Stereotactic Radiosurgery (SRS) and Stereotactic Radiation Therapy (SRT) are advanced and modernised forms of radiation therapy, which delivers high dose radiation to a small focused area. This specialised form of radiation treatment involves a team of specialists. This team includes radiation oncologists, radiologists, radiation physicists, other specialty doctors, and nurses.
"United Hospital Cancer Care Center pioneered SRS and SBRT in Bangladesh back in 2014. Since then we have performed more than 150 cases with this treatment modality for some liver, lung, spine, and brain tumours," says Dr Rashid Un Nabi, senior consultant for Radiation Oncology at United Hospital.
SRS stands for Stereotactic Radiosurgery and SBRT stands for Stereotactic Body Radiation Therapy. Both are more advanced cancer treatment options which allow for shorter treatment times, fewer side effects, and better chances for a cure. Stereotactic Radiosurgery is not a surgery in the traditional sense because there is no incision involved and general anesthesia is not required for adults, instead SRS uses 3D imaging to treat tumours and other problems in the brain, neck, lungs, liver, spine and other parts of the body, targeting high doses of radiation to the affected area with minimal impact on the surrounding healthy tissue. Stereotactic Radiation Therapy and Radiosurgery are ultra-focused radiation to the tumour only and like other forms of radiation treatment this controls the growth of a tumour or abnormal cells by either killing the cells directly or by damaging the DNA of the targeted cells disrupting the ability of the cells to grow. The affected cells then lose the ability to reproduce, which causes tumours to shrink.
When doctors use Stereotactic Radiosurgery to treat tumours in areas of the body other than the brain, it is sometimes called Stereotactic Body Radiotherapy (SBRT) or stereotactic ablative radiotherapy (SABR). SRS and SBRT are very similar, but SRS delivers a large dose of radiation on a single day and SBRT has a fractionated treatment schedule. This means that in SBRT the patient will have treatments spanning multiple days. The total dose in SBRT may be larger than in SRS, but in a single day SBRT will have a much smaller dose delivery.
Routine use of Stereotactic Radiosurgery (SRS) is mostly to treat brain tumours and lesions. It may be the primary treatment, used when a tumour is inaccessible by traditional surgical means, or as a boost or adjunct to other treatments for a recurring or malignant tumour. Stereotactic Radiosurgery of the brain and spine is typically completed in a single session. Stereotactic Body Radiation Therapy typically involves multiple (3-5) sessions. SRS (one-session treatment) and SBRT (3-5 session treatments) have such a dramatic effect in the target zone that the changes are considered "surgical". Through the use of three-dimensional computer-aided planning and high degree of immobilisation, the treatment can minimise the amount of radiation that passes through healthy tissue of the brain and other vital organs.
In some instances, SRS is advisable, but the location of a tumour may be in close proximity to a critical structure, such as the optic nerves, and in such cases the radiation may be divided into fractions and delivered in the same precise targeted manner. This is known as Stereotactic Radiotherapy (SRT), rather than SRS. Generally, SRS is reserved for tumours that are less than three centimeters in maximal diameter. The most common application of SRS in practice is for the treatment of metastatic brain tumours. Another very common application where SRS is very effective is in the treatment of small tumours arising from the vestibular nerve known as vestibular schwanomma (or acoustic neuroma). Stereotactic Radiosurgery is also a non-invasive treatment option for many patients with conditions such as: arteriovenous malformations (AVMs), arteriovenous fistulas, trigeminal neuralgia and various intracranial tumours.
Karthick Raj Mani, consultant medical physicist at United Hospital, says, "Due to the large dose delivered in SRS and SRT, it necessitates a very precise positioning of the patient. To accomplish this a special mask or position device is made for each patient at the time of CT. This enables the accurate positioning of the patient which allows for the delivery of radiation on the sub-millimetre scale."
Doctors use this method to treat areas that are hard to reach or close to vital organs, or they use it to treat tumours that have moved within the body. This technology makes it possible for neurosurgeons to reach the deepest recesses of the brain and correct disorders which are not treatable with conventional surgery. Since there is no incision, there are minimal surgical risks and little discomfort. Adult patients may be lightly sedated but are awake throughout the procedure. Hospitalisation is short, and at most requires an overnight stay. The majority of patients are treated on an outpatient basis. As a result, patients experience less discomfort and have much shorter recovery periods than having undergone conventional surgery. Doctors may use SRS to treat older adults or people who are too ill to have conventional surgery. Sometimes, after someone has had surgery to remove a cancerous tumour, a doctor will use SRS to kill any remaining tumour cells that the surgeon may have missed.
"SRS can be administered by different methods. United Hospital uses CyberKnife method which is able to treat cancer anywhere on the body in one to five radiation treatments whereas another method -- Gamma Knife -- can only target brain or cervical spine cancer with a single treatment of high-dose radiation," said Dr Rashid Un Nabi.