Single-agent pamidronate for palliative therapy of canine appendicular osteosarcoma bone pain

BACKGROUND: Canine appendicular osteosarcoma (OSA) causes focal bone destruction, leading to chronic pain and reduced quality-of-life scores. Drugs that inhibit pathologic osteolysis might provide additional treatment options for managing cancer-induced bone pain. Aminobisphosphonates induce osteoclast apoptosis, thereby reducing pain associated with malignant osteolysis in human patients with cancer. HYPOTHESIS: Treatment of dogs with pamidronate administered intravenously will alleviate bone pain and reduce pathologic bone turnover associated with appendicular OSA in dogs. ANIMALS: Forty-three dogs with naturally occurring appendicular OSA administered pamidronate intravenously. METHODS: Prospective study. Therapeutic responses in dogs treated with pamidronate administered intravenously and nonsteroidal anti-inflammatory drugs (NSAID) were evaluated by using a numerical cumulative pain index score (CPIS), and by quantifying urine N-telopeptide (NTx) excretion and relative primary tumor bone mineral density (rBMD) assessed with dual energy x-ray absorptiometry. In addition, variables, including pamidronate dose, skeletal mass, baseline and change for CPIS, urine NTx and rBMD during treatment, and baseline tumor volume and radiographic pattern were compared between dogs clinically responsive and nonresponsive to pamidronate therapy. RESULTS: Twelve of 43 dogs (28%) had pain alleviation for >4 months, lasting a median of 231 days. Changes in CPIS and rBMD during treatment were statistically different between responders and nonresponders (P = .046 and .03, respectively). CONCLUSIONS AND CLINICAL IMPORTANCE: Substantiated by reductions in CPIS and increases in rBMD, single-agent pamidronate administered intravenously with NSAID therapy relieves pain and diminishes pathologic bone turnover associated with appendicular OSA in a subset of dogs.     

A comparison of two pamidronate dosing protocols on bone turnover in normal dogs and dogs with osteosarcoma

Introduction: Dogs with appendicular osteosarcoma (OSA) excrete higher concentrations of urine cross‐linked N‐telopeptide of type I collagen (NTx) than normal dogs. NTx is a specific biochemical marker of osteoclastic activity. Pamidronate is a bone‐modulating agent that exerts potent inhibitory effects on osteoclasts. The use of pamidronate is currently being evaluated for the management of osteolytic bone pain in dogs with appendicular osteosarcoma. Despite pamidronate's increasing usage in veterinary oncology, optimal dosing has yet to be determined. Commonly utilized dosages range from 1–2 mg/kg, given intravenously (IV) as a 2‐hour constant rate infusion every 28 days. The purpose of this prospective study was to compare the biological activity of two pamidronate doses (1 mg/kg vs. 2 mg/kg) in the suppression of urine NTx excretion in normal dogs and dogs with appendicular osteosarcoma. Methods: Seventeen OSA dogs receiving single‐agent pamidronate as palliative therapy were evaluated. Group 1A (n = 10) received a dose of 1 mg/kg and group 2A (n = 7) received a dose of 2 mg/kg IV. Urine NTx level were measured at day 0 and 28 using a commercial ELISA (Ostex International). Urine NTx level were also measured in 6 normal dogs: Group 1B (n = 3) received a dose of 1 mg/kg and group 2B (n = 3) received a dose of 2 mg/kg. In normal dogs, urine NTx levels were recorded weekly for six consecutive weeks. Results: In dogs with osteosarcoma, greater reductions in urine NTx excretion from baseline values were demonstrated at 2 mg/kg versus 1 mg/kg (57% and 23%, respectively). Likewise, in normal dogs, urine NTx excretion was suppressed to a greater extent with a dosage of 2 mg/kg versus 1 mg/kg (69% and 23%, respectively). Conclusion: Pamidronate possesses biologic activity in both normal dogs and in dogs with osteosarcoma, as assessed by reductions in urine NTx excretion. Based upon reductions in urine NTx excretion, a dosage of 2 mg/kg appears more effective than 1 mg/kg.     

