Current treatment options for dogs with appendicular osteosarcoma - Veterinary Medicine
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Current treatment options for dogs with appendicular osteosarcoma
Your therapeutic choices for dogs with osteosarcoma in their limbs continue to expand. Deciding which option is best comes down to the site and extent of the tumor and the owner's preference.


VETERINARY MEDICINE


LIMB-SPARING PROCEDURES

Limb-sparing, or limb-salvage, procedures for cancer patients are performed in an attempt to resect the primary lesion and preserve a functional, pain-free limb.16 These procedures are often considered when adverse circumstances preclude or owners refuse amputation. Limb-sparing procedures described to treat appendicular osteosarcoma in dogs include frozen cortical bone allograft implantation,17 pasteurized tumoral autografting,18,19 bone transport osteogenesis,20,21 and endoprosthesis.22 Most limb-sparing procedures performed to treat osteosarcoma in dogs involve lesions affecting the distal radius.16 Although local tumor recurrence after resection ranges from 20% to 40% in dogs undergoing limb-sparing procedures,14,16,17 this recurrence does not appear to decrease survival rates.11,17 Previous studies have shown that with adjunctive chemotherapy, no significant difference exists in survival rates between dogs undergoing amputation and dogs undergoing limb-sparing procedures.11,17 Methods to prevent local recurrence include systemic, regional, or local presurgical and postsurgical chemotherapy and preoperative radiation therapy.1

Proper biopsy techniques should be followed when you are considering limb-sparing procedures. If owners express interest in limb-sparing, consider sending the patient to a referral institution for the biopsy procedure. Ideally, the biopsy should be performed by the same surgeon who will ultimately perform the limb-sparing surgery. A searchable directory of diplomates of the American College of Veterinary Surgeons can be found at http://www.acvs.org/. Techniques include open incisional biopsy, closed (hypodermic needle or Jamshidi biopsy needle) biopsy, and Michelle trephine biopsy.23-25 We prefer the closed technique with a Jamshidi biopsy needle. This technique can help minimize the risk of complications such as hematoma formation, infection, and pathologic fractures.25 Site selection should be based on evaluation of radiographs and consideration of subsequent treatments. Biopsy site selection is critical for lesions of the distal radius. Failure to place the biopsy tract in the correct location can compromise a successful limb-sparing procedure. Biopsies of distal radial lesions should be performed at the craniolateral aspect of the distal antebrachium and should not include a biopsy of the distal ulna unless the primary tumor is located within the ulna.

The clinician should review the radiographs before the biopsy and have the radiographs available for reference during the procedure. The center of the radiographic lesion should be targeted as the site most likely to yield a diagnosis.25 Areas of dense reactive bone should be avoided.25 The skin incision should be as small as possible and positioned in a location where the biopsy tract and any potentially seeded tumor cells can be easily resected en bloc with the tumor at the time of surgery.25

Proper case selection for limb-sparing surgery is essential for a favorable outcome. Several criteria are used to determine case eligibility. Tumors that radiographically involve greater than 50% of the bone's length are not amenable to adequate resection because of insufficient tissue for reconstruction.26 Extensive invasion into adjacent soft tissues, especially the palmar nerves, vessels, and tendons, will not allow adequate resection with concurrent preservation of essential neurovascular bundles to the paw.11,26 Unstable or catastrophic pathologic fractures result in local tumor dissemination and seeding of tumor cells, making complete excision of tumor-contaminated tissue difficult.27 Small pathologic fractures or telescoping collapse of lytic bone is commonly observed on preoperative radiographs; these minor pathologic fractures do not preclude limb-sparing surgery. Local infection and radiographic evidence of metastasis are also circumstances under which limb-sparing surgery is not recommended.7,11,26 When in doubt, it is best to seek the opinion of a specialist who regularly performs limb-sparing surgery to ensure appropriate case eligibility.


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Source: VETERINARY MEDICINE,
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