The risk of malignancies
after AN treatment
Incidences of malignancy following AN treatments, both microsurgical and radiosurgical, have been known. The following is from the British Journal of Neurosurgery, June 2002, pp. 284-9:
Up to now, eight cases of malignancy in eighth nerve tumours have been reported, four of which, including the present case, had previously been treated with radiosurgery and four cases that had not received radiation. Thus, it would seem, the overall incidence is extremely low.
Determining the cause of malignancy in any individual patient is impossible, so causality must be based on statistical evidence.
(From Dr. Lawrence Kleinberg at John Hopkins)
To really address this one would need to combine the incidence of malignancy found on surgery for suspected benign acoustic neuroma with the rare incidence of malignant recurrence after surgery and compare this with the rare incidence of malignant recurrence after radiotherapy to see if the chance of some sort of malignancy was more common.
The overall rate of brain cancer in AN patients who have been treated by radiosurgery has not been any higher than for neurosurgery patients. Since statistics do not show a correlation between radiosurgery and increased malignancy when compared to patients who had surgery, it must be assumed that radiosurgery is not the cause.
When malignancy is discovered in any post-treatment AN patient, there are therefore two possible causes: either the tumor was misdiagnosed from the beginning and was not an AN, or this is a case of a different tumor that happens to affect the same patient in the same area as the AN, rather than a "result" of the AN treatment.
(From Dr. Lawrence Kleinberg at John Hopkins)
All the current evidence indicates this is rare after surgery and at least almost as rare after radiosurgery.
Here is a quote from Bruce Pollock, M.D., et al. in their comparison study between microsurgery and radiosurgery (Neurosurgery, Vol. 36, No. 1, Jan. 1995, p. 221):
The concerns that stereotactic radiosurgery may lead to the development of delayed radiation-induced neoplasms remain unsubstantiated; an increased incidence of new neoplasm development has not been reported despite more than 26 years of experience and the treatment of more than 20,000 patients worldwide.
["neoplasm" = "A new growth of tissue serving no physiological function: tumor."]
Dr. Lederman at Staten Island University Hospital, one of the leading practitioners of fractionated stereotactic radiation for ANs, was also asked about this.
(11/03) At Dr Gil Lederman's lecture on Sunday in Yarm (Cleveland, England) the question was asked about the possibility of malignancy as a result of having radiosurgery. Dr. Lederman told the meeting that there are now figures accepted in the medical profession as a whole (based on world wide experience) which give an actual occurance of one case in 33,000 treatments!
Despite these opinions of leading radiosurgeons, unsubstantiated rumors linking AN radiosurgery with malignancy persist. We must remember that NO treatment of AN is risk free. In fact, there is somewhere between a 0.4 and 1% risk of not surviving surgery. If someone does not survive surgery, or dies as a result of complications, people do not say "surgery causes death". But radiation is perceived to cause malignancy, and therefore death. Why do we perceive radiosurgery as so much riskier?
Usually, these rumors are based on data relating malignancy to an outdated radiation treatment for cancer known as "X-ray therapy". This whole-head non-stereotactic massive-dose radiation treatment is very different from stereotactic radiosurgery that is used for ANs, and its data is irrelevant to AN treatments - just as data on head stabbings would be unrelated to AN surgery, even though both involve a knife and a head!
Our reaction, as a species, to risk is very interesting: most of us get in a car every day, with no apprehension, but hopefully caution. Quite a few of us are very apprehensive about flying, even though it is a 'safer' means of transport. This is completely illogical - but try telling that to someone who is frightened of flying! A similar process seems to be at work here: surgery has its risks, but they are not emotive risks, surgery is an accepted part of everyday life. Radiation is not, therefore we view it emotionally.
Theodore Rockwell, a founding director of Radiation, Science & Health Inc, wrote recently about the unfortunate fear of radiation in this country. In The Scientist (March 3, 1997) he observed:
About 1 million medical procedures involving radiation are performed each day in the United States. These are our latest and best medical techniques, yet thousands of people avoid such life-saving procedures out of fear of radiation.
Last Edited: Monday, November 17, 2003