Principles of surgical oncology

• Surgery is usually the surest way to remove a solid cancer completely, and therefore the only chance of cure in many patients. It can also relieve symptoms and obstruction when cure is no longer possible.
• The goal is decided before the first incision: curative (remove the tumour and its draining lymph nodes, leaving nothing behind) or palliative (ease a symptom or prevent an imminent problem).
• Margins matter. An R0 resection means no residual tumour; R1 means microscopic residual; R2 means gross residual. The chance of cure falls sharply as the margin worsens.
• Surgery is only one part of care. Timing with chemotherapy, radiotherapy and immunotherapy, multidisciplinary discussion and enhanced (ERAS) recovery determine how well the patient does.
• Surgery is sometimes directed at metastases themselves - the liver and lung most often - and can prolong survival or even cure, but only in carefully selected patients.

By the end of this page you should be able to:

1. Distinguish curative from palliative cancer surgery and describe the setting for each.
2. Explain the R (residual tumour) classification (R0, R1, R2) and why margins and lymph nodes determine stage.
3. Outline how and when sentinel node biopsy is used, and what its limits are.
4. Describe the place of neoadjuvant and adjuvant therapy around surgery, with real examples.
5. Explain what a multidisciplinary team (MDT) adds and how Enhanced Recovery After Surgery (ERAS) works.
6. State the principles that guide surgery for metastases and the role of the major oncology guidelines (ACS, ESMO, NCCN).

Surgical oncology is the part of cancer treatment in which a particular cancer is removed, or at least controlled, by an operation. It is the oldest of the cancer treatments and, for most solid cancers that can be removed safely, it remains the step that most often cures. Cancer surgery is not an isolated act: it sits inside a sequence that includes imaging, biopsy, staging, systemic treatment, radiotherapy and follow-up, and the operation is chosen by a team rather than by one surgeon acting alone ^[1].

Cancer operations are usually elective and planned, not emergencies, and they take months to complete once the first appointment is made ^[1]. They are grouped by how the patient presents:

• Oncological emergencies - obstruction, perforation, bleeding, compression of the airway or major vessels that need surgery now.
• Early or locally advanced cancers that are potentially curable, so cancer-directed surgery is the priority.
• Advanced or metastatic disease, where surgery is judged suitable for palliation only.

The same patient may pass between these groups as the disease changes.

No curative operation is planned before the disease is staged and the patient is staged for fitness. In practice this means:

• Confirming the tissue diagnosis, so that the operation is not planned on a scan alone. Many lumps are not cancer, and many cancers are not the kind the scan suggested.
• Imaging the body to look for spread. Cross-sectional CT of the chest, abdomen and pelvis is the usual starting point, with MRI added for the pelvis and for soft-tissue assessment, and PET/CT for staging when metastasectomy is being considered. Laparoscopy sometimes finds small liver or peritoneal deposits that were not visible on cross-sectional imaging ^[2].
• Molecular and nodal assessment, since mismatch repair and other markers change systemic treatment and sometimes surgical timing. In colorectal practice, mismatch-repair-deficient or MSI-high disease makes up about 10 to 15 % of colon cancers but only about 2.3 to 6.7 % of rectal cancers ^[2].
• Completing the endoscopic survey: for colon cancer, everyone should have a complete colonoscopy, because synchronous cancers occur in about 3 % of cases. If an obstructing primary prevents a full view, that limitation is recorded and the colon is re-examined within 6 months ^[2].
• An anaesthetic and fitness review, including nutrition. Malnourished patients carry a much higher complication rate, and major resection in a frail or malnourished patient can turn a survivable operation into a lethal one. Prehabilitation - exercise, protein, correcting the reversible - buys both safety and later recovery speed.
• Baseline markers and surveillance planning: a serum CEA in colorectal cancer is recorded so that recurrence can be detected later ^[2].

A good surgical oncologist plans the operation last of all, after the disease and the person have been understood.

