When A Knife Is Not A Knife, But Can Still Treat Brain Lesions
Doctors have an array of options when it comes to cancer treatment, and the latest technology that is available in Malaysia is called the Gamma Knife.
Contrary to its name, it’s not a knife in the conventional sense.
Instead, the technology involves precise intersecting beams of gamma radiation to treat lesions in the brain such as small to medium brain tumours, abnormal blood vessel formations and other neurological conditions.
The brainchild of Professor Lars Leksell (1907-1986), a Swedish physician and Professor of Neurosurgery at the Karolinska Institute in Stockholm, Sweden, the Gamma Knife is an advanced radiation treatment, delivering finely focused, high-dose radiation to lesions, with little or no damage to surrounding tissues.
Abnormalities in the brain measuring less than 4cm can be treated with the Gamma Knife.
Says consultant clinical oncologist Dr Tho Mun Lye: “There’s a strict selection criteria for patients who are suitable for the Gamma Knife – what type of tumour, which part of the brain is involved, risk of swelling (if there is a risk, then the patient may not be suitable), how far the tumour has spread into the brain.
“If it’s localised and not too big, then the Gamma Knife is suitable, especially with the kind of precision that it offers.”
Even patients with serious disorders can be treated with this non-invasive procedure in one day with no overnight hospital stay.
In essence, the Gamma Knife technology allows doctors to precisely target areas within the brain with the aid of various imaging techniques. These provide a 3D view of the target and surrounding brain structures.
Then, gamma radiation is directed at the tumour, destroying the abnormal tissue at one go.
However, according to consultant neurosurgeon Dr Ravi S. Krishnapillai, the latest version of the Gamma Knife also allows for staged or fractionated treatments.
“Traditionally, the Gamma Knife has always been a frame-based treatment – we fit a frame onto the patient’s head, which is anchored with four pins. This is to ensure that the patient’s head does not move while receiving the treatment.
“Then a single-shot dose of radiation is administered, which is, by definition, radiosurgery,” he says.
“The latest iteration of the Gamma Knife is called the Icon.
“Part of the evolution of the Gamma Knife is moving from a single-shot treatment to one that enables us to fractionate therapies as well, meaning that anything that could not be treated in a single dose (like a larger tumour or mass) can now be staged over a few days.
“And instead of a frame, a face-fitted mask can now be used,” he adds.
According to Dr Ravi, the whole logic of fractionating is to be able to treat larger lesions without any significant complications from using a higher dose of radiation for the larger lesion.
“Essentially, there’s a space problem in the brain,” he explains.
“When you treat a large lesion, sometimes when you use a very high dose, you can get swelling, oedema and pressure build-up.
“Then you’re running back to the operation theatre and trying to do a craniotomy to relieve the pressure and take the tumour out, specifically with patients with cancer.
“With fractionated treatments, you avoid that.
“And in the old days, if a patient has 12-13 brain metastases, you look at the scan, it’s stage 4. So that meant palliative treatment, tender loving care, keeping the patient comfortable.
“Now, in a lot of these stage 4 patients, the chemo(therapy) and systemic management has improved significantly as well; but some of these drugs don’t really get into the brain because of the blood brain barrier.
“And so a lot of these patients with multiple brain metastases, if you give them whole brain radiation, a lot of them get cognitive deficits, significant cognitive deficits.
“With the Gamma Knife, even with 15 met(astase)s, the results are stunning. These lesions completely disappear.
“It doesn’t mean that a patient is cured. We need to reappraise them, let’s say four to five months down the line with a repeat scan; if there are some new lesions, we can treat them again.
“So, by picking away at these brain metastases, we are able to preserve the cognitive function of these patients, and many of them have significantly improved quality of life and may even be able to get back to work,” says Dr Ravi.
The Gamma Knife is shifting the paradigm as to how treatments can be given, and how the patients are responding.
“During the treatment, the patient doesn’t feel anything,” says Dr Tho. “If we’re treating using the frame, you inject some local anaesthetic, there’s a bit of pain, a bit of pressure, but it’s very well tolerated; once the frame goes on, it looks quite ‘horrendous’, but actually it’s not. It’s quite comfortable, and you can even see patients walking around with the head frame.
“If we treat using the face mask instead of the head frame, it’s even less of a hassle. We immobilise the patient with a mask.
“The average length of treatment depends on the size of the tumour and the number of tumours,” he notes. “It can be as short as 15 minutes for one small tumour; to two-and-a-half hours for 15 met(astase)s, all at one go.”
According to Dr Ravi, with the Gamma Knife, the bulk of the work is metastatic brain tumours and benign lesions of the brain, such as meningiomas and acoustic neuromas.
“With the Gamma Knife, these lesions are now being treated in a single day, even lesions in traditionally hard-to-access areas.
“Imagine you come in the morning, you get your treatment done, you go home, and it’s treated – not a single cut on your head. And you have effectively treated your lesion.
“The vast majority, 99%, go back on that day, but we always tell them if they get any headaches, seizure, nausea, vomiting or anything they’re worried about, to come back to the hospital.”
Dr Tho emphasises that not all patients are suitable for Gamma Knife treatment; there’s a selection criteria. Some patients are more suitable for conventional radiation therapy that’s divided over six weeks, for example, he says.
However, he stresses that the Gamma Knife is easily tolerated by elderly patients and people with co-morbidities.
“At the moment, 4cm is the upper limit of the size of the lesion we treat. But we’re pushing the boundaries every year.
“We see the Japanese doing staged treatment – they take on big tumours where they give a third of the dose and wait, maybe two to three weeks to let it shrink, then give another one-third of the dose, then wait, then give the final third.
“This is also being done here.
“Conversely, we are also able to treat tiny lesions.
“Take, for example, trigeminal neuralgia, a painful and debilitating condition. The nerve is very small, 2-3mm, but we’re able to target that – hit it with very high dose radiation. Accuracy is very important.”
According to both doctors, the Gamma Knife is not just about the technology or the doctors.
It’s a team effort consisting of neurosurgeons, oncologists, rehabilitation specialists, ophthalmologists, ENT surgeons (to assess hearing and eyes), radiologists, physicists and so on.
“We even have a monitoring system which actually monitors the movement of the patient during treatment. There’s a graph that measures movement, and if it goes above a certain threshold, the machine cuts off, like a fail-safe mechanism,” says Dr Toh.
“We can’t see where the radiation is being delivered; the physicist has got to do all their quality assurances to ensure precision treatment,” says Dr Ravi.
“The Gamma Knife is a bit of a game changer. The clinical assessment and selection of patient is so important. The limitation is that we treat the head only,” he adds.