play in the diagnosis of neoplasia. As an example, the differential list for a flat‐coated retriever with a femoral bony lesion noted on radiographs that has been referred for a suspected diagnosis of osteosarcoma should be expanded to include histiocytic sarcoma; other diagnostics such as an abdominal ultrasound would be recommended to look for other foci of histiocytic disease.
Other portions of the signalment are also important to note, including the patient’s weight and body condition. Patients that are morbidly obese or those in poor body condition may not be able to function effectively or may be more severely debilitated by a major surgery. For example, a patient with cancer cachexia can have such profound alterations of their carbohydrate, protein, and fat metabolism that recovery may be compromised (Ogilvie 1998).
Staging/Concomitant Disease
Staging diagnostics such as a complete blood count, chemistry profile, urinalysis, thoracic radiographs and abdominal ultrasound, and/or thoracic and abdominal computed tomography (CT) are essential components for the preoperative assessment of veterinary oncologic patients. While there is debate about the timing of some of these diagnostics (i.e. before or after biopsy), for many patients, thorough preoperative staging diagnostics can unmask an underlying condition that may alter the plan or better assist the surgeon in providing a more accurate prognosis. Alternative surgical dose may also be recommended based on the results of staging.
Neoadjuvant Therapy
The surgical oncologist is often presented with extremely large tumors or tumors located in difficult anatomic locations. It is important to consider neoadjuvant treatments, if available and warranted, such as chemotherapy and radiotherapy before proceeding with surgery. In some cases, these treatments may decrease the overall surgical dose needed to achieve local control. Most commonly, recommendations about chemotherapy and/or radiation therapy are made after the grade of the tumor and the surgical margins have been determined. In tumors that are suspected to be sensitive to chemotherapy based on published literature or previous experience, a postoperative protocol can be discussed prior to surgery.
Neoadjuvant chemotherapy is rarely pursued in veterinary medicine. However, for certain tumor types, this may prove to be a beneficial adjunct to surgery. In human cases of osteosarcoma, neoadjuvant chemotherapy is commonly used prior to surgery and local tumor response (as measured by percent tumor necrosis) has been shown to be associated with increased survival. A veterinary study showed that neoadjuvant chemotherapy with prednisone administered to a group of dogs with intermediate‐grade mast cell tumors resulted in tumor size reduction; surgical excision of very large mast cell tumors or tumors that were in an anatomic site that precluded wide (3 cm lateral and one facial plane deep) excision was more successful (Stanclift and Gilson 2008). Microscopically complete margins were achieved in many of the pretreated cases. These patients would not likely have had complete surgical margins otherwise (Stanclift and Gilson 2008). Long‐term follow‐up was not the focus of this study, however, and controversy exists as to the risk of local recurrence in patients where neoadjuvant chemotherapy is used to shrink gross tumor volume with a view to allow a less aggressive surgical margin. Further study is needed to assess the benefit of neoadjuvant chemotherapy in veterinary cancer patients.
Neoadjuvant radiation therapy has also been advocated as a method of treating neoplastic disease to reduce the need for radical surgery (McEntee 2006). Advantages to neoadjuvant radiation therapy include a smaller radiation field, intact tissue planes, better tissue oxygenation, and a reduction in the number of viable neoplastic cells that may be left within a postoperative seroma or hematoma following microscopically incomplete margins. Complications such as poor wound healing may occur more commonly in irradiated surgical sites than in nonirradiated tissue due to the effects of radiation on fibroblasts and blood vessels (Seguin et al. 2005). Even so, surgery in previously irradiated fields can be quite successful, provided care is taken to ensure minimum tension, careful surgical technique, and appropriate timing (either before or after acute effects have occurred). Consultation with a radiation oncologist prior to surgery can help the surgeon identify those patients who may be good candidates. Considerations such as whether or not preoperative radiation will diminish the surgical dose and what type of reconstruction will be needed to ensure a tension‐free closure in an irradiated surgical field should be discussed at length prior to deciding if neoadjuvant radiation is warranted.
Surgical Planning
The first decision in the surgical planning in removing a tumor is to determine the “surgical dose.” The surgical dose refers to how aggressive the excision is with respect to the edges of the tumor. The surgical dose has been divided into: intracapsular, marginal, wide, and radical (Figure 1.1). An intracapsular excision is where the capsule of the organ where the tumor arises from (e.g. thyroid gland) or the pseudocapsule of the tumor (e.g. soft tissue sarcoma) is disrupted and the tumor is removed in pieces. A marginal excision is where the removal is done just outside or on the capsule or pseudocapsule. Oftentimes, the tumor is “shelled out.” A wide excision is when the tumor and its capsule are never entered and grossly normal tissue surrounds the specimen. This is often defined as 2–3 cm of normal tissue around the edges of the tumor and one fascial place beneath the cutaneous and subcutaneous tumors. The 2–3 cm of normal tissue is in situ and not histological. A radical excision is the removal of the entire compartment or structure where the tumor is arising from. An example of a radical excision is a limb amputation.
Figure 1.1 Diagram illustrating the different doses of surgery: marginal, wide, and radical being an amputation in this example. Intracapsular is not shown.
Source: Illustrated by Molly Borman.
When removing a tumor, there can be three different goals: curative, palliative, and cytoreductive. These goals will dictate the dose of surgery and several factors will guide which goal should be pursued. The first factor is tumor type. Because benign tumors are limited to their capsule and do not extend into the normal‐appearing tissues, a marginal excision is performed. Malignant tumors, however, have the ability to extend into the grossly normal‐looking tissue at the microscopic level (Figure 1.2). Other factors need to be considered to determine the goal and consequently the dose of surgery. With (most) malignant tumors, when the goal is curative, a wide or radical excision is required. For a palliative or cytoreductive goal, a marginal excision is performed. An intracapsular excision is rarely indicated.
Figure 1.2 Diagram showing the extension of tumor into the grossly normal‐looking tissue. These extensions are most typically at the microscopic level. This is the reason to perform a wide excision (2), as opposed to a marginal excision (1), with the goal to achieve a complete excision.
Source: Illustrated by Molly Borman.
The additional factors to consider to determine the goal of the surgery are: tumor size and location, stage of the cancer, overall health of the patient, risk of the surgery, prognosis, and goals of the owners. Table 1.1 provides examples of how these factors come into play, understanding there are always exceptions or nuances (see section on margins and palliative and cytoreductive surgery).
Because
