a mixed type of sarcoid based on their clinical appearance. Most of the tumours were located on the girth (30%), neck (24%), head (12%), and legs (12%). The average age of the horses at the first clinical examination was 5.7 years. The sarcoids occurred on the skin of mares (61%), geldings (31%) and stallions (8%), the predominant was Wielkopolska breed (41%) and mixed breeds with Wielkopolska breed (41%). The predominant colour was bay (80%). The data showed that the presence of characteristic, microscopic features was variable but it was not consistent enough to allow differentiation of the clinical types based on histopathology. PCNA expression was not characteristic for the clinical type of sarcoid but it appeared to be a useful tool for the determination of the biological activity of the tumour and the probability of its recurrence. No relationship was found between AgNORs and cell proliferation. The study demonstrated the presence of p53 positive cells in the epidermal and fibroblastic portions. Numerous p53-positive cells were observed in the sarcoids and tended to recurrence. The staining for cytokeratin and vimentin makes the diagnosis of tumour easier. The immunohistochemical studies of PCNA, and p53 are of great significance to the prognosis.     

The efficacy of imiquimod 5% cream (Aldara®) in the treatment of aural plaque in horses: a pilot open‐label clinical trial

Aural plaques affect at least 22% of horses and can be asymptomatic or cause ear sensitivity. Immunohistochemical and electron microscopy studies have shown a strong association between aural plaques and papilloma virus. The purpose of this study was to investigate the efficacy of imiquimod 5% cream, an immune response modifier with potent antiviral activity, in the treatment of equine aural plaques. Twenty‐one horses were enrolled and 16 completed the study. Imiquimod 5% cream was applied three times a week, every other week. When both ears were affected only the worst affected ear was treated. Adverse effects in all horses included marked local inflammation, exudation and thick crust formation at the site of treatment and the adjacent skin. Removal of the crust before treatment was painful and required sedation in most horses. Complete resolution of lesions was noted in all horses immediately post‐treatment and the long‐term resolution rate was 87.5%. Duration of therapy ranged from 1.5 to 8 months (median: 2.9 mean: 3.5). All horses were followed‐up for 12–22 months after treatment was discontinued and only two horses had a recurrence of lesions. Clinical signs related to the aural plaques prior to treatment were reported in 11 of 16 (68.8%) horses and included resistance to touching the ears and bridling. Complete resolution of these signs was reported by the owners in all of the horses followed‐up for at least 12 months. In conclusion, the topical application of imiquimod 5% cream is an efficacious treatment for aural plaques in horses.     

Molecular approaches to equine sarcoids

Sarcoids are the most commonly diagnosed skin tumours in equines. Bovine papillomaviruses (BPVs) are the primary causative agent of sarcoids. There has been intensive research to discover the molecular mechanisms that may contribute to the aetiopathogenesis of this disease and tumour suppressors and proto-oncogenes known to play a role in human neoplastic conditions have been investigated in equine sarcoids. Current approaches include the identification of gene expression profiles, characterising sarcoid and normal skin tissues, and an assessment of epigenetic alterations such as microRNA differential expression and DNA methylation status. This review focuses on selected groups of genes that contribute to the molecular mechanisms of sarcoid formation. These genes have the potential to complement current clinical examinations of equine sarcoid disease in diagnosis, prognosis, therapeutic response and screening.     

Treatment of periocular and non-ocular sarcoids in 18 horses by interstitial brachytherapy with iridium-192

Treatment of the equine sarcoid has posed a significant challenge to clinicians for years and many different methods have been tried with varying success, including ionising radiation. The aim of this study was to review the efficacy of iridium-192 interstitial brachytherapy for the treatment of eight periocular sarcoids and 15 non-ocular sarcoids on 18 horses. All the periocular sarcoids and 13 of the 15 non-ocular sarcoids were treated successfully.     

