Tumor-localized interleukin-2 and interleukin-12 combine with radiation therapy to safely potentiate regression of advanced malignant melanoma in pet dogs.

PURPOSE: Interleukin-2 and -12 cytokines have potent anti-cancer activity, but suffer a narrow therapeutic window due to off-tumor immune cell activation. Engineering cytokines with the ability to bind and associate with tumor collagen after intratumoral injection potentiated response without toxicity in mice, and was previously safe in pet dogs with sarcoma. Here we sought to test the efficacy of this approach with in dogs with advanced melanoma. EXPERIMENTAL DESIGN: This study examined fifteen client-owned dogs with histologically- or cytologically-confirmed malignant melanoma who received a single 9 Gray fraction of radiation therapy, followed by six cycles of combined collagen-anchored IL-2 and IL-12 therapy Q2W. Cytokine dosing followed a 3+3 dose escalation design, with the initial cytokine dose chosen from prior evaluation in canine sarcomas. No exclusion criteria for tumor stage or metastatic burden, age, weight, or neuter status were applied for this trial. RESULTS: Median survival regardless of tumor stage or dose level was 256 days and 10/13 (76.9%) dogs that completed treatment had CT-measured tumor regression at the treated lesion. In dogs with metastatic disease, 8/13 (61.5%) dogs had partial responses across their combined lesions, evidence of locoregional response. Profiling by Nanostring of treatment-resistant dogs revealed that B2m loss was predictive of poor response to this therapy. CONCLUSIONS: Collectively, these results confirm the ability of locally administered tumor-anchored cytokines to potentiate responses at regional disease sites when combined with radiation. This evidence supports the clinical translation of this approach and highlights the utility of comparative investigation in canine cancers.

Targeting glioblastoma tumor hyaluronan to enhance therapeutic interventions that regulate metabolic cell properties.

Despite extensive advances in cancer research, glioblastoma (GBM) still remains a very locally invasive and thus challenging tumor to treat, with a poor median survival. Tumor cells remodel their microenvironment and utilize extracellular matrix to promote invasion and therapeutic resistance. We aim here to determine how GBM cells exploit hyaluronan (HA) to maintain proliferation using ligand-receptor dependent and ligand-receptor independent signaling. We use tissue engineering approaches to recreate the three-dimensional tumor microenvironment in vitro, then analyze shifts in metabolism, hyaluronan secretion, HA molecular weight distribution, as well as hyaluronan synthetic enzymes (HAS) and hyaluronidases (HYAL) activity in an array of patient derived xenograft GBM cells. We reveal that endogenous HA plays a role in mitochondrial respiration and cell proliferation in a tumor subtype dependent manner. We propose a tumor specific combination treatment of HYAL and HAS inhibitors to disrupt the HA stabilizing role in GBM cells. Taken together, these data shed light on the dual metabolic and ligand - dependent signaling roles of hyaluronan in glioblastoma. Significance: The control of aberrant hyaluronan metabolism in the tumor microenvironment can improve the efficacy of current treatments. Bioengineered preclinical models demonstrate potential to predict, stratify and accelerate the development of cancer treatments.

Canine thyroid carcinomas: A review with emphasis on comparing the compact subtype of follicular thyroid carcinomas and medullary thyroid carcinomas.

Canine thyroid carcinomas are relatively common malignant endocrine neoplasms in dogs derived from either thyroid follicular cells (forming follicular thyroid carcinomas) or medullary cells (parafollicular, C-cells; forming medullary thyroid carcinomas). Older and recent clinical studies often fail to discriminate between compact cellular (solid) follicular thyroid carcinomas and medullary thyroid carcinomas, which may skew conclusions. The compact subtype of follicular thyroid carcinomas appears to be the least differentiated subtype of follicular thyroid carcinomas and needs to be differentiated from medullary thyroid carcinomas. This review includes information on the signalment, presentation, etiopathogenesis, classification, histologic and immunohistochemical diagnosis, clinical management, and biochemical and genetic derangements of canine follicular and medullary carcinomas, and their correlates with human medicine.

