Lung tumor development and spontaneous regression in lambs coinfected with Jaagsiekte sheep retrovirus and ovine lentivirus.

Ovine pulmonary adenocarcinoma (OPA) is a naturally occurring and experimentally inducible lung cancer of sheep caused by Jaagsiekte sheep retrovirus (JSRV). The first aim of this study was to monitor the development of OPA with minimally invasive, real-time observations of animals experimentally infected with JSRV as well as ovine lentivirus (maedi-visna virus). Worldwide, simultaneous infection of sheep with these 2 retroviruses is a common occurrence, naturally and experimentally; consequently, the lung tumor homogenates used as inocula contained both viruses. Following inoculation, computed tomography was used to detect tumor nodules early, before the onset of clinical signs, and to monitor tumor advancement. However, not only was OPA disease progression observed, but the apparent spontaneous regression of OPA was witnessed. In fact, regression was more common than progression following JSRV inoculation of neonatal lambs. Immune responses were detected, particularly involving CD3(+) T cells and the production of antibodies against JSRV that may mediate the spontaneous regression of JSRV-induced OPA. The second aim of this study was to determine whether OPA tumors harbor genetic alterations similar to those found in human lung adenocarcinoma. No mutations were found in the tyrosine kinase domain of the epidermal growth factor receptor, KRAS codons 12 and 13, or the DNA-binding domain of p53 in tumor DNA from naturally occurring and experimentally-induced OPA cases. Overall, the genetic profile combined with the disease development data provides further important characterization of OPA and describes, for the first time, spontaneous regression of OPA tumors in experimentally infected sheep.

Biomechanical characteristics of allogeneic cortical bone pins designed for fracture fixation.

The biomechanical characteristics of 1.2 mm diameter allogeneic cortical bone pins harvested from the canine tibia were evaluated and compared to 1.1 mm diameter stainless steel pins and 1.3 mm diameter polydioxanone (PDS) pins using impact testing and four-point bending. The biomechanical performance of allogeneic cortical bone pins using impact testing was uniform with no significant differences between sites, side, and gender. In four-point bending, cortical bone pins harvested from the left tibia (204.8 +/- 77.4 N/mm) were significantly stiffer than the right tibia (123.7 +/- 54.4 N/mm, P = 0.0001). The site of bone pin harvest also had a significant effect on stiffness, but this was dependent on interactions with gender and side. Site C in male dogs had the highest mean stiffness in the left tibia (224.4 +/- 40.4 N/mm), but lowest stiffness in the right tibia (84.9 +/- 24.2 N/mm). Site A in female dogs had the highest mean stiffness in the left tibia (344.9 +/- 117.4 N/mm), but lowest stiffness in the right tibia (60.8 +/- 3.7 N/mm). The raw and adjusted bending properties of 1.2 mm cortical bone pins were significantly better than 1.3 mm PDS pins, but significantly worse than 1.1 mm stainless steel pins (P < 0.0001). In conclusion, cortical bone pins may be suitable as an implant for fracture fixation based on initial biomechanical comparison to stainless steel and PDS pins used in clinical practice.

Status of the p53, Rb and MDM2 genes in canine osteosarcoma.

The key role of p53 and Rb alterations in human osteosarcoma is clear. For example, osteosarcoma is common in individuals inheriting mutant p53 or Rb genes. Osteosarcoma in dogs is similar to humans by histology, site, gender ratio and several other biological parameters. To study whether this similarity extends to the molecular level, 21 canine osteosarcomas were analyzed for alterations of p53, Rb and MDM2. MDM2 is a normal cell protein which antagonizes p53, amplification is seen in some human sarcomas. The gross structure of the p53, Rb and MDM2 genes was examined by Southern blotting. No deletions or rearrangements of the p53 or Rb genes were detected. The absence of gross gene alterations affecting these tumor suppressor genes is a significant difference between the disease in dogs and humans, since rearrangements or deletions of the p53 or Rb genes occur in 20-30 per cent of human osteosarcomas. The MDM2 gene appeared to be duplicated in one canine tumor but no cases of significant amplification were detected. Expression of normal Rb was detected in all cases. Mutations of the p53 gene were found in 38 percent of canine osteosarcomas. Analysis of mutations revealed a predominance of spontaneous mutation. These finding emphasize the key role that alterations of p53 have in the development of osteosarcoma in dogs and humans.