Equine Sarcoids. A Clinical and Epidemiological Study in Relation to Equine Leucocyte Antigens (ELA)

Associations between clinical parameters of sarcoids and the equine leucocyte antigen system (ELA) were analysed for 120 Swedish horses. Median age of affected horses was 5.2 years, and the majority presented with solitary tumors between 2 and 5 cm in diameter and ventral abdomen was a predilection site. Clinical signs first appeared at a median age of 3.5 years, and sarcoids at different locations first appeared at different ages. Lesions at different sites differed in size, and multiple tumors, early onset, long duration, and older age all had an association with large size. Clinical manifestations of sarcoids and the association between certain ELA-specificities and early onset (A5) and increased recurrence rates after surgery (W13), in addition to increased prevalence (A3W13), strengthen further that some horses are inherently predisposed to sarcoid growth. Unassociated with any clinical parameters, one third of the untreated horses became free of sarcoids due to “spontaneous” regression, perhaps as a result of immune responses against the tumors. Seventy percent of the horses were treated (mostly by excision), and large size was the main parameter promoting treatment. Excision had no significant effect on possibly remaining sarcoids. Recurrence rate after first treatment was about 35%, with the majority of tumors recurring within 4 months. Early onset, long duration, large size, and localization to distal limbs all appeared to increase risk of recurrence. Early treatment, performed under general anesthesia in recumbency which permits wide excision and measures to avoid autoinoculation, significantly reduced recurrence rates.     

Prevalence and body distribution of sarcoids in South African Cape mountain zebra (Equus zebra zebra)

There are no reports in the literature describing any tumours, and specifically sarcoids, in zebras. The equine sarcoid, a locally aggressive, fibroblastic skin tumour, is the most common dermatological neoplasm reported in horses. The Cape mountain zebra (CMZ) has been described as one of the most vulnerable mammals in South Africa with current populations existing in isolated units. All South African CMZ are descendants from no more than 30 individual animals originating from 3 populations, namely the Mountain Zebra National Park, and Kammanassie and Gamka Mountain Nature Reserves near Cradock. The possibility therefore exists that the existing populations arose from a very small gene pool and that they are considerably inbred. A reduction in major histocompatibility complex diversity due to genetic bottlenecks and subsequent inbreeding probably contributed to uniform population sensitivity and the subsequent development of sarcoid in two CMZ populations, namely in the Bontebok National Park and Gariep Nature Reserve. The entire population of CMZ in the Bontebok National Park was observed and sampled during 2002 to document the prevalence and body distribution of sarcoids. During the same year, a comparative study was carried out on an outbred population of Burchell's zebra in the Kruger National Park. The prevalence in CMZ in the Bontebok National Park was 53 %, while the Burchell's zebra in Kruger National Park had a prevalence of 1.9 %. The most common sites for sarcoid in CMZ were the ventral abdomen and limbs. Prevalence of sarcoids in horses recorded in the literature varies between 0.5 % and 2 %. The Gariep Nature Reserve recently reported a prevalence of almost 25 % in CMZ in the reserve.     

Owners’ perception of the efficacy of Newmarket bloodroot ointment in treating equine sarcoids

A retrospective questionnaire-based survey was used to determine the perceived efficacy of Newmarket bloodroot ointment in treating equine sarcoids. In 49 horses with 74 sarcoids, 64 sarcoids responded either completely (n = 49) or partially (n = 15) while 10 did not respond or worsened. Sarcoids < 2 cm responded better to treatment (P < 0.001) than did larger sarcoids.     

Differential expression of microRNAs in bovine papillomavirus type 1 transformed equine cells

Bovine papillomavirus (BPV) types 1 and 2 play an important role in the pathogenesis of equine sarcoids (ES), the most common cutaneous tumour affecting horses. MicroRNAs (miRNAs), small non‐coding RNAs that regulate essential biological and cellular processes, have been found dysregulated in a wide range of tumours. The aim of this study was to identify miRNAs associated with ES. Differential expression of miRNAs was assessed in control equine fibroblasts (EqPalFs) and EqPalFs transformed with the BPV‐1 genome (S6‐2 cells). Using a commercially available miRNA microarray, 492 mature miRNAs were interrogated. In total, 206 mature miRNAs were differentially expressed in EqPalFs compared with S6‐2 cells. Aberrant expression of these miRNAs in S6‐2 cells can be attributed to the presence of BPV‐1 genomes. Furthermore, we confirm the presence of 124 miRNAs previously computationally predicted in the horse. Our data supports the involvement of miRNAs in the pathogenesis of ES.