A4.1 Oncological principles of resection

Topic

Oncological surgery acts more directly than any other treatment on the patient's tumor cell count: rather than destroying tumor cells in situ—as radiotherapy does—or killing them chemically—as chemotherapy does—oncological surgery physically removes the tumor tissue from the patient's body.

This physical removal of tumor tissue results in a reduction of the tumor cell count that is both dramatic and instantaneous—far more rapid than the gradual reduction achieved by radiotherapy or chemotherapy. However, the oncological success of the surgery depends not only on this immediate reduction but also on whether any residual tumor cells remain—either at the edge of the excised specimen or elsewhere in the patient's body in the form of micrometastatic disease that had already spread prior to surgery.

Whether or not residual tumor cells remain at the edge of the surgical specimen is, in turn, a matter of distance: the physics of oncological surgery is fundamentally the physics of margins—that is, the distance between the edge of the tumor and the edge of the specimen removed by the surgeon. When this distance is sufficient, all tumor cells are contained within the excised specimen, resulting in a negative margin—meaning there are no tumor cells at the edge. However, when this distance is reduced to zero—when the tumor edge reaches the very edge of the excised specimen or extends beyond it—residual tumor cells remain in the patient; if these residual cells are visible only under a microscope, the margin is termed "microscopically positive," whereas if they form a tumor visible to the naked eye, the margin is termed "macroscopically positive." This classification of the margin—negative, microscopically positive, or macroscopically positive—is what ultimately determines the patient's prognosis and the need for adjuvant treatment following surgery: the poorer the margin resulting from oncological surgery, the greater the likelihood that residual tumor cells capable of causing a recurrence remain, and the more necessary additional post-surgical treatment becomes to attempt to eliminate those residual tumor cells that the oncological surgery—however precise—failed to remove.

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