ESTRO 2024 - Abstract Book

S5961

RTT - Treatment planning, OAR and target definitions

ESTRO 2024

The graphs in Fig. 1 show an increase in EAR mean values (linear, linear-exponential, and plateau models) by 4 times for the CB (p=0.002), by 2 times for the IL (p<0.001) and by 9 times (p<0.001) for the CL in the VMAT values compared to the 3D-CRT ones. Considering the EAR values for the VMAT technique, in our series the OAR most exposed to the risk of a second tumor resulted the CB (EAR approximately 26), followed by the IL (EAR approximately 13) and the CL (EAR approximately 9). This ranking could be used as a prioritization guideline in treatment plan optimization studies.

EAR values obtained for the VMAT technique in this study are comparable with literature values concerning radiotherapy targeting different thoracic sites, such as mediastinum [3], and involving the same OARs.

Conclusion:

According to literature data, our study confirmed that the VMAT technique in right breast radiotherapy, concerning the increased risk of secondary tumors and the dose conformity, could be a valid alternative to 3D-CRT for the patients, such as with unfavorable anatomical conformation ones. Furthermore, from the obtained results, a prioritized dose optimization ranking for different OARs can be derived for the treatment planning based on their own second radiation-related cancer risk.

Keywords: Radiotherapy, right breast, secondary tumor risk

References:

1. Van’t Riet A, Mak AC, Moerland MA, et al. A conformation number to quantify the degree of conformality in brachytherapy and external beam irradiation: Application to the prostate. Int J Radiat Oncol Biol Phys 1997; 37(3): 731-6.

2. Zwahlen DR, Ruben JD, Jones P, et al. Effect of intensity-modulated pelvic radiotherapy on second cancer risk in the postoperative treatment of endometrial and cervical cancer. Int J Radiat Oncol Biol Phys 2009; 74: 539–45.

3. Timlin C, Loken J, Kruse J, et al. Comparing second cancer risk for multiple radiotherapy modalities in survivors of hodgkin lymphoma. Br J Radiol 2021; 94: 20200354.

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Poster Discussion

Bridging the Care Gap: Radiographer CTV contours to support implementing 5# Prostate SABR in the UK

Susannah Jansen van Rensburg 1 , Emily Chan 2

1 GenesisCare, Maidstone, Kent, United Kingdom. 2 GenesisCare, Southampton, Hampshire, United Kingdom