22 Feb 2016
Kathryn Pratschke reviews the use of surgical oncology in relation to its diagnosis, treatment and management of cancer and tumours (1/2).
Kathryn Pratschke
Job Title
Figure 5. In this patient, a 2cm diameter mass was resected with a postoperative diagnosis of intermediate grade soft tissue sarcoma containing dirty margins. A revision surgery was performed when the tumour, which failed to achieve clean margins, regrew after three months. This image was taken nine months after the first surgery and, in addition to numerous local nodules of regrowth, several tumour nodules were palpable along the triceps tendon, parallel to a previous surgical incision. The extent of local tissue invasion at this stage mandated forequarter amputation.
Cancer treatment and management is rapidly changing and evolving thanks to the development of sophisticated diagnostic and therapeutic modalities.
Despite the increasing availability of alternative modalities, such as chemotherapy and radiation therapy, in human surgical oncology 60% of patients with cancer are cured by surgery alone (Poston, 2007). Likewise, in veterinary patients, surgery is considered the most important component of treatment in those with solid tumours because it frequently offers the best chance for improving the patient’s quality of life (Liptak, 2009; Farese et al, 2012).
Conversely, poorly planned and executed surgery can be counter-productive and may adversely affect prognosis.
In this article, and the second part to follow, the author reviews good principles of surgical oncology and provides practical advice on how to maximise case management and outcome.
For many years, the Halsted theory (named after William Stewart Halsted, former professor of surgery at Johns Hopkins University, US) of cancer prevailed, which held local cancer always spread in a regional fashion, such as into the local tissues, then the local lymph node, then the next node and so on. The belief was bigger surgical excisions would lead to more cures.
Halsted developed the radical mastectomy for the treatment of breast cancer during the last decade of the 19th century, based on these beliefs (Halsted, 1894), although the general concept of the radical mastectomy can be traced back to Lorenz Heister, a German surgeon who wrote about mastectomy and lumpectomy in his book, Chirurgie, published in 1719.
As these very aggressive surgical procedures were being pioneered, another surgeon, Stephen Paget, was considering the question “which organs shall suffer in a case of disseminated cancer?” (Paget, 1889). His conclusion cells from a primary tumour spread widely through the bloodstream, but only grow in certain organs, was an accurate and highly sophisticated hypothesis for the time, subsequently confirmed almost 100 years later by the techniques of modern cellular and molecular biology.
This understanding of metastasis became a key element in recognising the limitations of cancer surgery, as well as improving the appreciation of surgery’s role as part of an overall treatment plan.
To help obtain the best outcome with tumour removal, vets need a thorough understanding of the basic principles of surgical oncology, including:
Inherent in obtaining the best possible outcome is to keep in mind the paramount goal of any therapeutic plan – to improve the patient’s quality of life. A key part of this process is clear – well-informed communication with the client regarding each step of the diagnostic and treatment plan.
A note should be made of all tumours or lumps, including the approximate size and location on the patient, and should be kept in the records for future reference.
The majority of cancer patients will be older individuals, which means comorbidities may exist that limit or compromise treatment options (Figure 1). This is not the same as saying the “patient is too old”; age should not be considered a negative prognostic indicator and an older patient in good general health is just as worthy and deserving of treatment as a patient half its age (Ehrhart and Culp, 2012).
A patient’s breed may influence diagnosis and management – for example, a flat-coated retriever with a femoral lesion should have histiocytic sarcoma on the differential list alongside osteosarcoma, with a staging protocol including abdominal ultrasound in addition to thoracic imaging.
Prior to surgery, it is important to look at the patient as a whole and evaluate general health status. Thorough
preoperative evaluation allows identification of tumour-related concerns or concurrent disease problems, such as renal insufficiency, hepatic disease, osteoarthritis and paraneoplastic syndromes (Table 1).
For example, in a patient with hypercalcaemia associated with anal sac adenocarcinoma, additional care needs to be taken
preoperatively to minimise risk to renal function. Patients in poor body condition may have a compromised recovery from surgery (Figure 2), while obese patients may be prone to anaesthetic complications, including obesity hypoventilation (Pickwickian syndrome; Lin and Lin, 2012; Gompf, 2015).
It is sometimes necessary to consider when not to operate. Several scenarios exist where surgery is not the best option for the patient. If surgery will only remove some of the tumour, but leave significant residual local disease, it is of questionable benefit to the patient. This type of piecemeal debulking should probably only be considered where the tumour is physically causing obstruction or abnormal function, and the owner is completely cognisant that surgery will do no more than buy time.
Some cases exist where surgery may potentially achieve tumour resection, but will be associated with significant morbidity, such as complete cystectomy. Subjectively, from the client’s viewpoint, some of these morbidities may be as bad as the problems caused by the original cancer. Although challenging, and sometimes very unpleasant to deal with, there may also be occasions where the owner’s wishes are not in line with realistic expectations or go against what is in the patient’s best welfare interests.
