Validation of a new method for dose determination in radiosurgery: "The Sosa Model"

• DOI: 10.22533/at.ed.1593712308091

• Palavras-chave: Radiosurgery, Gamma Knife, Dose Calculation, Sosa Model, Brain Tumors.

• Keywords: Radiosurgery, Gamma Knife, Dose Calculation, Sosa Model, Brain Tumors.

• Abstract:

  Objectives: to compare and validate the doses determined according to the novel method for calculating doses in radiosurgery called the Sosa Model (MS) with the dose protocols of national and international institutions. Material and Method: retrospective study on 403 tumor lesions of different histology found in 172 patients treated by radiosurgery at the Gamma Knife Dominican Center (CGKD), using MRI images of 1.5 and 3.0 Tesla with protocol for neuronavigation. In MS, the Sosa Score (SS) is obtained by adding 3 scores to a constant of 10Gy: Volume Score (VS), Radioresistance Score (RS), Eloquence Score (ES) of the lesion, complying with the formula that supports it. : SS= VS+RS+ES+10. Using the Wilcoxon Signed-Rank Test, it was compared with the conventional doses used in the CGKD, which are similar to those used internationally. Results: most lesions received between 12 and 24 Gy, calculated by both methods. Of the meningiomas treated in the CGKD, 65% received a dose of 12 to 14 Gy. Most of the doses suggested by the MS were between 15 and 18 Gy. On average, metastases treated in CGKD received between 16 and 24 Gy (220 of 247, 89%). The doses recommended by the MS were very close, ranging between 15 and 21 Gy (232 of 247, 93.9%). In Non-Functional Pituitary Adenomas, the MS (17-18 Gy) yields doses above those of the CGKD (12-16 Gy) since it does not include adaptations to protect the visual pathway. In Functional Pituitary Adenomas, MS falls below the particularly high doses (25 to 35 Gy) internationally recommended. The Acoustic Neuromas all received between 12 and 13 Gy in the CGKD and most of the doses recommended by the MS were between 14 and 15 Gy. Conclusions: Comparing the doses used by CGKD and those recommended by MS, there is a close proximity when it comes to Acoustic Neuromas and Metastases, but an important difference when it comes to Adenomas and Meningiomas. When applying the Wilcoxon Signed Rank Test to the 403 lesions studied, the mean difference between the two dose calculation systems was 0.23 Gy (95% CI: -0.127-0.60).