Intracavitary treatment of soft tissue sarcomas in dogs using cisplatin in a biodegradable polymer.

BACKGROUND: The purpose of this study was to evaluate the toxicity and efficacy against local disease recurrence of soft tissue sarcomas (STS) in dogs using intracavitary cisplatin released from a polymer device (OPLA-Pt). MATERIALS AND METHODS: OPLA-Pt was placed into the wound following marginal (histologically incomplete) resection of STS in 30 dogs (32 tumors) with a median tumor diameter of 3 cm (range = 1-14 cm). Median cisplatin dose was 35.5 mg/m2 (body surface area) with a range of 5.3-133.3 mg/m2. RESULTS: The OPLA-Pt was removed from 9/32 (28%) sites due to local wound complication. Local recurrence occurred in 10/32 (31%) tumors. Higher tumor grade had a significant negative influence on local tumor recurrence (p = 0.031). CONCLUSIONS: The rate of recurrence appeared to be similar using intracavitary cisplatin compared to previous reports of STS treated by marginal surgery followed by radiotherapy. The complication rate indicates the need for further refinement of the polymer/cisplatin system.

Apparent interaction of dimethyl sulfoxide with cisplatin released from polymer delivery devices injected subcutaneously in dogs.

Local tissue toxicity, systemic toxicity and platinum pharmacokinetics were evaluated in 6 normal healthy beagle dogs injected subcutaneously with two formulations of a polylactide biodegradable polymer (Atrigel) system containing cisplatin. Dogs were injected 4 times at 30 day intervals at platinum dosages of 70, 105 and 157.5 mg/m2 (dose escalation). Once pharmacokinetics were established, 29 dogs with spontaneous stage IIb appendicular osteosarcoma were treated with 4 injections of the same polymer system containing cisplatin at 70 mg/m2 (20 dogs) and 100 mg/m2 (9 dogs) to establish efficacy against micrometastatic disease. Local tissue toxicity was variable. Systemic toxicity, as judged by clinicopathologic evaluation was not noted at any dose level or injection number. Interim (6 month) survival analysis revealed a median disease-free interval of 180 days. Consistent platinum release characteristics were found, however, the lack of toxicity and decreased disease-free-interval raised concerns over the biologic activity of the cisplatin. Prior to completion of the study, it was discovered that dimethyl sulfoxide, the solvent used in the co-polymer system, may be responsible for biologic inactivation of cisplatin. This was subsequently demonstrated in tissue culture assays. The clinical trial was suspended and dogs were treated with traditional chemotherapy.

Preparation and in vitro characterization of gentamycin-impregnated biodegradable beads suitable for treatment of osteomyelitis.

A new method for preparing poly(L-lactide) (PLA) biodegradable beads impregnated with an ionic aminoglycoside, gentamycin, is described. The process employs hydrophobic ion pairing to solubilize gentamycin in a solvent compatible with PLA, followed by precipitation with a compressed antisolvent (supercritical carbon dioxide). The resulting precipitate is a homogeneous dispersion of the ion-paired drug in PLA microspheres. The microspheres are approximately 1 microm in diameter and can be compressed into beads (3-6 mm in diameter) strung on surgical sutures for implantation. The bead strings exhibit no significant change in release kinetics upon sterilization with a hydrogen peroxide plasma (Ster-Rad). The kinetics of gentamycin release from the PLA beads are consistent with a matrix-controlled diffusion mechanism. While nonbiodegradable poly(methyl methacrylate) (PMMA) beads initially release gentamycin in a similar manner, the drug release from PMMA ceases after 8 or 9 weeks, while the PLA beads continue to release drug for over 4 months. Moreover, only 10% of the gentamycin is released from the PMMA beads, while PLA beads release more than 60% of their load, if serum is present in the release medium. The PLA system displays improved release kinetics relative to PMMA, is biodegradable, is unaltered by gas sterilization, can be used for a range of antibiotics, and can be manipulated without disintegration. These are all desirable properties for an implantable drug delivery system for the prevention or treatment of osteomyelitis.

