Outcomes in dogs undergoing surgical stabilization and non-stereotactic radiation therapy for axial and appendicular bone tumors

Background

Information on dogs that undergo radiation therapy (RT) with non-stereotactic protocols in addition to surgical stabilization with implant placement for treatment of bone tumors is limited.

Objective

Our primary objectives were to describe the clinical characteristics as well as short- and long-term outcomes, including complications, function, and disease progression, in dogs that underwent both surgical stabilization with implant placement and non-stereotactic RT for local treatment of a bone tumor.

Methods

A bi-institutional retrospective case series was performed.

Animals

Eight client-owned dogs that underwent both surgical stabilization with implant placement and non-stereotactic RT for local treatment of a bone tumor were included.

Results

Tumor types included osteosarcoma or suspected osteosarcoma (5), plasma cell tumor (2), and grade 3 fibrosarcoma (1). Radiation protocols were hypofractionated (palliative intent) in 5 dogs and fractionated (definitive intent) in 3 dogs. Five dogs experienced complications following both RT and surgery, including grade 1 complications in two dogs, a grade 2 complication in one dog, both grade 1 and 2 complications in one dog, and both grade 2 and 3 complications in one dog. Clinical signs subjectively improved in all dogs that had outcomes relative to function documented post-surgery/RT (7). Of these 7 dogs, 4 maintained long-term improvement in function and clinical signs, whereas 3 experienced subsequent recurrence/progression of clinical signs at a median of 133 days (range 91-186) postoperatively in association with biomechanical complications (screw loosening), surgical site infection, and local disease progression in 1 dog each; subsequent treatment resulted in improved clinical signs for each of these 3 dogs, such that overall good long-term functional outcomes were experienced. No dogs required amputation or additional vertebral surgery as salvage for local disease control or palliation. The median progression free interval was 206 days (range 25-1078), and the median survival time was 253 days (range 122-1078) with 1 additional dog lost to follow-up at 575 days. Two dogs experienced local disease progression, and 6 dogs experienced systemic disease progression; both dogs that developed local disease progression received palliative intent RT protocols.

Clinical relevance

In this cohort, dogs with primary bone tumors that underwent surgical stabilization with implant placement and hypofractionated or fractionated non-stereotactic RT for local treatment had a low incidence of major complications, good limb function and ambulation post-treatment, and relatively prolonged survival times despite disease progression.

Partial ulnar ostectomy, stereotactic body radiation therapy, and palliative radiation therapy as local limb sparing treatment modalities for ulnar tumors in dogs

Background

Information on dogs that undergo limb preserving local treatment for ulnar tumors is currently limited.

Objective

To describe the clinical characteristics and outcomes in dogs that underwent partial ulnectomy or radiation therapy (RT) for ulnar bone tumors, and to evaluate potential risk factors for outcomes as well as pre-treatment factors for association with treatment modality selected.

Animals

Forty client-owned dogs that underwent partial ulnectomy or RT for an ulnar tumor from July 2006 to July 2021.

Methods

The medical records database from a single institution were retrospectively reviewed, and data were recorded and analyzed.

Results

Radiation therapy was performed in 24 dogs, with 12 stereotactic body RT (SBRT) and 12 palliative RT (PRT) plans, and partial ulnectomy was performed in 16 dogs. Biomechanical complications occurred in 6/12 (50%) dogs that underwent SBRT, 6/12 (50%) dogs that underwent PRT, and 3/16 (18.8%) dogs that underwent ulnectomy. The majority of dogs had a good functional outcome following partial ulnectomy, and no dogs required surgical stabilization of the carpus even with lateral styloid process excision. Pathologic fracture occurred in 4/12 (33.3%) dogs following SBRT and 5/12 (41.7%) dogs following PRT. Local progression or recurrence was documented in 5/12 (41.7%) dogs that underwent SBRT, 2/12 (16.7%) dogs that underwent PRT, and 2/16 (12.5%) dogs that underwent ulnectomy. The overall median survival time was 198 days, and factors that were significantly associated with improved survival time included adjuvant chemotherapy administration and partial ulnectomy as local treatment method for dogs that received chemotherapy.

