Page 185 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

PART III Therapeutic Modalities for the Cancer Patient

VetBooks.ir 10

Surgical Oncology

JAMES P. FARESE, JULIUS M. LIPTAK, AND STEPHEN J. WITHROW

Complete surgical removal of localized cancer cures more can- biopsies are one of the most crucial steps in the management of
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cer patients than any other form of treatment, in part because the cancer patient. Not only does the surgeon need to procure
this modality is generally applied as the sole treatment for local adequate and representative tissue to establish a diagnosis, but
disease, early stage disease, and tumors with limited potential to also the biopsy must not compromise subsequent curative surgi-
metastasize. In humans, 60% of patients who are cured of can- cal resection or radiation field planning.
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cer are cured by surgery alone. Before this hope for cure can be
realized in veterinary medicine, surgeons must have a thorough Levels of Tumor Excision
understanding of anatomy, physiology, resection, and reconstruc-
tion options for all organs; expected tumor behavior; and the The aggressiveness of surgical resection, or surgical dose, is catego-
various alternatives or adjuvants to surgery. Surgical oncologists rized as intralesional (or debulking), marginal, wide, and radical
should not only be good technical surgeons, but also dedicated (Fig. 10.1). These categories were first proposed for musculoskeletal
tumor biologists. Surgery will likely play a role at one point or tumors by Dr. William Enneking, but they have since gained wide
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another in the management of most cancer patients. acceptance for all solid tumors. The most common mistake in sur-
Surgical procedures may include any of the following: diagno- gical oncology is to use too low a surgical dose, particularly because
sis (biopsy), resection for cure, resection for palliation of symp- of the fear of being unable to close the resultant defect. In human
toms, and a wide variety of ancillary procedures to enhance and medicine, two surgical teams are sometimes involved in the excision
complement other forms of treatment. of tumors, one team for surgical resection and another team for
Surgical resection of cancer was introduced in the 16th century subsequent reconstruction, to avoid this situation. Because this is
BC and remained relatively underutilized until the development unrealistic in veterinary medicine, the use of sterile surgical markers
of general anesthesia (1840s), antisepsis (1860s), and effective to delineate margins before incision assists in orientating the sur-
analgesia, which made aggressive resection safer and more toler- geon and overcoming the subconscious concerns of wound closure.
able for the patient. Dr. William Halstead developed the basic
principles of surgical oncology in the 1890s. In the 21st century, Surgery for Cure
radical resection has increasingly been customized to meet the
needs of the patient. Further refinements in surgery have been Before a surgeon can provide the optimal operation for the patient
made possible with newer equipment, advanced imaging, modifi- with cancer, the following questions need to be considered:
cations in analgesic drugs and techniques, use of blood products, 1. What is the histologic type, histologic grade, and clinical stage
and advancements in critical care medicine. of the cancer to be treated?
Most dogs and cats with cancerous conditions are geriatric; 2. What are the expected local and systemic effects of this tumor?
however, with normal major organ function, dogs and cats at an 3. Is a cure possible and at what price in terms of function and
advanced age can still be good candidates for surgery, and age has cosmetics?
not been shown to affect the tumor-related prognosis for tumor 4. Is an operation indicated at all?
types. In fact, dogs with osteosarcoma that are younger than 2 5. Are there alternative options to surgery, or does surgery need
years of age have a worse prognosis than dogs that are older than to be combined with other modalities?
2 years of age after amputation alone. In most instances older A recurring theme in surgical management of cancer is that
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animals will tolerate aggressive surgical intervention as well as the first surgery has the best chance of cure. Several reasons for
younger patients do. Screening for comorbidities (e.g., thoracic this improvement in survival have been proposed. Untreated
radiographs and abdominal ultrasound) is recommended before tumors often have had less chronologic time to metastasize and
major surgical procedures, especially in older dogs and cats. acquire more biologically aggressive phenotypes than recurrent
cancers. Untreated tumors and adjacent normal tissues have near
Surgery for Diagnosis normal anatomy, which facilitates surgical dissection and resec-
tion. Recurrent tumors may contaminate previously uninvolved
Although biopsy principles are covered in Chapter 9, it is worth tissue planes, thereby requiring wider resection than otherwise
emphasizing that properly timed, performed, and interpreted would have been needed on the initial tumor excision.

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