Radiotherapy for the treatment of periocular tumours in the horse

Periocular tumours are a relatively common problem in the horse, and present some unique challenges. Radiotherapy has long been considered the ‘gold standard’ for the treatment of periocular tumours in the horse, and there are various techniques of delivering this treatment. Although teletherapy and plesiotherapy are occasionally used, the most commonly used technique is interstitial brachytherapy. Low-dose rate interstitial brachytherapy has reported success rates of between 74 and 100% for the treatment of periocular sarcoids, and other tumours can also be successfully treated using this technique. There are significant disadvantages to the low-dose rate brachytherapy approach, and recently, a technique using high-dose rate brachytherapy has been described with a reported success rate of 100% for periocular sarcoid treatment. Electronic brachytherapy is a technique which may provide an alternative to high-dose rate brachytherapy, but its use for the treatment of periocular tumours has not been reported, and the requirement for general anaesthesia is a significant disadvantage.     

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.     

A review of equine sarcoid

Equine sarcoid is the most common tumour of horses and accounts for over half of all equine skin tumours. Six types of sarcoid based on gross appearance and clinical behaviour have been described including occult, verrucous, nodular, fibroblastic, mixed and malevolent. Common locations for sarcoid development include the periocular region, ear pinnae, lips, neck, extremities and ventrum (including groin region). Bovine papillomavirus (BPV) is causally associated with equine sarcoid with genetic haplotype, fly vectors and skin trauma identified as potential risk factors for development of the disease. Histopathology is required for definitive diagnosis of equine sarcoid but incomplete excision is thought to activate latent BPV and stimulate growth. Although there are no uniformly effective treatment options, several modalities have been successful in eliminating or managing equine sarcoid. Surgical excision, intratumoural chemotherapy, cryotherapy, hyperthermia, radiotherapy, immunotherapy and immune modulators are used with degrees of success relative to the accessibility and invasiveness of the tumour. Prevention of equine sarcoid may be facilitated by future development of vaccines against bovine papillomavirus.     

High dose rate interstitial 192-Ir brachytherapy for the treatment of a recurrent dermal vascular hamartoma in a horse

The successful application of an interstitial brachytherapy course is reported in a 14-month-old male Anglo European Studbook (AES) foal for the treatment of a recurrent dermal vascular hamartoma at the dorsal aspect of the pastern on the right hindlimb. The lesion was irradiated four times over 4 days to a total dose of 28 Gy. Progressive tumour shrinkage and necrosis were observed over 2 months. No significant acute side effect was reported at the end of the treatment, with excellent and long-lasting cosmetic results observed. The only reported late effect was permanent leukotrichia within the treated area, which remained otherwise tumour-free 1224 days after treatment. Results of this report suggest the potential use of radiation therapy (and specifically brachytherapy techniques), as an effective and safe treatment modality for vascular malformations in horses.     

High-dose-rate brachytherapy for intranasal tumours in dogs: results of a pilot study

This prospective study describes the feasibility and toxicity of ¹⁹²Iridium high‐dose‐rate (HDR) brachytherapy as an alternative strategy for the treatment of canine intranasal tumours. Fifteen dogs with malignant intranasal tumours were treated twice weekly using a hypofractionated protocol with eight fractions, 5 Gy per fraction, resulting in a total dose of 40 Gy. Acute and chronic adverse side‐effects appeared to be rare. Only 7% of the acute side‐effects and 5% of the chronic were classified as severe (grade 3). Eight dogs showed clinical complete remission, and five dogs had partial remission, with a resolution of tumour‐related symptoms. Magnetic resonance imaging showed a reduced tumour mass in 12 cases. Median survival time was 17 months (range 4–48 months), with four dogs (three without disease) still alive. Median time to recurrence of these dogs was 14 months. In nine dogs, progression or recurrence of the tumour was the cause of death. This study suggests that HDR brachytherapy is feasible and well tolerated.     

