Samarium Sm 153 lexidronam for the palliative treatment of dogs with primary bone tumors: 35 cases (1999–2005)

The role of companion animal models in radiopharmaceutical development and translation

Advancements in molecular imaging and drug targeting have created a renaissance in the development of radiopharmaceuticals for therapy and theranostics. While some radiopharmaceuticals, such as Na[131I]I, have been used clinically for decades, new agents are being approved using small-molecules, peptides, and antibodies for targeting. As these agents are being developed, the need to understand dosimetry and biologic effects of the systemically delivered radiotherapy becomes more important, particularly as highly potent radiopharmaceuticals using targeted alpha therapy become clinically utilized. As the processes being targeted become more complex, and the radiobiology of different particulate radiation becomes more diverse, models that better recapitulate human cancer and geometry are necessary. Companion animals develop many of the same types of cancer, carrying many of the same genetic drivers as those seen in people, and the scale and geometry of tumours in dogs more closely mimics those in humans than murine tumour models. Key translational challenges in oncology, such as alterations in tumour microenvironment, hypoxia, heterogeneity, and geometry are addressed by companion animal models. This review paper will provide background on radiopharmaceutical targeting techniques, review the use of radiopharmaceuticals in companion animal oncology, and explore the translational value of treating these patients in terms of dosimetry, treatment outcomes, and normal tissue complication rates.

Updates in Osteosarcoma

Clinical care of osteosarcoma (OSA) in dogs has seen little change during the past 2 decades, relying on amputation and platinum-based chemotherapy for pain control and survival. Recent advancements offer hope for improved outcomes. Genomic research reveals shared genetic abnormalities between canine and human OSA. Multidimensional imaging provides valuable staging and prognostic information. Limb-sparing approaches including stereotactic body radiation therapy are routine. Ablative therapies such as microwave ablation and histotripsy show promise. Immunotherapy including cell therapy and immune checkpoint inhibition are available. Radiopharmaceuticals are tuned to target OSA cells directly. These innovations may enhance treatment and prognosis for dogs with OSA.

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.

Canine Osteosarcoma Treated by Post-Amputation Sequential Accelerated Doxorubicin and Carboplatin Chemotherapy: 38 Cases

Canine appendicular osteosarcoma is an important clinical problem in veterinary medicine. Current standard therapy includes amputation followed by chemotherapy, which improves outcomes; however the percentage of long-term survival is still relatively low at 15-20%. Established prognostic factors include serum alkaline phosphatase level, histologic grade, and lymphocyte and monocyte counts. We used a protocol with shorter inter-treatment intervals than standard, but which we expected to still be well-tolerated, based on drugs known to be active agents, with the aim of improving outcomes by increasing dose intensity. Thirty-eight dogs with confirmed appendicular osteosarcoma and no pulmonary metastases that underwent amputation followed by this chemotherapy protocol were retrospectively evaluated. The median survival time was 317 days and 1- and 2-yr survival percentages were 43.2% and 13.9%, respectively. Toxicity was comparable to that seen with other standard dose protocols, with 5.2% of dogs hospitalized for complications that resolved with supportive care and no chemotherapy-related mortality. Serum alkaline phosphatase level (normal or high) (p = 0.004) and whether or not chemotherapy was completed (p = 0.001) were found to significantly impact survival time on multivariate analysis. Outcomes were similar to those reported with most other published chemotherapy protocols for dogs with this disease.

