HOW TO OPERATE TUMOURS BETTER

Laurent Findji
AURA Veterinary
Guildford, Surrey
United Kingdom

To operate tumours better, it is essential to know their biology. Concretely, it means that the tumour type
should always be determined, so that the biological behaviour of the tumour can be understood. This, in
turn, makes it possible to determine the “dose” of surgery required. The most complex surgeries can then
be planned based of advanced imaging (CT, MRI).

Practically, the possibility to apply the required surgical dose can be limited by the possibilities to reconstruct
resulting tissue defects, as well as by the severity of the functional deficits that the resection would cause.
To some degree, the ability to reconstruct tissue defects are surgeon-dependant and, from a technical point
of view, the most efficient way to be able to operate tumours better is often to become better at
reconstructive surgery.

Lastly, the surgical oncologist must avoid the contamination of healthy tissues with neoplastic cells.

BEFORE SURGERY

Knowing tumour biology

No tumour should ever be resected without the surgeon knowing what type of neoplasia they are facing. At
the very least, fine-needle aspirates of the tumour should allow to have a broad idea of the tumour type.
Depending on this type and on the localisation of the tumour, it can be sufficient to determine the surgical
dose required for treatment. Every time determining the tumour type more precisely or knowing the tumour
grade would have a significant impact on the surgical dose to apply, an incisional biopsy should be
considered.

The tumour type and grade, together with the clinical data, allow to know its expected behaviour, from which
the surgical dose required for treatment can be determined. This dose is tailored to each individual case,
which requires a knowledge of oncology which goes far beyond oncologic surgery technique. This
knowledge is critical to determine the optimal course of action for each patient, depending on the
characteristics of the tumour, on the current possibilities of veterinary oncology, as well as on the constraints
and expectations of the owners. At times, knowing that a procedure is possible despite not being able to
perform it allows a veterinarian to refer and offer the patient a chance to have the best treatment.
Conversely, the mere fact that a surgical procedure is technically possible does not necessarily make it the
right thing to do for a particular patient.

Stage the tumour

Once the type and sometimes grade of the tumour are known, the necessity of staging the tumour can be
determined. The TNM staging includes the evaluation of the local extension of the tumour itself (T) and the
screening for signs of metastasis in the locoregional lymph nodes (N) and key distant sites (M). The most
appropriate distant sites to screen depend on the type of the tumour and most commonly include the lungs,
liver and spleen.
From a biological viewpoint, all three T, N and M staging are important, but from a surgical technique
perspective, the T and N staging are most relevant. They are most often carried out by advanced imaging
and lymph node mapping. It is based on the T staging that it can be assessed whether a tumour can be
resected surgically with the required margins determined previously and what functional and cosmetic
consequences can be expected from such a resection. These consequences, together with the anticipated
recovery time, must be weighed against the hoped benefits from the surgery with regards to quality of life
and life expectancy. Generally, it is more ethically acceptable to put a patient through a heavy surgery with
a significant recovery time when the procedure has reasonable chances of being curative or provide tumour
control for a long period of time (curative intent) rather than when the life expectancy is thought to be short
regardless of treatment. In this latter case, only surgeries with short recovery times, aimed at rapidly
improve the patient’s quality of life should be considered (palliative intent).

SURGICAL TECHNIQUE

Biopsies

Surgical biopsies can be incisional or excisional. An incisional biopsy consists in the resection of a small
portion of the tumour in view of its pathological examination. An excisional biopsy consists in the excision
of the entire mass, often marginally, in the same view.

An excisional biopsy should only be performed when knowing the precise nature and grade of the tumour
would not change significantly the dose of surgery applied, either for biological or practical reasons. The
excessive resort to excisional biopsies is a major cause for treatment failure in surgical oncology. In doubt,
fine-needle aspirates or an incisional biopsy should be carried out in order to determine with confidence
the extent of the surgical resection required to meet its objectives.

In general, it is preferable to take biopsies at the junction between the tumour and the surrounding healthy
tissues, so that the pathologist can assess the patterns of the tumoral invasion. In addition, many tumours
have an inflammatory, infected or necrotic centre, which hinders the pathological diagnosis. However, some
tumours must nonetheless be biopsied in their centre because the intense reaction their cause in
surrounding tissues complicate diagnoses made from peripheral samples. It is particularly true for
aggressive bone tumours, such as osteosarcomas. In any case, it is critical not to jeopardise later local
treatments (surgery, radiotherapy) by a lack of anticipation and planning of the biopsies. Indeed, all biopsy
tracts must be resected en-bloc with the tumour at the time of treatment, which can be made difficult or
impossible by insufficiently planned biopsy approaches. In addition, the use of electrocautery should be
proscribed when taking small biopsy samples, as it creates a particular artefact (cautery artefact) which can
prevent reaching a pathological diagnosis. If cautery is required, it can be applied once the samples have
been collected.