Clinical relevance

Both RT and ulnectomy were effective and well tolerated local treatment modalities for dogs with ulnar tumors.

Deep Domain Adversarial Learning for Species-Agnostic Classification of Histologic Subtypes of Osteosarcoma

Osteosarcomas (OSs) are aggressive bone tumors with many divergent histologic patterns. During pathology review, OSs are subtyped based on the predominant histologic pattern; however, tumors often demonstrate multiple patterns. This high tumor heterogeneity coupled with scarcity of samples compared with other tumor types render histology-based prognosis of OSs challenging. To combat lower case numbers in humans, dogs with spontaneous OSs have been suggested as a model species. Herein, a convolutional neural network was adversarially trained to classify distinct histologic patterns of OS in humans using mostly canine OS data during training. Adversarial training improved domain adaption of a histologic subtype classifier from canines to humans, achieving an average multiclass F1 score of 0.77 (95% CI, 0.74-0.79) and 0.80 (95% CI, 0.78-0.81) when compared with the ground truth in canines and humans, respectively. Finally, this trained model, when used to characterize the histologic landscape of 306 canine OSs, uncovered distinct clusters with markedly different clinical responses to standard-of-care therapy.

Local Administration of Carboplatin in Poloxamer 407 After an Ulnar Osteosarcoma Removal in a Dog

An 8 yr old male castrated hound presented for a left distal ulnar osteosarcoma. Staging (computed tomography and nuclear scintigraphy) did not reveal any metastases. A limb-sparing ulnectomy with local adjunctive carboplatin in a poloxamer copolymer gel (poloxamer 407) was performed. The patient recovered without complications after surgery. No wound healing complications or adverse effects occurred after local use of carboplatin in poloxamer 407. The local recurrence-free interval was 296 days from surgery, and the survival time was 445 days from initial diagnosis. This is the first report in the veterinary literature of using poloxamer 407 as a carrier for local delivery of chemotherapeutic drugs in a clinical patient.

A Holistic Approach to Bone Tumors in Dogs and Cats: Radiographic and Histologic Correlation

The skeletal system is a common site for neoplasia in dogs and cats, and primary bone tumors may develop from any of the mesenchymal tissues present in bone. Imaging and histopathology are routinely used in the diagnosis of bone tumors, and the 2 techniques are highly complementary. While imaging may be highly suggestive of a specific diagnosis and treatment may be instituted based on this, definitive diagnosis requires histopathology of either incisional or excisional biopsies or an amputation specimen. However, there are a number of diagnostic dilemmas when the pathologist interprets bone biopsy samples, such as distinguishing reactive bone and tumor bone, fracture callus and tumor bone, different benign fibro-osseous lesions, and different types of bone sarcoma. This review outlines the characteristic radiographic and histologic changes associated with these diagnostic problems to aid in resolving them. When a holistic approach is taken to evaluation of the signalment, history, and clinical, radiologic, and microscopic features, a diagnosis may be possible. The pathologist is greatly assisted in the interpretation of bone samples by having access to imaging and should routinely request either the images or the imaging reports if they are not received from submitting veterinarians.

Ulnar ostectomy decreases the stability of canine cadaver carpi as assessed with stress radiography