Canine osteosarcoma: a naturally occurring disease to inform pediatric oncology

Osteosarcoma (OSA) is the most common form of malignant bone cancer in children and dogs, although the disease occurs in dogs approximately 10 times more frequently than in people. Multidrug chemotherapy and aggressive surgical techniques have improved survival; however, new therapies for OSA are critical, as little improvement in survival times has been achieved in either dogs or people over the past 15 years, even with significant efforts directed at the incorporation of novel therapeutic approaches. Both clinical and molecular evidence suggests that human and canine OSA share many key features, including tumor location, presence of microscopic metastatic disease at diagnosis, development of chemotherapy-resistant metastases, and altered expression/activation of several proteins (e.g. Met, ezrin, phosphatase and tensin homolog, signal transducer and activator of transcription 3), and p53 mutations, among others. Additionally, canine and pediatric OSA exhibit overlapping transcriptional profiles and shared DNA copy number aberrations, supporting the notion that these diseases are similar at the molecular level. This review will discuss the similarities between pediatric and canine OSA with regard to histology, biologic behavior, and molecular genetic alterations that indicate canine OSA is a relevant, spontaneous, large animal model of the pediatric disease and outline how the study of naturally occurring OSA in dogs will offer additional insights into the biology and future treatment of this disease in both children and dogs.

Pain management in veterinary patients with cancer

Pain is a widespread clinical symptom in companion animals with cancer, and its aggressive management should be a priority. Education and skills can be acquired by health care professionals and caregivers to better understand, recognize, and treat cancer-associated pain. The early and rational institution of multimodality analgesic protocols can be highly effective and maximize the chances of improving quality of life in dogs and cats with cancer. This article describes the pathophysiology of pain in companion animals diagnosed with cancer. The foundational causes of cancer-associated pain and treatment strategies for alleviating discomfort in companion animals with cancer are discussed.

Beyond Palliation: Therapeutic Applications of 153Samarium-EDTMP

Primary and metastatic malignant bone lesions result in significant pain and disability in oncology patients. Targeted bone-seeking radioisotopes including ¹⁵³Samarium ethylene-diamine-tetramethylene-phosphonic acid (¹⁵³Sm-EDTMP) have been shown to effectively palliate bone pain, often when external beam radiotherapy (EBRT) is not feasible. However, recent evidence also suggests ¹⁵³Sm-EDTMP has cytotoxic activity either alone or in combination with chemotherapy or EBRT. ¹⁵³Sm-EDTMP may be useful as anti-neoplastic therapy apart from pain palliation in a variety of malignancies. For prostate cancer patients, several phase I and II clinical trials have shown that combined ¹⁵³Sm-EDTMP and docetaxel-based chemotherapy can result in >50% decrease in prostate-specific antigen with manageable myelosuppression. In hematologic malignancies, ¹⁵³Sm-EDTMP produced clinical responses when combined with bortezomib in multiple myeloma. ¹⁵³Sm-EDTMP also can be used with myeloablative chemotherapy for marrow conditioning prior to stem cell transplant. In osteosarcoma, ¹⁵³Sm-EDTMP infusion delivers radiation to multiple unresectable lesions simultaneously and provides local cytotoxicity without soft tissue damage that can be combined with chemotherapy or radiation. Prior to routine incorporation of ¹⁵³Sm-EDTMP into therapeutic regimens, we must learn how to ensure optimal delivery to tumors, determine which patients are likely to benefit, improve our ability to assess clinical response in bone lesions and further evaluate the efficacy ¹⁵³Sm-EDTMP in combination with chemotherapy, radiation and novel targeted agents.

Osteosarcoma of the penile bone (os penis) in a dog

Osteosarcoma of the penile bone was diagnosed in a 5-year-old neutered male Rottweiler with recurrent dysuria. Imaging and cytological findings raised the suspicion for an osteosarcoma and ablation of the entire penis and scrotal urethrostomy was performed. The diagnosis was confirmed histologically. The dog recovered well and no postoperative signs of dysuria were observed. The dog survived without adjuvant chemotherapy for 12 months when multiple tumours in the thorax and abdomen led to it being euthanased. Penile osteosarcoma is a rare disease, but must be considered as a differential diagnosis in dogs presenting with dysuria. This is the second recorded case of a penile osteosarcoma in a dog, but the first with a detailed description of the diagnosis, treatment and outcome.