Adjuvant chemotherapy using cisplatin by subcutaneous administration.

BACKGROUND-MATERIALS: Based on previous polymer release experience, this study was conducted to evaluate the toxicity, efficacy and systemic absorption of cisplatin administered subcutaneously in dogs. METHODS-RESULTS-CONCLUSIONS: Fifty to 70 mg/m2 cisplatin was suspended in saline and injected subcutaneously in 6 dogs as an adjunct to their primary treatment for sarcoma. Gastrointestinal, bone marrow, renal or local tissue toxicity occurred following the first (dogs 1-3,5,6) and second (dogs 1 and 2) treatments. Low, yet measurable levels of platinum were present in serum through day 14 following injection in all dogs. Due to the toxicity seen, all further planned treatments were discontinued and adjuvant regimes were completed with intravenous carboplatin. Although slow systemic absorption of platinum can occur following subcutaneous administration, the degree of toxicity seen following this treatment would indicate that a drug delivery vehicle may be necessary if cisplatin is to be administered for sustained release and adsorption.

Thromboxane as a measure of cutaneous vascular damage following irradiation.

The present study was designed to evaluate the role of thromboxane in radiation-induced cutaneous injury and to use the quantitation of cutaneous thromboxane B2 as an indicator of vascular alteration and tissue viability in canine skin. Ten adult intact male dogs underwent epithermal neutron irradiation with or without boron neutron capture. Skin biopsies were obtained from (1) within, (2) the edge of, and (3) outside the radiation field at 5, 8, 11, 14, 21, and 90 days after irradiation. Clinical changes at each sampling time were assigned a numerical score. One-half of each biopsy was assigned a numerical score based on histologic changes. Thromboxane B2 was measured from the second half by enzyme immunoabsorbent assay. Thromboxane B2 concentration paralleled the response of clinical and histologic score over time, indicating the value of thromboxane measurement for evaluation of skin changes secondary to irradiation.

Identification of matrix metalloproteinases in canine neoplastic tissue.

OBJECTIVE: To identify matrix metalloproteinases (MMP) 2 and 9 in canine tumor tissue and to compare the amount of activity to that in unaffected stromal tissue. ANIMALS: 30 dogs with spontaneously developing, high-grade osteosarcoma. PROCEDURE: Tumor and nearby stromal tissue (muscle) were obtained at the time of surgery. Specimens were homogenized, and supernatants were assayed, using gelatin zymography. Human derived standards were run concurrently. Densitometry was done to obtain a semiquantitative arbitrary unit value for each specimen. The amount of activity in tumor tissue was compared with the amount in stromal tissue. RESULTS: Gelatinolytic bands were observed from the analysis of all tumor tissues and in most stromal tissues. These bands migrated in the same molecular weight area as the human MMP 2 and 9 standards. Gelatinolytic activity could be quenched by the addition of 50 mM EDTA and 1 microg of synthetic tissue inhibitor of metalloproteinase (TIMP) 2 per 100 ml. There was significantly more gelatinolytic activity in tumor tissue than in stromal tissue. CONCLUSIONS AND CLINICAL RELEVANCE: MMP 2 and 9 are detectable in canine neoplastic tissue. Matrix metalloproteinases activity in tumor tissue is higher than in unaffected stromal tissue, indicating that canine MMP may be involved in the pathogenesis of tumor growth and metastasis.

Effects of a controlled-release cisplatin delivery system used after resection of mammary carcinoma in mice.

