Page 557 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 25 Tumors of the Skeletal System 535

TABLE 25.1 Treatment Options for Osteosarcoma by Site
Site Treatment Options Comments
VetBooks.ir Humerus, femur, tibia Limb amputation Generally high complication rate for limb salvage 162 209
Diaphyseal locations amenable to intercalary allografts
Limb salvage (stereotactic radiation therapy)
Total hip salvage possible for proximal femoral tumors 214,217
Intraoperative extracorporal radiation technique may apply 225
Radius Limb amputation -
Limb salvage (allograft, 201–206 endoprosthesis, 214 intercalary
bone graft, 209 ulnar transposition, 223,224 bone transport
osteogenesis, 218,219,221,222 intraoperative extracorporal
radiation therapy 225 )
Ulna Limb amputation Often does not require allograft reconstruction
Ulnectomy 255
Scapula Limb amputation Proximal lesions best; partial and total scapulectomy described
Scapulectomy 173,253,248
Pelvis Pelvectomy with or without limb amputation 176,246 Lateral portion of sacrum can be excised; may include body wall
Metacarpus/metatarsus Digit amputation 250 Limb function dependent on prosthetic design and patient
Partial limb amputation with prosthesis tolerance
Mandible Mandibulectomy 122 Often requires total mandibulectomy
Bilaterally limited to fourth premolar
Maxilla/orbit Maxillectomy 256 Limited by midline palate or cranial vault invasion
Orbitectomy 260 Combined approach may assist exposure
Calvarium Resection ± Radiation Resection dependent on venous sinus involvement
Vertebrae Decompression (palliative) ± Radiation ± Chemotherapy 175 Vertebrectomy techniques not well developed; limited local
disease control
Rib Rib resection 170–172,181 Requires removal of normal rib cranial and caudal to the tumor

limited follow-up, were published. 201–205 To date, more than 600 poor function. 162 Resulting poor function, combined with a high
LSSs have been performed at Colorado State University’s Flint complication rate, has generally led surgeons away from recom-
Animal Cancer Center (CSU-FACC). Limb function has been fair mending LSS near these joints. LSS is a complicated process and
to good in most dogs, and survival has not been adversely affected requires a coordinated team effort between surgical and medical
by removing the primary tumor with marginal resection. 206 oncologists, radiologists, pathologists, and technical staff. Several
Suitable candidates for LSS include dogs with nonmetastatic methods of LSS have been described, each with unique advantages
OSA and when the primary tumor affects <50% of the bone (as and limitations. The choice of LSS method depends on several fac-
determined radiographically). Other criteria for consideration tors, including owner choice, patient personality, and individual
include absence of pathologic fracture, less than 360-degree risk factors. At the CSU-FACC, owners are given a choice of LSS
involvement of soft tissues, and a firm/definable soft tissue mass options and informed about the risks and benefits of each method
rather than an edematous lesion. Early on in the development of compared with amputation. A brief description of the surgical
LSS procedures, many dogs treated at CSU-FACC received some options for a distal radial location (most common) follows. Metic-
form of preoperative treatment, (i.e., primary or neoadjuvant ulous aseptic technique is essential.
intraarterial [IA] cisplatin, intravenous [IV] cisplatin, RT to the Allograft limb salvage surgery. For a distal radial site, the dog
tumor bone, or a combination of RT with IV or IA cisplatin). is placed in lateral or dorsal recumbency with the affected limb
Results from 21 dogs treated with RT alone given in large doses uppermost. A skin incision is made on the dorsolateral aspect of
per fraction before LSS were unsatisfactory for preservation of life the antebrachium from a point just distal to the elbow to just
or limb. 203 Many of the dogs treated with two preoperative IA cis- proximal to the metacarpophalangeal joint. Any biopsy tracts are
platin doses 21 days apart, with the last treatment 21 days before excised en bloc. Soft tissue is dissected to the level of the tumor
LSS, showed marked decrease in the degree of vascularization of pseudocapsule. Care is taken not to compromise the tumor cap-
the tumor. This represented a high degree of induced tumor necro- sule. The bone is osteotomized with an oscillating bone saw 3 to
sis in the resected specimen, especially when combined with RT, 5 cm proximal to the proximal radiographic (or scintigraphic)
and facilitated LSS. 205,207 Most dogs at CSU-FACC receive sys- margin of the tumor. Extensor muscles attached to the tumor
temic carboplatin, DOX, or combination therapy after surgery. 208 pseudocapsule are transected at this level to maintain 2- to 3-cm
The most suitable cases for LSS are dogs with tumors in the soft tissue margins. The joint capsule is incised, keeping close to
distal radius or ulna, as function after LSS and carpal arthrod- the proximal row of carpal bones. For tumors of the mid diaphy-
esis is good. Arthrodesis of the scapulohumeral, coxofemoral, sis, tumor resection follows similar guidelines with the exception
stifle, or tarsal joints after LSS generally results in only fair to that the extensor and flexor muscle groups should be spared as the