Curative surgery aims to remove every detectable cancer with margins that are free of disease, together with the lymph nodes that drain it. When the operation succeeds and no disease is left, the patient has the best chance of long-term survival, and often of cure. Surgery is the backbone of curative treatment for most solid cancers ^[2]. Examples include removing a breast with all the axillary nodes large enough to matter, or taking out a colon cancer together with its blood supply and its mesentery.

Curative surgery only makes sense when:

• the tumour can be removed completely without unacceptable damage (technically resectable disease);
• there is no distant spread, or any spread is limited and itself removable;
• the patient is fit enough for major surgery and will survive the operation and recovery;
• the biology of the tumour allows time to recover and to receive any adjuvant treatment needed.

Palliative surgery is performed not to cure, but to relieve a problem the cancer is causing now, or to prevent one that is about to happen: relieving an obstruction, controlling bleeding, closing a fistula, decompressing the spinal cord, removing a mass that is painful or infected. It is usually simpler and faster, and the plan is agreed with palliative-care and medical-oncology teams as part of shared decision making ^[1].

The line between the two is not always obvious. A tumour that looks unresectable at presentation may become resectable after chemotherapy (down-staging), and a patient operated on with "curative" intent may be found to have positive margins at pathology. The operation that looked palliative can turn out to have removed all disease. This is why intent is a working hypothesis, not a label fixed at the first consultation.

Surgery removes what the eye can see. Microscopy then decides whether anything was left. The residual-tumour (R) classification records that result, and it is one of the strongest predictors of outcome.

• R0 - complete resection. No tumour is seen at the cut edge under the microscope and no disease is left behind. This is the only result that supports cure. Surgery remains the cornerstone of curative treatment, and an R0 resection is the goal of every curative operation ^[2].
• R1 - microscopic residual. The surgeon's eye could not see it, but tumour cells are found at the cut margin on histology. The bulk of disease is gone, but microscopic disease remains. It usually brings radiotherapy or re-excision, and it is not a cure.
• R2 - macroscopic residual. Tumour that the surgeon could see and left behind, either because it was stuck to something vital, or knowingly, as in debulking for symptom control. Almost never curative.

Two points follow. First, margins cannot be judged in the operating theatre alone; frozen section helps sometimes, but final histology is what counts. Second, the same margin can mean different things for different tumours: a surgeon may accept a narrower margin for some resectable cancers if the tumour is biologically favourable, but a wider margin for cancers that spread along nerves or vessels. Adequate margins depend on the disease ^[2]: in colon cancer, for example, major guidelines recommend gross longitudinal margins of at least 5 cm, while Japanese anatomical studies suggest that 10 cm is needed to capture all pericolic lymphatic spread.

Margins are not measured only at the cut edge of the main specimen. For a rectal cancer, the crucial measurement is the circumferential resection margin (CRM) - the distance from the tumour to the painted edge of the specimen. Tumours lying below the peritoneal reflection are not covered by serosa, so they are at higher risk of radial margin involvement, and locally advanced tumours in such a position may approach the mesorectal fascia unless neoadjuvant treatment is given first ^[2].

Staging surgery means removing the lymph nodes that drain the tumour. Lymph node involvement is both a prognostic marker and a guide to adjuvant treatment. General rules:

• Resect the draining nodes en bloc with the main specimen, tied off at their source vessels.
• Examine enough nodes: for colon cancer, at least 12 lymph nodes should be present in the specimen for reliable staging ^[2]. Inadequate nodal harvest is itself a high-risk feature.
• The extent of nodal dissection is tailored to the tumour: for colon cancer, a complete D2 lymphadenectomy is considered the minimum standard in modern practice, while more extensive clearance (D3 or complete mesocolic excision) adds central nodal dissection in some centres ^[2].

A sentinel lymph node is the first node that tumour-carrying lymph fluid reaches. It is the node most likely to contain metastasis if spread has begun. Sentinel lymph node biopsy (SLNB) removes only that node (or those nodes). It was introduced to avoid the long-term side effects of removing all the nodes.

