Page 562 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

540 PART IV Specific Malignancies in the Small Animal Patient

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A B C D
• Fig. 25.10 Radiographs of internal fixation after fracture (A) and preemptive stabilization (B, C, and D) for
stereotactic radiation therapy limb salvage cases with lytic lesions.

contributed to amputation or euthanasia. The high rate of com- OSA 3 weeks before amputation to evaluate the potential for
plications in this study resulted in the authors not recommend- decreased systemic toxicity and to induce clinically meaningful
ing stabilization concurrently with SRT. tumor necrosis before primary tumor removal. No systemic toxic-
Theoretically, fractionated SRT may offer a reduction in the ity was observed. Despite good dosimetry to the lesion, the mean
rate of pathologic fracture in comparison to severely hypofraction- percentage TN was 27.6%, which was similar to mean percentage
ated SRS, which results in pathologic fracture in 63% of patients. TN of 26.8% in untreated OSA cases. 233 This low percentage TN
The rate of fracture after SRT has not been published to date. In may be due to incomplete perfusion of the 153 Sm-EDTMP, the
a recent study of an accelerated palliative protocol, in which dogs heterogenous nature of OSA, and the inability of the beta particles
were manually planned to receive two daily fractions of 10 Gy to exert a cytotoxic effect on the noncalcified regions of the tumor
using parallel opposed geometry, the rate of fracture was 35.7% due to their short track length (3 mm).
after RT. 234
The advantages of SRS/SRT techniques include limb preserva- Summary of Outcome After Limb Salvage for Dogs
tion in anatomic sites not amenable to LSS, the normal tissue- with Osteosarcoma
sparing effects of SRT compared with conventional RT, a lack of There is no significant difference in survival rates for dogs treated
surgical alternatives, and good to excellent limb function. Disad- with amputation and cisplatin compared with dogs treated with
vantages of the technique include limited but increasing access to LSS and cisplatin. 206 Overall, limb function has been satisfactory
equipment capable of delivering SRT and the high rate of postir- with approximately 80% of dogs experiencing good to excellent
17
radiation pathologic fracture. limb function. LSS requires a dedicated owner and clinical team.
LSS is usually combined with some form of adjuvant therapy, and
Isolation of Limb Circulation and Perfusion complications can arise in any or all phases of treatment (che-
Isolated limb perfusion (ILP) with chemotherapy has been used in motherapy, RT, or surgery). High dose, external beam RT may
people and dogs with sarcomas and melanomas as a sole treatment complicate wound and bone healing and potentiate infection. 203
or to downstage local disease to allow LSS. 235–237 ILP allows deliv- Moderate dose, external beam RT in combination with chemo-
ery of high concentrations of chemotherapy as well as delivery of therapy may, however, be useful for control of local disease, as
compounds that are poorly tolerated systemically. Varying degrees indicated by tumor necrosis data. 205,239 The major complications
of local toxicity are reported and these are dependent on the drugs related to LSS are infection, local recurrence, and implant com-
used. Successful use of ILP in canine OSA has been reported. 235 plications. In a review of 220 LSSs performed at CSU-FACC, the
One study determined that appendicular bone tumors have sig- 1-year local recurrence-free rate was 76% with 60% of dogs alive
nificantly higher interstitial fluid pressure and lower blood flow at 1 year. 206 Local disease control was improved with certain treat-
than do adjacent, unaffected soft tissues. 238 ILP may be a method ments such as pretreatment with moderate doses of RT and intra-
to facilitate delivery of therapeutic drug concentrations to primary arterial cisplatin or local implantation of biodegradable cisplatin
tumors for preoperative downstaging before LSS. polymer. The percentage of TN has been shown to be predictive
Systemic administration of 153 Samarium ethylenediamine- of outcome. 7
tetramethylene phosphonate ( 153 Sm-EDTMP) is limited by sys- In two case series, 40% and 47.5% of dogs, respectively, devel-
temic myelotoxicity. In a study at CSU-FACC, 153 Sm-EDTMP oped allograft infections. 206,240 The majority had their infections
(37 MBq/kg) was administered via ILP through isolated limb adequately controlled with systemic antibiotics with or without
circulation for 1 hour in nine dogs with primary appendicular local antibiotics (antibiotic-impregnated polymethylmethacrylate