Gus, a 10-year old, castrated male, Rottweiler mix, presented to the Oncology Service at Hope Veterinary Specialists for consultation for a recently diagnosed malignant bone lesion.
Gus had a 4-week history of progressive lameness of left forelimb. Upon presentation to the primary care veterinarian a partial-weight bearing lameness of left forelimb noted as well as firm, painful swelling at distal left humerus. The remainder of the physical exam was normal. Regional radiographs revealed mixed osteolytic and osteoproliferative bone lesion associated with metaphyseal region of left distal humerus. The primary care veterinarian was concerned for malignancy, thus recommended CBC and chemistry, which was within normal limits, as well as three view thoracic radiographs, which were confirmed negative for metastasis on radiologist review. Gus has had no history of travel outside of PA and NJ. He was adopted at 12-weeks of age. No other major medical history. The primary care veterinarian prescribed Rimadyl and Gabapentin at standard doses and recommended oncology referral.
At the time of oncology consultation, all previously performed diagnostics were reviewed with client. The concern for malignancy, based on patient age, breed, radiographic appearance of lesion, lesion location and lack of travel history, was discussed. Differential diagnoses include: primary malignant bone tumor (osteosarcoma vs chondrosarcoma vs osseous plasma cell tumor vs other) vs bone metastasis (less likely given negative staging results) vs fungal or bacterial osteomyelitis (less likely given no history of travel to fungal endemic areas and exam findings negative for obvious signs of bacterial infection including fever, draining tract, history of trauma).
Osteosarcoma is the most common primary bone malignancy1. Large and giant breed dogs are at increased risk1. Median age of onset is 7 years, with a small early peak in age frequency at 18-24 months1. Etiology of this tumor is largely unknown; genetic, physiologic, and molecular influences have all been implemented in possible causative factors1.
The biggest challenges associated with this cancer are: (1) the aggressive nature of this tumor as it expands through and destabilizes the bone causing pain, and (2) the high metastatic risk, estimated at 90%, most common sites including regional lymph nodes, lung, and other bones.
Diagnostic staging recommended includes general health profile (CBC/chemistry), regional radiographs, three-view thoracic radiographs. Osteosarcoma most often occurs in the metaphyseal region of long bones, specifically distal femur, proximal tibia, proximal humerus, distal radius (‘away from the elbow and towards the knee’ is a helpful hint to remember the most common tumor locations) 1. Radiographically these lesions do not ‘cross the joint’.
Definitive diagnosis of osteosarcoma is typically achieved by way of histopathology obtained via incisional biopsy (e.g. Jamshidi biopsy method). This method has an accuracy rate of 91% for detecting malignancy (versus other disorder) and 82% accuracy for diagnosis of specific tumor subtype2. Tumor heterogeneity and/or small sample size may cause false negative result (“reactive bone”) in 15% of cases. Complications of bone biopsy, such as hematoma formation, infection, local seeding of tumor and fracture, may outweigh the benefits of this procedure in some cases. In certain patients, obtaining definitive diagnosis prior to surgical treatment may not be mandatory if the patient is of the typical signalment (large or giant breed dog), has not traveled to regions where fungal infections are common,
has no history or physical exam findings indicative of bacterial infection, has typical radiographic appearance and location of osteosarcoma.
Standard of care treatment in most institutions involves amputation of the affected limb. At the time of surgery, it is recommended to remove the regional lymph node and submit separately for histopathology assessment to rule out lymph node metastasis. Limb-sparing surgery1 may be considered in limited cases, however, the high morbidity rate and limited availability of this technically specialized procedure makes it a less attractive option for most dogs and their owners.
Amputation surgery addresses the first challenge – resolving the pain associated with the growing bone tumor. Chemotherapy addresses the second challenge by slowing the growth of metastatic cells. Multiple different chemotherapy protocols have been studied to date. In our practice the standard of care is carboplatin chemotherapy given every three weeks for an average of six treatments. Chemotherapy side effects are typically mild and transient but may include gastrointestinal upset and myelosuppression1. Carboplatin has a double nadir in which the white blood cells counts may be reduced at 7-10 days then again 16-21 days after treatment1.
Prognosis of patients with this disease depends on multiple factors, the most commonly cited including: presence of metastasis (negative), elevated alkaline phosphatase (negative), large tumor size (negative), humerus location (negative), treatment chosen (dogs receiving amputation and chemotherapy have improved survival times over dogs receiving amputation alone) 1. Median survival time with amputation and chemotherapy is 9-11 months3-4. Dogs receiving amputation alone (no chemotherapy) have average survival time of 3-5 months1.
In Gus’ case, the clients elected to proceed with amputation surgery without a definitive diagnosis. Prior to amputation Gus’ bone pain was managed with rimadyl, gabapentin, and acupuncture. Studies have shown that acupuncture can help increase beta endorphin levels, one of the body’s natural opioids5. Gus received acupuncture twice weekly prior to amputation then immediately post-op, examples of acupoints used included: Bladder Channel points 11, 23, 26, Gallbladder Channel points 10, 21, Kidney Channel points 1, 3. Left forelimb and shoulder region avoided as this is tumor limb. Chemotherapy (carboplatin every three weeks for six treatments) was initiated 10 days post-op. Acupuncture was provided at the time of each chemotherapy treatment. The goal of acupuncture in this setting was to help reduce chemotherapy-induced side effects including nausea, diarrhea, vomiting, neutropenia. Studies in people have shown that acupuncture can help reduce chemotherapy-induced emesis and myelosuppression6-11. Examples of acupoints treated include: Bladder Channel points 18, 21, 23, 24, 26; Stomach Channel point 36; Large Intestine Channel point 11, Great Vessel 14, Gall Bladder channel points 10, 21, 39.
Gus sailed through his chemotherapy treatments with limited side effects. His clients reported that after each acupuncture treatment he seemed to have bursts of energy, he continued to enjoy playing ball with their children and go on daily walks in the neighborhood. After chemotherapy was completed Gus continued with acupuncture treatments on monthly maintenance protocol. He had thoracic radiographs performed every three months for restaging purposes. At 15 months post diagnosis pulmonary metastasis was diagnosed. His quality of life was still excellent. At 19 months past initial diagnosis of osteosarcoma his quality of life was declining from the metastatic disease and clients elected to say goodbye. While they were very sad to say goodbye, they commented that his quality of life was
excellent throughout the past 19 months and that it was not until about 1 week prior to saying goodbye that he was clinically ill from his cancer.
Gus’ case is an excellent example of how a cancer patient may benefit from acupuncture. The traditional treatment approach of amputation and chemotherapy helped control his cancer while integrating acupuncture into his treatment protocol helped support him through the treatment and post-treatment periods.
Gus’ case is just one example of how we at Hope Veterinary Oncology strive for a patient-centered treatment approach. Improving and maintaining a good quality of life is at the forefront of our treatment goals.
Radiographic Evaluation of Osteosarcoma of Distal Humerus in a Dog. Osteosarcoma lesions typically have mix of osteolysis and abnormal osteoproliferation. In this picture there is destruction of trabecular and cortical bone.
Submitted by: Kate Vickery, VMD, MS, DACVIM (Oncology), CVA
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