ESTRO breast cancer CTV contouring guideline - does it work on MRI in prone position?
Marciana Nona Duma,
Germany
MO-0799
Abstract
ESTRO breast cancer CTV contouring guideline - does it work on MRI in prone position?
Authors: Theresa Kulms1, Tobias Teichmann1, Daniele Steinhaus-Wittig2, Andrea Wittig1, Marciana-Nona Duma1
1University Hospital Jena, Department of Radiotherapy and Radiation Oncology, Jena, Germany; 2University Hospital Düsseldorf, Institute for Diagnostic and Interventional Radiology, Düsseldorf, Germany
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Purpose or Objective
The aim of this study is to assess the suitability of ESTRO (European society for Radiotherapy and Oncology) computed tomography breast contouring guideline for magnetic resonance imaging (MRI) contouring of the whole breast clinical target volume (CTV) in the prone position.
Material and Methods
56 consecutive left sided breast cancer patients (pts) with breast MRIs were retrospectively chosen for this study. The MRI was performed for diagnostic purposes during the course of the disease, before surgery. On the MRI, the CTV breast was contoured according to the ESTRO CTV guideline (MRI_ESTRO_CTV) in RayStation (V.8, RaySearch Laboratories, Stockholm, Sweden). Further, the glandular tissue only was contoured as well. The delineation was performed by the same observer (TK) and was reviewed by both, a specialized breast cancer radiologist and a breast cancer radiation oncologist. Patients were divided into groups by age (<60 years old, ≥60 y.o.), body mass index (BMI: <25; ≥25), breast size (<1006cm³ and ≥1006cm³) and therapeutic approach (neoadjuvant systemic therapy (NACT); no NACT). We report median with range and/or average±standard deviations. A value of P<0.05 was considered to be statistically significant.
Results
27 pts had a BMI <25, 29 pts a BMI ≥25; 30 pts were ≥60 y.o., 26 pts <60 y.o.; 28 pts had NACT, 28 had no NACT before the MRI. The MRI_ESTRO_CTV volume was 1006cm3(280-2175cm³) and the glandular breast tissue volume was 161cm³(60-552cm³). Patients with BMI <25 and patients with small breasts had a significantly higher portion of glandular breast tissue not included within the MRI_ESTRO_CTV (9.14%±4.78% and 9.48%±4.39% of the contoured glandular tissue were outside the ESTRO CTV, respectively), than patients with BMI ≥25 (4.74%±1.83%) and patients with larger breasts (4.45%±1.43%). Figure 1 depicts the typical regions of glandular tissue outside the MRI_ESTRO_CTV (i.e. subcutaneous and extension towards the axilla).
There were no statistical differences in the glandular tissue outside the MRI_ESTRO_CTV neither in younger vs. older patients nor in patients with or without NACT.
Conclusion
ESTRO CTV breast guidelines can be used for MRI delineation. However, women with a lower BMI or small breasts will benefit from adapted contouring combined with assessment of diagnostic MRIs, as the ESTRO guidelines will not include glandular breast tissue located closely underneath the skin.