OBJECTIVE: To evaluate efficacy of a controlled-release cisplatin delivery system, used after marginal resection of mammary carcinoma (ie, resection of grossly evident tumor) in mice, to prevent tumor regrowth and metastasis. ANIMALS: 42 female C3H-HeJ mice. PROCEDURE: Mice were inoculated with mammary carcinoma cells. Between 2 and 6 days later, tumors were marginally resected and mice were assigned to 1 of 3 groups: no treatment (control; n = 14), cisplatin administered intraperitoneally (i.p. cisplatin; 14), and cisplatin delivered by use of an open-cell polylactic acid system placed within the tumor bed (slow-release cisplatin; 14). Tumor regrowth was measured daily. Mice were euthanatized 14 days after surgery, and complete necropsies were performed. RESULTS: Tumor regrowth was not detected in the slow-release cisplatin group; however, tumor regrowth was detected in 7 of 14 mice in the i.p. cisplatin group and 14 of 14 mice in the control group. Median (+/-SD) number of days to tumor regrowth was 13.5+/-0.64 and 7.79+/-0.87 in the i.p. cisplatin and control groups, respectively. Mice in the i.p. cisplatin group had significantly delayed tumor regrowth, compared with control mice. Metastases to lungs were detected in 8 of 14 control mice but were not detected in mice in either cisplatin treatment group. CONCLUSIONS AND CLINICAL RELEVANCE: The open-cell polylactic acid with cisplatin delivery system was successful in delaying local tumor regrowth and metastasis in mice with marginally resected mammary carcinoma. Use of a controlled-release cisplatin delivery system may be an effective adjunct treatment following excision of mammary carcinoma in humans and other animals.

Prognostic factors for surgical treatment of soft-tissue sarcomas in dogs: 75 cases (1986-1996).

OBJECTIVE: To determine results of surgery for treatment of soft-tissue sarcomas in dogs and to identify prognostic variables that can be used to predict outcome. DESIGN: Retrospective case series. ANIMALS: Dogs with soft-tissue sarcomas that had surgical treatment only. PROCEDURE: Records were examined for clinically relevant data. Histologic samples were reviewed. Follow-up information was obtained by physical examination or telephone conversations with referring veterinarians or owners. RESULTS: 75 dogs with soft-tissue sarcomas of the trunk and extremities were identified. Median age was 10.6 years. Malignant peripheral nerve sheath tumors were of a significantly lower grade than other tumors. Tumors recurred locally in 11 of 75 (15%) dogs. Evaluation for lack of tumor cells at surgical margins was prognostic for local recurrence. Metastatic disease developed in 13 of 75 (17%) dogs. Tumor mitotic rate was prognostic for development of metastasis. Twenty-five of 75 (33%) dogs died of tumor-related causes. Percentage of tumor necrosis and tumor mitotic rate were prognostic for survival time. Median survival time was 1,416 days. CLINICAL IMPLICATIONS: On the basis of a low local recurrence rate and high median survival time, wide excision of tumor margins or radical surgery appeared to be an effective means for managing soft-tissue sarcomas of the trunk and extremities. Analysis of histologic characteristics for prognosis supported use of preoperative biopsy. Surgical margins should be evaluated, and early use of aggressive surgery is indicated in the management of soft-tissue sarcomas in dogs.

Prognostic importance of alkaline phosphatase activity in serum from dogs with appendicular osteosarcoma: 75 cases (1990-1996).