Phase I evaluation of CycloSam® (Sm-153-DOTMP) bone seeking radiopharmaceutical in dogs with spontaneous appendicular osteosarcoma.

153 Sm-DOTMP (CycloSam® ) is a newly-patented radiopharmaceutical for bone tumor treatment. DOTMP (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylene-phosphonate) is a macrocyclic chelating agent with superior binding properties to 153 Sm when compared with EDTMP (Quadramet™, used for palliative treatment of bone cancer). CycloSam® was administered at 1 mCi/kg (37 MBq/kg) in a prospective pilot study to seven dogs with bone cancer resulting in no myelosuppression. Then, 13 dogs were enrolled in a prospective clinical trial study using traditional 3+3 dose escalation and starting at 1.5 mCi/kg. Baseline evaluation included hematologic and biochemical testing, diagnosis confirmation, thoracic and limb radiographs, technetium-99 m-HDP bone scintigraphy, and 18 F-FDG PET scan (SUVmax). Toxicity (primary endpoint) was assessed through weekly blood counts and adverse events. Dogs received 1.5 mCi/kg (n = 4), 1.75 mCi/kg (n = 6), and 2 mCi/kg (n = 3) of 153 Sm-DOTMP. Dose-limiting neutropenia and thrombocytopenia were seen at 2 mCi/kg. No dose-limiting nonhematologic toxicities occurred. Efficacy (secondary endpoint) was assessed by objective lameness measurement (body-mounted inertial sensors), owner quality-of-life (QoL) questionnaire, and repeat PET scan. Objective lameness measurement improved in four dogs (53%-60% decrease) was equivocal in three dogs, and worsened in four dogs (66%-115% increase); two dogs were not evaluable. Repeat 18 F-FDG PET scan results varied and change in lameness did not consistently correlate with SUVmax changes. QoL score worsened (n = 5) or was improved/stable (n = 7). Carboplatin chemotherapy (300 mg/m2 IV every 3 weeks ×4) started 4 weeks after 153 Sm-DOTMP injection. No dog died of chemotherapy-related complications. All dogs completed study monitoring. The recommended dose for CycloSam® in dogs is 1.75 mCi/kg, which resulted in some pain control with minimal toxicity and was safely combined with chemotherapy.

Combining radiation therapy with zoledronate for the treatment of osteo-invasive feline oral squamous cell carcinoma.

Feline oral squamous cell carcinoma (FOSCC) is the most common oral tumour diagnosed in pet cats and carries a poor prognosis with <10% one-year survival despite multi-modal therapies. Tumours of the mandible or maxilla are frequently osteo-invasive and pain can result from osteolysis. Zoledronate is a bisphosphonate that inhibits osteoclasts and reduces bone resorption. Radiation therapy (RT) is used to treat FOSCC due to anti-cancer activity and ability to improve quality of life. We hypothesized RT can be safely combined with zoledronate, and that this combinatory therapy would be efficacious, well tolerated, and result in decreased bone resorption in cats with FOSCC. SCCF1 cell line was treated with zoledronate before, concurrently, or after RT, and clonogenic assays were performed to determine if an optimal dosing schedule would be identified. Nine cats with osteoinvasive FOSCC were recruited for treatment with 4 weekly doses of 8 Gy RT combined with zoledronate administered at the first and fourth treatments. Serial CT scans were performed to assess tumour response. Safety and tolerability were monitored with hematologic and biochemical parameters, and acute radiation effects were characterized. Serum c-telopeptide (CTx) and relative bone mineral density (rBMD) by dual -energy X-ray absorptiometry (DEXA) quantified bone resorption. In vitro studies showed no clear benefit to timing of zoledronate with RT, therefore all zoledronate was administered concurrently with RT in FOSCC patients. Based on tumour volume, 4/9 (44.4%) cats achieved partial remission, 4/9 (44.4%) stable disease and 1/9 (11.1%) had progressive disease. The combinatory therapy was well-tolerated based on biochemical measurements, and all patients experienced decreased serum CTx. Combining RT with zoledronate in tumour-bearing cats is safe, well-tolerated, results in a partial remission rate of up to 44%, and decreases serum CTx, a marker of bone resorption.

