BCG emulsion immunotherapy of equine sarcoid

Histological evidence of superficial inflammation is associated with lower recurrence of equine sarcoids following surgical removal: A follow-up study of 106 tumours in 64 horses

Although the equine sarcoid is the most common skin neoplasm in domesticated horses, histopathological characteristics have not previously been evaluated for association with recurrence. The aim of this retrospective cohort study was to investigate clinical and histopathological features of excised equine sarcoids and to evaluate their association with recurrence at the original surgical site and at new sites. Clinical records and excisional biopsies from 106 equine sarcoids from 64 horses referred to Leahurst Equine Hospital, University of Liverpool, between March 2010 and February 2015 were retrieved. Biopsies were re-evaluated histologically. Clinical data were obtained from hospital records, and owner-reported follow-up data were obtained by telephone questionnaire. Associations between clinical and histopathological features of sarcoids and their recurrence at the surgical site were determined using uni- and multivariable mixed effects logistic regression. Recurrence of sarcoids at the surgical site occurred in 30 horses (46.9%). Sarcoids developed at a distant site in 21 horses (32.8%). In the final mixed effects logistic regression model, only superficial inflammation was associated with reduced odds of recurrence at the surgical site (adjusted odds ratio, 0.32; 95% confidence intervals, 0.10-0.96; P = 0.04). This suggests that the inflammatory process may play a role in protecting horses against the recurrence of sarcoids.

Management of equine sarcoids

Sarcoids are the most common cutaneous neoplasm of the horse, arising as a result of a neoplastic proliferation of fibroblasts associated with infection with bovine papillomavirus, most notably types 1 and 2. Although they do not metastasise, they are locally invasive and aggressive, and can lead to important welfare concerns, interfere with tack and therefore impede athleticism, and undoubtedly lead to a reduction in the value of affected horses. This review discusses the evidence behind the most commonly used treatments for equine sarcoids. The most commonly used treatments are discussed. No one treatment is universally successful, and there are many treatments with varying level of scientific evaluation and reported success rates.

Treatment of equine sarcoids using recombinant poxviruses expressing feline interleukin-2

BACKGROUND

Interleukin (IL)-2 stimulates antitumour immunity and is successfully used for the treatment of different neoplasias.

HYPOTHESIS/OBJECTIVES

Canarypox virus locally expressing feline IL-2 is safe and can be used to treat equine sarcoids.

ANIMALS

Twenty horses of different breeds with a median age of eight years (interquartile range 6.0-13.3 years) and a total number of 59 sarcoids were included in the study.

METHODS

In this prospective clinical trial, sarcoids were injected twice seven days apart, with a recombinant canarypox virus expressing feline IL-2. Complete blood counts (CBC) and fibrinogen levels were measured before treatment and on days 1, 2, 7 and 8.

RESULTS

Complete regression was achieved in eight horses (40%) and partial regression in two horses (10%). No change in sarcoid size was observed in two horses (10%) and the disease progressed in five horses (25%). Sarcoids of three horses (15%) showed initial response followed by tumour growth. There were no significant changes in CBC and fibrinogen levels after either injection. One horse developed a mild fever the day after each injection, which subsided without treatment the following day.

CONCLUSIONS

Treatment of equine sarcoids with recombinant canarypox virus expressing feline IL-2 seems to be a safe therapy option. Although the expression of IL-2 after vector injection and its biological activity in horses were not proven in this study, the treatment resulted in regression and partial regression in 50% of the cases. Further studies are necessary to verify these findings and to establish a treatment protocol.

