Intracranial meningiomas following low-dose irradiation to the head

Abstract

Earlier reports have suggested that low-dose ionizing irradiation might be involved in induction of intracranial meningiomas. One of the problems in evaluating irradiation-induced neoplasms is the belief that these tumors have no distinguishing features to indicate their etiology. In an attempt to identify such features in meningiomas following irradiation, a group of 42 post-irradiation meningiomas (PIM's) has been compared with a group of 84 non-PIM control meningiomas. These 42 PIM's included all the intracranial meningiomas diagnosed at the Hadassah University Hospital during the years 1952 to 1981 in individuals treated in childhood with low-dose x-ray therapy for tinea capitis. Although the individual PIM does not seem to differ from a "spontaneous" meningioma, this study indicates that PIM's as a group have distinct characteristics, namely, their location at the site of maximal irradiation, and features suggesting rapid growth and aggressive biological behavior. There was a significantly higher number of calvarial tumors (p less than 0.001), a high proportion of multiple meningiomas, a higher recurrence rate following apparent complete excision (p less than 0.02), and an increased number of histologically malignant meningiomas (p less than 0.01). The demonstration of features that distinguish PIM's from meningiomas of other etiology supports the suggestion that low-dose ionizing irradiation was involved in the pathogenesis of these tumors.

A possible association between ionizing radiation and pituitary adenoma

“…Nevertheless, this characteristic also was observed for radiation-induced meningiomas. 18 The biologic behavior of these tumors in terms of aggressiveness, judged by recurrences and postoperative deaths, does not seem to differ from previously published results. 30,31 We find it extraordinary that 25% of this study group later developed a second primary tumor, and, furthermore, that all of these neoplasms occurred in the irradiated area (head and neck).…”

“…18 The latency reported for most other series of patients with benign solid tumors in this group seems shorter (e.g., thyroid adenomas: mean, 17.9 years; range, 5.1-23.7 years; benign salivary gland tumors: mean, 21.5 years). 35,38 A relatively long latent period, like what was seen in our study, may add to the obstacles of relating higher rates of neoplasms to exposure that occurred many years earlier.…”

“…Although several studies support the role of previous radiation exposure in the development of brain tumors, most of them do not specifically mention PAs. 10,[15][16][17][18][19][20][21] This also holds true for the Israeli Tinea Capitis Study, in which comparisons between the rate of tumors in the irradiated group and the nonirradiated control group showed a significant excess risk for various tumors arising in the irradiated area, including benign and malignant brain tumors. 20 However, to date, an excessive risk for PA has not been indicated.…”

“…Several investigators have pointed at characteristics that differentiate radiation-induced tumors from spontaneous tumors 18 ; therefore, comparing our patient group with other series is of interest when discussing the possibility of past irradiation involvement in the pathogenesis of these tumors. Overall, the clinical phenotype distribution in our series of patients with PA appears to be in accordance with the literature.…”

“…32 It is interesting to note that, for patients with meningiomas, for whom low-dose irradiation is a proven risk factor, relatively young age at the time of diagnosis is considered one of the characteristics of postirradiation tumors compared with nonirradiationrelated tumors. 18 The lack of a reported female predominance observed in our group (female/male: overall, 0.77; prolactinomas, 0.75; NFPAs, 0.25 vs. 1.73, 4.4, and 0.65, in a large series of patients with non-radiation induced PAS, respectively 32 ) may not be a genuine finding that reflects different sensitivities to low-dose irradiation among men and women but, rather, represents a higher percentage of males among individuals who apply for compensation. Nevertheless, this characteristic also was observed for radiation-induced meningiomas.…”