Evaluation of high-grade astrocytoma recurrence patterns after radiotherapy in the era of temozolomide: A single institution experience

Abstract

Aim

Evaluating the recurrence patterns of high-grade astrocytomas in patients who were treated with radiotherapy (RT) plus temozolomide (TMZ).

Background

The current literature suggests that reducing the margins added to the CTV does not significantly change the risk of recurrence and overall survival; thus, we decided to analyze our data and to examine the possibility of changing the adopted margins.

Materials and methods

From February 2008 till September 2013, 55 patients were treated for high-grade astrocytomas, 20 patients who had been confirmed to have recurrence were selected for the present study. Post-operative MRI was superimposed on the planning CT images in order to correlate the anatomical structures with the treatment targets. Recurrences were defined according to the Response Assessment Criteria for Glioblastoma. The mean margins of the PTV_initial and PTV_boost were 1.2[[ce:hsp sp="0.25"/]]cm and 1.4[[ce:hsp sp="0.25"/]]cm, respectively. The analysis of the percentage of the recurrence volume (Vol_rec) within the 100% isodose surface was based on the following criteria: (I) Central: >95% of the Vol_rec; (II) In-field: 81–95% of the Vol_rec; (III) Marginal: 20–80% of the Vol_rec; and (IV) Outside: <20% of the Vol_rec.

Results

Of the 20 patients, 13 presented with central recurrences, 3 with in-field recurrences, 2 with marginal recurrences and 2 with outside recurrences. Therefore, the lower Vol_rec within 100% of the prescribed dose was considered in the classification.

Conclusions

Of the selected patients, 80% had ≥81–95% of the Vol_rec within 100% of the prescribed dose and predominantly had central or in-field recurrences. These results are comparable with those from the literature.