Urine N-telopeptide excretion in dogs with appendicular osteosarcoma

Canine appendicular osteosarcoma (OSA) is a commonly diagnosed cancer that is capable of inducing pathologic bone remodeling. Investigating surrogate indices of bone metabolism may contribute to the diagnostic and therapeutic management of bone malignancies in companion animals. This study evaluated the excretion of N-terminal telopeptide (NTx), a marker of bone resorption that is detected in urine. Sixty-three dogs with appendicular OSA were compared with 29 age-matched healthy dogs. Dogs with appendicular OSA had significantly higher baseline urine NTx excretion than healthy controls (P < .0001). In 17 dogs with OSA treated with either amputation or standardized palliative therapies, significant reductions in urine NTx excretion were observed, suggesting that excessive bone resorption in dogs with OSA may be linked with focal skeletal osteolysis or its consequences. To identify any relationship between indicators of pathologic bone turnover, baseline urine NTx excretion was correlated with serum bone alkaline phosphatase (bALP) or radiographic tumor lengths at diagnosis. No significant correlations were identified between baseline urine NTx excretion and either bALP or tumor length. The findings from this study suggest that high urinary NTx excretion may support the diagnosis of focal skeletal osteolysis in dogs, and reductions in urine NTx excretion after treatment may reflect elimination or minimization of pathologic bone resorption.     

Monitoring response to aminobisphosphonate therapy in canine osteosarcoma using dual energy x‐ray absorptiometry (dexa)

Introduction: Palliative therapy is essential to improve the quality of life of dogs with osteosarcoma (OSA), when definitive therapy is not considered a valid option. Bisphosphonates, a novel class of antiosteoclastic drugs, are widely used in humans for several painful osteolytic conditions. Dual energy x‐ray absorptiometry (DEXA) is recognized as a reliable tool to measure bone mineral density (BMD), and to monitor treatment response to bisphosphonates in humans. A prospective evaluation of pamidronate, an injectable aminobisphosphonate, is ongoing in dogs with appendicular OSA. The potential value of DEXA for objective evaluation of BMD variations with palliative therapies is concurrently being assessed. Materials and Methods: Dogs with naturally occurring appendicular OSA treated with pamidronate constitute the patient population. A DEXA scan (QDR‐4500 W, Hologic, Bedford, MA) is performed on day 0 (baseline) and on every treatment day with pamidronate thereafter (every 28 days). For each dog, a whole body scan is performed, followed by a scan of the tumor, and contralateral normal bone. Three regions of interest are subsequently analyzed for BMD changes in tumor and normal bone. Statistical analysis was performed using Student t‐test and paired t‐tests, with significance being set at p < 0.05. Results: Nineteen dogs have been enrolled to date. Seven responders and 6 non‐responders have suitable data for analysis. A significant difference is observed (p = 0.04) between tumor BMD variations of responders and non‐responders at day 28 (mean variations +18.0% and ?4.6% respectively). The changes at day 28 are significant only in the responders (p = 0.038 vs p = 0.05 in non‐responders). When BMD of tumor and normal bone at day 84 is compared to day 0 in six responders, only tumor had a significant increase (p = 0.017 vs p = 0.279, respectively). Conclusions: Objective measurements of response to therapy are essential in pain palliation studies. Increased tumor bone BMD, as obtained by DEXA analysis, may correlate with subjective clinical improvement in pamidronate‐treated dogs with appendicular OSA.     

A comparison of five different bone resorption markers in osteosarcoma-bearing dogs, normal dogs, and dogs with orthopedic diseases

BACKGROUND: Various bone resorption markers in humans are useful for supporting the diagnosis of malignant skeletal pathology, with certain bone resorption markers appearing to be more discriminatory for detecting cancer-induced osteolysis than others. Canine osteosarcoma (OSA) is characterized by focal bone destruction, but a systematic investigation for determining which bone resorption marker best supports the diagnosis of OSA in dogs has not been reported. HYPOTHESIS: Dogs with OSA will have increased concentrations of bone resorption markers compared with healthy dogs and dogs with orthopedic disorders. Differences will exist among various bone resorption markers for their ability to support the diagnosis of malignant osteolysis in dogs with OSA. ANIMALS: Single time point, cross-sectional, cohort study including dogs with OSA (n = 20) or orthopedic disorders (n = 20) and healthy dogs (n = 22). METHODS: Basal concentrations of urine and serum N-telopeptide (NTx), urine and serum C-telopeptide (CTx), and urine deoxypyridinoline (DPD) were compared among all 3 groups. RESULTS: Compared with healthy dogs and dogs with orthopedic disorders, urine NTx, serum NTx, and serum CTx concentrations were significantly increased in dogs with OSA. For urine NTx and serum NTx, the calculated lower and upper 95% confidence limits in dogs with OSA did not overlap with dogs diagnosed with orthopedic disorders or healthy dogs. CONCLUSIONS AND CLINICAL IMPORTANCE: Of the markers evaluated in this study, urine NTx and serum NTx appear to be the most discriminatory resorption markers supporting the diagnosis of focal malignant osteolysis in dogs with OSA.     

