ESTRO meets Asia 2024 - Abstract Book

S388

RTT – Treatment planning, OAR and target definitions

ESTRO meets Asia 2024

CARMEN GIL LOPEZ

Radiofísica, Hospital Son Espases, Palma de Mallorca, Spain

Purpose/Objective:

Breast cancer is the main cause of mortality in women, being a type of cancer that presents different anatomical classifications: right breast, left breast, bilateral, internal mammary, axillary nodes, supraclavicular nodes, with boost. The objective of this work is to analyze a completed clinical case of right breast cancer with irradiation of the three glands (internal mammary, axillary and supraclavicular) and with boost in the internal mammary with VMAT.

Material/Methods:

To perform VMAT treatment plans, the squeme was 40,05Gy (2,67 Gy/fraction) to the whole breast and glands and 48Gy (3,2 Gy/fraction) to the integrated boost in order to plan the whole treatment in 15 sessions. The VMAT plan was calculated with Monte Carlo algorithm and the techniques performed have been:

a) 2 beams with 4 partial arc (2 go and 2 return) each one, the first one started in 60º and finished in 220º and the second one started in 200º and finished in 220º.

b) 2 beams with 2 partial arc (2 go and 2 return) each one, the first one started in 60º and finished in 220º and the second one started in 200º and finished in 220º.

c) 2 beams with 2 partial arc (2 go and 2 return) each one, the first one started in 60º and finished in 50º and the second one started in 200º and finished in 50º.

d) 2 beams with 4 partial arc (2 go and 2 return) each one, the first one started in 60º and finished in 50º and the second one started in 200º and finished in 50º.

All of them with 20º of radiation modulation and with collimator to 0º. The main point of this plan was the importance of limiting the maximum dose of PTV in order to avoid the irradiation of the right lung. Treatment was evaluated using cumulative dose–volume histogram (DVH) data for Organs at risk (OARs) and PTVs.

Results:

Plans c) and d) were not accepted in the first optimization because the dose didn’t cover the entire PTV.

In the following table we compared plans a) and b):