Evaluation of Locally Injected Mycobacterium Cell Wall Fraction in Horses with Sarcoids

A reformulation of Mycobacterium cell wall fraction immunotherapeutic can be used to successfully treat sarcoids in horses. Sarcoids are reported to be the most common equine skin tumors with tumor type and location influencing the choice of treatment. Wide surgical excision is curative for many tumors, but may not always be feasible. Previous studies have reported sarcoid regression after injection with mycobacterial cell wall immunotherapeutics. A new formulation of the Mycobacterium phlei cell wall fraction immunostimulant (Immunocidin Equine) was used to treat cutaneous tumors in horses. Equids with skin tumors diagnosed as sarcoids were enrolled in the study. Sarcoids were injected at the initial visit with Immunocidin Equine and subsequently at approximately 2-week intervals. Of 17 cases, nine cases were completely resolved at the end of the study period evaluation or at the time of final follow-up (52.9%). Three cases were reported as improved (smaller), but not resolved (17.6%). Three cases were discontinued from the study as the respective masses were growing larger or not resolving (17.6%). One case (5.8%) with two masses had resolution of one mass, whereas the other tumor had a small regrowth 5 months after the last treatment. One case (5.8%) was lost to follow-up. All cases had mild to moderate swelling of the injection site, and some cases had discharge after the second, third, or fourth injections. No serious systemic side effects or complications were encountered during the study.

The Equine Sarcoid: Why Are There so Many Treatment Options?

This article discusses the main treatments for sarcoid and the specific difficulties of these. It explains to some extent why the frustrations of a condition for which there is no single treatment option have led to the burgeoning of an industry of irrational treatments. The factors that need to be considered before selecting an option for treatment are wider than is the case in most other disease entities as a result of the complexity of the condition, its variable phenotypes, and the individual perceptions and experiences of both veterinarians and owners.

Treatment of sarcoids in equids: 230 cases (2008-2013)

OBJECTIVE To evaluate outcomes following treatment of sarcoids in equids and to identify risk factors for treatment failure in these patients. DESIGN Retrospective case series. ANIMALS 230 equids with 614 sarcoids. PROCEDURES Records were searched to identify equids treated for ≥ 1 sarcoid between 2008 and 2013. A standardized protocol was used to determine treatment choice (electrosurgery, electrosurgery with intralesional placement of cisplatin-containing beads, topical administration of imiquimod or acyclovir, cryosurgery, bacillus Calmette-Guerin vaccine injection, or intralesional injection of platinum-containing drugs). Data regarding animal, tumor, treatment, and outcome variables were collected. Complete tumor regression without recurrence for ≥ 6 months was considered a successful outcome. Success rates were calculated; binary logistic regression analysis was used to identify risk factors for treatment failure and to compare effects of the 2 topical treatments. A χ(2) test was used to compare effects of the number of Bacillus Calmette-Guerin vaccine or cisplatin-containing drug injections on outcome. RESULTS The overall success rate was 460 of 614 (74.9%). Electrosurgical excision resulted in the highest treatment success rate (277/319 [86.8%]); odds of treatment failure were significantly greater for intralesional injection of platinum-containing drugs, cryosurgery, and topical acyclovir treatment. Odds of treatment failure were also significantly greater for sarcoids on equids with multiple tumors than for solitary lesions, and significantly lower for sarcoids on equids that received concurrent immunostimulating treatment for another sarcoid than for those on patients that did not receive such treatment. CONCLUSIONS AND CLINICAL RELEVANCE Selection bias for treatments was inherent to the study design; however, results may assist clinicians in selecting treatments and in determining prognosis for equids with sarcoids treated according to the described methods.

Management of equine sarcoids: 1975–93

Treatment options for equine sarcoids are briefly reviewed and the results of a retrospective study of 63 cases of equine sarcoid (66 lesions) treated by clinicians from the Rural Veterinary Centre, Camden, Australia from 1975 to 1993 presented. Five different treatments were employed in the management of these 66 lesions, including surgical excision alone or in combination with cryotherapy, radiotherapy, immunotherapy and tumour transfer to a subcutaneous site on the neck. The majority of cases were treated with surgical excision alone (18/66), excision followed by cryotherapy (31/66) and immunotherapy (16/66), with success rates of 28%, 42% and 81% respectively. Success was defined as no sign of recurrence of the lesion at the time of follow-up, at least 6 months later.

Treatment of clinically diagnosed equine sarcoid with a mistletoe extract (Viscum album austriacus)

BACKGROUND

Equine sarcoids (ES) are common, difficult to treat, and have high recurrence rates. Viscum album extracts (VAE) are used in human cancer treatment.

