Читать книгу Veterinary Surgical Oncology - Группа авторов - Страница 147

STS are a heterogeneous group of tumors. Because of this heterogeneity, it is hard to obtain sufficient data to set up a solid treatment protocol based on adequately proven clinical trials. The effectiveness of chemotherapy as an adjuvant therapy after resection of STS is thus unclear. Chemotherapy may be beneficial in cases of metastasis, incomplete resection of high‐grade tumors, and tumors not treatable with surgery or radiation therapy. Several chemotherapy protocols are used either as single agent or in combination. Metastases are uncommon in STS, however, and are reported to be 13% for low‐grade to 44% for high‐grade cutaneous STS. Single‐agent doxorubicin, mitoxantrone, or combination protocols using vincristine, doxorubicin, and cyclophosphamide have been reported to have effectiveness for STS (Thornton 2008). One study evaluating adjuvant doxorubicin for high‐grade STSs in dogs failed to find a benefit (Selting et al. 2005).

Elmslie et al. (2008) treated 30 dogs after incomplete removal of soft tissue sarcoma by metronomic, continuously low dose, cyclophosphamide (10 mg/m²), and standard‐dose piroxicam (0.3 mg/kg) therapy. Disease‐free interval (DFI) was 410 days for STS at all sites (trunk, extremities) in treated dogs compared to 211 days for 55 untreated controls. Even though the median DFI was not reached for the treated dogs, it was significantly prolonged. It is important to note that a selection bias in the control population may have skewed the conclusions of this study because 100% of the control dogs developed tumor recurrence or were censored from the analysis.

Local chemotherapy to prevent the local recurrence of an STS has been evaluated by using intralesional cisplatin‐impregnated bead placement following marginal excision of the tumor. About 47% of dogs had local toxicosis and 29% of tumors recurred locally (Bergman et al. 2016).

No clinical studies in the dog suggest whether neoadjuvant chemotherapy has any beneficial impact on patient outcome or surgical margins (Bray 2016; Elmslie et al. 2008; Kuntz et al. 1997; Rassnick 2003; Schlieman et al. 2006).

In cats, doxorubicin chemotherapy may play a role in extending the disease‐free interval in combination with radiotherapy for treatment of incompletely excised soft tissue sarcomas (Hahn et al. 2007). Radiotherapy was performed on an alternate‐day schedule, with a total dose of 58.8–63 Gy delivered in 21 fractions. Doxorubicin was administered every 21 days for 3–5 cycles. Median DFI with concurrent radiotherapy and doxorubicin chemotherapy (15.4 months) was significantly longer than median DFI with radiotherapy alone (5.7 months). However, survival time was not significantly different between groups.

Electrochemotherapy uses electroporation to increase cell membrane permeability to cytotoxic drugs. This is done by locally applying electric field pulses over the tumor area or tumor excision bed to enhance transmembrane uptake of locally or systemically administered cytotoxic agents. Complete and partial responses have been reported in few cases of macroscopic STS after electrochemotherapy with intravenous bleomycin administration in dogs (Torrigiani et al. 2019). Interesting results have been published of adjuvant electrochemotherapy to treat the scar/wound bed after incomplete excision of STS of different grades with perilesional bleomycin injections (Spugnini et al. 2007a), systemic bleomycin administration (Torrigiani et al. 2019), and a combination of local cisplatin with systemic bleomycin (Spugnini et al. 2019) in dogs. In cats, both intraoperative and postoperative adjuvant electrochemotherapy with local application of bleomycin has been studied (Spugnini et al. 2007b) and remarkable long‐term local control has been described for adjuvant electrochemotherapy with local cisplatin injections of the scar/wound bed after incomplete surgical excision of FSAs (Spugnini et al. 2011), and a combination of local cisplatin with systemic bleomycin for incompletely excised FISASs (Spugnini et al. 2020).