Metastasectomy
Encyclopedia
In oncology
, metastasectomy is the surgical
removal of metastases, which are secondary cancer
ous growth
s that have spread from cancer originating in another organ in the body.
In many cases, metastases are not treated surgically. There are two common reasons for this. Often, even with a successful surgery the patient would have a poor prognosis
. If the cancer is widely disseminated, it is likely that after surgical removal of all known metastases, new ones would occur elsewhere. Sometimes, surgery itself would have a low likelihood of success due to the location and/or extensiveness of the cancer. If complete surgical excision is feasible, however, removing both the primary cancer and its metastases may substantially improve the patient's prognosis. Some patients may even be in effect cured.
The use of metastasectomy evolved in the field of liver resection
for metastasised colorectal cancer
, but has evolved to include resection of metastases from different primary cancers (such as breast cancer
, melanoma
, renal cell carcinoma
, etc.) to the lungs, brain
, and other organs. Not all of these applications are equally evidence-based
, although with respect to some other primary cancers metastasectomy may be underutilized.
Surgical resection of liver metastases from colorectal cancer has been found to be safe and cost-effective.
Reports from several large retrospective patient series suggest that it has a 5 year overall survival rate (5y OSR) averaging 30 to 40% and a 10y OSR around 16%, whereas the highest 5y OSR for modern chemotherapy regimens
is only 9% (with FOLFOX
). However, no randomized clinical trial has directly compared surgical management to chemotherapy or treatment with bevacizumab
. Some have argued that the excellent results of liver metastasectomy for colorectal cancer are partially confounded by selection bias
or reporting bias
. Nevertheless, surgery for resectable metastases has become the standard of care, probably making such a trial (ethically
) infeasible.
Previously, liver metastasectomy was limited to patients with less than four sites of metastasis in the liver, with a tumour-free margin of at least 1 centimetre, and no cancer elsewhere.
These criteria have been challenged, however, and today the main criteria are a tumour-free margin and enough functional liver tissue (70%) preserved after surgery. Patients with initially unresectable liver metastases can be pre-treated with chemotherapy (this is called neoadjuvant chemotherapy
). This pre-treatment causes the tumors to shrink, resulting in a larger proportion of liver tissue that is functional, with broader margins.
Preoperative evaluation involves imaging of the liver and its metastases, for example with ultrasound, computed tomography
or magnetic resonance imaging
. Positron emission tomography can be useful to check the entire body for metastases, although the test can be falsely normal with small lesions or preoperative chemotherapy. Baseline blood test
s typically include liver function tests
and tumour markers. During surgery, intraoperative ultrasound can aid the surgeon to find additional metastases.
For patients in whom the primary tumour is controlled and metastases are limited to the lung, criteria for eligibility include the technical resectability of the metastases and the general fitness and lung function reserve of the patient. If there are both liver and lung metastases, a resection of both can be attempted. In general, only 10% of patients with pulmonary metastases from colorectal cancer are resectable.
Blalock
reported the first lung resection for metastasis from colorectal cancer in 1944.
Oncology
Oncology is a branch of medicine that deals with cancer...
, metastasectomy is the surgical
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
removal of metastases, which are secondary cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
ous growth
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
s that have spread from cancer originating in another organ in the body.
In many cases, metastases are not treated surgically. There are two common reasons for this. Often, even with a successful surgery the patient would have a poor prognosis
Prognosis
Prognosis is a medical term to describe the likely outcome of an illness.When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because...
. If the cancer is widely disseminated, it is likely that after surgical removal of all known metastases, new ones would occur elsewhere. Sometimes, surgery itself would have a low likelihood of success due to the location and/or extensiveness of the cancer. If complete surgical excision is feasible, however, removing both the primary cancer and its metastases may substantially improve the patient's prognosis. Some patients may even be in effect cured.
The use of metastasectomy evolved in the field of liver resection
Hepatectomy
Hepatectomy consists on the surgical resection of the liver. While the term is often employed for the removal of the liver from a liver transplant recipient, this article will focus on partial resections of hepatic tissue.-History:...
for metastasised colorectal cancer
Colorectal cancer
Colorectal cancer, commonly known as bowel cancer, is a cancer caused by uncontrolled cell growth , in the colon, rectum, or vermiform appendix. Colorectal cancer is clinically distinct from anal cancer, which affects the anus....
, but has evolved to include resection of metastases from different primary cancers (such as breast cancer
Breast cancer
Breast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...
, melanoma
Melanoma
Melanoma is a malignant tumor of melanocytes. Melanocytes are cells that produce the dark pigment, melanin, which is responsible for the color of skin. They predominantly occur in skin, but are also found in other parts of the body, including the bowel and the eye...
, renal cell carcinoma
Renal cell carcinoma
Renal cell carcinoma is a kidney cancer that originates in the lining of the proximal convoluted tubule, the very small tubes in the kidney that filter the blood and remove waste products. RCC is the most common type of kidney cancer in adults, responsible for approximately 80% of cases...