HYPOTHESIS

That therapy with VAE (Iscador P) is effective in the treatment of ES.

ANIMALS

Fifty-three horses (444 ES); 42 were treated with VAE or placebo as monotherapy; 11 were treated with VAE or placebo after selective excision of ES.

METHODS

Prospective, randomised, blinded, clinical trial. Horses were randomly assigned to treatment (VAE; n=32) or control group (Placebo; n=21). One milliliter of VAE (Iscador P) in increasing concentrations from 0.1 to 20 mg/mL or physiological NaCl solution was given SC 3 times a week over 105 days. Number, localization, and type of the ES were documented over 12 months. A subset of 163 clinically diagnosed equine sarcoid (CDES) lesions (95 VAE, 68 Placebo) was evaluated in detail, considering clinical findings and tumor volume.

RESULTS

No undesired adverse effects were observed except for mild edema at the injection site in 5 of 32 horses (16%). Complete or partial regression was observed in 13 horses of the VAE group (41%) and in 3 of the control horses (14%; P<.05). After VAE treatment, 48 of 95 CDES (67%) showed an improvement compared with 17 of 68 CDES in the control group (40%; P<.01). Twenty-seven CDES had disappeared completely in the VAE group (38%) compared with 9 CDES in the control group (13% NS).

CONCLUSIONS AND CLINICAL IMPORTANCE

VAE (Iscador P) represents a safe and effective treatment for CDES.

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.

Periocular sarcoid in a horse

A periocular nodular sarcoid of the right upper and lower eyelids was diagnosed in an 11-year-old Thoroughbred mare. Computed tomography scan revealed the extent of the tumor. The mass was surgically debulked under general anesthesia, and the affected periocular region was injected intralesionally with Bacillus of Calmette and Guerin (BCG). An emulsion of cell wall fractions was used, which has been modified to reduce the toxic and allergic effect, but retain the antitumor activity. In total, five injections were performed at 2-week intervals. At follow-up 7 months after the last BCG injection, the tumor was completely resolved. Two years after the last treatment, the horse remains tumor-free.

Comparison of the efficacy of local treatment of equine sarcoids with IL-2 or cisplatin/IL-2

Local interleukin-2 (IL-2) is effective in a number of experimental animal models and in veterinary and human cancer patients without discomforting side effects. The primary goal of this study was to compare the therapeutic effects and side effects of the local intratumoral administration of five or ten low doses of IL-2 with those of a combination of cisplatin and a single high dose of IL-2 in the treatment of equine sarcoids. The therapeutic effect (complete and partial regression) of local cisplatin together with a single high dose of IL-2 was significantly better than the combined effect of low doses of local IL-2 administered daily over 5 or 10 days (80% and 43%, respectively; P=0.02). Cisplatin/IL-2 and low doses of IL-2 induced 53% and 14% complete regressions, respectively ( P=0.02). Histological changes after cisplatin/IL-2 treatment were far more pronounced than after IL-2 only treatment and in several cases showed an enormous eosinophilic infiltrate.

Use of a carbon dioxide laser for surgical management of cutaneous masses in horses: 32 cases (1993-2000)

OBJECTIVE

To determine outcome of horses in which cutaneous masses were removed with a carbon dioxide laser.

DESIGN

Retrospective study.

ANIMALS

32 horses.

PROCEDURE

Medical records of horses with 1 or more cutaneous masses treated with a carbon dioxide laser were examined. Follow-up information was obtained through telephone interviews with owners and referring veterinarians.

RESULTS

Cutaneous masses were classified as sarcoids (15 horses), neoplastic masses other than sarcoids (squamous cell carcinoma [91; fibroma [1]; and melanoma [1]), and nonneoplastic masses (6). Minimum follow-up time was 6 months. Five sarcoids and 2 squamous cell carcinomas recurred. Seven (21%) horses had complications associated with dehiscence of wounds that had been closed primarily or failure of wound healing because of recurrence of the mass. Twenty-six (81%) owners were satisfied with the cosmetic appearance following surgery.

