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Selecting a patient for radiosurgery
Selecting a patient for radiosurgery
Selecting a patient for radiosurgery is the most important step. We have to consider whether a particular case will do well after radiosurgery. There are no fixed rules. The decision to treat a patient is personal, and it comes with experience. If you wish to refer a patient, you must know basic information about how radiosurgery works. The best way is to contact the treating doctor and send all relevant documents so that he can evaluate them before the patient arrives in the clinic.
factors that play an important role in the case selection:
factors that play an important role in the case selection:
Diagnosis: A list of diseases given in the previous section shows tumours and diseases which can be effectively treated and are in common use.
Clinical situation: Neurological deficit at the time of diagnosis and later if operated or observed over time. How fast are his symptoms rising or worsening?
Growth pattern of tumours: How fast are they growing? If a patient is deteriorating quickly, then evaluation must be done to determine whether he needs an adjuvant surgery or not.
Type of tumours: Benign tumours grow slowly; therefore, their clinical deterioration is slow. Malignant tumours may grow faster causing faster clinical deterioration.
Speed of growth: Tumours which grow slowly may even reduce slowly. Long compression may hamper recovery.
Organ at risk (OAR): OAR evaluation is very important. For example, evaluation of optic nerves in Pituitary adenomas or Sella region tumours.
Clinical condition of patient: If a patient has comorbidity, like coronary artery disease, is old, immunocompromised or diabetic, consideration is needed when weighing the choice of surgery and radiosurgery. Radiosurgery is much safer if it is a borderline case.
Larger tumours: Large tumours cause serious compressive symptoms and should be operated upon before radiosurgery. It needs to be assessed clinically, or by imaging, growth pattern and known response to radiation. Other effects like development of hydrocephalus or isolated dilation of ventricles goes against the choice of radiosurgery and may need a pre-radiosurgery procedure.
The Myth of 2.5 Centimetres
The Myth of 2.5 Centimetres
It is widely believed that if a tumour is 2.5 centimetres in size, it may not be suitable for radiosurgery. However, there is no such strong evidence to support this statement. We might consider that a smaller tumour is better, and the decision to treat it is on the clinical condition of the patient.
Age, comorbidity, history of previous surgery or treatment; everything must be considered. Where did this assumption come from? In 1992, Linskey et al published their way to measure acoustic schwannoma. The purpose was to use the same method for comparing in post-treatment imaging.
Later in 1994, Linskey et al published that facial neuropathy following radiosurgery was associated with the irradiated length of cranial nerve VII. Therefore, a tumour having a mid-porous transverse diameter more than 2.5 cm may have a greater chance of facial nerve dysfunction as a longer length of the nerve is irradiated.
Later, Piazza F. et al emphasized the same. However, many later on many people did not find such a correlation. Unfortunately, Acoustic Schwannoma was the first popular indication for Radiosurgery with Gamma Knife and it stuck in the mind of surgeons that a tumour of 2.5 cm was the standard limit to select patients for radiosurgery in any indication.
Large tumour, but still makes good indications as patient is asymptomatic except hearing loss, and mid-porous to pons distance less than 2.0 cm while largest length along petrous is 3.2 cm.
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