The best established use is in early breast cancer in a clinically node-negative axilla, which is what every SLNB trial has tested. Choosing between SLNB and full axillary clearance is a genuine trade-off:

• Full axillary clearance causes lymphedema in roughly 13 to 48 % of patients, depending on how it is defined and when it is measured; worse rates are seen when 10 or more nodes are removed ^[3].
• SLNB finds the sentinel node in about 96 % of cases, is correct in about 99 % overall, has a sensitivity of about 93 % and a false-negative rate of about 5 to 6 % ^[3].
• SLNB is therefore used as the minimally invasive staging step, with full clearance reserved for the cases it flags.

Landmark trials show how staging has been de-escalated over time ^[3]:

• NSABP B-32 showed that SLNB was as good as routine axillary clearance in women with clinically negative nodes, with far less arm morbidity.
• ACOSOG Z0011 found that women treated conservatively with only one or two positive sentinel nodes and breast radiotherapy did not need further axillary surgery, without loss of disease-free survival.
• AMAROS and OTOASOR showed that axillary radiotherapy can replace further surgery in selected node-positive patients, with much less lymphedema.

• SLNB only answers a question: "has the tumour reached the least likely node to be involved?" If the answer is yes, the next step (clearance, radiotherapy, or no more treatment) depends on how many nodes and how much disease is there.
• In the neoadjuvant setting the nodes change with treatment, so dual mapping and removal of three or more sentinel nodes (and, for a previously node-positive axilla, retrieving the clipped node itself) is used to push the false-negative rate down. Single-tracer SLNB after neoadjuvant therapy carries a higher false-negative rate, which is why guidelines prescriptively modify the technique ^[3].
• For low-risk disease, modern trials and current guidance increasingly ask whether SLNB is needed at all ^[3]. That is a direction of change, not yet standard practice for most.

Neoadjuvant therapy is systemic or local treatment given before surgery. It is one of the three ways surgery interacts with other treatments. Its jobs are to:

• shrink a tumour so that it can be removed at all (down-staging, or "conversion" to a resectable tumour);
• sterilise the margins around the tumour;
• treat micrometastases earlier, before the operation and its recovery delay systemic treatment;
• test whether the tumour responds to a drug, which informs later treatment.

When a tumour is too large or too fixed to surrounding structures at presentation, neoadjuvant treatment is the route by which surgery becomes possible. A bulky colon cancer with threatened margins is the sort of situation in which NCCN allows preoperative chemotherapy, while ESMO reserves it for clinically complex cases and for trials ^[2]. In rectal cancer, total neoadjuvant therapy (TNT) - giving all the intended chemotherapy and radiotherapy before rather than after surgery - is now the approach most guidelines prefer for stage III or high-risk stage II disease ^[2].

For dMMR (microsatellite-unstable) colorectal cancers, neoadjuvant checkpoint-blockade immunotherapy has produced dramatic responses in recent trials, and neoadjuvant immunotherapy is becoming the preferred strategy in such locally advanced disease, though ESMO and JSCCR have not adopted it as standard outside trials ^[2].

Flowcharts used in day-to-day practice fold these decisions into a single multidisciplinary pathway:

Adjuvant therapy is treatment given after successful surgery, when the primary tumour is gone but there is a risk of recurrence. Surgery creates a window in which residual micrometastases are most vulnerable. Two rules govern it:

1. The benefit comes from disease that was already there but too small to see - it is prevention, not treatment of something we know is present.
2. Timing matters. In colon cancer, adjuvant therapy should ideally start within 6 weeks of surgery; delays beyond that blunt its effect ^[2].

Adjuvant chemotherapy after surgery is standard in node-positive (stage III) colon cancer, and oxaliplatin-based regimens such as FOLFOX or CAPOX are used. Stage II patients with high-risk features gain only a modest benefit, roughly 3 to 5 % absolute survival benefit, so treatment is reserved for those features (for example T4 disease, perforation, poorly differentiated histology, lymphovascular or perineural invasion, obstruction or close margins) ^[2]. Genetic status matters: mismatch-repair-deficient stage II cancers do not benefit from fluoropyrimidine alone and are usually observed after surgery ^[2].

