Tumor excision is arguably one of the most commonly performed surgeries on animals. We talked with Stephen Withrow, DVM, a surgical oncologist at the Colorado State University Animal Cancer Center in Fort Collins. Dr. Withrow is double boarded in surgery and internal medicine (oncology).
A pioneer of cancer surgery, he has dedicated his career to improving protocols, surgeries and patient care. Plus, he literally wrote the book—“Withrow and MacEwen’s Small Animal Clinical Oncology” (Fourth edition, Saunders 2007). He kindly shares 10 pearls to improve the care of your cancer patients.
1 Work It Up
It is beneficial to reach a probable diagnosis before excising any mass beyond a wart or a straightforward presumed lipoma. It would be good to obtain a fine needle aspirate or biopsy to determine if the mass is benign or malignant.
This determines what Withrow calls the “surgical dose.” This guides how aggressive the surgical excision has to be: Can we live with narrow margins for a benign tumor, or do we need 1-2-3 cm margins in every direction for a malignant mass? We know that the first surgery is the most likely to provide clean margins.
If a biopsy is performed, it would be ideal if the practitioner harvesting it could be the one doing the final excision. The biopsy tract should be excised with the mass, which means the biopsy has to be planned accordingly.
2 Advanced Imaging
Although plain radiographs are a great screening tool, ultrasounds, CT scans or MRIs can provide invaluable information. Advanced imaging can help determine whether a mass is operable.
“That said, we should not become so dependent on technology that we forget to use our hands—and our heads,” says Dr. Withrow.
For example, some tumors may seem firmly attached to the underlying tissue when the patient is awake. But when the patient is under anesthesia and you can wrap your fingers around the mass, it may turn out to be easily movable. Anal sac, mammary gland and thyroid tumors come to mind.
3 Be a (Tumor) Behaviorist
Staging the patient, or checking for metastasis, is critical before surgery. Each tumor type has its own metastatic behavior: It may spread to the lungs, liver, lymph nodes or bones. We need to know the natural behavior of the suspected tumor type to choose the staging technique. For example, with a mast cell tumor, we should focus on the regional lymph nodes and abdomen rather than the lungs.
When metastasis is subtle but suspected based on thoracic radiographs, advanced imaging such as thoracic CT scanning can be helpful.
4 Know Your Pathologist
“Pathology is an art form,” says Dr. Withrow. Studies show that 5 to 10 percent of biopsy reports are inaccurate. The only person who can decide whether the pathologist’s diagnosis makes sense is the clinician in charge of the patient. “The running joke at CSU is that you need to know five people very well: your significant other, your banker, your clergy, your radiologist and your pathologist,” he says. ”This means you should know your pathologist on a first name basis and not hesitate to call if you have questions about the diagnosis.”
5 The Wave of the Future
Advanced diagnostic tests (PCR, immunohistochemistry, cell typing, special stains) and a better understanding of complex molecular pathways can be confusing. Yet recent technology enables us to provide more targeted therapies, such as tyrosine kinase inhibitors (masitinib, toceranib) for mast cell tumors.
The Holy Grail would be a cancer-specific treatment that limits or prevents collateral damage.
6 Be Pain-centric
“I am very proud of the profession, specialists and general practitioners, for embracing the concept of analgesia or, even better, of pre-emptive pain management,” says Dr. Withrow. From nerve blocks to constant-rate infusions, from potent opioids to safe anti-inflammatory drugs, pre-, intra- and postop pain medications have greatly improved patient care.
“I am always impressed to see 99 percent of amputees go home on the day after surgery,” he adds. “We can now perform massive resections (mandibulectomies, maxillectomies) and send home a patient that is comfortable and willing to eat readily.”
7 A Team Approach
It is critical to create a team of like-minded professionals when working with cancer patients. Some doctors prefer the surgical aspect of cancer management, while others prefer the medical treatment, including chemotherapy.
“I can’t emphasize enough how important technicians are in the management of these patients,” says Dr. Withrow. Beyond placing IV catheters, taking “met check” radiographs and administering chemotherapy drugs, technicians are frequent points of contact for the pet owner. They can act as confidants and certainly can be excellent patient advocates.
8 Be Stingy with ABs
With the emergence of serious antibiotic resistance, we need to be wiser with antibiotics. After a short and “clean” surgery that does not involve viscera, the patient probably does not need much antibiotherapy beyond the perioperative period. In addition, there is no need to choose a potent antibiotic when a simple cephalosporin will do.
9 Safe Anesthesia
Although we sometimes take them for granted, we have made tremendous progress with the safety of anesthesia protocols. We now can perform reconstructions, thoracotomies and brain surgeries, and our patients seem to magically wake up quickly and smoothly.
10 Critical Care
Critical care is now a specialty. Once the surgical team finishes the final skin suture, those who have the luxury of a critical care team who can take over the patient can move on to the next challenge. This second team can manage wound drains, chest and feeding tubes, monitor skin flaps and grafts, and adjust pain medications.
“I am fortunate to be able to entirely rely on my criticalist to take my patients over,” Dr. Withrow says.
During our interview, Dr. Withrow mentioned numerous specialties and facets of our profession: A well-rounded cancer surgeon has to know about surgery, medicine, oncology, imaging, pathology, anesthesia, pain management and client communication, and needs to assemble a good team of professionals.
Dr. Zeltzman is a mobile, board-certified surgeon near Allentown, Pa. His book, “Walk a Hound, Lose a Pound: How You and Your Dog Can Lose Weight, Stay Fit and Have Fun Together,” is now available from Purdue University Press.