Читать книгу Veterinary Surgical Oncology - Группа авторов - Страница 45

Chemotherapy can sometimes be used neoadjuvantly to “down‐stage” (shrink) a primary tumor prior to surgery, and thus make it more amenable to surgical resection with clean margins. This may be appropriate for cutaneous and subcutaneous masses such as hemangiosarcoma (Wiley et al. 2010). Similarly, corticosteroids may be used to pre‐operatively down‐stage mast cell tumors with good success, although it is unknown if local recurrence is less likely with this approach (Stanclift et al. 2008). In this setting, the surgeon needs to involve the medical oncologist prior to surgery. Chemotherapy also can prolong life post‐operatively by addressing systemic metastasis; the classic example is appendicular osteosarcoma in dogs. Chemotherapy can be used immediately post‐operatively or once the wound has healed, at the discretion of the medical oncologist and the surgeon. Surgery may have only a small role, such as for diagnostic biopsy, with the sole treatment being chemotherapy, as is the case with lymphoma. Metronomic chemotherapy uses standard chemotherapy agents in a continuous administration, which requires lower doses to be used. The target of the drug is the tumor’s continually proliferating microvasculature, which is susceptible to chemotherapeutic effects with minimal systemic toxicity (Gately and Kerbel 2001; Mutsaers 2009; Biller 2014). Bisphosphonates concentrate within areas of active bone remodeling and induce osteoclast apoptosis, which is of therapeutic benefit in managing pathological bone resorptive conditions such as osteosarcoma, multiple myeloma, and metastatic bone cancer. Bone pain is decreased, quality of life is improved, and progression of bone lesions is delayed (Fan et al. 2005, 2007, 2008, 2009; Fan 2007, 2009; Spugnini et al. 2009; Oblak et al. 2012).

Embolization treatments include “bland arterial embolization” (without chemotherapy) and chemoembolization (embolization with chemotherapeutic agents) that can be used as a sole therapy or pre‐operatively to decrease tumor mass and size. Chemoembolization delivers chemotherapy to the tumor, allowing prolonged contact of the tumor to the chemotherapy without high systemic toxicity (Granov et al. 2005) and augmenting tumor ischemia (Weisse et al. 2002a). There are several experimental studies of embolization treatments in healthy dogs, including chemoembolization with gemcitabine (Granov et al. 2005), carboplatin (Chen et al. 2004; Song et al. 2009), and cisplatin (Nishioko et al. 1992). Bland arterial embolization resulted in decreased tumor growth, pain palliation, and control of hemorrhage in two dogs and one goat (Weisse et al. 2002a) and decreased primary tumor size in a dog with a soft tissue sarcoma (Sun et al. 2002). A recent review of veterinary interventional oncology discusses embolization treatments (Weisse 2015).

Figure 2.3 (a) Anal sac adenocarcinomas treated with adjuvant megavoltage radiation. (b) Lead block used to spare normal tissue from RT. (c) Final setup including a tissue‐equivalent “bolus” to allow the maximum dose of radiation to reach the tumor.

Source: Courtesy of Mary‐Kay Klein.

Figure 2.4 (a) focal necrosis on the antebrachium following extravasation of doxorubicin. (b, c) Surgical debridement of the necrotic tissue.