Utilizing feline oral squamous cell carcinoma patients to develop NQO1-targeted therapy.

Developing effective therapies for the treatment of advanced head-and-neck squamous cell carcinoma (HNSCC) remains a major challenge, and there is a limited landscape of effective targeted therapies on the horizon. NAD(P)H:quinone oxidoreductase 1 (NQO1) is a 2-electron reductase that is overexpressed in HNSCC and presents as a promising target for the treatment of HNSCC. Current NQO1-targeted drugs are hindered by their poor oxidative tolerability in human patients, underscoring a need for better preclinical screening for oxidative toxicities for NQO1-bioactivated small molecules. Herein, we describe our work to include felines and feline oral squamous cell carcinoma (FOSCC) patients in the preclinical assessment process to prioritize lead compounds with increased tolerability and efficacy prior to full human translation. Specifically, our data demonstrate that IB-DNQ, an NQO1-targeted small molecule, is well-tolerated in FOSCC patients and shows promising initial efficacy against FOSCC tumors in proof-of-concept single agent and radiotherapy combination cohorts. Furthermore, FOSCC tumors are amenable to evaluating a variety of target-inducible couplet hypotheses, evidenced herein with modulation of NQO1 levels with palliative radiotherapy. The use of felines and their naturally-occurring tumors provide an intriguing, often underutilized tool for preclinical drug development for NQO1-targeted approaches and has broader applications for the evaluation of other anticancer strategies.

Cytotoxicity of Cultured Canine Primary Hepatocytes Exposed to Itraconazole Is Decreased by Pre-treatment With Glutathione.

Objective: To identify the effect of glutathione (GSH) on cell survival in a novel in vitro model of itraconazole (ITZ)-associated hepatotoxicity using canine primary hepatocytes. Sample: Commercially sourced, cryopreserved male dog (Beagle) primary hepatocytes from a single donor. Procedures: Using a sandwich culture technique, canine primary hepatocytes were exposed to serial dilutions of ITZ. Calcein AM, 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), and neutral red were investigated as potential cell viability assays. Hepatocytes were then pre-incubated with GSH, exposed to serial dilutions of ITZ, and cell viability determined at 4 and 24 h post-ITZ exposure. Each condition was performed in technical triplicate and the effect of time, GSH concentration, and ITZ concentration on % cytotoxicity assessed using a multivariate linear regression model. Tukey's post-hoc test was used to detect individual differences. Results: The neutral red cell cytotoxicity assay was chosen based on its superior ability to detect dose-dependent changes in viability. Hepatocyte cytotoxicity significantly increased with ITZ concentration (P < 0.001) and time (P = 0.004) and significantly decreased with GSH treatment (P < 0.001). Conclusions and Clinical Relevance: This in vitro model demonstrates dose- and time-dependent ITZ-induced cytotoxicity, which is similar to clinical changes observed in canine patients and in in vivo rodent studies. Pre-treating with GSH is protective against in vitro cell death. These results suggest that GSH precursors may have a role in the management or prevention of ITZ-associated hepatotoxicity in dogs. Clinical trials are needed to evaluate their utility for this adverse drug reaction.

Medulloblastoma in a 6 Year Old Mixed Breed Dog: Surgical Debulking and Chemotherapy.

A medulloblastoma was surgically debulked from a 6 year old American Staffordshire Terrier, who then received a modified lomustine (CCNU), vincristine, procarbazine, and prednisolone (LOPP) protocol. The dog improved significantly and continued to do well until deterioration and euthanasia 5 months following surgery. This is the first known published case report of surgical cytoreductive surgery of a medulloblastoma in a dog with documented response to surgery and chemotherapy. Medulloblastoma is a primitive neuroectodermal tumor that is the most common malignant central nervous system (CNS) tumor in children, though it is less common in adults. This case illustrates the value of considering human literature when creating treatment plans for uncommon brain tumors in veterinary patients. Medulloblastoma should be a differential for cerebellar tumors in young to middle aged dogs, and surgery and chemotherapy should be considered.

