Aim: To quantify the dosimetric impact of contouring variability of axillary lymph nodes (L2, L3, L4) in breast cancer (BC) locoregional radiotherapy (RT). Materials and methods: 18 RT centres were asked to plan a locoregional treatment on their own planning target volume (single centre, SC-PTV) which was created by applying their institutional margins to the clinical target volume of the axillary nodes of three BC patients (P1, P2, P3) previously delineated (SC-CTV). The gold standard CTVs (GS-CTVs) of P1, P2 and P3 were developed by BC experts' consensus and validated with STAPLE algorithm. For each participating centre, the GS-PTV of each patient was created by applying the same margins as those used for the SC-CTV to SC-PTV expansion and replaced the SC-PTV in the treatment plan. Datasets were imported into MIM v6.1.7 [MIM Software Inc.], where dose-volume histograms (DVHs) were extracted and differences were analysed. Results: 17/18 centres used intensity-modulated RT (IMRT). The CTV to PTV margins ranged from 0 to 10 mm (median 5 mm). No correlation was observed between GS-CTV coverage by 95% isodose and GS-PTV margins width. Doses delivered to 98% (D98) and 95% (D95) of GS-CTVs were significantly lower than those delivered to the SC-CTVs. No significant difference between SC-CTV and GS-CTV was observed in maximum dose (D2), always under 110%. Mean dose ≥ 99% of the SC-CTVs and GS-CTVs was satisfied in 84% and 50%, respectively. In less than one half of plans, GS-CTV V95% was above 90%. Breaking down the GS-CTV into the three nodal levels (L2, L3 and L4), L4 had the lowest probability to be covered by the 95% isodose. Conclusions: Overall, GS-CTV resulted worse coverage, especially for L4. IMRT was largely used and CTV-to-PTV margins did not compensate for contouring issues. The results highlighted the need for delineation training and standardization.

The dosimetric impact of axillary nodes contouring variability in breast cancer radiotherapy: an AIRO multi-institutional study / M.C. Leonardi, M. Pepa, R. Luraschi, S. Vigorito, S. Dicuonzo, L.J. Isaksson, M.R. La Porta, L. Marino, E. Ippolito, A. Huscher, A. Argenone, F. De Rose, F. Cucciarelli, M.C. De Santis, F. Rossi, A. Prisco, R. Guarnaccia, P.T. de Fatis, I. Palumbo, S.P. Colangione, M. Mormile, V. Ravo, A. Fozza, C. Aristei, R. Orecchia, F. Cattani, B.A. Jereczek-Fossa. - In: RADIOTHERAPY AND ONCOLOGY. - ISSN 0167-8140. - 168(2022 Mar), pp. 113-120. [10.1016/j.radonc.2022.01.004]

The dosimetric impact of axillary nodes contouring variability in breast cancer radiotherapy: an AIRO multi-institutional study

R. Luraschi;S. Vigorito;S. Dicuonzo
;
L.J. Isaksson;S.P. Colangione;R. Orecchia;B.A. Jereczek-Fossa
2022-03

Abstract

Aim: To quantify the dosimetric impact of contouring variability of axillary lymph nodes (L2, L3, L4) in breast cancer (BC) locoregional radiotherapy (RT). Materials and methods: 18 RT centres were asked to plan a locoregional treatment on their own planning target volume (single centre, SC-PTV) which was created by applying their institutional margins to the clinical target volume of the axillary nodes of three BC patients (P1, P2, P3) previously delineated (SC-CTV). The gold standard CTVs (GS-CTVs) of P1, P2 and P3 were developed by BC experts' consensus and validated with STAPLE algorithm. For each participating centre, the GS-PTV of each patient was created by applying the same margins as those used for the SC-CTV to SC-PTV expansion and replaced the SC-PTV in the treatment plan. Datasets were imported into MIM v6.1.7 [MIM Software Inc.], where dose-volume histograms (DVHs) were extracted and differences were analysed. Results: 17/18 centres used intensity-modulated RT (IMRT). The CTV to PTV margins ranged from 0 to 10 mm (median 5 mm). No correlation was observed between GS-CTV coverage by 95% isodose and GS-PTV margins width. Doses delivered to 98% (D98) and 95% (D95) of GS-CTVs were significantly lower than those delivered to the SC-CTVs. No significant difference between SC-CTV and GS-CTV was observed in maximum dose (D2), always under 110%. Mean dose ≥ 99% of the SC-CTVs and GS-CTVs was satisfied in 84% and 50%, respectively. In less than one half of plans, GS-CTV V95% was above 90%. Breaking down the GS-CTV into the three nodal levels (L2, L3 and L4), L4 had the lowest probability to be covered by the 95% isodose. Conclusions: Overall, GS-CTV resulted worse coverage, especially for L4. IMRT was largely used and CTV-to-PTV margins did not compensate for contouring issues. The results highlighted the need for delineation training and standardization.
Breast cancer; Dosimetry; Inter-observer variability; Nodal contouring; Radiotherapy
Settore MED/36 - Diagnostica per Immagini e Radioterapia
13-gen-2022
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/906646
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