Universal guidelines for the management of cancer patients are difficult to define. Clearly, every tumor, every situation, every patient is different. But let’s try to define five general rules anyway.
The first challenge is to suspect or recognize cancer. It may seem straightforward with a skin mass, but it can be much more challenging in the intestine or the bladder. Confirming the suspicion is the next step, and it usually involves a fine needle aspirate (FNA) or a biopsy.
Let’s simplify and only consider skin masses. There are two main FNA techniques: aspiration and trephination.
The traditional aspiration technique requires a needle and a syringe. The needle is introduced into the tumor in various directions, while negative pressure is applied to the syringe. “The microtrauma created may cause bleeding, which will lead to hemodilution of the sample,”
Explains Ken Mero, DVM, Ph.D., a pathologist at Histology of Stone Ridge in Stone Ridge, N.Y.
Another method is the trephination technique, which doesn’t involve negative pressure and reduces the risk of hemodilution. Tiny cores of the mass are harvested without using negative pressure, which may allow a higher cellular yield by avoiding hemodilution.
Incisional biopsy techniques include Tru-Cut, wedge or punch biopsy. Excisional biopsy is a fancy synonym for “trying to remove a tumor entirely,” i.e. with clean margins.
The results of an FNA and a biopsy have two important differences. An FNA sometimes will provide an actual diagnosis (e.g. mast cell tumor) and often will include several rule-outs. A good biopsy will typically provide a definite diagnosis and the grade of the tumor, when applicable. In addition, the pathologist can study the architecture of the sample and visualize cells in their original microstructure. Last but not least, an excisional biopsy helps with assessing the surgical margins—“clean” or “dirty.”
“Grading is a complex and subjective endeavor. Grading a tumor involves describing how differentiated or aggressive it is. The pathologist will describe a tumor as being low, moderate or high grade. Another description is a poorly, moderately or highly differentiated tumor,” Dr. Mero explains.
A mast cell tumor is somewhat easier to grade—1, 2 or 3, with 3 being the most aggressive.
For a variety of medical or financial reasons, an FNA or an incisional biopsy may not be performed.
The second step is staging a tumor, which helps specify whether it has metastasized. The tests involved can include:
• Simple palpation, such as of the peripheral lymph nodes.
• Radiographs—thoracic or abdominal.
• Ultrasound—thoracic or abdominal.
• CAT scanner, most often of the thorax.MRI, possibly adequate for the abdomen but usually not for the thorax because of the constant motion of the heart and lungs.
Cynics will say that surgeons would walk the patient straight to the OR at this point. In fact, the third step should be a heart-to-heart discussion with the pet owner. The goals are multiple:
• Review what is known and what is unknown.
• Make sure the client understands the situation and its consequences.
• Explain the expected prognosis.
• Describe what is involved in surgery.
• Suggest the possibility of other treatment modalities, such as chemotherapy and radiation therapy. These options may be offered in addition to surgery.
• Estimate the cost of surgery and postop care.
Snippets of such conversations could include:
• “Kiki’s spleen mass looks aggressive on ultrasound, but the liver looks good. During surgery we will remove the spleen and take a liver biopsy. Once the biopsies are back, we can discuss chemo options.”
• “Buddy’s epulis will require removing part of the lower jaw, but most Labradors will eat readily the day after surgery. In addition, the surgery area typically looks fairly cosmetic.”
• “It is impossible to remove the soft tissue sarcoma entirely on Fluffy’s leg, and radiation therapy would help us get rid of some more cancer cells after surgery.”
Once client and practitioner are on the same page, then and only then can surgery take place. Even if an incisional biopsy had been submitted, it is critical to send the entire mass, or at least representative samples, to confirm the diagnosis and, very importantly, to examine the margins.
If margins are not clean, the need for follow-up treatment must be recommended and explained. Whether the owner accepts the suggestion is a different story. Our job always should be to recommend follow-up options when applicable regardless of what we think the owner will choose or can afford.
This conversation should be documented in the medical record, which is a legal document.
Chemotherapy most of the time is a systemic treatment, whether oral or injectable. Side effects are generally systemic but surprisingly rare. Only about 15 percent of dogs and 5 percent of cats will get sick temporarily.
Radiation therapy is a local treatment with predictable and often reversible complications. With skin masses, for example, the most common complication is a radiation burn, which is somewhat comparable to a bad sunburn.
General guidelines for cancer management can be defined after all. They involve diagnosing and grading the tumor, staging the patient, communicating with the owner, performing surgery and recommending possible follow-up treatment.
Without question, these concepts will vary with the situation, but these simple steps are a good template to keep in mind next time you suspect cancer in your patient.
Phil Zeltzman is a board-certified mobile surgeon in Allentown, Pa. His website is DrPhilZeltzman.com.
This article first appeared in the April 2010 issue of Veterinary Practice News