A comparison of risk factors for metastasis at diagnosis in humans and dogs with osteosarcoma.

BACKGROUND: Canine osteosarcoma (OS) is a relevant spontaneous model for human OS. Identifying similarities in clinical characteristics associated with metastasis at diagnosis in both species may substantiate research aimed at using canine OS as a model for identifying mechanisms driving distant spread in the human disease. METHODS: This retrospective study included dog OS cases from three academic veterinary hospitals and human OS cases from the Surveillance, Epidemiology, and End Results program. Associations between clinical factors and metastasis at diagnosis were estimated using logistic regression models. RESULTS: In humans, those with trunk tumors had higher odds of metastasis at diagnosis compared to those with lower limb tumors (OR = 2.38, 95% CI: 1.51, 3.69). A similar observation was seen in dogs with trunk tumors compared to dogs with forelimb tumors (OR = 3.28, 95% CI 1.36, 7.50). Other associations were observed in humans but not in dogs. Humans aged 20-29 years had lower odds of metastasis at diagnosis compared to those aged 10-14 years (OR = 0.67, 95% CI: 0.47, 0.96); every 1-cm increase in tumor size was associated with a 6% increase in the odds of metastasis at diagnosis (95% CI: 1.04, 1.08); compared to those with a white, non-Hispanic race, higher odds were observed among those with a black, non-Hispanic race (OR: 1.51, 95% CI: 1.04, 2.16), and those with a Hispanic origin (OR 1.35, 95% CI: 1.00, 1.81). CONCLUSION: A common mechanism may be driving trunk tumors to progress to detectable metastasis prior to diagnosis in both species.

Osteochondrodysplasia in a Scottish Fold Cat Treated with Radiation Therapy and Samarium-153-1,4,7,10-Tetraazacyclododecane-1,4,7,10-Tetramethylene-Phosphonic Acid.

Osteochondrodysplasia is a painful, progressive clinical syndrome unique to Scottish fold cats because of a heritable missense mutation in the TRPV4 gene. An 8 yr old male neutered Scottish fold cat was presented for a mass on his hind paw. The mass caused decreased mobility in the metatarsal region and digits and resulted in significant discomfort. Because of extensive skeletal abnormalities attributed to breed-related osteochondrodysplasia, the owner was reluctant to pursue amputation. Radiation therapy was pursued for palliation of pain. After coarsely fractionated external beam radiotherapy resulted in stabilization of the mass with eventual progression after 14 mo, samarium-153-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylene phosphonic acid was administered systemically, and the cat showed immediate, whole-body improvement in mobility. Concurrent intestinal and respiratory disease was evaluated and managed. Samarium-153-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylene phosphonic acid administration was repeated approximately every 6 mo for three treatments until the cat succumbed to thromboembolic disease attributed to previously diagnosed cardiac disease. Radiation therapy administered using either external beam or bone-seeking radioisotopes can be effective at palliating clinical signs associated with the skeletal abnormalities that accompany this disease.

Evaluation of intravenous and subcutaneous administration of a novel, excipient-free, nanoparticulate formulation of paclitaxel in dogs with spontaneously occurring neoplasia.

Carriers used to solubilize taxane chemotherapy drugs cause severe hypersensitivity. Nanoparticle formulations can provide improved dissolution and bioavailability of taxanes. Thus, a nanoparticulate, excipient-free formulation of paclitaxel (CTI52010) was evaluated in tumour-bearing dogs with intravenous and subcutaneous delivery. Tumour-bearing dogs were treated with intravenous CTI52010 using a modified rapid dose escalation scheme. Subcutaneous administration was then planned for a small cohort of dogs for comparison. For both groups, serial blood samples were collected after first dosing for pharmacokinetic analysis by LCMSMS. Tumour response was measured using RECIST criteria. Toxicity was recorded using VCOG-CTCAEv1.1. Fifteen dogs were treated with intravenous delivery at increasing dosages (80-136 mg/m2 ), with one objective response in the urethral component of a prostatic carcinoma (probable transitional cell carcinoma) and four dogs with durable stable disease (two carcinomas, two sarcomas). Pharmacokinetic data indicate a rapid initial clearing of the drug from serum followed by an extended elimination half-life, similar to normal dogs and suggesting reticuloendothelial clearance. Parameters and toxicity were highly variable and a maximally tolerated dosage could not be reliably confirmed. Three dogs were treated with subcutaneous delivery and no drug was detected in circulation, resulting in termination of the study. This novel formulation of paclitaxel is well tolerated in dogs and no unique toxicity or hypersensitivity was noted. The preliminary responses suggest biologic activity. The lack of systemic absorption after subcutaneous administration suggests a possible role for intratumoural anticancer therapy.