Distal ulnar ostectomy may be performed palliatively in patients with distal ulnar osteosarcoma. Concurrent arthrodesis of the carpus has been proposed to counteract joint instability following transection of carpal ligaments associated with removal of the distal ulna. The objective of this prospective one group pretest, posttest study was to assess stability of the carpus following distal ulnar ostectomy using pre- and postoperative stress radiographic views in a group of canine cadaver limbs. Seven thoracic limbs from six canine cadavers weighing more than 20 kg were obtained. Lateral and dorsopalmar, extended lateral, medial stress, and lateral stress radiographs were made before and after distal ulnar ostectomy. Presurgical canine cadaver carpal angle measurements were as follows (mean ± standard deviation): extension 205.9° ± 5.4; medial stress 25.1° ± 5.7; and lateral stress 13.3° ± 5.2°. Cadaver limb joint angles exceeded those previously reported in live dogs. A significant increase in carpal angle was noted following ulnar ostectomy. The mean increases in carpal angle were as follows: (mean ± standard deviation (95% confidence interval)): extension 6.2° ± 4.9 (2.6-9.8) (P = 0.007); medial stress 3.2° ± 3.0 (1.0-5.5) (P = 0.015); lateral stress 6.2° ± 5.2 (2.4-10.1) (P = 0.010). Findings from this cadaver study support the use of supplementary stabilization for clinical patients undergoing distal ulnar ostectomy. Future studies are needed in clinical patients to evaluate changes in limb positioning and gait associated with distal ulnar ostectomy.

Primary appendicular hemangiosarcoma and telangiectatic osteosarcoma in 70 dogs: A Veterinary Society of Surgical Oncology retrospective study

OBJECTIVE

To define and compare clinical characteristics of canine primary appendicular hemangiosarcoma (HSA) and telangiectatic osteosarcoma (tOSA), including signalment, presentation, response to treatment, and prognosis.

STUDY DESIGN

Multi-institutional retrospective study.

ANIMALS

Seventy dogs with primary appendicular HSA or tOSA.

METHODS

Patient data were obtained from institutions' medical records. Immunohistochemistry was applied to archived tissues to establish tumor type. Patient characteristics, treatment responses, and outcomes were described and compared by tumor type.

RESULTS

Forty-one HSA and 29 tOSA were identified. Dogs with HSA were more likely than dogs with tOSA to be male and have hind limb tumors; 78% of HSA occurred in hind limbs, particularly the tibia. Dogs with tOSA weighed a median of 9.9 kg (95% CI 4.6-15.3) more than dogs with HSA. Most dogs received antineoplastic treatment, predominantly amputation with or without adjuvant chemotherapy. Overall survival with local treatment and chemotherapy was 299 days (95% CI 123-750) for HSA and 213 days (95% CI 77-310) for tOSA. Younger age and more aggressive treatment were associated with longer survival in dogs with HSA but not tOSA. One-year survival rates did not differ between dogs with HSA (28%) and those with tOSA (7%).

CONCLUSION

Distinct clinical features were identified between HSA and tOSA in this population. Both tumors were aggressive, with a high incidence of pulmonary metastases. However, local treatment combined with chemotherapy led to an average survival 7 months for tOSA and 10 months for HSA.

CLINICAL SIGNIFICANCE

HSA should be considered as a differential in dogs with aggressive lytic bone lesions, particularly medium-sized dogs with tibial lesions. HSA has a unique clinical presentation but similar therapeutic response and outcome to OSA. Amputation and chemotherapy appear to prolong survival in some dogs with HSA and tOSA.

Fibroblastic osteosarcoma with epithelioid and squamous differentiation in a dog

A fibroblastic osteosarcoma with epithelioid and squamous differentiation in the distal femur of a 9-y-old spayed female Greyhound dog is described. Grossly, the tumor consisted of a pale-white, firm-to-hard mass that replaced the medullary and cortical areas of the distal end of the right femur. Histologically, the mass was composed predominantly of spindle cells admixed with areas of mineralized and non-mineralized osteoid matrix that were surrounded by stellate osteoblasts and scattered multinucleate giant cells, consistent with the diagnosis of a fibroblastic osteosarcoma. In addition, well-demarcated clusters of neoplastic epithelioid cells and foci of squamous differentiation with keratin pearls were present throughout the neoplasm. The spindle cells, epithelioid cells, and areas of squamous differentiation expressed cytoplasmic immunostaining for osteocalcin and osteonectin. The spindle cells and epithelioid cells were also immunopositive for vimentin. Epithelioid cells also expressed occasional cytoplasmic immunostaining for pancytokeratin (PCK) Lu-5, and areas of squamous differentiation were immunoreactive for PCK Lu-5 and high molecular weight CK; these areas were inconsistently immunoreactive for CK 5-6 and immunonegative for low molecular weight CK. Foci of squamous differentiation were not located within blood or lymphatic vessels, given that no immunoreactivity for factor VIII-related antigen was observed around these areas. A thorough autopsy and an evaluation of the medical history excluded a primary carcinoma or other neoplasm elsewhere in the dog. The findings were consistent with a diagnosis of fibroblastic osteosarcoma with epithelioid and squamous differentiation.

