ESTRO 2022 - Abstract Book

S928

Abstract book

ESTRO 2022

Results The 3D technique provides good dose control to the SC with a median maximum dose received of 7.28 (±4.86 Gy). In contrast, the dose to the bilateral carotid arteries is high with a median mean dose of 47.12 (± 6.76Gy) and 45.28 (±7.44 Gy) to the right and left carotid arteries respectively. The values of the VMAT plans are very similar at the carotid level, with a mean dose in the right carotid of 32.92 (±5.49 Gy) with a full arc and 35.88 (±5.96 Gy) with B-VMAT and mean doses of 33.61 (±7.16 Gy) and 34.80 (±6.92 Gy) in the left carotid. However, at SC we reduced the maximum dose with the two partial arcs from 31.09 (±3.28 Gy) to 20.01 (±6.59 Gy). In the thyroid irradiation, the average dose is 28.33 (±10.73 Gy) with the 3D plan and 19.28 (±9.89 Gy) and 19.90 (±9.89 Gy) with VMAT and the proposed B-MAT, so we reduce the dose and the risk of hypothyroidism.

G2 skin toxicity was presented in 62,5% of patients treated with 3D and only in 25% of patients with VMAT and B-VMAT.

Conclusion The VMAT technique compared to 3D provides better skin tolerance and greater dose conformity, reducing the dose received by the internal carotids and the thyroid but collaterally increasing the dose at the spinal cord. The proposed B-VMAT planning achieves smaller field sizes, shorter treatment time and associated dose reduction at the medullary level with similar doses in the other organs at risk compared to full arc VMAT, becoming a good choice of treatment option.

PO-1093 Effect of primary tumor volume on the clinical outcomes of nasopharyngeal carcinoma

A. Hafiz 1 , B.M. Qureshi 1 , N. Ali 1 , S. Abrar 1 , N.A. Abbasi 1

1 The Aga Khan University, Oncology, Karachi, Pakistan

Purpose or Objective To determine the effect of primary tumor volume on clinical outcomes of nasopharyngeal carcinoma treated with definitive chemoradiation in the present staging framework. Materials and Methods Between February 2006 and December 2012, 40 patients with non metastatic nasopharyngeal carcinoma treated with definitive chemoradiation at our institution were reviewed after approval from institutional ethics review committee. The primary tumor volume was calculated from planning computed tomography scans retrospectively. Demographic characteristics, stage of the disease and treatment parameters were recorded from medical charts. The clinical outcomes that was assessed include loco-regional failure free survival (LFFS), disease free survival (DFS) and distant metastasis free