ESTRO 2020 Abstract book

S699 ESTRO 2020

lungs, liver, and kidneys (Table). Doses to lens, optic nerves, optic chiasm, cochleae, heart, and non-target tissue were no difference between 2 techniques. Table. Dosimetric comparison between IMRT and VMAT Parameter s IMRT (mean±SD ) VMAT (mean±SD ) P Go al Endpoint s PTV95% (cc) 1967.96± 195.09 1939.31± 197.43 0. 006 NA PTV107% (cc) 48.23±11 1.44 18.00±20 .61 0.3 9 NA CI 0.83±0.0 2 0.87±0.0 3 0. 011 1 HI 1.12±0.0 3 1.09±0.0 1 0. 02 ≤2

Cataract, blindness, double vision, dry eyes Cataract, blindness, double vision, dry eyes Hypothyr

Right eye (mean±SD)

19.52±1.

17.91±2.

<1

0.

69

74

0

017

Left eye (mean±SD)

19.70±2.

18.01±2.

<1

0.

12

86

0

029

Thyroid (mean±SD) Left lung (mean ±SD) Right lung (mean ±SD) Liver (mea n±SD) Right kidney (me an±SD) Left kidney (me an±SD)

15.40±2.

12.96±1.

<1

0.

30

63

0

oidism

003

Fig 2: Cumulative incidence of local failure. Conclusion

Abnormal

5.64±1.0

6.54±0.7

0.

lung function

Re-RT with spine SBRT with or without combination surgery offers the chance of radiographic control and effective symptom relief with acceptable toxicity for recurrent chordomas. Given the unfavorable tumor biology, even after optimal LC is obtained, the propensity for metastases must also be addressed to substantially change OS.

0

7

<7

022

Abnormal

5.24±1.0

6.23±0.6

0.

lung function

2

8

<7

023

Veno-

4.67±0.7

5.40±0.6

<1

0.

occlusive disease Chronic renal dysfunctio n Chronic renal dysfunctio n

3

0

0

012

Poster: Clinical track: Paediatric tumours

<1

5.28±1.2

7.68±0.7

0.

3

7.8

5

001

PO-1237 Assessing the role of IMRT relative to VMAT in children with medulloblastoma treated with CSI W. Rongthong 1 , S. Pleanarom 1 , N. Suntornpong 1 , T. Treechairusame 1 , K. Thephamongkhol 1 1 Faculty of Medicine Siriraj Hospital, Radiation Oncology, Bangkok, Thailand Purpose or Objective This study evaluates and compares the dose distribution of target coverage and normal tissue sparing between IMRT and VMAT. Material and Methods Patients 3-18 years old with standard risk medulloblastoma treated with computer-based planning CSI in supine position between 2006 and 2016 were selected for treatment planning simulation. Both IMRT and VMAT were done and compared for each patient. The prescription was CSI 23.4Gy in 1.8 Gy-fraction. Planning target volume (PTV) was the first priority; at least 95% of PTV was covered by 95% of prescribed dose for both plans. All patients were re-planned by the second author and evaluated by the first author. Results Nine patients’ CT data set were available for dose calculation and evaluation. Better target coverage was observed in IMRT: IMRT 1967.96 cc vs. VMAT 1939.31 cc (p=0.006). More conformal dose distribution and homogeneous dose distribution were noted in VMAT: IMRT 0.83 vs. VMAT 0.87 (p=0.011) and IMRT 1.12 vs. VMAT 1.09 (p=0.02), respectively. VMAT significantly reduced dose to eyes and thyroid gland. IMRT significantly reduced dose to

5.21±1.0

7.13±1.1

<1

0.

3

2

7.8

002

Abbreviations: CI, conformity index; Dmean, mean dose; HI, homogeneity index; PTV, planning target volume; PTVx%, volume of PTV receiving ≥ x% of prescribed dose. Conclusion We observed the better target coverage in IMRT. With the more conform and homogeneous dose, VMAT achieved better normal tissue sparing in head and neck region while IMRT provided better dose reduction to organs at risk in chest and abdominal regions. PO-1238 Dosimetric study comparing IMRT to VMAT in completed resection pediatric abdominal neuroblastoma T. Treechairusame 1 , N. Suntornpong 1 , K. Thephamongkhol 1 , P. Ieumpongpaibool 1 , W. Rongthong 1 1 Faculty of Medicine Siriraj Hospital, Radiation Oncology, Bangkok, Thailand Purpose or Objective This study evaluates and compares the dose distribution of target coverage, integral dose and normal tissue sparing between IMRT and VMAT in completed resection pediatric abdominal neuroblastoma Material and Methods Patients 1 month to 15 years old with completed resection abdominal neuroblastoma treated with induction