A further complicating factor is it is difficult for clinicians to completely divorce their own feelings and opinions from clinical case management, but, ultimately, the decision must be right for the patient and owner (Main, 2006; 2010).
Histopathologic analysis of tissues obtained through biopsy allows definitive diagnosis of tumour type (hyperplasia, metaplasia or neoplasia), biological behaviour (malignant or benign), level of aggression and tumour grade.
Four main options exist for tumour biopsy:
FNA is cost-effective and minimally-invasive, although the accuracy depends on a number of factors including tumour type, location and degree of inflammation (Figure 3).
Intracavitary structures (especially splenic and hepatic masses) may be sampled with ultrasonography or CT guidance, depending on availability and operator experience (Soderstrom and Gilson, 1995; Aitken and Patnaik, 2000; Bonfanti et al, 2004).
Some tumours, such as mast cell tumours and lymphoma, are readily identifiable on most needle aspirates, while others (for example, sarcomas) may not exfoliate cells well, giving false-negative results (Figure 4).
In one study, the overall accuracy rate for intraoperative cytopathological examination of aspirates taken from a range of body organs was 83% (Eich et al, 2000), while the cytologic diagnosis was in agreement with the histopathologic diagnosis in 90.9% of patients with cutaneous and subcutaneous lumps in another (Ghisleni et al, 2006).
Needle core biopsy is more invasive than FNA, but has proven to be highly diagnostic, with an accuracy of 100% reported for epithelial cell tumours and 94% for mesenchymal cell tumours, as shown in one study (Aitken and Patnaik, 2000). Needle core biopsy may involve
Tru-Cut needle core biopsy for soft tissue or Jamshidi needle core biopsy for ossified tissue.
Sedation and local anaesthesia will often provide sufficient analgesia for biopsy collection, but caution should be used when infiltrating local anaesthetic to be sure the tumour edges are not distorted by fluid blebs (Soderstrom and Gilson, 1995). Collecting multiple tissue samples increases the accuracy of the biopsy result when using needle core techniques.
Incisional or wedge biopsy is used when less invasive techniques fail to yield a diagnosis. This technique is effective for masses in all locations and generates a larger tissue mass for the pathologist to examine. They are particularly useful for diagnosis of soft, friable, inflamed and/or necrotic tumours, and are often used to sample peripheral lymph nodes (Ehrhart, 1998).
The incision location for this type of biopsy should be carefully planned, as it will need to be removed en bloc with the tumour during surgery or incorporated in the radiation field in the event of radiation therapy.
Although the junction between normal and abnormal tissue has been (and still is) frequently suggested as the most suitable location for an incisional biopsy, this does carry the risk of disseminating neoplastic cells more widely and of opening intact fascial planes between the tumour and surrounding tissues (Ehrhart and Culp, 2012).
In the author’s opinion, this type of marginal biopsy is perhaps more suitable for investigation of other conditions, such as dermatological disease, than it is for tumour biopsy where malignancy is suspected.
The key objective when taking a biopsy from a tumour should be to obtain a representative sample without worsening the situation or creating a wider tumour bed.
Excisional biopsy is where the tumour is either excised with a marginal approach or randomly selected margins, without knowing the tumour type in advance.
Excisional biopsy has the advantage of being both diagnostic and therapeutic, and is a common approach for mass removal in veterinary medicine – particularly in first opinion practice (Bray et al, 2014). However, it carries significant risks and remains controversial because it can result in contamination of clean tissue planes and can complicate or compromise future surgical procedures (Figure 5).
Once a tumour excision has been performed, including excisional biopsy, the local anatomy is permanently altered in the surrounding tissue planes. This provides an opportunity for any residual tumour cells to extend and seed deeper and wider into the surrounding tissues than would otherwise have been the case. If this happens with a malignant tumour, the extent of the resulting local changes and infiltration may adversely affect the patient’s prognosis by compromising the possibility of further effective treatment – hence the mantra that the first surgical excision is the best chance for complete excision.
Conversely, if a 3cm margin is selected to remove a lump “just in case”, the lesion is malignant and proves to be a low grade soft tissue sarcoma requiring only a 1cm margin, the patient has undergone an unnecessarily aggressive procedure with an increased cost to the client and risk of morbidity to the patient.
Surgery remains a cornerstone of tumour management in veterinary practice, whether as a definitive treatment or combined with adjunctive treatment.
To ensure surgery is being used appropriately, it is essential to follow a logical approach, starting with a thorough patient assessment and identification of the tumour type. With this information, veterinary surgeons can give owners an informed and accurate recommendation for the best treatment.