Rectal surgery has similar staged logic: after neoadjuvant therapy and resection, the risk of recurrence can be lower and not every patient needs further chemotherapy; the modern trend is to give all planned treatment before surgery so that no patient misses it by being too unwell afterwards.

Modern cancer care is multidisciplinary by design, and shared management decisions are the norm ^[1]. An MDT brings together the surgeons, medical oncologists, radiation oncologists, pathologists, radiologists, anaesthetists or critical-care clinicians and the palliative-care team, and it holds a pre-treatment review of each new cancer patient. Its value is not box-ticking:

• It stops the patient seeing three different plans from three different specialists.
• It allows a down-staging plan to be chosen before the first incision is made.
• It protects against one surgeon's particular habit becoming the standard locally.
• It ensures that surgical, systemic and radiotherapy options are combined, not offered one after another by default.

Rectal cancer is the classic example given: it is a complex disease that needs precise staging, MDT evaluation, tailored neoadjuvant strategies and meticulous surgical technique, and outcomes have improved dramatically with that combined approach ^[2]. The same applies to metastatic disease: for hepatic or pulmonary metastases, optimal selection between surgery, ablation, radiotherapy and systemic therapy is achieved only through multidisciplinary evaluation ^[5], and the same holds across surgical oncology.

ERAS is not a single operation or a single drug. It is a bundled, multimodal, evidence-based care pathway from preoperative preparation to discharge, revising the traditional approach in which patients stayed in hospital for two weeks after colon surgery. It has become the accepted standard of perioperative care in most units ^[4].

What the numbers show ^[4]:

• Across different specialties ERAS shortens hospital stay by an average of 2 days and cuts complications by about 30%. ^[4]
• Complications fall by roughly 30 to 50% in some series.
• These gains depend on compliance: programmes with over 70 to 80 % compliance realise them; most units actually run at 40 to 60 % compliance, which is why auditing an ERAS programme is as important as writing it. ^[4]

The key insight of ERAS is that best care needs a team, not just an individual surgeon ^[4]. It breaks down the silos between preoperative, intraoperative and postoperative staff so that fluid strategy, pain control, early mobilisation and early feeding are managed as one plan for the patient rather than piecemeal.

For the surgical oncologist, ERAS matters because the sicker patient (older, malnourished, chemotherapy-pretreated) is the one who benefits most from getting the small things right. It is where surgery for cancer is learned in practice rather than in theory.

A small group of patients with cancer that has spread, but in a limited way, may still be offered surgery aimed at the metastases themselves (metastasectomy). It is a high-stakes decision because the downside is a major operation in a patient who may not benefit. Several concepts underlie it:

• Oligometastatic disease is the situation of limited spread - for example 1 to 3 deposits per organ of up to 7 cm, or 1 to 5 deposits of up to 5 cm, depending on the scheme ^[5]. It is increasingly the target of coordinated local treatment as well as systemic therapy ^[5].
• Complete tumour removal (R0 resection) while preserving enough functioning organ is the technical goal, and it is more likely to be achievable and worth doing for liver and lung deposits ^[5].
• Surgery for metastases is therefore reserved for patients selected on anatomy, biology, response to treatment, fitness and where it is judged curative or meaningfully prolonging rather than experimental ^[5].
• Common examples are resection of colorectal liver metastases, resection of isolated pulmonary nodules, and repeat resections of further deposits after a previous metastasectomy, which can still confer a benefit in very selected patients.
• Whether surgery actually improves long-term survival compared with other local treatments is debated for some sites, and metastasectomy must be reviewed in MDT, not agreed at a single consultation ^[5].

The 5-year results that are reported after resection of colorectal pulmonary metastases reach roughly 50%, rising to about 70% in the most carefully selected cohorts, but these are retrospective figures in highly selected patients, and a Cochrane review and the PulMiCC trial have questioned whether the benefit is as large as had been assumed ^[5]. The tension between surgical optimism and evidence is genuine; it is best faced in MDT with the trial literature on the table.