The bone biologic effects of zoledronate in healthy dogs and dogs with malignant osteolysis

BACKGROUND: Malignant osteolysis is a process whereby cancer cells in concert with osteoclasts erode bone matrix. Aminobisphosphonates (NBPs) such as zoledronate induce osteoclast apoptosis and thereby decrease malignant skeletal destruction, severity of bone pain, and frequency of pathologic fracture. HYPOTHESIS: IV-administered zoledronate will reduce homeostatic bone turnover in healthy dogs and pathologic bone resorption in dogs diagnosed with primary and secondary bone tumors. ANIMALS: Six healthy dogs and 20 dogs with naturally occurring primary or metastatic bone tumors were administered zoledronate IV. METHODS: Prospective study: In all dogs, healthy (n = 6) and with malignant osteolysis (n = 20), the bone biologic effects of zoledronate were evaluated by quantifying changes in serum C-telopeptide (CTx) or urine N-telopeptide (NTx) concentrations or both. In dogs with osteosarcoma (OSA) (n = 10), serial changes in tumor relative bone mineral density (rBMD) assessed by dual-energy x-ray absorptiometry were used to characterize zoledronate's antiresorptive effects within the immediate tumor microenvironment. Additionally, the biochemical tolerability of zoledronate was assessed in 9 dogs receiving multiple (> or =2) consecutive treatments. RESULTS: All dogs had significant reductions in serum CTx or urine NTx concentrations or both after zoledronate administration. In a subset of dogs with appendicular OSA, reduced urine NTx concentrations and increased primary tumor rBMD coincided with improved limb usage as reported by pet owners in dogs treated with zoledronate and concurrent oral analgesics. Multiple zoledronate infusions were not associated with biochemical evidence of toxicosis. CONCLUSIONS AND CLINICAL IMPORTANCE: In dogs with skeletal neoplasms, IV-administered zoledronate exerts bone biologic effects, appears safe, and can provide pain relief.     

Evaluation of intravenous pamidronate administration in 33 cancer-bearing dogs with primary or secondary bone involvement

The purpose of this study was to evaluate the clinical safety of pamidronate when administered at a mean dosage of 1.0 mg/kg IV q28d in 33 tumor-bearing dogs. Biochemical tests of renal function were evaluated before each successive pamidronate treatment. Of 33 dogs treated with pamidronate, 1 dog had clinically relevant increases in serum creatinine and blood urea nitrogen concentrations. The biologic activity of IV pamidronate was assessed prospectively in 10 dogs with appendicular osteosarcoma and was assessed on reductions in urine N-telopeptide excretion (P = .042) and enhanced bone mineral density of the primary tumor measured with dual-energy x-ray absorptiometry (P = .024). Additionally, in these 10 dogs, pamidronate's therapeutic activity was supported by subjective improvement in pain control in 4 of the 10 dogs treated. IV pamidronate appears clinically safe in tumor-bearing dogs and may possess modest biologic activity for managing neoplastic complications associated with pathologic bone resorption.     

Retrospective analysis of axial skeleton osteosarcoma in 22 large-breed dogs

Medical-records of 22 large-breed dogs (>15 kg) with osteosarcoma (OSA) of the axial skeleton were reviewed to determine prevalence of metastasis and survival associated with this neoplasm. All dogs were treated with more than 1 mode of therapy including palliative radiation (n = 12), definitive radiation (n = 8), surgery (n = 7), chemotherapy (n = 12), or some combination of these therapies. Metastasis was documented in 10 of 22 dogs (46%), and the median survival for all dogs was 137 days. Primary cause of death was local tumor recurrence (54%). Breed (retriever versus purebred versus mixed-breed survival was 100, 182, and 264 days, respectively) and radiation therapy protocol (survival in dogs treated with palliative radiation therapy versus those treated with definitive radiation therapy was 79 and 265 days, respectively) were significantly related to survival (P < .05). Prevalence of metastasis and median survival for large-breed dogs with axial skeleton OSA seems to be similar to that reported for large-breed dogs with appendicular skeleton OSA. Definitive radiation therapy may have a role in the treatment of axial skeleton osteosarcoma.     