Fine-needle aspirates of the locoregional lymph nodes must frequently be taken, regardless of their
presentation and size, as these criteria are not reliable indicators of their possible neoplastic infiltration.
However, tumours do not necessarily drain in the closest lymph node and can even drain contralaterally.
Therefore, ideally a lymphatic mapping should be performed to determine the position of the sentinel lymph
node, which is the first lymph node on the draining route of the tumour. Evaluation of this sentinel lymph
node is consequently the most sensitive indicator of any lymphatic metastasis (N staging). In practice, such
a mapping is only uncommonly carried out and, in its absence, it can only be recommended to excise for
biopsy any lymph nodes which could be the sentinel lymph node, as long as it does not prolong the surgical
time and morbidity unreasonably.

Tumour resection

The most important point, when resecting a tumour is contemplated, it to consider the consequences of the
surgery and its potential complications against its anticipated benefits. In other words, the treatment should
never be worse that the disease! Surgeons can easily be tempted to perform invasive, technically
challenging procedures, which turn out to be of little, if any, benefit for the patient. Conversely, a veterinarian
should not deter owners from seeking surgical treatment when the required procedure may seem heavy
but is known to be well-tolerated (e.g., amputations, maxillectomies, mandibulectomies), just because this
veterinarian cannot perform such a procedure themselves. Referral to a specialist surgeon or, better, a
surgical oncologist should be offered.

It is primordial to make the patient’s wellbeing the highest priority, before the wishes of its owners. The
discussion with the owners of a pet with cancer should allow the veterinarian to understand their wishes
and hopes, and determine whether they are compatible with medical possibilities. Setting clear expectations
for the owners is the best way to avoid misunderstandings and later disagreements.

Knowing the type and behaviour of the tumour to treat is essential to plan its resection. The determination
of the “dose” of surgery to administer relies on it. The first attempt at surgical resection is the best chance
of a cure that the patient will ever have, and it should not be wasted by lack of, or inappropriate, planning.
Whenever possible, the wide resection of a tumour should be sought. The concern that the resulting tissue
defect will not be amenable to closure should not lead to compromise in the oncologic resection. Depending
on the tumour type and size, lateral margins of 1 to 3 cm are most commonly sought, but wider margins
can be indicated for the most locally aggressive tumours, such as feline injection-site sarcomas for which
5-cm lateral margins have been recommended. In depth, depending on the tumour type and size, a
minimum of 1 or 2 fascial plane(s) should be resected en-bloc with the tumour.

Alternatively, if an adjuvant treatment is anticipated (radiotherapy especially), the surgical resection can be
more conservative. Taking intraoperative pictures and leaving metallic vascular clips at the periphery of the
surgical site will assist the radiation oncologist in the treatment planning.

Tumours must be manipulated a minima and as delicately as possible to minimise the risk of dissemination
of neoplastic cells. Ideally, a tumour should be resected by only manipulating the healthy surrounding
tissues resected en-bloc with it, and it should not be approached or seen directly. Any biopsy tracts should
be resected en-bloc with the tumour. When possible, major veins draining the resected tissues should be
ligated as early as possible during the procedure, before the associated arteries, to limit the risks of sending
macro-emboli of neoplastic cells in the systemic circulation when mobilising the tumour.

Tumours should be handled like infected tissues would be. Any tissues, instruments, gloves, gowns and
drapes having potentially been in contact with tumour cells should be changed. The same instruments
should not be used to biopsy or resect two separate masses. Similarly, when the surgical wound is closed,
it is important to remember that any distant tissues used for or approached during reconstruction (e.g., skin
flaps) have to be considered contaminated with tumour, which can have dramatic consequences if revision
surgery or an adjuvant treatment is later considered (radiotherapy especially). The use of extensive skin
flaps must be proscribed until the status of the surgical margins is known as free of cancer cells, to avoid
distant seeding of the tumour. The enlargement of the potentially contaminated field when using a skin flap
can render greatly more difficult, if not impossible, adjuvant radiotherapy. A solution to the use of skin flaps
without contamination consists in elevating any flaps required for reconstruction before resecting the
tumour. This strategy however requires solid planning before execution.

Postoperative care must also be anticipated at the time of surgery. Feeding tubes must be considered in
every patient which may not rapidly get back to normal feeding habits. Likewise, placement of a wound-
soaking catheter should be considered after any extensive resection, to regularly inject local anaesthetics
in the wound and potentiate postoperative analgesia.

Even if the tumour was biopsied before excision, it is submitted for pathology. It is orientated (with sutures,
for example) and its margins are inked. Larger excision pieces are sliced on a portion of their thickness to
ensure their good fixation in 10% formalin, which only penetrates approximately 1-cm deep in tissues.

AFTER SURGERY
Non-specifically, postoperative care of the cancer patient includes wound care, analgesia, nutritional
support and medical treatments. Depending on tumour types, potential paraneoplastic syndromes can need
managing (hyper- or hypocalcaemia, hypo- or hyperglycaemia, etc.). Similarly, care specific to the type of
surgery performed may be required (chest drains for thoracic tumours, physiotherapy for spinal tumour
patients or amputees, etc.).
When adjuvant treatments are required, they must be started as early as possible. In most cases,
chemotherapy can safely be started 7 to 10 days after surgery. Most chemotherapy agents negatively
impact on wound healing experimentally, but this has little clinical relevance. Conversely, radiotherapy is
clearly deleterious to all stages of wound healing, and adjuvant radiotherapy should only be started once
wound healing is well-advanced, that is 2 to 3 weeks postoperatively.