Radiotherapy of malignant gliomas: results from conventional treatment methods and the prospects of advanced techniques

Abstract

Purpose: The results of post-operative radiation therapy of malignant gliomas are disappointing, with mean survival time (MST) of 16-70 weeks and 2-year survival rates ranging from 8.5% to 25% in the literature. A slightly more favourable prognosis is found in the following cases: in anaplastic astrocytomas with respect to glioblastoma multiforme; in younger patients with respect to the more elderly; the longer the duration of symptoms before diagnosis; and in the event in which surgery has been macroscopically radical. An improvement in treatment outcome is foreseeable with the use of advanced volume definition techniques for radiation therapy.

Materials and methods and results: Our experience with conventional radiation treatment shows therapeutic results in agreement with other institutions. In the overall 134 cases MST was 50 weeks and the 2-year survival rate was 10%. In patients affected by anaplastic astrocytoma MST was 58% and 2-year survival rate was 17%, whereas the figures for glioblastoma multiforme were 47 weeks and 8% (p>0.05, not statistically significant, probably due to the small number of cases). Patients of sixty years of age or less showed a more statistically favourable prognosis: MST was 59 weeks and 2-year survival rate was 16%, compared with 44 weeks and 4% in patients above 60 years of age (p<0.05). The duration of symptoms of 6 months or less had a less favourable prognosis with respect to symptom onset of greater than 6 months: in the former MST was 49 weeks and 2-year survival was 7%, and in the latter the figures were 68 weeks and 40% (P<0.05). Lastly, the presence of residual neoplastic tissue after surgery is an unfavourable element: in this case MST was 41 weeks and 2-year survival was 7%, compared with 68 weeks and 13% (P<0.05) after macroscopically radical surgery.

Discussion and conclusions: Computed tomography (CT) is still today an indispensable technique for radiation therapy planning. Magnetic Resonance (MR) imaging, nonetheless, provides greater definition of the neoplastic extension. The possibility of combining CT and MR neuroimaging data together with stereotactic radiotherapy techniques enables the optimal development of the three-dimensional treatment plane. This translates into high dose delivery to the neoplastic volumes without affecting the regions of the brain with no tumour involvement. Furthermore, a real improvement in the prognosis of malignant gliomas must also consider the results from research in the fields of tumour biology and functional neuroimaging.