Investigating the in vitro interactive effects of ionizing radiation and pamidronate in a canine osteosarcoma cell line

Introduction: Dogs with osteosarcoma suffer intense bone pain. Conventional palliative treatment options include ionizing radiation with or without systemic chemotherapy. Intravenous pamidronate is a first‐line therapeutic agent in people with painful skeletal metastases and is currently being evaluated for the management of osteolytic pain associated with canine osteosarcoma. The theoretical combination of radiation and pamidronate for managing bone pain appears to be a rational treatment option, however, in vitro experiments demonstrating additive or supraadditve cytotoxic effects of these two modalities would further support the clinical institution of this novel combination therapy. The purpose of this study was to evaluate the in vitro cytotoxicity of ionizing radiation and pamidronate in a canine OSA cell line and to characterize the interaction between these two therapeutic modalities when used in combination. Methods: The canine osteosarcoma cell line, HMPOS, was subjected independently to varying doses of ionizing radiation (100 cGy, 300 cGy, 400 cGy, 600 cGy, 800 cGy, or 1000 cGy) or different concentrations of pamidronate (10, 25, 50, 66, 75, 100, 150, 200, and 250 μM). Cells were harvested following 48 hours of incubation and cell viability was assessed by flow cytometric analysis. Dose‐response curves were generated, and a theoretical ED₅₀ for each treatment modality calculated. An ED₅₀ isobologram was created to determine if different combinations of ionizing radiation and pamidronate (isoboles) would demonstrate subadditive, additive, or supraadditve cytotoxic effects. Results: The ED₅₀ of ionizing radiation and pamidronate were 614 cGy and 65.3 μM, respectively. Of the six different isobole combinations evaluated, three produced supraadditve effects, one produced a subadditive effect, and two produced additive effects. Conclusions: Both ionizing radiation and pamidronate independently exert in vitro cytotoxic effects. Positive interactive effects can be generated, but only with specific isobole combinations. The results from this in vitro study support the use of specific combinations of ionizing radiation and pamidronate in order to maximize the cytotoxic properties of both treatment modalities.     

Results of the Combined Treatment with Piroxicam and Carboplatin in Canine Oral Non‐Tonsillar Squamous Cell Carcinoma

Introduction:  Over‐expression of COX‐2 has been observed in several human and animal malignancies and is implicated in carcinogenesis through the conversion of arachidonic acid to PGE‐2. Use of platinum‐containing cytostatic agents and/or (non‐)specific COX‐2 inhibitors, has been reported as a treatment option for canine oral non‐tonsillar squamous cell carcinomas (ONT‐SCC). However, no study describes the effect of a combination of carboplatin and piroxicam on this tumor type.
Methods:  7 dogs with a T3 (WHO‐TNM) ONT‐SCC were treated with piroxicam and carboplatin. Five had bone involvement and no detectable metastasis. Two dogs without bone involvement had metastasis in the regional lymph nodes. Piroxicam was given orally 0.3 mg/kg s.i.d. Each dog was scheduled to receive between 6 and 12 carboplatin infusions (300 mg/m² i.v.) at 3 week intervals. Ondansetron and metoclopramide were used as anti‐emetic agents. The dogs are planned to receive piroxicam on a lifelong basis.
Results:  Complete response (CR) without adjuvant surgery was achieved in 4 of the 7 dogs. Two dogs needed adjuvant surgery to achieve CR. One dog had progressive disease and was euthanised 231 days after start of therapy. All the others were still alive and in CR at date of analysis. Median follow‐up was 335 days (107–689 days).
Conclusions:  Our study suggests that a combination of piroxicam and carboplatin is a useful treatment option for canine ONT‐SCC. All dogs tolerated therapy well and the 57% response rate for reaching a complete and durable remission without adjuvant surgery is promising.     

