Three-dimensional analysis of patterns of locoregional recurrence after treatment in breast cancer patients: Validation of the ESTRO consensus guideline on target volume

Background and purpose To explore the validity of the ESTRO-clinical target volume (CTV), we conducted three-dimensional analyses of locoregional recurrence (LRR) patterns according to the ESTRO- and RTOG-CTVs. Moreover, we explored which factors contribute to metastasis development outside the recommended CTV. Materials and methods We identified patients with post-treatment LRR explicitly exhibited on computed tomography (CT) images. All recurrences on CT were overlaid on representative CT images at the equivalent location, based on reference anatomic structures. Results A total of 235 recurrent lesions were identified in 129 patients. We depicted all LRR patterns in relation to the ESTRO- and RTOG-CTVs on CT and maximum intensity projection images. The ESTRO-CTV successfully contained the extent of the LRR within the RTOG-CTV in 96.4% of all early-stage breast-conserved women. Geographic misses of local recurrence were frequently observed in mastectomy patients (P = .002) and tended to originate from deep, but thin, chest walls. The rate of geographic misses of regional recurrence was low (3.6%) at the early stage, but increased in patients aged <45 years and with triple-negative tumors (P < .05). