The Importance of Using the Modified Fisch Classification and the Determination of the Natural Rate of Growth of Tumor by Wait-and-Scan Approach Before Offering Radiosurgery for Tympanojugular Paragangliomas
It is with great interest that we read the article titled “Stereotactic radiosurgical treatment of glomus jugulare tumors” by Winford et al. (1). Having the largest series of tympanojugular paragangliomas treated and reported in the literature (2), we wish to put forth our comments on this article. First, we think it is high time that the pathology be addressed by its proper name that is tympanojugular paraganglioma. “Glomus” is a misnomer the use of which has been criticised by eminent authors on the subject. The authors have adhered to the Fisch classification but have classified Class D as separate from Class C. This is wrong as Classes C and D go together (e.g., C3Di or C3De) signifying the extent of carotid and dural involvement. The authors have included five (13%) Class B tumors that are not tympanojugular paragangliomas (glomus jugulare as the title suggests). They are tympanomastoid paragangliomas (glomus tympanicum) that can be completely removed by standard approaches like radical mastoidectomy with or without a blind sac closure by most experienced otologists (3). There are practically no sequelae and the patient is offered complete and permanent cure with intact inner ear function. Stereotactic radiotherapy for Class B tumors is clearly not indicated. Similarly, in experienced skull base centers, Class C1 and C2 tumors can be removed completely using the infratemporal fossa approach type A without any significant morbidity and with preservation of inner ear hearing and lower cranial nerve function. It is only in Class C3 and C4 tumors that surgery may lead to new cranial nerve deficits (4). Fifty percent of the tumors in this series were either Class C1 or C2 (and another 13% were Class B). This is reflected by the fact that the mean tumor volume at the time of surgery was 5.8 cm3 which are essentially small tumors. Hence, 63% of the tumors in this series could have been offered complete and permanent cure with practically no sequelae by surgery. Treatment failure was observed in an additional 10 (26.3%) of the patients.
Tumors were followed up after radiation for 39.1 months. Reported success rates were 82%. It would have been interesting to know the rate of growth of tumors that underwent stereotactic radiotherapy: were they growing tumors or not? Were any of the patients subjected to a policy of wait-and-scan before radiotherapy. We have studied 47 patients with tympanojugular paragangliomas (Fisch Class C and D) (5) that were followed up with wait-and-scan at our center. We divided the study population into three groups. In the first group with a follow-up of less than 36 months, 92% of the tumors remained stable or showed regression. In the second group of patients with 36 to 60 months follow-up, tumor stability or regression was observed in 83% of the patients (similar to this series with the same follow-up duration) and in the third group of follow-up of greater than 60 months, tumor stability or regression was observed in 45% of patients. This leads us to the question as to how much of the tumor stability cited in articles like this one, is actually due to the natural history of tumor growth. As far as cranial nerve deficits are concerned, only 30% of our patients on wait-and-scan progressively developed new lower cranial nerve deficits. However, all of them were well compensated by the cranial nerves of the opposite site due to the slow nature of tumor growth.