Interstitial brachytherapy in the management of haemangiosarcoma of the rostrum of the horse: Case report and review of the literature

Sarcomas arising in the equine species are rare tumours, and treatment is generally surgical. Radiotherapy has been used in the management of malignancies of large animals; however, conventional external radiotherapy delivery is difficult. Interstitial brachytherapy has been used in the management of human sarcomas with reasonable success, although equine experience is minimal. We report a case of equine haemangiosarcoma treated with brachytherapy demonstrating the feasibility of the procedure and the highly malignant natural history of haemangiosarcoma. An 8‐year‐old American Saddlebred gelding presented for evaluation of a soft tissue mass on the forehead which had been present for at least 6 months. Initial surgical attempts at management were unsuccessful; therefore a radiation oncologist specialising in brachytherapy was consulted. The radiation oncologist and veterinary surgeon performed an interstitial implant of the tumour mass on the rostrum of the horse under general anaesthesia. The procedure was well tolerated by the horse. The tumour demonstrated immediate response and was noted to have completely regressed within 6 weeks of the implant removal. Unfortunately, the horse developed widespread metastatic disease and required euthanasia. At the time of necropsy, no visible tumour was identified at the implant site. Interstitial brachytherapy is feasible in soft tissue sarcomas of the horse; however, supportive demands are great with this procedure and we recommend it only be done at large speciality centres.     

Intralesional bovine papillomavirus DNA loads reflect severity of equine sarcoid disease

Reasons for performing study: Sarcoids are nonmetastasising, yet locally aggressive skin tumours that constitute the most frequent neoplasm in equids. Infection by bovine papillomaviruses types 1 and 2 (BPV‐1, BPV‐2) has been recognised as major causative factor in sarcoid pathogenesis, but a possible correlation of intralesional virus load with disease severity has not been established thus far. Hypothesis: Given the pathogenic role of BPV‐1 and BPV‐2 in sarcoid disease, we suggest that intralesional viral DNA concentration may reflect the degree of affection. Methods: Severity of disease was addressed by recording the tumour growth kinetics, lesion number and tumour type for 37 sarcoid‐bearing horses and one donkey. Viral load was estimated via quantitative real‐time PCR (qPCR) of the E2, E5, L1 and L2 genes from the BPV‐1/‐2 genome for one randomly selected lesion per horse and correlated with disease severity. Results: Quantitative PCR against E2 identified viral DNA concentrations ranging from 0–556 copies/tumour cell. Of 16 horses affected by quiescent, slowly growing single tumours or multiple mild‐type lesions, 15 showed a viral load up to 1.4 copies per cell. In stark contrast, all equids (22/22) bearing rapidly growing and/or multiple aggressive sarcoids had a viral load between 3 and 569 copies per cell. Consistent results were obtained with qPCR against E5, L1 and L2. Conclusions: While tumours of the same clinical type carried variable virus load, confirming that viral titre does not determine clinical appearance, we identified a highly significant correlation between intralesional viral load and disease severity. Potential relevance: The rapid determination of BPV viral load will give a reliable marker for disease severity and may also be considered when establishing a therapeutic strategy.     

Calcified tumours of the paranasal sinuses in three horses

Three horses, a 10-year-old Thoroughbred mare, a 9-year-old Thoroughbred gelding and a 6-year-old Arab gelding, with calcified tumours of the paranasal sinuses, are described. All horses presented with purulent nasal discharges and facial distortion. Exophthalmos, blepharospasm and ocular discharge were also a feature in individual horses. A presumptive diagnosis of a calcified tumour was made on the basis of clinical signs and radiographic and endoscopic findings. The tumours ranged from 15 to 25 cm in diameter. A large frontonasal bone flap was used to expose the tumours, which were cleaved into several pieces with an osteotome and removed. Histological examination of the masses identified cementomas in two cases and an osteoma in the third. Long term follow up from 18 months to 5 years after surgery indicated that there was no recurrence. This case series demonstrates that, although calcified tumours of the paranasal sinuses are rare in horses, they should be considered in the differential diagnosis of purulent nasal discharge, facial swelling and ocular distortion, and are amenable to surgical treatment.     

PCR for antigen receptor rearrangement (PARR) in equine veterinary medicine

PCR for antigen receptor rearrangement (PARR) is a technique developed to aid with the assessment of lymphoid malignancies. The technology relies on the assessment of clonality of T or B cells, and there are many pitfalls. One major advantage is that only a small amount of sample is required to detect clonality, and it can be performed on any type of sample, including effusions, formalin-fixed paraffin-embedded tissues and cytological samples. However, the risk of both false negative and false positive results means that PARR should not be used to diagnose a lymphoid malignancy in isolation, but that results should be considered in conjunction with a full clinical and clinicopathological assessment.     