CONCLUSION AND CLINICAL RELEVANCE

Results suggest that a carbon dioxide laser may be effective for treatment of cutaneous masses in horses.

Partial orbital rim resection, mesh skin expansion, and second intention healing combined with enucleation or exenteration for extensive periocular tumors in horses

Ocular and periorbital sarcoids and squamous cell carcinoma are common in equine practice. Extensive involvement of periorbital tissues often necessitates removal of the globe if the function of the eyelids can not be maintained with tumor removal alone. This report describes a modification of the standard enucleation or exenteration technique for cases in which there is insufficient skin to achieve primary closure following complete surgical excision. The caudal portion of the dorsal orbital rim is protuberant; partial excision with an osteotome facilitates skin closure by decreasing the size of the wound. Mesh expansion of skin via multiple rows or parallel stab incisions can also be used as an adjunct to facilitate closure. Four horses underwent enucleation or exenteration using the orbital rim resection and mesh skin expansion techniques for extensive periocular tumors that were unresponsive to prior treatments. Follow-up intervals ranged from 6 to 42 months and no horses had tumor regrowth.

Evaluation of excision, cryosurgery and local BCG vaccination for the treatment of equine sarcoids

Ninety-five horses with sarcoids were subjected to three types of treatment: surgical excision (conventional or carbon dioxide laser), cryotherapy or local BCG vaccination. The type of treatment was selected on the basis of the size, location and clinical appearance of the tumours. The choice between conventional and laser excision was empirical. A successful outcome was obtained in 11 of 14 (79 per cent) of the horses treated by cryosurgery, 18 of 27 (67 per cent) treated by BCG vaccination, 18 of 22 (82 per cent) treated by conventional excision, and 20 of 28 (71 per cent) treated with a carbon dioxide laser. For both excision methods, rigorous measures were taken to avoid autoinoculation and to ensure a wide margin of normal skin. The probability of local recurrence after excision was significantly higher for large sarcoids and sarcoids which had previously failed to respond to treatment. In 10 of the 31 horses with remaining sarcoids, some or all of the untreated sarcoids were observed to regress spontaneously.

Immunomodulation in horses

Nonspecific immunomodulators are substances that induce non-antigen-specific enhancement of the body's native or acquired defense mechanisms. Immunomodulant preparations are most often used for treatment of chronic, viral, or bacterial infection with evidence of secondary immunosuppression. The proposed mechanism of action of these products is macrophage activation and subsequent release of cytokines that enhance humoral and cell-mediated immunity. In equine medicine, nonspecific immunostimulant products are used for prevention and treatment of infectious respiratory disease and treatment of sarcoid skin tumors.

Intralesional and topical chemotherapy and immunotherapy

Surgery is the mainstay of treatment for equine tumors. Conservative treatment approaches which preserve function and appearance are increasingly used in clinical practice. This article covers the principles and applications of two conservative treatment modalities including local chemotherapy and immunotherapy. The therapeutic benefit of local chemotherapy is based on the direct drug delivery to tumor tissue, i.e., topical and intratumoral administration of cytotoxic agents in slow release formulation. This treatment modality is very effective for cutaneous tumors and does not result in any permanent damage to normal tissue. Immunotherapy produces antitumor effects primarily through the action of natural host defense mechanisms against tumor cells. Although the use of immunotherapy is still under investigation there are many examples of its successful application to treatment of selected equine tumors.

Equine sarcoids

Sarcoids, the most common tumor of the horse, are fibroblastic, wart-like skin lesions that show variable manifestations. They are often invasive and recurrent, although they do not fulfill all criteria of malignancy. Due to their anatomic location, these tumors can sometimes cause loss of use of the horse. There is very strong evidence that sarcoids are caused by viruses closely related or identical to bovine papilloma viruses, and genetic studies have shown associations between genes in or near the equine major histocompatibility complex (MHC) and susceptibility to sarcoid. Several types of treatments have been successful in treating sarcoids, although the response to therapy is not consistent. Current treatment of sarcoids primarily involves antitumor therapy, but the development of preventative measures in the future may be directed against the causative papilloma virus. Sarcoid continues to be an important clinical entity for the equine practitioner.