Principles of Surgical Oncology
Principles of Surgical Oncology
Surgical oncology, as its name suggests, is the specific application of surgical principles to the oncologic setting. These principles have been derived by adapting standard surgical approaches to the unique situations that arise when treating cancer patients.
The surgeon is often the first specialist to see the patient with a solid malignancy, and, in the course of therapy, he or she may be called upon to provide diagnostic, therapeutic, palliative, and supportive care. In each of these areas, guiding paradigms that are unique to surgical oncology are employed.
In addition, the surgical oncologist must be knowledgeable about all of the available surgical and adjuvant therapies, both standard and experimental, for a particular cancer. This enables the surgeon not only to explain the various treatment options to the patient but also to perform the initial steps in diagnosis and treatment in such a way as to facilitate and avoid interfering with future therapeutic options.
Invasive diagnostic modalities
As the surgeon approaches the patient with a solid malignancy or abnormal nodal disease or the rare individual with a tissue-based manifestation of a leukemia, selection of a diagnostic approach that will have a high likelihood of a specific, accurate diagnosis is paramount. The advent of high-quality invasive diagnostic approaches guided by radiologic imaging modalities has limited the open surgical approach to those situations where the disease is inaccessible, a significant amount of tissue is required for diagnosis, or a percutaneous approach is too dangerous (due, for example, to a bleeding diathesis, critical intervening structures, or the potential for unacceptable complications, such as pneumothorax).
Lymph node biopsy
The usual indication for biopsy of the lymph node is to establish the diagnosis of lymphoma or metastatic carcinoma. Each situation should be approached in a different manner.
Lymphoma The goal of biopsy in the patient with an abnormal lymph node and suspected lymphoma is to make the general diagnosis and to establish the lymphoma type and subtype. Additional analyses of the cells in the node, its internal architecture, and the subpopulations of cells are critical for subsequent treatment. Although advances in immunocytochemical and histochemical analyses have been made, adequate tissue is the key element in accurate diagnosis.
Consequently, the initial diagnosis of lymphoma should be made on a completely excised node that has been minimally manipulated to ensure that there is little crush damage. When primary lymphoma is suspected, the use of needle aspiration does not consistently allow for the complete analyses described above and can lead to incomplete or inaccurate diagnosis and treatment delays.
When recurrent lymphoma is the primary diagnosis, analysis of a specific cell type is important for assessing changes in the type of lymphoma and whether a transformation has occurred. In the rare situation in which recurrent Hodgkin lymphoma is suspected, a core biopsy may be adequate if the classic Reed-Sternberg cells are identified. However, in the initial and recurrent settings, biopsy of an intact node is often required.
Carcinoma The diagnosis of metastatic carcinoma often requires less tissue than is needed for lymphoma. Fine-needle aspiration (FNA), core biopsy, or subtotal removal of a single node will be adequate in this situation. For metastatic disease, the surgeon will use a combination of factors, such as location of the node, physical examination, and symptoms, to predict the site of primary disease. When this information is communicated to the pathologist, the pathologic evaluation can be focused on the most likely sites so as to obtain the highest diagnostic yield. The use of immunocytochemical analyses can be successful in defining the primary site, even on small amounts of tissue.
Head and neck adenopathy The head and neck region is a common site of palpable adenopathy that poses a significant diagnostic dilemma. Nodal zones in this area serve as the harbinger of lymphoma (particularly Hodgkin lymphoma) and as sites of metastasis from the mucosal surfaces of the upper aerodigestive tract; nasopharynx; thyroid; lungs; and, occasionally, intra-abdominal sites, such as the stomach, liver, and pancreas.
Because treatment of these nodal metastases varies widely, and subsequent treatments may be jeopardized by inconveniently placed biopsy incisions, the surgical oncologist must consider the most likely source of the disease prior to performing the biopsy. FNA or core biopsy becomes a valuable tool in this situation, as the tissue sample is usually adequate for basic analysis (cytologic or histologic), and special studies (eg, immunocytochemical analyses) can be performed as needed.
Biopsy of a tissue-based mass
Several principles must be considered when approaching the seemingly simple task of biopsying a tissue-based mass. As each of the biopsy methods has unique risks, yields, and costs, the initial choice can be a critical factor in the timeliness and expense of the diagnostic process. It is crucial that the physician charged with making the invasive diagnosis be mindful of these factors.
Mass in the aerodigestive tract In the aerodigestive tract, biopsy of a lesion should include a representative amount of tissue taken preferably from the periphery of the lesion, where the maximum amount of viable malignant cells will be present. Because the treatment of in situ and invasive diseases varies greatly, the biopsy must be of adequate depth to determine penetration of the tumors. This is particularly true for carcinomas of the oral cavity, pharynx, and larynx.
Breast mass Although previously a common procedure, an open surgical biopsy of the breast is rarely indicated today. Palpable breast masses that are highly suspicious (as indicated by physical findings and mammography) can be diagnosed as malignant with close to 100% accuracy with FNA. However, because the distinction between invasive and noninvasive diseases is often required prior to the initiation of treatment, a core biopsy, performed either under image guidance (ultrasonography or mammography) or directly for palpable lesions, is the method of choice.
An excellent example of the interdependence of the method of tissue diagnosis and therapeutic options is the patient with a moderate-sized breast tumor considering breast conservation who chooses preoperative chemotherapy for downsizing of the breast lesion. The core biopsy method establishes the histologic diagnosis, provides adequate tissue for analyses of hormone-receptor levels and other risk factors, causes little or no cosmetic damage, does not perturb sentinel node analyses, and does not require extended healing prior to the initiation of therapy. In addition, a small radioopaque clip can be placed in the tumor to guide the surgical extirpation. This step is important because excellent treatment responses can make it difficult for the surgeon to localize the original tumor site.
Mass in the trunk or extremities For soft-tissue or bony masses of the trunk or extremities, the biopsy technique should be selected on the basis of the planned subsequent tumor resection. The incision should be made along anatomic lines in the trunk or along the long axis of the extremity. When a sarcoma is suspected, FNA can establish the diagnosis of malignancy, but a core biopsy will likely be required to determine the histologic type and plan neoadjuvant therapy.
As with any surgical patient, the preoperative evaluation of the cancer patient hinges primarily on the individual's underlying medical condition(s). Because most new cancers occur in older patients, careful attention must be paid to evaluation of cardiovascular risks. Adequate information can usually be obtained from a standard history, physical examination, and electrocardiogram (ECG), but any concerns identified should be subjected to a full diagnostic work-up.
The evaluation should also include a detailed history of current and previous therapies. Many patients will be on anticoagulation, aspirin, or analgesics, all of which may impact on their perioperative management. Previous use of doxorubicin or trastuzumab (Herceptin) may be associated with cardiac dysfunction and the use of bleomycin with severe lung sensitivity to oxygen concentrations > 30%. Due to the association of bowel anastomotic perforation with the use of bevacizumab (Avastin), the timing of colonic surgery should be modified. Some of the cytotoxic agents (oxaliplatin [Eloxatin], irinotecan) used to treat colon and rectal cancers are associated with liver injury.