Central Nervous System
PV QA 2 - Poster Viewing Q&A 2
Purpose/Objective(s): The optimal clinical target volume (CTV) definition for the malignant gliomas is still debated. To compare the role of margin or edema in CTV’s delineation, we analyzed the pattern of recurrence and the impact on outcomes of the two different CTV in patients (pts) with GBM, treated with RT plus TMZ.
Materials/Methods: Pts with a histological diagnosis of GBM, observed from 2002 to 2008, were evaluated. All pts received 3D-CRT with a total dose of 5940 cGy on CTV1 including tumor bed +/- residual mass + 1,5 cm and 4500 cGy on CTV2 including tumor bed +/- residual mass plus edema (Group A) or plus 3 cm subsequently (Group B). TMZ was administered according to Stupp’s schedula. An independent review an expert radiation oncologist was carried out for CTV validation. Relapse was defined as in-field, marginal or distant if greater than 80%, 20-80%, or less than 20% of the recurrent volume fell within the 95% isodose line. The acute toxicity was assessed according to RTOG score. The primary endpoint was the impact of the two different CTV2 delineations on recurrence pattern; the secondary endpoints were overall survival (OS) and disease free survival (DFS).
Results: Among 261 pts observed, 141 were evaluable: 66 in group A and 75 in group B. Median age was 61 years (range 21-81), 88 males (75%) and 53 females (25%). The two groups were comparable for the age (p: 0.78), the sex (p: 0.34) and the surgery (p: 0.45). In Group A recurrences were observed in 61 (92%) pts: 43 in field (70%), 23 marginal (23%), and 7 distant (7%). The median PTV1 volume was were 361 cc (Range 98-623). In Group B recurrences were observed in 66 (85%) pts: 38 in filed (61%), 19 marginal (30%), and 7 distant (19%). The median PTV1 volume was 223 cc (Range 2-540). The median follow-up was of 57 months (range 6-116). No significant difference was observed for patterns of failure (p: 0.9). No difference in the two groups in terms of acute toxicity was recorded. Median PFS and OS were respectively 13 and 17.8 months. Incomplete surgery significantly impact on DFS (p: 0.009) and OS (p: 0.008); old age (<65yrs pts) impact only on OS (p:0.01 and p:0.003). At the multivariate analysis five unfavorable predictive factors on survival outcome were indentified: male sex (p: 0.003), age > 65 yrs (p: 0.03), presence of residual disease after the first surgery (p: 0.002), CTV size (p: 0.01) and edema included in CTV (p: 0.02).
Conclusion: Our study shows that there is no correlation between the way to delineate CTV and the patterns of failure. The pattern of failure seems not to be correlated with the way of delineating the CTV2, while adding the edema negatively impacts both the DFS and OS, increases the PTV volume, without influencing the acute toxicity.
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