OBJECTIVE: To determine whether alkaline phosphatase activity in dogs with appendicular osteosarcoma can be used as a prognostic indicator. DESIGN: Retrospective study. ANIMALS: 75 dogs with appendicular osteosarcoma. PROCEDURE: Serum total alkaline phosphatase (TALP) and bone-specific alkaline phosphatase (BALP) activities were determined from archival serum samples obtained at various times during treatment of appendicular osteosarcoma and follow-up evaluations. Associations among activities of TALP and BALP and survival and disease-free intervals, percentage of bone length involved with tumor, histologic subtype, and method of surgical treatment were evaluated. RESULTS: High activities of TALP and BALP before surgery were significantly associated with shorter survival and disease-free intervals in dogs undergoing surgery (amputation or limb-sparing procedure) and adjuvant chemotherapy. Activity of BALP significantly decreased in 29 dogs for which postoperative samples were available. Failure of BALP activity to decrease after surgery was correlated with shorter survival and disease-free intervals. CLINICAL IMPLICATIONS: Activities of TALP and BALP in serum are important prognostic factors for appendicular osteosarcoma in dogs. Prognostic factors may help clinicians initiate more aggressive treatment for dogs that are at higher risk of death or relapse.

Clinical outcome of dogs with grade-II mast cell tumors treated with surgery alone: 55 cases (1996-1999).

OBJECTIVE: To determine outcome for dogs with grade-II mast cell tumors treated with surgery alone. DESIGN: Retrospective study. ANIMALS: 55 dogs. PROCEDURES: Medical records were examined, and signalment; location and size of tumor; staging status; dates of local recurrence, metastasis, death, or last follow-up examination; status of surgical margins; previous surgery; postoperative complications; and cause of death were recorded. Follow-up information was obtained via reexamination or telephone conversations with owners or referring veterinarians. Univariate analysis was performed to identify prognostic factors. RESULTS: 60 tumors in 55 dogs were included. Median follow-up time was 540 days. Three (5%) mast cell tumors recurred locally; median time to local recurrence was 62 days. Six (11%) dogs developed another mast cell tumor at a different cutaneous location; median time to a different location was 240 days. Three (5%) dogs developed metastases; median time to metastasis was 158 days. Fourteen dogs died; 3 deaths were related to mast cell tumor, and 7 were unrelated. The relationship with mast cell tumor was not known for 4. Median survival times were 151, 841, and 827 days, respectively, for these 3 groups. Forty-six (84%) dogs were free of mast cell tumors during the study period. A reliable prognostic factor could not be identified. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that additional local treatment may not be required after complete excision of grade-II mast cell tumors and that most dogs do not require systemic treatment.

Treatment with a combination of doxorubicin, surgery, and radiation versus surgery and radiation alone for cats with vaccine-associated sarcomas: 25 cases (1995-2000).

OBJECTIVE: To compare use of doxorubicin, surgery, and radiation versus surgery and radiation alone for treatment of cats with vaccine-associated sarcoma. DESIGN: Retrospective study. ANIMALS: 25 cats with vaccine-associated sarcomas. PROCEDURE: Time to first recurrence and survival time were compared between the 2 treatment groups. The number of surgeries (1 or > 1) were compared with respect to time to first recurrence and survival time. RESULTS: Median time to first recurrence was 661 days for the group that received doxorubicin, surgery, and radiation. Median time to first recurrence has not yet been attained for the group treated with surgery and radiation alone. Median survival time was 674 days for the group treated with doxorubicin, surgery, and radiation and 842 days for the group treated with surgery and radiation alone. For time to first recurrence and survival time, significant differences were not detected between cats that had 1 surgery and those that had > 1 surgery. CONCLUSIONS AND CLINICAL RELEVANCE: Significant differences between the 2 treatment groups were not detected. The efficacy of doxorubicin in the treatment of vaccine-associated sarcomas is uncertain.

Spontaneous regression of osteosarcoma in four dogs.

Spontaneous regression of primary malignant bone tumors is rare but has been reported in the human literature. To the authors' knowledge, spontaneous regression of primary bone tumors in dogs or cats has not been reported. Osteosarcoma (OSA) is the most common primary bone tumor in humans, and it has been reported that the incidence of OSA is 40 to 50 times greater in dogs than humans. In this report, high-grade OSA was diagnosed in biopsy specimens obtained from 4 dogs that subsequently underwent spontaneous regression without tumor-specific treatment. Osteosarcoma in dogs has characteristics similar to that of OSA in humans.

Treatment of severe orthopedic infections.