Outcome after repair of a sarcoma-related pathologic fracture in dogs: a Veterinary Society of Surgical Oncology Retrospective Study

Objective: To report outcome in dogs after internal fixation of a sarcoma‐related pathologic fracture of the appendicular skeleton. Study Design: Multi‐institutional case series. Animals: Dogs (n=16). Methods: Medical records of participating VSSO members were reviewed for dogs with pathologic fracture associated with a confirmed bone sarcoma of the appendicular skeleton repaired by external or internal fixation. Dogs were included if they had a histological diagnosis of osteosarcoma or sarcoma and excluded if they had radiation before fracture. Data collected were analyzed for signalment, fracture location, staging performed, method of fracture fixation, histopathology, adjunctive treatment and outcome. Results: Signalment and fracture location of 16 dogs that met the inclusion criteria was similar to dogs with appendicular OSA without fracture. One of 14 dogs had pulmonary metastasis and 3 of 5 dogs had bone metastasis. Bone plate or interlocking nail were used for repair in 12 dogs. Limb use immediately after surgery in 13 dogs was good (4), weight‐bearing but lame (7) and non‐weight bearing (2). Adjunctive therapy was administered in 5 dogs (chemotherapy, 3; radiation, 4; pamidronate, 3). Survival time ranged from 18 to 897 days; median survival was 166 days. Conclusions: Repair of pathologic fracture can result in palliation and prolonged survival.     

Hypotonic water as adjuvant therapy for incompletely resected canine mast cell tumors: a randomized, double-blind, placebo-controlled study

Objective— To evaluate efficacy of hypotonic water as adjuvant therapy after marginal resection of canine mast cell tumors (MCT).
Study Design— Double-blinded, placebo-controlled, prospective, randomized study.
Animals— Dogs (n=30) with spontaneous, cutaneous, solitary MCT.
Methods— The wound bed of MCT, resected with margins <0.5 cm, was injected with either hypotonic or isotonic water according to a standardized protocol. Follow-up was obtained by clinical examination at 1, 2, 3, 6, and 12 months and annual telephone contact with the owner.
Results— Eighteen dogs were treated with isotonic lactated Ringer's solution and 12 dogs with hypotonic distilled water. All MCT were stage 0 tumors and most grade II. Six tumors (4 isotonic, 2 hypotonic) recurred locally, 3 of these dogs died from disease-related reasons within 4 months. The surviving 3 dogs were alive with a median survival time (ST) of 1092 days. The calculated 2-year recurrence-free rate was 92.7%; the 2-year disease-free rate 79.1%; and the 2-year survival rate 89.5%. No significant differences in local recurrence and ST were observed between treatment groups. Histologic grading was the only significant prognosticator for ST and recurrence-free periods.
Conclusion— No significant differences in local recurrence and ST were observed between adjunctive hypotonic water and placebo treatment after marginal resection of solitary MCT.
Clinical Relevance— Hypotonic water does not decrease the rate of local recurrence in dogs with solitary MCT after marginal surgical excision.     

Surgical decompression,with or without adjunctive therapy,for palliative treatment of primary vertebral osteosarcoma in dogs

Vertebral osteosarcoma (OSA) is the most common primary vertebral tumor in dogs, however studies examining the survival time after surgical decompression of these tumors are limited. There is also limited information regarding the benefit of adjunctive treatments such as radiation therapy or chemotherapy in these patients. The goal of this study was to determine survival time of dogs with primary vertebral OSA after palliative decompressive surgery alone and combined with radiation therapy and/or chemotherapy. Records from 22 client‐owned dogs diagnosed with primary vertebral OSA and treated with decompressive surgery were collected retrospectively from eight referral institutions. Survival time was assessed for dogs treated with surgery alone as well as dogs who received adjunctive radiation therapy and/or chemotherapy. Median survival time in the 12 dogs treated with surgery alone was 42 days (range: 3‐1333 days). The three dogs treated with surgery and chemotherapy had a median survival time of 82 days (range: 56‐305 days). Only one dog was treated with surgery and radiation therapy; this dog survived 101 days. Six dogs were treated with surgery, radiation therapy and chemotherapy; these dogs had a median survival time of 261 days (range: 223‐653 days). Cause of death in all cases that survived the initial postoperative period was euthanasia secondary to confirmed or suspected tumor regrowth. The results of this study suggest that definitive radiation therapy, possibly combined with concurrent chemotherapy, significantly improves survival in dogs treated with palliative decompressive surgery for vertebral OSA and should be the treatment of choice in selected cases.     