The effect of diet on serum 25-hydroxyvitamin D concentrations in dogs.

BACKGROUND: Vitamin D (vitD) deficiency is linked to many disease states including rickets and cancer, and vitD supplementation to improve response to cancer therapy has been explored. Supplementation may be most appropriate for dogs with suboptimal vitD concentrations. In dogs, the primary source of vitD is diet (predominantly via commercial dog food). Our goal was to determine how food source and supplements affect 25(OH)D concentrations, the storage form of vitD. Serum was collected from clinically healthy dogs, and pet owners were surveyed about food source and supplements. Serum 25(OH)D concentration was measured using a quantitative chemiluminescent assay (LIASON, DiaSorin, Stillwater, MN). RESULTS: Dogs (n = 320) were tested for serum 25(OH)D concentrations (range 9.5-249.2 ng/mL). Dogs were fed commercial diets from forty different manufactures (n = 292); additionally some dogs were fed homemade diets (n = 18) or a combination of commercial and homemade diets (n = 10). Median serum 25(OH)D concentrations in dogs fed commercial foods ranged from 47.4 to 100.1 ng/mL with an overall median of 67.9 ng/ml (CV 29%). Analysis for differences among manufacturers was significant (P = 0.0006). Serum 25(OH)D concentrations amongst dogs fed homemade diets had the largest range (9.5-129 ng/mL) and the lowest value (9.5 ng/mL). Dogs receiving salmon oil as a supplement (n = 22) had significantly higher serum 25(OH)D (on average a 19.6 ng/mL increase) than those not receiving a supplement (P = 0.007). CONCLUSIONS: Serum 25(OH)D concentrations in dogs vary widely which likely reflects varying dietary vitD content. Notable differences exist among manufacturers and brands and may reflect differences in proprietary formulations. Given the variability of measured serum 25(OH)D concentrations in dogs and the importance vitD appears to have on health status, dietary vitD content should be optimized.

Gum arabic-coated radioactive gold nanoparticles cause no short-term local or systemic toxicity in the clinically relevant canine model of prostate cancer.

INTRODUCTION: Gum arabic-coated radioactive gold nanoparticles (GA-(198)AuNPs) offer several advantages over traditional brachytherapy in the treatment of prostate cancer, including homogenous dose distribution and higher dose-rate irradiation. Our objective was to determine the short-term safety profile of GA-(198)AuNPs injected intralesionally. We proposed that a single treatment of GA-(198)AuNPs would be safe with minimal-to-no evidence of systemic or local toxicity. METHODS: Nine dogs with spontaneously occurring prostatic cancer were treated. Injections were performed with ultrasound or computerized tomography guidance. Complete blood counts, chemistry panels, and urinalyses were performed at weekly intervals for 1 month and imaging was repeated 4 weeks postinjection. Planar scintigraphic images were obtained within 30 minutes of injection. RESULTS: No statistically significant difference was found in any hematologic or biochemical parameter studied, nor was any evidence of tumor swelling or abscessation found in eight dogs with repeat imaging; one dog died secondary to urethral obstruction 12 days following injection. At 30 minutes postinjection, an average of 53% of injected dose in seven dogs was retained in the prostate, with loss of remaining activity in the bladder and urethra; no systemic uptake was detected. CONCLUSION: GA-(198)AuNP therapy had no short-term toxicity in the treatment of prostatic cancer. While therapeutic agent was found in the prostate immediately following injection, some loss of agent was detected in the bladder and urethra. Localization of radioactivity within the prostate was lower than anticipated and likely due to normal vestigial prostatic ducts. Therefore, further study of retention, dosimetry, long-term toxicity, and efficacy of this treatment is warranted prior to Phase I trials in men.