Severe infections are uncommon following orthopedic surgery, yet they can be frustrating for the veterinarian and owner to treat and can result in devastating consequences for the patient. This article reviews the common causes for postoperative infection, reviews established treatment, and introduces newer methods for treatment and control. A thorough understanding of the pathogenesis, application of appropriate diagnostic procedures, the institution of aggressive treatment regimens, with adherence to established principles, will often result in satisfactory outcomes even with severe orthopedic infections. For those more refractory to treatment, the use of newer treatment methods, specifically locally implantable materials for sustained release of antimicrobials can improve success in the treatment of these more difficult cases.

Haemangiosarcoma of the urinary bladder in a dog.

Haemangiosarcoma of the urinary bladder is reported in a dog. The bladder mass was detected incidentally during physical examination. Partial cystectomy with unilateral ureteroneocystostomy were performed to remove the tumour en bloc. Necrosis of the urinary bladder was diagnosed 10 days postoperatively and the dog was euthanased.

Preoperative patient planning and margin evaluation.

Preoperative assessment of the cancer patient can be broken down into: (1) What is it? (2) Where is it? and (3) What is the status of the patient? Evaluation of local disease begins with obtaining and interpreting cytologic or histologic (biopsy) samples. Tumor staging involves the assessment of tumor invasion into local tissues, draining lymph nodes, and distant sites, especially the pulmonary parenchyma. Staging is performed with the aid of imaging techniques and special procedures such as lymph node and bone marrow aspiration. Because many veterinary cancer patients are geriatric, examination of physiologic patient status through laboratory and other diagnostic avenues is vital to the appropriate selection and success of therapy. After these questions are answered, appropriate treatment options and an ultimate treatment plan can be formulated. This article describes logical and practical approaches for diagnosis, staging, patient assessment, and treatment planning of the animal presented with tumor disease. With appropriate preoperative assessment, we can offer our patients and clients the best care possible.

Tumor biology and pathology.

The correct pathologic diagnosis of tumor type affecting the veterinary patient is of utmost importance to the veterinary surgical oncologist. The surgical oncologist may be presented with benign or malignant diseases, and an accurate pathologic diagnosis may be necessary to distinguish between the two conditions. In either case, assessment of surgical margins to determine completeness of surgical removal is necessary. In cases of malignancy, the pathologist should grade the tumor, if appropriate, and be able to perform specialized techniques, such as immunohistochemistry, if a diagnosis is in question. The surgical oncologist needs to understand the principles of tissue collection, fixation, and submission to help the pathologist provide an accurate diagnosis. Finally, the oncologic surgeon and surgical pathologist need to establish a cooperative working relationship and function as a team to discuss difficult cases. This will ensure the best treatment for the veterinary patient.

Principles of treatment for soft tissue sarcoma.

Soft tissue sarcomas (STS) are mesenchymal tumors arising from connective tissue elements and are grouped together based on a common biologic behavior. The most common histologic types include malignant peripheral nerve sheath tumors (schwannoma and neurofibrosarcoma) "hemangiopericytoma," fibrosarcoma, and malignant fibrous histiocytoma. These tumors are relatively slow growing yet locally invasive with a high rate of recurrence following conservative management. Appropriate preoperative planning and aggressive surgical resection often result in long-term remission or cure. Identification and evaluation of resection margins are paramount in appropriate case management. The addition of radiotherapy after surgical resection can aid in remission for incompletely resected masses. Systemic chemotherapy for STS should be considered for high-grade tumors with a moderate metastatic potential. Potential prognostic factors include grade, resection margins, size, location, histologic type, and previous treatment, with grade and margins being the most important. Tumor types classified as STS that differ slightly in their presentation or treatment, including synovial cell sarcoma, rhabdomyosarcoma, liposarcoma, and vaccine-associated STS in cats, are discussed. Soft tissue sarcomas can be a frustrating disease to treat, but adherence to solid surgical oncology principles can greatly increase the odds of good disease control.