Percutaneous Cementoplasty in the Palliative, Multimodal Treatment of Primary Bone Tumors of the Distal Aspect of the Radius in Four Dogs

Objective— To (1) evaluate the analgesic effect of percutaneous cementoplasty (PC) in dogs with primary bone tumor (PBT) of the distal aspect of the radius and (2) evaluate the impact on the course of disease by adding PC to a palliative, multimodal treatment protocol in these dogs.
Study Design— Prospective pilot study.
Animals— Dogs (n=4) with PBT of the distal aspect of the radius.
Methods— Tumor lesions were filled percutaneously with polymethylmethacrylate under fluoroscopic guidance. Pamidronate was administered once in a week before PC. Radiotherapy and chemotherapy were initiated 2 and 6 weeks after PC, respectively. Force plate analysis was performed immediately before 2, and 6 weeks after PC. Survival time was defined from PC to euthanasia.
Results— Two dogs had a significant increase in peak vertical force 2 weeks after PC ( P =.043) and remained free of lameness for 18 and 20 weeks, respectively. One dog had an acute relapse after an initially lame-free period of 10 days. The remaining dog failed to improve ( P =.686). Three dogs developed at least 2 complications including transient worsening of the lameness after PC, cement leakage, wound infection and suspected thromboembolism in combination with cough and anemia. Median survival was 4.8 months (range, 1–5.7 months).
Conclusions— PC in combination with pamidronate significantly improved lameness in 2 dogs; however, PC is not risk-free. Deep wound infection, intraarticular cement leakage, and venous thrombosis were the main complications.
Clinical Relevance— PC might be a useful addition to established palliative, multimodal treatment protocols in dogs with PBT; however, because of the complications encountered PC warrants further study before routine use can be considered.     

Transverse ulnar bone transport osteogenesis: a new technique for limb salvage for the treatment of distal radial osteosarcoma in dogs

Objective— To develop instrumentation and a technique for transverse ulnar bone transport osteogenesis in dogs.
Study Design— Cadaveric study and in vivo validation (1 dog).
Sample Population— Paired cadaveric antebrachii (n=10 dogs) and 1 live dog.
Methods— Circular fixator constructs were applied and fitted with reeling or linear motors designed to transport an ulnar segment transversely into a defect created by excising the distal 50% of the ipsilateral radius. A longitudinal osteotomy of the adjacent ulna was created and the segment was transported across the radial defect. Pre- and post-distraction CT scans were used to compare the efficacy of each construct. The procedure was performed unilaterally in a live dog using the reeling motor (RM) construct.
Results— Both constructs effectively transported the ulnar segment into the defect. Subjectively, the RMs were easier to apply and operate. No significant differences were observed in the objective measures of efficacy between the 2 construct types. The live dog produced viable regenerate bone after transverse ulnar bone transport.
Conclusions— Transverse ulnar bone transport should be considered a potential method for limb salvage in dogs with osteosarcoma (OSA) of the distal radius. The RMs were effective and clinically applicable.
Clinical Relevance— Transverse ulnar bone transport osteogenesis affords the benefits of longitudinal radial bone transport osteogenesis, allowing resolution of large longitudinal radial defects in a substantially less time as a result of shortening the transport distance. This would be beneficial when treating conditions such as OSA where minimizing convalescence and maximizing quality of life is a priority.     

Adjuvant carboplatin and gemcitabine combination chemotherapy postamputation in canine appendicular osteosarcoma

Background: Appendicular osteosarcoma (OSA), the most common bone tumor in dogs, is typically treated by amputation and adjuvant chemotherapy. Despite numerous efforts, the median survival time (MST) for dogs receiving a platinum compound, doxorubicin, or a combination of these remains at 8–12 months. Evidence from studies in mice suggests that gemcitabine has activity against OSA in vivo. Our preliminary work demonstrated that the addition of low‐dosage (10 mM) gemcitabine to carboplatin resulted in synergistic inhibition of OSA cell viability in vitro. Objective: The purpose of the following study was to determine whether the addition of low‐dosage (2 mg/kg) gemcitabine to carboplatin chemotherapy in dogs with OSA after amputation would improve MST over carboplatin monotherapy. Animals: Fifty dogs with histologically confirmed appendicular OSA. Methods: Dogs were treated prospectively with amputation and up to 4 dosages of carboplatin and gemcitabine in combination every 3 weeks. Results: The chemotherapeutic regimen was well tolerated with only 5 episodes of grade 3 or 4 hematologic toxicity. The median disease‐free interval (DFI) was 203 days and the MST was 279 for all dogs in this study. The 1‐ and 2‐year survival rates were 29.5 and 11.3%, respectively. Dogs with proximal humeral OSA had a shorter median DFI (P= .04) compared with dogs with OSA in other locations. Conclusions and Clinical Importance: These results are comparable to those reported for carboplatin monotherapy indicating that the addition of gemcitabine to carboplatin in dogs with appendicular OSA does not appear to improve outcome.     

