Rules of Surgical Oncology: Any Evidence?

The principles of surgical oncology are well known: biopsy for diagnosis and prognosis; clinical staging to determine the extent of disease; and surgical excision in a manner that maximizes the chances of a successful outcome. But are these principles based on scientifically proven facts or unproven theories and practices?

Clinical staging is the diagnostic workup of a patient to determine the size of the local tumor, whether there is regional lymph node metastasis, and the presence of distant metastasis. The size of skin tumors can often be measured with calipers, but caliper measurements frequently underestimate the size of the tumor when compared to ultrasound or advanced imaging of the tumor; yet we rarely perform imaging on skin tumors to determine the true extent of these tumors and hence plan the surgical approach. The same is true for bone tumors with various imaging modalities either underestimating or overestimating the true extent of the tumor. For limb- sparing candidates, his results in either over-treatment, which can potentially increase the risk of construct failure, or under-treatment, which increases the risk of incomplete tumor excision, local recurrence and poorer survival times.

The determination of regional lymph node status has traditionally been based on palpation of the nearest anatomical lymph node. However, palpation of the regional lymph node is an unreliable method for the determination of nodal metastasis because metastatic lymph nodes are not necessarily firm, fixed or painful. Furthermore, normal lymphatic drainage patterns are quite variable and hence the nearest draining anatomical lymph node may not be the sentinel lymph node for that tumor. For instance, thyroid carcinomas will metastasize cranially to the submandibular lymph node bed; oral tumors metastasize to any of the submandibular, medial retropharyngeal or parotic lymph nodes; oral tumors metastasize to the contralateral lymph nodes; and mammary tumors can metastasize to the inguinal or axillary lymph nodes regardless of the location of the mammary tumor. For this reason, sentinel lymph node mapping with blue dyes, nuclear scintigraphy and/or intraoperative gamma probes is used in human oncology to identify the sentinel lymph node, or the first lymph node draining the tumor. The sentinel lymph node is representative of the entire lymph node bed and helps determine prognosis and the need for adjuvant therapy. Yet sentinel lymph node mapping is rarely used in veterinary surgical oncology. Furthermore, determining nodal metastasis can be difficult, especially in canine mast cell tumors.  [...]