In vitro model for the response to irradiation of different types of human intracranial tumours

Potential complications following radiotherapy for meningiomas

BACKGROUND

The rationale for radiotherapy of meningiomas is based on retrospective studies utilizing life-table statistics and historical controls. Most of these report minimal morbidity and high efficacy, while one study of radiation therapy for benign diseases reported a high complication rate during long-term follow-up. These reports were at variance with our personal experience in three patients. This study was therefore undertaken to corroborate the previous reports by retrospectively investigating possible adverse effects and efficacy.

METHODS

The charts at Karolinska hospital were searched to identify all patients with meningiomas who were treated with conventional fractionated radiotherapy between 1975 and 1995. Surgical radicality was assessed according to Simpson. The patients were followed until recurrence, death, or a minimum of 5 years.

RESULTS

Forty-five out of 1,820 patients were treated with fractionated radiotherapy. Fifty-six percent of these patients experienced serious complications from fractionated radiation treatment. The complications encompassed neuropsychological and neurologic motor and sensory deficits and were severe enough to cause hospitalization or a major change in lifestyle. Seventy-five percent of all subtotally resected and radiated meningiomas recurred during follow-up.

CONCLUSION

Our historical data from a heterogenous group of consecutive patients undergoing fractionated radiation therapy in meningioma management showed an unexpectedly high rate of complications and failed to corroborate previous historical reports of low morbidity and tumor control. Dose planning and radiation treatment has improved. Our data indicate a need for prospective investigations.

Intracranial meningeomas: time- and dose-dependent effects of irradiation on tumor microcirculation monitored by dynamic MR imaging

The purpose of this study was the characterization of the time- and dose-dependent effects of irradiation on tumor microcirculation by means of dynamic MR imaging and correlation of the estimated data with tumor response in patients with meningeomas. Dynamic MR imaging studies were performed in 20 patients with intracranial meningeomas prior to (n = 20) and at 6 (n = 17), 18 (n = 17), and 50 wk (n = 14) after the end of radiotherapy. In seven of these patients, dynamic measurements were also performed during fractionated radiotherapy after approximate 20 Gy and 54 Gy. During and after short-time infusion of gadopentetate dimeglumine, the kinetics of lesion response was resolved using a strongly T1-weighted saturation recovery TurboFLASH (SRTF) sequence. The signal-time courses of the suspected lesions were analyzed using a pharmacokinetic two-compartment model. The calculated parameters amplitude A (reflecting gadopentetate dimeglumine accumulation in the extracellular space) and exchange rate constant k21 (depending on vascular permeability and blood flow) were displayed as color-coded images and analyzed as a function of time of therapy and radiation dose. All meningeomas showed a high exchange rate constant k21 (median, 5.7 min-1; range, 1.9-23.0 min-1) and a high amplitude A (median, 1.5 arbitrary units; range, 1.1-2.7) prior to X-ray treatment. During radiotherapy we found a dose related significant (p < .01) increase of k21 accompanied by an increase of the amplitude A as compared to the pretreatment values. Analysis of tumor volume 6, 18, and 50 wk after X-ray treatment revealed two different groups. In the responder group (n = 13) the median of the tumor volume decreased from 10.0 to 7.5 cm3. For this group, we found a significant drop (p < .01) of the median of the amplitude A and a decrease of the exchange rate constant k21. In the nonresponder group (n = 4) the median of the tumor volume increased after radiation from 3.5 to 4.5 cm3. The pharmacokinetic analysis revealed a decrease of the amplitude A-and an increase of the exchange rate constant k21. The response of meningeomas to radiotherapy is influenced by the effect of X-rays on tumor microcirculation. This effect on tumor microcirculation can be derived by analysis of pharmacokinetic maps obtained from dynamic MR images. Furthermore, these pharmacokinetic maps can possibly be used to differentiate groups of patients who respond or do not respond to radiotherapy and, thus, could benefit from another treatment modality.