TeacherOfMedicine: [Oncology] Principles of management

The first step to optimal therapy is to understand the situation. There are a few key questions which must be continuously asked and answered.

This requires tissue diagnosis. A biopsy must be taken to assess the depth of the invasion. Histopathologists can assess the cells with microscopy and molecular studies.
Some types of cancer are faster to grow (by mitosis).
Some types of cancer are faster to metastasise.
Some types of cancer are more sensitive to chemotherapy, radiotherapy, hormonal therapies or specific biological therapies.
Some types of cancer may cause dangerous syndromes beyond their invasive growth (paraneoplastic syndrome)

Is there any metastasis?
Where are the known metastases?
The more sites reached by metastasis, the less likely it is to be cured.
Certain sites are unsuitable for classic radiotherapy. For example, the liver is relatively radiosensitive.

The probability of curable disease depends on the type of cancer and the extent of spread.

Enzyme inhibitors
Hormonal therapy: antagonism (blockade) of any growth receptors in the cancerous tissue, for example:

Finasteride, a 5-alpha-reductase inhibitor, reduces testosterone agonism (stimulation) in the prostate cells. This reduced 7-year incidence (new onset) of prostate cancer.

Any of the above therapeutic methods
External Beam Radiotherapy: An external beam of high energy radiation is directed at a target site to induce cell-death in cancerous cells. The dose delivered to the tissues is calculated to damage sensitive cells (such as cancer cells), whilst most stable cells (such as normal tissue cells) can recover.

Conformal radiotherapy (3DCRT): The radiation beam is carefully shaped to fit the treatment area. The shape is guided by computer software.

Intensity modulated radiotherapy (IMRT): thin slices of lead are slid up and down to block the beam leaving the radiation source. The gap formed by the adjustable slices allows a shaped beam to escape the machine and reach the patient. The computer coordinates a rapid dynamic adjustment of the slices as necessary to change the shape of the beam as necessary.

Stereotactic radiotherapy: An external beam is directed by computer software to rotate around the body, with a constant point of focus at the target site. The tissues at the target site receive a relatively high dose, but all of the tissues surrounding the target site receive a relatively low dose.

Brachytherapy: A radioactive material is implanted into an affected organ, to maintain a low constant dose of radiation, killing unstable cancer cells in the organ.
Radiosurgery: Hundreds of low dose radiation beams converge to deliver a high dose of radiation to a small point. The energy at the focus point is so high, that it causes instantaneous destruction of the cells at the target site. Today, radiosurgery is usually used for intracranial malignancies.

Leksell Gamma Knife ® - an extensively studied radiosurgery system created by Professor Lars Leksell and Elekta Instrument AB, Stockholm.

It was eventually proven in clinical trials that patients will often benefit from a course of therapy after the primary intervention. For example:

It is now commonplace to initiate therapy before the primary intervention. For example:

Short-term chemotherapy, and monitoring of the size and location of known tumours, before surgical removal of these tumours.

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