Nanoparticulate paclitaxel demonstrates antitumor activity in PC3 and Ace-1 aggressive prostate cancer cell lines.

BACKGROUND: Paclitaxel is an effective antimitotic agent in cancer treatment; however, one of its most common toxicities is hypersensitivity due to excipients used for water solubility. Nanoparticulate paclitaxel (Crititax®, CTI52010) is paclitaxel that consists only of nanoparticulate drug in saline. Our objective was to examine the effect of nanoparticulate paclitaxel on prostate cancer cells derived from castration-resistant prostate cancer in men and dogs, as companion dogs represent a unique naturally occurring model of castration-resistant prostate cancer. We hypothesized that nanoparticulate paclitaxel would be effective in affecting cell viability, colony forming ability, apoptosis, and induction of structural changes to the microtubules of prostate cancer cells. METHODS: Human PC3 and canine Ace-1 cells were treated with 0.001-1.0 µm concentrations of paclitaxel and nanoparticulate paclitaxel. Cell viability, apoptosis, and colony forming assays were analyzed and compared in the presence of both drugs. Microtubule structure was examined by fluorescence microscopy following incubation with drug. RESULTS: Nanoparticulate paclitaxel was as effective as standard paclitaxel in decreasing cell viability, decreasing colony forming ability, and inducing apoptosis in human and canine prostate cancer cells in a dose-dependent manner. Fluorescence microscopy confirmed the microtubule target of nanoparticulate paclitaxel. CONCLUSIONS: Nanoparticulate paclitaxel is as effective as paclitaxel in decreasing cell viability, initiating apoptosis, decreasing cell survival, and causing rigidity of microtubules in both human and canine castration-resistant prostate cancer. This represents an attractive area for further study, using the companion dog as a model for disease in men.

Evaluation of fixation time using Diff-Quik for staining of canine mast cell tumor aspirates.

BACKGROUND: Mast cell tumors are the most common cutaneous tumor in the dog and are often diagnosed via fine-needle aspiration and cytology. Many veterinary practices use Diff-Quik stain for these cases because it is easy to use and provides rapid results. Anecdotal reports suggest that Diff-Quik does not stain mast cell tumor granules well and that increased duration of fixation time can improve staining quality; however, this has not been prospectively evaluated. OBJECTIVES: The aim of this study was to determine if varying fixation time would affect the staining quality of mast cell granules using the Diff-Quik stain. The null hypothesis was that there would be no difference in the staining of the granules based on duration of time in the fixation solution. METHODS: Fine-needle aspirates of cutaneous mast cell tumors were obtained from 21 dogs and distributed on multiple slides. These slides were then stained in Diff-Quik at varying fixation times (ie, 5 seconds, 30 seconds, 1 minute, 2 minutes). One slide was stained with modified Wright stain as a control. Mast cell staining quality was evaluated either by blinded clinicopathologic review (n = 12) or by computer analysis of photomicrographs (n = 6). Results were compared with histopathologic grade. RESULTS: There was no difference in staining quality among groups. CONCLUSIONS: Alteration in fixation time using Diff-Quik does not improve staining characteristics of mast cell tumors.

Phase I dose escalation safety study of nanoparticulate paclitaxel (CTI 52010) in normal dogs.