Surgical excision of large melanocytic tumours in grey horses: 38 cases (2001–2013)

Melanocytic tumours are common in grey horses. Large tumours can obstruct the rectum, or prepuce, inhibit food intake and impinge upon the upper airway. Surgical excision is locally curative, but is controversial for large or confluent tumours. Limited information on outcome following surgical excision of large melanomas is available. The objective of this study was to report outcome following surgical excision of large (≥4 cm) melanocytic tumours in horses. Our hypothesis was that surgical excision of large (≥4 cm) single and coalescing melanomas would be locally curative. Medical records were reviewed and cases that underwent excision of a single or coalescing melanoma, with at least one lesion ≥4 cm in diameter, included. Follow‐up information was obtained a minimum of 12 months post‐surgery from owners and referring veterinarians via telephone interviews, questionnaire, or direct examination. A total of 48 cases were identified; 38 horses with follow‐up were included in the study. Tumours involved the parotid, perianal or mid‐cervical regions, ventral tail base, prepuce, penis, ear, or thoracic inlet. There were no cases of tumour regrowth following excision. Post‐operative complications occurred in five cases and were easily resolved in all but one. Continued or new growth of distant melanocytic tumours occurred in 50% of cases. Results suggest that excision of large melanocytic tumours in horses is a viable treatment option that is locally curative with minimal complications.     

Three types of anomalous vasculature in the equine umbilical cord

Anomalies in the number of major blood vessels in the umbilical cord are well documented in man and have been associated with both placental abnormalities and congenital problems in the neonate. This paper describes 5 cases of anomalies in the number of umbilical arteries or veins within the equine umbilical cord at term. In 4 cases, the anomalies affected vessels in the amniotic part of the cord, and in one case, vessels in the allantoic part. In all the cases placental morphology was essentially normal and fetal health and post natal development were not compromised as a result of the unusual arrangement of blood vessels within the cord.     

Clinical and ultrasonographic evaluation of three suture techniques for closure of the equine linea alba

Surgical technique plays an important role in preventing ventral midline incisional complications. The aim of this study was to compare the clinical and ultrasonographic outcome of three suture techniques for closure of the linea alba. In this prospective case series (n = 43), horses operated for acute abdominal intestinal disease through a midline incision were randomised in three groups: closure with a conventional continuous technique (Group 1), a small stitches continuous technique (Group 2) and the UX-technique (shoe-lace configuration, Group 3). Age, sex, body weight, type and duration of surgery were recorded and the suture to wound length ratio was calculated. Clinical evaluation of the wound (wound discharge) was performed daily during hospitalisation. At 7 weeks post-operatively the linea alba was evaluated clinically and ultrasonographically. The linea alba width was measured halfway along the length of the incision. One horse in Group 1 had acute incisional dehiscence, but there were no further significant differences between the groups in the short term. Seven weeks post-operatively two horses had complete herniation in Group 1 and one horse had partial herniation in Group 2. In the UX group no herniation occurred. The incidence of herniation was not significantly different between the groups. On ultrasound at 7 weeks the linea alba width was significantly smaller in Group 2 (P = 0.00029) and Group 3 (P = 0.0018) compared with Group 1, even with exclusion of the acute incisional dehiscence and two herniated horses. Limitations were the small group size and relatively low incidence of incisional complications for statistical analysis. It was concluded that the use of small stitches and the UX-technique resulted in a smaller linea alba width compared with the conventional continuous suture technique and might therefore be preferred for closure of the linea alba in equine colic surgery.     

Computed tomography in the diagnosis of malignant sinonasal tumours in three horses

Malignant tumours are uncommon in horses, but when they do occur, they are most frequently found in the head. Clinical findings, such as facial swelling and nasal discharge, are frequently encountered but are nonspecific. To highlight the usefulness of a computed tomography (CT) examination in malignancy in the equine head, this Case Report describes the CT features of a leiomyosarcoma, an osteosarcoma and a sarcoma in 3 horses. CT of the equine head was able to provide more information about the extent and severity of lesions than conventional radiography in these cases.