Good cancer surgery is evidence-based and protocol-driven, but the protocols are written by professional societies rather than by the law. Three bodies are quoted most often, in two overlapping contexts:

• American College of Surgeons (ACS). The ACS advises on elective and emergency cancer surgery and, through the Commission on Cancer, sets the standards by which cancer programmes are accredited (multidisciplinary working, documentation of intent and margin status, and so on). It is also the author, with the Society of Surgical Oncology, of many site-specific operative standards. Recent reviews of cancer surgery during the COVID-19 pandemic named ACS alongside SSO, ESSO, NCCN, BASO and others as the bodies whose triage recommendations guided surgeons ^[1].
• European Society for Medical Oncology (ESMO). ESMO writes disease-by-disease clinical-practice guidelines, covering colon and rectal cancer among many others. They tend to be consensus-based, are published openly and are revised periodically. NCCN and ESMO are compared head to head on resectable colorectal cancer in the series summarised here, including neoadjuvant chemotherapy, adjuvant therapy, margins and surveillance ^[2].
• National Comprehensive Cancer Network (NCCN). US-based, multidisciplinary, continuously updated guidelines and decision pathways for cancer. For example, NCCN assigns category 2A support for neoadjuvant chemotherapy in selected pMMR colon cancers and supports total neoadjuvant therapy as the preferred sequence in rectal cancer ^[2].

It is worth quoting a few named differences where these bodies genuinely disagree, rather than smoothing them over:

• Neoadjuvant chemotherapy for colon cancer. NCCN permits it for cT4 or bulky nodal pMMR disease; ESMO reserves it for investigational or technically unresectable situations; JSCCR (the Japanese guidelines) still favours upfront surgery for resectable cases ^[2].
• Neoadjuvant immunotherapy in MSI-high colorectal cancer is endorsed by NCCN but not yet by ESMO or JSCCR outside trials ^[2].
• Margins. NCCN and ESMO agree on at least 5 cm longitudinal for colon cancer; Japanese anatomical data argue for 10 cm to clear pericolic lymphatic spread ^[2].
• Lymphadenectomy. Japan prescribes by T stage (D1/D2/D3), while NCCN and ESMO state the principles (adequate nodal harvest, central resection when disease is high) without naming a level ^[2].

That kind of open disagreement is honest evidence-based medicine in action, and it is exactly why the MDT matters: local practice will follow one set of guidelines and document why, and guidelines are revised as trials arrive.

• Curative surgery aims for R0 resection of the tumour plus draining nodes. Any lesser margin (R1, R2) escalates the risk of recurrence.
• Surgery is only a step within a multidisciplinary plan: imaging, molecular status, team review, neoadjuvant and adjuvant therapy.
• Intention - curative or palliative - shapes how much tissue is removed, and must be chosen before the operation.
• Lymph nodes are part of the operation, not an afterthought; adequate nodal harvest is required for staging.
• Sentinel lymph node biopsy has replaced full axillary clearance for staging the clinically negative axilla, with far less lymphedema and similar cancer outcomes; it has well defined limits, especially after neoadjuvant treatment.
• Neoadjuvant therapy can make an unresectable tumour resectable; TNT is now preferred for stage III or high-risk stage II rectal cancer.
• Adjuvant therapy after surgery must usually be given within a few weeks if it is to work; mismatch-repair-deficient tumours may not need it.
• MDT review is the standard, not an optional extra, for any complex cancer surgery.
• ERAS pathways shorten stay and cut complications, but only where the whole team delivers them; 70 to 80% compliance is the threshold at which gains appear. ^[4]
• Surgery for metastases is real and sometimes curative, but depends on selection and is properly debated in MDT.
• The major guidelines (ACS, ESMO, NCCN) do not always agree - that disagreement is itself clinically useful information.

No other MedGrasp topics are linked from this page; its prerequisite list is empty by design. Topics that overlap (ERAS components, surgical sepsis, abdominal and pelvic trauma, wound healing, cancer staging) will be cross-linked once those pages are verified.

Last reviewed by a clinician: pending.