BACKGROUND: Paclitaxel is highly effective in the treatment of many cancers in humans, but cannot be routinely used in dogs as currently formulated due to the exquisite sensitivity of this species to surfactant-solubilizing agents. CTI 52010 is a formulation of nanoparticulate paclitaxel consisting of drug and normal saline. Our objectives were to determine the maximally tolerated dose, dose-limiting toxicities, and pharmacokinetics of CTI 52010 administered intravenously to normal dogs. METHODS: Three normal adult hound dogs were evaluated by physical examination, complete blood count, chemistry profile, and urinalysis. Dogs were treated with staggered escalating dosages of CTI 52010 with a 28-day washout. All dogs were treated with a starting dosage of 40 mg/m(2), and subsequent dosages were escalated at 50% (dog 1), 100% (dog 2), or 200% (dog 3) with each cycle, to a maximum of 240 mg/m(2). Dogs were monitored by daily physical assessment and weekly laboratory evaluation. Standard criteria were used to grade adverse events. Plasma was collected at regular intervals to determine pharmacokinetics. Dogs were euthanized humanely, and necropsy was performed one week after the last treatment. RESULTS: The dose-limiting toxicity was grade 4 neutropenia and the maximum tolerated dosage was 120 mg/m(2). Grade 1-2 gastrointestinal toxicity was noted at higher dosages. Upon post mortem evaluation, no evidence of organ (liver, kidney, spleen) toxicity was noted. CONCLUSION: CTI 52010 was well tolerated when administered intravenously to normal dogs. A starting dosage for a Phase I/II trial in tumor-bearing dogs is 80 mg/m(2).

Reirradiation of recurrent canine nasal tumors.

Canine nasal tumors are typically treated with radiation therapy but most patients develop local recurrence. Our purpose was to evaluate tumor and normal tissue response to reirradiation in nine dogs. The median dose delivered with the first protocol was 50 Gy (range 44-55 Gy) and the median fraction number was 18 (range 15-20). For the second protocol, the median dose was lower intentionally, median of 36 Gy (range 23-44 Gy), without changing the median fraction number of 18 (range 14-20) to avoid late effects. The median time between protocols was 539 days (range 258-1652 days). Median survival was 927 days (95% confidence interval [CI] 423-1767 days). Median time to progression following the first and second courses was 513 days (95% CI 234-1180 days) and 282 days (95% CI 130-453 days), respectively. These were not significantly different (P=0.086). The qualitative response assessment was better for the first course compared with the second (P=0.018). Severity and timing of skin, mucous membrane, and ocular effects were similar for early side effects between the two courses (P>0.05 for all comparisons). All dogs experienced some late side effects, with two out of nine being classified as severe. These severe effects were blindness in each dog, possibly related to tumor recurrence. Reirradiation of canine nasal tumors resulted in a second clinical remission in eight of nine dogs, although the second response was less complete. Acute and late effects for seven of nine patients were not life threatening, indicating that reirradiation of canine nasal tumors may be a viable treatment option after recurrence.

Evaluation of factors associated with second remission in dogs with lymphoma undergoing retreatment with a cyclophosphamide, doxorubicin, vincristine, and prednisone chemotherapy protocol: 95 cases (2000-2007).

OBJECTIVE: To evaluate factors associated with second remission in dogs with lymphoma retreated with a cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) protocol after relapse following initial treatment with a first-line 6-month CHOP protocol. DESIGN: Retrospective case series. ANIMALS: 95 dogs with lymphoma. PROCEDURES: Medical records were reviewed. Remission duration was estimated by use of the Kaplan-Meier method. Factors potentially associated with prognosis were examined. RESULTS: Median remission duration after the first-line CHOP protocol was 289 days (range, 150 to 1,457 days). Overall, 78% (95% confidence interval [CI], 69% to 86%) of dogs achieved a complete remission following retreatment, with a median second remission duration of 159 days (95% CI, 126 to 212 days). Duration of time off chemotherapy was associated with likelihood of response to retreatment; median time off chemotherapy was 140 days for dogs that achieved a complete remission after retreatment and 84 days for dogs that failed to respond to retreatment. Second remission duration was associated with remission duration after initial chemotherapy; median second remission duration for dogs with initial remission duration ≥ 289 days was 214 days (95% CI, 168 to 491 days), compared with 98 days (95% CI, 70 to 144 days) for dogs with initial remission duration < 289 days. CONCLUSIONS AND CLINICAL RELEVANCE: Findings suggested that retreatment with the CHOP protocol can be effective in dogs with lymphoma that successfully complete an initial 6-month CHOP protocol.