Novotny et al developed a model for predicting the probability of intracranial edema following resection of a meningioma with a gamma knife. The authors are from the University of Texas Southwestern, Na Homolce Hospital (Prague), and University Hospital L. Pasteur (Kosice).
Parameters:
(1) history of previous surgery
(2) presence of intracranial edema before gamma knife surgery (GKS)
(3) tumor volume in cubic cm
(4) tumor location
(5) radiation dose to the tumor margin in Grays
Parameter |
Finding |
Points |
previous surgery |
no |
0 |
|
yes |
1 |
intracranial edema before surgery |
no |
0 |
|
yes |
1 |
tumor volume |
|
(volume in cc) |
tumor location |
no risk (middle cranial fossa, posterior cranial fossa, tentorium, cerebellum) |
0 |
|
at risk (anterior cranial fossa, convexity, falx) |
1 |
dose to margin |
|
(dose in Grays) |
where:
• The risk of edema was lower with a radiation dose to the margin was <= 16 Grays than if it was higher.
• The relative risks for edema based on location are shown in Figure 6.
Z =
= (-0.786 * (points for previous surgery)) + (3.896 * (points for edema before)) + (0.104 * (tumor volume)) + (0.855 * (points for tumor location)) + (0.17 * (radiation dose to margin)) - 5.080
probability of intracranial edema after the surgery =
= 1 / (1 + EXP((-1) * Z))
Interpretation:
• If the estimated probability is < 05 it is assumed that edema will not occur.
• If the estimated probability is > 05 it is assumed that edema will occur.
Specialty: Hematology Oncology, Surgery, general, Neurology