ESTRO meets Asia 2024 - Abstract Book

S191

Interdisciplinary – Head & neck

ESTRO meets Asia 2024

417

Digital Poster

Spatial correlation of EBRT and Interstitial Brachy with DIR based dose summation in oral cancers Ashutosh Mukherji, Shubham Dokania, Sambit S Nanda, Sanju Sanju, Ajay Kr Choubey, Ninad H Patil, Ajay S Krishnan, Satyajit Pradhan

Radiation Oncology, Mahamana Pandit Madan Mohan Malaviya Cancer Centre and Homi Bhabha Cancer Hospital, Varanasi, India

Purpose/Objective:

The aim of this study is to evaluate Planning Target Volume and OARs dosimetric parameters with combined HDR BT boost and EBRT in early T1/T2N0 cancers of lip and buccal mucosa, using DIR software (Velocity®). Combined EQD2 calculated manually (EQD2-D90 BT + EQD2-D98 EBRT ) is compared with that achieved, using DIR, taking in account the spatial correlation.

Material/Methods:

An analysis was performed on patients of histopathological proven T1/T2N0 SCC of Lip and Buccal Mucosa, who underwent Interstitial BT boost followed by EBRT. The Planning Computed Tomography (CT) images and respective treatment plans of both BT and EBRT for all patients were imported in Velocity® software and DIR was employed to fuse the respective CT images individually for all the patients. Asynthetic plan incorporating both plans were generated. Dosimetric parameters of both PTV and OAR (mandible) were analyzed.

Results:

This study included a total of 10 patients (6 cT1N0, and 4 cT2N0) with median age 57 years (range 30-69 years), with male:female ratio of 7:3. Median dose delivered to PTV in HDR-BT was 21 Gy (range- 20-21 Gy), delivered in 5-6 fractions at 3.5-4Gy/fraction and that of EBRT was 44 Gy (range- 40-46Gy), delivered in 20-23 fractions at 1.8 2 Gy/fraction.

Table 1 - Dosimetric parameters of PTV and OAR using DIR

PTV vol (cc)

PTV Dmean (Gy)

PTV Dmin (Gy)

PTV D50 (Gy)

PTV D2cc (Gy)

PTV V150 (cc)

PTV V200 (cc)

Mandible Dmax (Gy)

PT. NO

Mandible D2cc (Gy)

16.1

91

18.6

77.9

114.6

3

1.3

62.9

54.1

1

17.7

88.9

19.1

74.8

119.5

3

1.5

57.7

50.7

2

11.6

79.3

6.4

72.2

91.8

1.4

0.7

64

48.8

3.

8

94.5

22.1

77.68

92.5

1.52

0.75

70.2

50.5

4

8.4

83.1

9.1

74

89.6

1.25

0.6

49.6

45.4

5

2.2

96

62.3

81.5

67.8

0.32

0.14

65.6

51.5

6