Effect of distal ulnar ostectomy on carpal joint stability during weight bearing in the dog

OBJECTIVE

To assess the influence of a 50% distal ulnectomy on mediolateral carpal stability in the dog.

STUDY DESIGN

Canine cadaveric study.

SAMPLE POPULATION

Seven canine thoracic limbs METHODS: Thoracic limbs were placed in a jig to mimic weight bearing with a load representing 30% of body weight. Carpal extension angle was standardized at 190° ± 5°. Frontal plane carpal angles were measured with the limb loaded on craniocaudal radiographs before and after ulnectomy. Valgus and varus stress radiographs with the limb loaded were acquired before and after ulnectomy. The limbs were palpated and were subjectively graded for valgus or varus instability by 2 investigators before and after ulnectomy.

RESULTS

Mean (±SD) valgus angulation increased after ulnectomy (2.1° ± 1.7°; P = .017; CI₉₅  = 0.5°-3.7°) when the limb was loaded without valgus or varus stress applied. Mean valgus angulation increased after ulnectomy (2.7° ± 2.8°; P = .032; CI₉₅  = -0.2°-5.5°) when valgus stress was applied to the loaded limb. Varus angulation was unchanged after ulnectomy (0.6° ± 4.6°; P = .383; CI₉₅  = -4.2°-5.3°) when varus stress was applied to the loaded limb. Palpation detected increased valgus score after ulnectomy.

CONCLUSION

Distal ulnectomy with excision of the lateral styloid process induces a slight increase in valgus in canine cadaver carpi. The clinical consequences of that valgus on carpal function and health should be assessed in clinical patients.

Evaluation of P16 expression in canine appendicular osteosarcoma

BACKGROUND

Osteosarcoma (OSA) is a common malignant bone tumor of large breed dogs that occurs at predictable anatomic sites. At the time of initial diagnosis, most affected dogs have occult pulmonary metastases. Even with aggressive surgical treatment combined with chemotherapy, the majority of dogs diagnosed with OSA live less than 1 year from the time of diagnosis. The ability to identify canine OSA cases most responsive to treatment is needed. In humans, OSA is also an aggressive tumor that is histologically and molecularly similar to canine OSA. The expression of the tumor suppressor gene product P16 by human OSA tissue has been linked to a favorable response to chemotherapy.

RESULTS

We identified an antibody that binds canine P16 and developed a canine OSA tissue microarray in order to test the hypothesis that P16 expression by canine OSA tissue is predictive of clinical outcome following amputation and chemotherapy. Although statistical significance was not reached, a trend was identified between the lack of canine OSA P16 expression and a shorter disease free interval.

CONCLUSIONS

The identification of a molecular marker for canine OSA is an important goal and the results reported here justify a larger study.

A chondroblastic osteosarcoma of the coronoid process mimicking a fragmented coronoid process in a dog

A 6-year-old Rhodesian Ridgeback was presented with a 1.5 year history of right forelimb lameness. Clinical, radiological and computed tomographic findings suggested the presence of fragmented medial coronoid process. A subtotal coronoidectomy was performed and, due to the atypical appearance of the medial coronoid process on imaging and at surgery, histopathology of the fragments was performed which revealed chondroblastic OS. Ten months after surgery, the dog was re-presented with the same clinical signs and the radiographic changes were suggestive of a recurrence of the OS. Palliative therapy was instigated at the owner’s request. Thirty months after surgery of the neoplasm, the dog was presented with dyspnea. Thoracic radiographs showed lesions consistent with lung metastases. Euthanasia was requested by the owner, who declined post-mortem examination.