ESTRO 2022 - Abstract Book

S719

Abstract book

ESTRO 2022

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.

MO-0800 CANTO-RT: Skin toxicities evaluation of prospective cohort of irradiated patients for breast cancer

S. allali 1 , M. Carton 2 , T. Sarrade 3 , S. Everhard 4 , O. Querel 4 , S. Rivera 5 , K. Peignaux 6 , P. Guilbert 7 , C. Chara-Brunaud 8 , J. Blanchecotte 9 , A. Labib 3 , D. Pasquier 10 , S. Racadot 11 , C. Bourgier 12 , G. Julien 13 , P. Cottu 14 , I. Vaz-Luis 15 , Y. Kirova 1 1 Curie Paris, radiation oncology, Paris, France; 2 Curie Paris, biostatistics department, Paris, France; 3 Curie St Cloud, radiation oncology, Saint Cloud, France; 4 Unicancer, Unicancer, Paris, France; 5 Institut Gustave Roussy, radiation oncology, villejuif, France; 6 Centre Georges-François Leclerc, radiation oncology, Dijon, France; 7 Jean Godinot, radiation oncology, Reims, France; 8 Institut de cancérologie de Lorraine, radiation oncology, Vandoeuvre les Nancy, France; 9 Institut de Cancérologie de L'ouest - Paul Papin , radiation oncology, Angers, France; 10 Centre Oscar Lambret, radiation oncology, Lille, France; 11 Centre Léon Berard, radiation oncology, Lyon, France; 12 ICM, radiation oncology, Montpellier, France; 13 Centre François Baclesse, radiation oncology, Caen, France; 14 Curie Paris, oncology , Paris, France; 15 Institut Gustave Roussy, biostatistics department, Villejuif, France

Purpose or Objective

Skin damage is the most common and important toxicity during and after radiotherapy (RT). Its assessment and understanding of the factors influencing its occurrence, is a major issue in the management of patients irradiated for an early breast cancer (eBC).

Materials and Methods

We included 3480 patients with stage I-III eBC, treated with RT and with collected raw RT data from 2012-2017 in 10 cancer centers from the prospective CANTO cohort (NCT01993498) in the CANTO-RT study.

We are focus on specifical skin toxicities: erythema, fibrosis, telangectasia . These toxicities were assessed at 3–6 (M0), 12 (M12) and 36 (M36) months after acute treatment using CTCAE V4.0.

The RT-related variables were independent variables. Multivariable logistic regression models assessed associations between RT-related variables and skin toxicities of interest.

Results

CANTO-RT patients had a median age of 56.8 years and a mean BMI of 26 kg/m 2 . The majority had SBR grade 1-2, T1-2, RH+/HER2- tumours. Most patients (80%) had conservative surgery and 52.7% received chemotherapy (CT). All the patients received RT mainly normofractionated 50Gy in 25 fractions, in 3D, with a boost of 16Gy in 8fractions. The prevalence of toxicities of interest varied over time, at M0, 41.1% of patients had erythema while 24.8% of patients had fibrosis. At M12 and M36, the prevalence of erythema decreased from 8.8% to 2.9% respectively while fibrosis remains stable from 25.1% to 22.5%. The prevalence of telangiectasia increases from 1% to 7.1% from M0 to M36. After adjustments, at M0 and M12, we showed a statistically significant association between the occurrence of skin erythema and obesity OR: 1.3 [1.09; 1.54] (p <0.003); the presence of axillary dissection (p <0.003); the type of surgery (p <0.001); the use of taxane- based CT (p <0.005) and the 3DvsIMRT irradiation technique OR: 0.42 [0.28; 0.62] (p <0.001). However, no RT factors were statistically related to erythema from M12.