Abstract Book

S1006

ESTRO 37

>5Gy to 1 kidney, and 1 patient received >5Gy to both kidneys. The highest maximum renal dose was >13Gy in two patients. Interestingly, both of these patients received radiotherapy to the supraclavicular fossa (SCF) in addition to the breast or chest wall. Table 1 shows that radiation dose to the kidneys was easily reducible on re-planning 5 patients with the highest renal dose, without compromising coverage of the planned tumour volume or significantly increasing dose to other organs at risk. For example, 11Gy maximum dose to the left kidney was reduced to 2.4Gy in a patient receiving treatment for left sided breast cancer. Table 1 - Dose to the left and right kidneys before and after inclusion in the optimisation process. Site treated (left or right) Dose to Left (L) kidney and Right (R) kidney on existing IMRT plan in Gy Dose to Left (L) and Right (R) kidney on revised IMRT plan in Gy

relevant during 3D-CRT breast cancer radiotherapy. 2.An evaluation of maximum dose delivered was prepared. 3.A correlation between prognostic factors and irradiated volume of liver has been performed. Results 1.Comparison between lungs and liver during 3D-CRT breast cancer radiotherapy has shown that dose distributions are comparable (p=0,012). Particular attention should be paid to the fact that 6,44% volume of liver received dose above 20 Gy (Fig.1). The same dose is delivered to 10,31% volume of lungs. 2.During 3D-CRT breast cancer radiotherapy averaged maximum dose received by liver was 47 Gy. 3.Averaged mean liver dose in group of patients was estimated to 4 Gy. A correlation between mean dose in liver and treated volume has been noticed (p=0,37). Beam’s Eye View from treatment field illustrates that for some patients significant part of liver is located in an irradiated field (Fig.2).

L

-

2.7

Patient 1 Patient 2 Patient 3 Patient 4 Patient 5

L

-

8.6

Left

R - 0.8

R - 0.7

L

-

3.9

L

-

1.6

Right

R - 8.8

R - 2.1

L

-

7.4

L

-

1.8

Left

R - 0.9

R - 0.6

L

-

3.2

L

-

9.6

Left

R - 0.9

R - 0.7

L

-

2.4

L

-

11.1

Left

R - 4.3

R - 1.3

Fig. 1.Dose distribution in liver and lungs during 3D- CRT breast cancer radiotherapy.

Conclusion When treating breast patients using IMRT techniques, the kidneys should be routinely contoured and included in the optimisation process, to ensure that doses to this organ are minimised. Incorporating the kidneys as organs at risk when planning treatment with IMRT for breast cancer showed doses to kidneys could easily be reduced, without compromising coverage of the planned tumour volume, or increasing doses to other organs at risk. EP-1863 Dose delivered to liver during right breast cancer radiotherapy. U. Sobocka-Kurdyk 1 , E. Bukowicz 2 , S. Kubicka 2 , P. Borowska 1 , D. Kowalczyk 2 , A. Rychter 2 1 Greater Poland Cancer Centre, Department of Medical Physics, Kalisz, Poland 2 Greater Poland Cancer Centre, Department of Radiotherapy III, Kalisz, Poland Purpose or Objective Liver is not recognized as typical critical structure during breast cancer radiotherapy (BCRT). In the past it was considered as a very fragile organ to irradiation. Similarity to lung, liver can lose ability to function within the irradiated volume. The main aim of this study was to find out whether he dose delivered during BCRT to the liver is medically significant. Material and Methods In this work, radiotherapy treatment plans in 3D- Conformal Radiation Therapy (3D-CRT) technique for a selected group of patients (20 women with breast cancer, aged 55 to 78 years old) were created. Fractionation scheme was 25X2Gy. To consider the importance of doses received by the liver during BCRT, it was contoured as an organ at risk. A comparison, based on qualitative analysis of averaged Dose Volume Histograms (DVH) for selected parameters, has been performed: 1.Doses delivered to liver to doses delivered to lungs comparison was created to investigate whether they were

Fig. 2. Beam’s Eye View from treatment field. Visualization illustrates that significant part of liver is located in an irradiated field. Conclusion According to QUANTEC normal liver tolerance defined for the primary liver carcinomas radiotherapy are estimated: mean dose <30-32 Gy. Exceed of this limits may cause radiation-induced liver disease (RILD). The dose delivered to liver is surprisingly high in view of the fact that it isn’t recognized as a typical critical structure during breast cancer radiotherapy. It is worth to consider placing the liver in a group of organs at risk for right breast radiotherapy. EP-1864 Design of an optimised bow-tie filter for low dose paediatric cone beam CT A. Bryce-Atkinson 1 , G. Whitfield 2 , M. Van Herk 1 1 The University of Manchester, Faculty of Biology Medicine and Health, Manchester, United Kingdom 2 The Christie NHS Foundation Trust, Clinical Oncology, Manchester, United Kingdom Purpose or Objective Lower dose cone beam CT (CBCT) imaging protocols would particularly benefit children, who can receive excessive imaging dose when using protocols designed for