, etc.) to the lungs, brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
, and other organs. Not all of these applications are equally evidence-based
Evidence-based medicine
Evidence-based medicine or evidence-based practice aims to apply the best available evidence gained from the scientific method to clinical decision making. It seeks to assess the strength of evidence of the risks and benefits of treatments and diagnostic tests...
, although with respect to some other primary cancers metastasectomy may be underutilized.
Colorectal cancer
Among colorectal cancer patients, 15-25% will have liver metastases already when the colorectal cancer is discovered, and another 25-50% will develop them in the three years after resection of their primary cancer. Of patients who die from metastasised colorectal cancer, 20% have metastasis in the liver alone.Surgical resection of liver metastases from colorectal cancer has been found to be safe and cost-effective.
Reports from several large retrospective patient series suggest that it has a 5 year overall survival rate (5y OSR) averaging 30 to 40% and a 10y OSR around 16%, whereas the highest 5y OSR for modern chemotherapy regimens
Chemotherapy regimens
A fundamental philosophy of combination cancer therapy is that different drugs work through different cytotoxic mechanisms. Because they have different dose-limiting adverse effects, they can be given together at full doses in chemotherapy regimens....
is only 9% (with FOLFOX
FOLFOX
FOLFOX is a chemotherapy regimen for treatment of colorectal cancer, made up of the drugs* FOL– Folinic acid * F – Fluorouracil * OX – Oxaliplatin - FOLFOX4 :...
). However, no randomized clinical trial has directly compared surgical management to chemotherapy or treatment with bevacizumab
Bevacizumab
Bevacizumab is a drug that blocks angiogenesis, the growth of new blood vessels. It is commonly used to treat various cancers, including colorectal, lung, breast, kidney, and glioblastomas....
. Some have argued that the excellent results of liver metastasectomy for colorectal cancer are partially confounded by selection bias
Selection bias
Selection bias is a statistical bias in which there is an error in choosing the individuals or groups to take part in a scientific study. It is sometimes referred to as the selection effect. The term "selection bias" most often refers to the distortion of a statistical analysis, resulting from the...
or reporting bias
Reporting bias
In empirical research, reporting bias refers to a tendency to under-report unexpected or undesirable experimental results, attributing the results to sampling or measurement error, while being more trusting of expected or desirable results, though these may be subject to the same sources of error...
. Nevertheless, surgery for resectable metastases has become the standard of care, probably making such a trial (ethically
Medical ethics
Medical ethics is a system of moral principles that apply values and judgments to the practice of medicine. As a scholarly discipline, medical ethics encompasses its practical application in clinical settings as well as work on its history, philosophy, theology, and sociology.-History:Historically,...
) infeasible.
Previously, liver metastasectomy was limited to patients with less than four sites of metastasis in the liver, with a tumour-free margin of at least 1 centimetre, and no cancer elsewhere.
These criteria have been challenged, however, and today the main criteria are a tumour-free margin and enough functional liver tissue (70%) preserved after surgery. Patients with initially unresectable liver metastases can be pre-treated with chemotherapy (this is called neoadjuvant chemotherapy
Neoadjuvant chemotherapy
Neoadjuvant therapy is the administration of therapeutic agents before a main treatment. One example is neoadjuvant hormone therapy prior to radical radiotherapy for adenocarcinoma of the prostate...
). This pre-treatment causes the tumors to shrink, resulting in a larger proportion of liver tissue that is functional, with broader margins.
Preoperative evaluation involves imaging of the liver and its metastases, for example with ultrasound, computed tomography
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
or magnetic resonance imaging
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
. Positron emission tomography can be useful to check the entire body for metastases, although the test can be falsely normal with small lesions or preoperative chemotherapy. Baseline blood test
Blood test
A blood test is a laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a needle, or via fingerprick....
s typically include liver function tests
Liver function tests
Liver function tests , are groups of clinical biochemistry laboratory blood assays designed to give information about the state of a patient's liver. The parameters measured include PT/INR, aPTT, albumin, billirubin and others...
and tumour markers. During surgery, intraoperative ultrasound can aid the surgeon to find additional metastases.
Pulmonary metastasectomy
Surgery is the mainstay of treatment for patients with isolated lung metastasis from colorectal cancer. Again, no randomized clinical trials exist, and the scientific evidence is weak, limited only to case series. The surgery can be performed with a low operative mortality.For patients in whom the primary tumour is controlled and metastases are limited to the lung, criteria for eligibility include the technical resectability of the metastases and the general fitness and lung function reserve of the patient. If there are both liver and lung metastases, a resection of both can be attempted. In general, only 10% of patients with pulmonary metastases from colorectal cancer are resectable.
Blalock
Alfred Blalock
Alfred Blalock was a 20th-century American surgeon most noted for his research on the medical condition of shock and the development of the Blalock-Taussig Shunt, surgical relief of the cyanosis from Tetralogy of Fallot—known commonly as the blue baby syndrome—with Vivien Thomas and pediatric...
reported the first lung resection for metastasis from colorectal cancer in 1944.