Leading-edge Developments in Radiotherapy Treatments
There are ever-changing and more sophisticated methods of tackling cancer cells with radiotherapy. However, some of the treatments described here have not yet reached the UK.
Intensity Modulated Radiation Therapy
This is precision radiotherapy that targets the tumour with a high dose over less time. Because it is so precise, it reduces radiation exposure to healthy tissues.
In addition to boosting effectiveness, the combination of accuracy and increased dose also cuts treatment time by 90 per cent compared with conventional radiotherapy. This significantly reduces side-effects and improves tolerance of treatment.
Treatment outcomes are expected to be the same as with standard radiotherapy. So far, this has been used on a wide range of tumours, with much better cosmetic effects when used on breast cancer. It is likely to become a standard method in the future.
Its main disadvantage – as with any precise treatment at this time – is that your doctor has to be absolutely certain that he is able to target the entire tumour within the exact treatment field. If this is not possible, your doctor may choose to use a more conventional form of radiotherapy.
Intraoperative Radiotherapy
Intraoperative treatments involve a miniature X-ray source inserted into the body during surgery to administer the radiotherapeutic dose.
This may be used to apply radiotherapy to where the surgeon has just removed a tumour or to a space where a tumour has been removed previously. While this treatment has been around for a while, new developments mean that more precise technology can deliver the radiotherapy to the appropriate tissue without damaging the surrounding areas.
Radiofrequency Ablation
This uses electrical energy to create heat at a specific location up to a specific temperature and for a specific period of time and, ultimately, results in the death of unwanted tissue.
The ablation probe is placed directly into the tumour tissue. The radiofrequency energy flows through electrodes, causing ionic agitation and, therefore, friction in the nearby tissue. This friction creates heat and, once sufficient temperatures have been reached, the heat will kill the target tissue within a matter of minutes.
This procedure can be used for liver tumours:
• by putting an electrode through the skin and using an ultrasound, CT or MRI scanner to guide the needle to the tumour
• during open abdominal surgery, when the specialist has direct access to the liver
• during a laparoscopic or ‘keyhole’ surgical technique.
Heat is a very effective means of killing cancer tissue. As tissue temperatures rise above 113°F (50°C), protein is permanently damaged and cell membranes fuse. The process is rapid, typically requiring less than 10–15 minutes of exposure for a 3-cm tumour. This can be done without causing too much damage to surrounding tissues. There are some specialists in the UK who use this procedure, but it is only useful for tumours that are 5 cm or less in size.
Effects are similar to that of a microwave, where heat is generated from the inside out. Destroyed cells are reabsorbed by the body over time.
Therasphere
This is a system whereby millions of microscopic glass beads embedded with a radioactive element are delivered directly into the blood vessels feeding a tumour.
It is currently used for tumours in the liver – both primary and secondary. The tiny beads (one-third the diameter of a human hair) are passed through a catheter placed in the femoral artery (in the thigh). They are then guided via the hepatic artery (the main blood vessel in the liver) to the blood vessel supplying the tumour. The beads remain in the body and lose their radiation within two weeks.
Patients can return home the same day, and there is no risk to family members. Possible side-effects include vomiting, mild fever, abdominal pain and gastric ulcers but, so far, the main complaints have been fatigue and nausea.
Clinical trials in many different countries so far show that patients are living twice as long with this treatment – and with good quality of life. It has also been successfully combined with chemotherapy. There have even been one or two recorded incidences where a liver cancer had shrunk sufficiently to become operable, or potentially curable. Its limitations, as with all forms of treatments involving radiation, are related to the size and volume of the tumour, as too large a tumour would require an unsafe dose of radiation.
Fractionated Stereotactic Radiosurgery
This is a non-invasive therapy for brain tumours that, in the past, have been very difficult to treat. It directs precisely guided beams of radiation from many hundreds of different angles to converge on the tumour. It is called radiosurgery because the surgeon uses the radiation beams like a knife to cut out the tumour. By focusing these beams from so many different positions, the effects on the normal healthy brain and tissue are minimized while striking only the target with the prescribed treatment.
The main difference between standard radiation and fractionated stereotactic radiosurgery is that standard radiation will also irradiate large amounts of normal healthy brain compared with radiosurgery, which is focused almost exclusively on the tumour.
This approach is also proving effective for treating tumours of the head and neck, where there are many important nerves and structures very close together in one area.
Traditional surgery may result in a degree of facial paralysis and functional loss, so this form of treatment, if available, is highly desirable.
Brachytherapy
This is being used for prostate cancer that has been detected early and not spread beyond the gland. In this case, tiny radioactive ‘seeds’ or pellets, containing radioactive iodine, are implanted directly into the middle of the cancer via thin needles, where they will keep on giving off radiation for up to a year. Up to a hundred pellets are implanted through the skin, under either a spinal or general anaesthetic.
The radioactivity of the pellets slowly decays during the months after the operation; few long-term risks have been reported with this treatment.
Chemotherapy
We have seen how surgery and radiotherapy are used to deal with disease that is localized in a particular area. But if the disease has spread, or metastasized, then the treatment has to reach all parts of the body to eliminate cancer cells wherever they have lodged. Such treatments are called ‘systemic’, as they go right round the system. Since the 1940s, around 150 drugs with anti-cancer effects have been developed. They act in various ways to destroy or slow down the growth of rapidly dividing cancer cells.
There are several ways in which different types of anti-cancer drugs work:
• by preventing the DNA in the cancer cell nucleus from being copied, a vital process for cell division and growth of the tumour
• by depleting the cancer cell of the building blocks for DNA so that fewer raw materials are available for DNA to replicate itself
• by preventing the binding of enzymes that enable the production of key protein molecules in the cancer cells
• by blocking protein synthesis, especially those that maintain healthy cell activity as well as cell division.