Surgery is the oldest form of treatment for neoplasia. Although many tumors are amenable to surgical therapy, surgery is now a part of a much larger team that considers all aspects of patient/tumor relationships. Veterinary surgeons with a serious interest in oncology must understand the biology of a wide variety of animal tumors and must be prepared to interact with medical oncologists, radiation oncologists, radiologists, anesthesiologists, and pathologists as well as with owners and other veterinarians. Conventionally, the role of surgery in oncological therapy involved sharp surgical excision of the neoplasm with a scalpel. Surgeons now use more modern techniques such as electrosurgery, radiofrequency surgery, cryosurgery, and laser surgery.
Surgery in the overall management of tumor patients includes prevention of neoplasia, diagnostic surgery, surgical excision of tumors, cytoreductive, surgery for metastatic disease, and palliative surgery.
Prevention of Neoplasia
Surgery can be performed on an elective basis to prevent the development of neoplasia. The pathogenesis of many tumors is in part hormonally based, and neutering early in life can reduce the incidence of these tumors. An example is the decrease in the incidence rate of mammary gland neoplasia in dogs and cats that had ovariohysterectomy performed early in life.
The primary role of surgery in the diagnosis of neoplasia is the acquisition of tissue for histological examination. Various biopsy techniques include incisional biopsy, Tru-Cut biopsy, punch biopsy, etc.
Cytoreductive surgery is generally avoided unless complete excision is deemed impossible or unlikely and radiation therapy is planned.
Surgery for Metastatic Disease
Although surgical resection of metastatic lesions is rarely performed in veterinary medicine, it has the potential to prolong life in carefully selected cases.
Palliative surgery is surgery that relieves clinical signs without curing the underlying disease. Palliative surgery can often provide short good quality life and is often a worthwhile therapeutic option.
Surgical Excision of Tumors
Before a surgeon can be in a position to provide optimal surgery for the patient with neoplasia, he/she needs to consider the following information:
1. The tumor type, stage, and grade (if available and clinically relevant).
2. The expected local and systemic effect of this tumor type and stage.
3. The probability of local tumor control.
4. Predicted functional outcome.
5. Predicted cosmetic outcome.
6. Salvage potential.
7. Is surgery indicated at all?
8. Other patient factors (concomitant disease).
9. Other options for alternative treatments.
A recurring theme in surgical management of cancer is that the first surgery has the best chance for cure. Several mechanisms for this improvement in survival include the following: Untreated tumors have had less chronologic time to metastasize than recurrent cancer. Untreated tumors have near normal anatomy that will facilitate operative maneuvers. Recurrent tumors may have had seeding of previously noninvolved tissue planes requiring wider resection than would have been required on the initial tumor.
The actual surgical technique will vary with the site, size, and stage of tumor. Some general statements about oncologic surgery that need to be emphasized are:
1. All fine-needle aspiration, punch biopsy, and incisional biopsy tracts should be excised in continuity with the primary tumor, since tumor cells are capable of growth in these wounds. All biopsies should be positioned is a manner that they can be removed at surgery.
2. Early vascular ligation should be attempted.
3. Local control of malignant cancer requires that wide margins of normal tissue be removed around the tumor. Tumors with a high probability of local recurrence should have at least 3 cm margins removed three-dimensionally. One should strive for a level of dissection that is at least one tissue plane away from the mass.
4. Tumors should be handled gently to avoid the risk of breaking off tumor cells into the operative wound, where they may grow.
5. The aggressiveness of resection should only rarely be tempered by fears of wound closure. It is better to leave a wound partially open with no cancer than closed with residual cancer.
6. Because it is not possible for pathologists to evaluate all margins of a mass, the surgeon should assist the pathologist by providing information about the specific margins that are of greatest concern. An example of such aid is to mark key margins with suture tags. Staining the excised mass with India ink can facilitate this process as well.
Author: Michael B. Mison, D.V.M., Diplomate ACVS Seattle Veterinary Specialists