ESTRO 2022

Session Item

Monday

May 09

16:45 - 17:45

Room D5

Multicentre validation studies

Chair: Ditte Sloth Møller, Denmark;

Co-Chair: Patricia Diez, United Kingdom

Session Code: 3480

Session Type: Proffered Papers

Track: Physics

17:35 - 17:45

Impact of guidelines on nationwide breast cancer treatment planning practices (DBCG RT Nation study)

Lasse Refsgaard, Denmark

Presentation Number: OC-0941

Abstract

Abstract Title:

Impact of guidelines on nationwide breast cancer treatment planning practices (DBCG RT Nation study)

Authors:

Lasse Refsgaard¹, Emma Riis Skarsø^2,3, Thomas Ravkilde², Henrik Dahl Nissen⁴, Martin Berg⁴, Mikael Olsen⁵, Kirsten Legaard Jakobsen⁶, Kristian Boye⁷, Claus Kamby⁷, Kasper Lind Laursen⁸, Ingelise Jensen⁸, Susanne Nørring Bekke⁹, Louise Wichmann Matthiessen⁹, Ebbe Laugaard Lorenzen¹⁰, Lise Bech Jellesmark Thorsen^1,11, Birgitte Vrou Offersen^1,3,2, Stine Sofia Korreman^12,2

¹Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus, Denmark; ²Aarhus University Hospital, Department of Oncology, Aarhus, Denmark; ³Aarhus University Hospital, Danish Center for Particle Therapy, Aarhus, Denmark; ⁴Vejle Hospital, University Hospital of Southern Denmark, Department of Oncology, Vejle, Denmark; ⁵ Zealand University Hospital, Department of Clinical Oncology and Palliative Care, Næstved, Denmark; ⁶Zealand University Hospital, Department of Clinical Oncology and Palliative Care, Næstved, Denmark; ⁷Copenhagen University Hospital - Rigshospitalet, Department of Oncology, Copenhagen, Denmark; ⁸Aalborg University Hospital, Department of Oncology, Aalborg, Denmark; ⁹Herlev and Gentofte Hospital, Department of Oncology, Herlev, Denmark; ¹⁰Odense University Hospital, Laboratory of Radiation Physics, Odense, Denmark; ¹¹Department of Oncology, Aarhus University Hospital, Aarhus, Denmark; ¹²Aarhus University Hospital, Danish Center for Particle Therapy, , Aarhus, Denmark

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Purpose or Objective

The aim of this study is to show the effect of implementation of Danish Breast Cancer Group (DBCG) and ESTRO guidelines on dosimetric parameters for heart and internal mammary nodes (IMN) over time for patients treated with radiotherapy (RT) for loco-regional (LR) breast cancer (BC). This demonstrates the value of the DBCG RT Nation study cohort, of detailed treatment plans for all retrievable LR BC RT treatments in Denmark 2008-2016.

Material and Methods

We conducted a national data collection based on patients identified from the DBCG database with an indication for LR RT. Images, structures and treatment plans from 9861 patients treated at seven centres are being collected (ongoing). We implemented automatic solutions to extract and quality assure DICOM files nationwide and evaluated doses, volumes and laterality using in-house developed software.

The effect of three events (E) on the volume and dose of the heart and IMN was investigated.

E1: Between 2010 and 2012, national workshops were organized to discuss and strengthen the DBCG delineation consensus.

E2: In June 2014, the DBCG RT guidelines were modified to include the IMN in the RT target for all LR RT irrespective of laterality of the BC.

E3: In 2015, the DBCG RT guideline was modified to follow the ESTRO consensus guideline for target volume delineation in BC.

Results

The centres could be divided into two groups. Group 1 did not treat IMN for left-sided patients (LSP) before E2, while group 2 treated IMN for all LSP in the whole period, utilising respiratory gating. Group 1 delineated the heart for all patients, and group 2 only delineated the heart for patients receiving non-standard RT. Instead, group 2 prioritised dose constraints to delineation of left anterior descending coronary artery above CTV IMN coverage until E2.

Figure 1 shows the median V90% CTV IMN coverage and the average delineated volume for IMN each year for 3479 patients. After E2, 98% of all LSP had IMN delineated with a median CTV V90% of 93% (IQR 79% - 98%). Over the whole period, 98% of the right sided patients had IMN delineated with a median CTV V90% of 95% (IQR 76% -100%). After E3, the mean volume of IMN converged to an average of 7.4mL (SD=3.4).

Figure 2 shows the mean heart dose (MHD) and volume of the heart for centres in group 1 over time. The volume of the heart stabilised after E1 and a small increase in MHD after E2 was detected associated with the increase in CTV IMN V90% for LSP.

Conclusion

Dosimetric data collected in a nationwide study (all patients to be included within 2021) showed the effect of delineation consensus guidelines on the volume of the heart, which stabilised after E1 and the IMN which showed a reduction in the variance of the volume between the centres after E3.

Furthermore, an increase in coverage of the CTV IMN for LSP and a corresponding increase in MHD after E2 was shown.

In conclusion, there was an evident impact of introducing DBCG and ESTRO guidelines on the clinical RT planning practice in Denmark.