Retropective Evaluation of Survival Time of Dogs with Stage III Osteosarcoma that Undergo Treatment

Introduction:  Stage III osteosarcoma generally carries a grave prognosis. Despite this, some owners elect to treat using palliative or curative intent protocols. The purpose of this study was to determine the survival times for dogs with stage III osteosarcoma that undergo treatment and to evaluate the variables that affect survival time.
Methods:  Retrospective study using the CSU Animal Cancer Center osteosarcoma data base. Search criteria included dogs diagnosed with osteosarcoma 1985–2004 with metastasis at the time of presentation. Dogs were excluded if they were euthanized at the time of diagnosis (13 dogs) or lost to follow‐up (10 dogs). There were 90 cases for analysis. The survival times were compared based on the primary tumor site, site of metastasis, treatment given, age, sex and breed.
Results:  Survival times in days ranged from 0 to 1583 days. The overall median survival time was 76 days. The one‐year, two‐year and three‐year percent survival were 7%, 4.7% and 3.5%, respectively. Treatment included various combinations of chemotherapy, surgery, radiation therapy, bisphosphonates and NSAIDs. Findings included an increased survival time with surgery and adjuvant therapy compared with surgery alone and a decreased survival time with metastasis to the lung or lymph node.
Conclusions:  Treatment of dogs with stage III osteosarcoma can result in variable survival times. Multimodality therapy appears to result in longer survival times. Metastasis to the lung or lymph node correlated with a decreased survival time.     

Differentiating effect of pamidronate on canine osteo‐sarcoma cell lines in vitro

Introduction: Pamidronate has been traditionally used to manage pathologic osteoclastic disorders. In addition to its effects on osteoclasts, pamidronate has also been demonstrated to promote phenotypic maturation and inhibition of proliferation in osteoblasts. Canine osteosarcoma (OSA) consists of malignant, undifferentiated osteoblasts. The objective of this study was to determine if micromolar concentrations of pamidronate could induce malignant osteoblastic differentiation as evaluated by an increase in alkaline phosphatase (ALP) activity and/or osteocalcin (OC) production, two specific markers of normal osteoblastic activity. Methods: Two canine OSA cell lines (HMPOS and COS 31) were used for all experiments. Cells were incubated for 48 or 72 hours with various pamidronate concentrations (0, 0.1, 1, 5, 10, and 20 μM). After incubation, the supernatants were sampled and the relative amounts of viable cells were determined with a cell proliferation assay (Cell Titer 96^® AQ_uous, Promega). An ALP detection kit (Starbright^®, Sigma^®) was used to measure the ALP activity and an ELISA (Osteocalcin EIA kit, Biomedical Technologies) was used to determine the concentration of osteocalcin in the supernatants. The ALP and osteocalcin values were corrected for the amount of viable cells. Results: Pamidronate induced a dose‐dependent reduction in the number of viable COS 31 and HMPOS cells at both 48 and 72 hours. A dose‐dependent elevation in ALP activity from baseline was observed. At 20 μM, a 2.3‐fold increase was observed for HMPOS at 72 hours, while a 1.43‐fold increase was observed for COS 31 at 72 hours. Very low level (less than 2 ng/ml) of osteocalcin pre‐ and post‐pamidronate treatment was detected for both COS 31 and HMPOS. Conclusion: The data suggests that pamidronate increases alkaline phosphatase activity in canine OSA cells in a dose‐dependent manner. However, cytotoxic assays are needed in order to accurately characterize any concurrent decrease in the number of viable cells. The potential differentiating effect of pamidronate on malignant osteoblasts provides an additional argument for its use in the palliative treatment of OSA.