ESTRO 2024 - Abstract Book

S3568

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2024

1428

Digital Poster

“Lattice – The Unsolved Mystery of the Geometry Diagram”

Magdalena Peszyńska-Piorun 1 , Wojciech Kapuściński 2

1 Regional Multispecialty Center for Oncology and Traumatology Named M. Copernicus, Radiotherapy Planning Department, Łódź, Poland. 2 Regional Multispecialty Center for Oncology and Traumatology Named M. Copernicus, Radiotherapy Department, Lodz, Poland

Purpose/Objective:

Patients diagnosed with very large tumors pose a huge challenge in the field of radiotherapy. The size of these tumors, often located near at-risk critical organs, makes stereotactic radiotherapy ineffective. Therefore, the basic effective treatment method seems to be the use of lattice radiotherapy (LRT). Analysis of the existing literature in this field shows a convincing median reduction in tumor size of more than 50% within 3–6 months after LRT. However, the limited quality of evidence and heterogeneity of studies make it difficult for us to draw definitive conclusions regarding the effectiveness of LRT.

Material/Methods:

So far, we have used this therapeutic method in three patients, each of whom underwent regular medical examinations and diagnostic tests, including computed tomography.

The first patient, a 52-year-old, was diagnosed with kidney cancer in 2021. At the time of diagnosis, the primary tumor was inoperable, with numerous metastatic lesions in the lungs and bone structures. We delivered a 6MV photon beam, delivering a dose of 25.0 Gy to the lytic lesion in the sacrum and up to 50.0 Gy locally in 5 fractions. The treatment plan included 3 partial arcs (RapidARC), in which the maximum doses reached 132.6% in an area with a diameter of 3 mm - 66,298 Gy. The second patient, aged 60, was previously diagnosed with right kidney cancer with metastatic lesions in the lungs. Computed tomography performed on April 6, 2022, revealed an infiltration of the chest wall on the left side with dimensions of approximately 140 x 70 mm. In this case, we used a photon beam with an energy of 6MV, delivering a dose of 25.0 Gy and increasing it pointwise to 60.0 Gy in 5 fractions. The third patient presented with stage IV rectal cancer, diagnosed as rcTxNxM1 adenocarcinoma, with painful lesions in the L1 vertebra and the right VIII and IX ribs and large lung mass. Prescribed doses as for the second patient. Choosing the right lattice drawing scheme was a big challenge. For the first patient, we placed high-dose centers symmetrically 3 cm apart while removing high-dose areas 1.5 cm from the end of the PTV to minimize OAR toxicity. For the second and third patients, additional areas of 4, 10, and 14 mm in diameter were included in the high dose areas to ensure precise dose escalation at specific central points. Additional patients will benefit from an automated script developed by our team, designed to map high-dose areas based on the patient's individual anatomy.