RTY2001 – Cancer Pathology – Oncologic Surgery
Being one of the main arms of treatment modalities for cancer, surgery has gained an important role in today’s oncology landscape. In this chapter, we will discuss the following:
The history of oncologic surgery is relatively simple.
Although many means of surgical or otherwise invasive cancer treatment have been carried out over the years dating back to 1600 B.C., surgery really only got its act together around 1975, with the establishment of the Society of Surgical Oncology (SSO), before which everything had to be totally resected.
Radiation therapy was first developed by Roentgen in 1896, and chemotherapy in the 1940s.
The outline for the role of cancer surgery roughly goes like this:
Biopsy
A procedure to remove a piece of tissue or a sample of cells from your body so that it can be analysed in a laboratory is called a biopsy. It may be guided by imaging, as with the case for many gynaecological cancers. Some cancers have an exception where biopsy is not performed, like hepatocellular carcinoma and renal cell carcinoma, where the patient is scanned and signs of elevated tumour markers are surfaced, as well as history of hepatitis. However, the biopsy is still considered the gold standard in diagnosis of cancer.
Endoscopic biopsy
This type of biopsy is typically used for luminal / tubular structures, like the gastrointestinal tract, and areas of the oesophagus. The type of scope used for the biopsy varies with the type of cancer:
Needle biopsy
This technique uses a special needle to extract cells from a particular suspicious area. It is often used on tumours that can be felt through skin, such as breast lumps or palpable enlarged lymph nodes. Because this is an invasive procedure, local anaesthetic has to be administered to numb the area to be biopsied in order to minimise the pain.
Image guided needle biopsy can be used to collect cells from a region that cannot be felt through skin. This is usually done with x-rays.
There are two types of needle biopsy:
Certain tumours, like lymphomas, require a core biopsy because there needs to be an involvement with a strip of cells.
Surgical Biopsy
Surgery is done if the cells in question cannot be accessed with other biopsy procedures or if the other biopsy results have been inconclusive. It involves making an incision in the skin to access the suspected area of cells.
There are two types of surgical biopsy:
Incisional biopsy: to remove part of an abnormal area of cells, for example, removal of breast lump for a possible breast cancer diagnosis
Excisional biopsy: to remove an entire area of abnormal cells, for example, removal of a lymph node for a possible lymphoma diagnosis
Local anaesthetics are used to numb the area of the biopsy. Some surgical biopsy procedures require general anaesthesia to ensure unconsciousness during the procedure. Patients may also be required to stay in the hospital for observation after the procedure.
Surgical Staging
Surgical staging is determined during / after surgery, and will affect the tumour staging (T staging).
This implication is that it affects oncological management, one of the most common changes being that it necessitates adjuvant chemo-RT after surgery due to the discovery of positive margins. It also affects the prognosis, and the other staging, like pathological and clinical staging, which are only based on history, physical examinations or scans.
Surgical staging is still the gold standard of staging and diagnosis. However, it is worth noting that no test or indicator is a 100% reliable indicator of cancer or prognosis.
Lymph Node Staging
One technique to stage lymph nodes is through sentinel lymph node biopsy (SLNBx). The assumption is that cancer metastasises to one or more sentinel nodes first in the regional LN basin as defined by the anatomic distribution of lymphatic vessels present within and adjacent to the tumour.
One can then determine whether the LN basin is involved by removing the sentinel LNs and performing careful histologic examination of the nodes.
Should the sentinel LNs be negative, one can be fairly certain that the remaining nodes within the basin will also be uninvolved with the tumour. However, should there be positive LNs, even just a single one, complete dissection of the affected nodes should be performed.
Other examples of surgical staging
In lung malignancy, a mediastinoscopy is performed to resect tissue from the lung.
In pelvic malignancies, like ovarian and endometrium cancers, surgery is involved if there is a requirement for:
Pelvic washings
Peritoneal biopsy of metastases
Infra colic omentectomy, standard in gynaecological cancers
Bilateral PLND or PAND
In pancreatic cancer (think Steve Jobs), an exploratory laparotomy might be performed for borderline resectable pancreatic cancers. However, in most cases, pancreatic cancer usually heavily involves with arteries, making it unresectable.
Curative / radical surgery for primary tumour
The main objective for surgery of the primary cancer is to achieve optimal local control of the lesion. Local control is defined as the elimination of the neoplastic process and to minimise local tumour recurrence. The major principle is also to achieve negative margins around the primary tumour.
One example of curative surgery is radical mastectomy. More specifically, Halsted’s procedure on radical mastectomy, which involves the removal of adjacent skin, which often necessitates a skin graft, and removal of underlying pectoral muscles, and axillary lymph nodes.
Removal of a primary colon cancer that involves an adjacent loop of small bowel or bladder (local invasion beyond capsular wall, Stage IV colon carcinoma) requires the resection of the primary tumour along with removal of the involved segment of the small bowel and bladder wall.
This approach avoids violation of the primary tumour margins that could lead to tumour spillage and possible implantation of malignant cells in the surrounding normal tissues. Aside from biopsies of the primary tumour, the lesion should not be entered during a definitive resection. In fact, any biopsy tract or incision that was performed before the tumour resection should be included in the procedure to reduce the risk of local recurrence
The risk of local recurrence for all solid malignancies is clearly increased if negative margins are not achieved. The adequacy of the negative margin has been defined for most tumour types either from retrospective clinical experience or prospective clinical trials. For example, a 5cm margin is an adequate bowel margin for primary colon cancers that has been established from clinical experience. Likewise, it is accepted that a 2cm distal margin for rectal cancers results in adequate local control.
These are the magic numbers for the corresponding sites of cancer.
Local control is significantly improved after surgical resection of breast, rectal, sarcoma, head and neck, and pancreatic primary cancers. In fact, the addition of RT as an adjunctive therapy has allowed for less radical procedures to be performed with an improvement in the quality of life of patients.
For example, in breast cancer, several clinical trials have demonstrated that the overall survival of patients with invasive breast cancer was comparable if treated by mastectomy versus lumpectomy plus adjuvant RT.
For high grade soft tissue sarcomas, limb amputation was no longer the only option available. A study was conducted to compare between limb amputation and limb-sparing surgery. Although it demonstrated a higher local recurrence rate in the limb salvage group, there were no significant differences in overall survival.
Regional LN is the most prevalent site for metastasis. Lymphadenectomy is usually performed as same sitting as resection of primary tumour. The more extended lymphadenectomy appears to result in more accurate staging of patients at a cost of increased morbidity, like onset of lymphedema.
There are, of course, many opportunities for surgery to be part of the multimodality treatment.
Oligometastatic disease
The prefix ‘oligo’ means small number, and it is a class of metastasis that presents with a small enough number that it has potential to be curable. This means that they are Stage IV, but radical / curative. Today, these are treated with SBRT.
Palliative surgery of metastatic disease is required when there are indications for it. This includes the following:
Pain
Bleeding
Obstruction
Malnutrition
Infection
Pain can be caused by a metastatic lesion (usually to the spine) compressing on an organ or adjacent nerve. A large enough breast cancer can induce pain.
Malnutrition can be mitigated by supplementing or replacing intravenous hyperalimentation or enteral feedings via a gastrostomy or jejunostomy tube.
There are two types of rectum resections.
The anterior resection enters from the anterior pelvic wall, and necessitates a temporary stoma while the rectum recovers.
The abdominal perineal resection, however, leaves the patient with a permanent stoma, and the anus is sealed. This is usually selected if the involvement is towards the distal end of the anus. The gluteal fold is flapped over anus to reinforce the closure.
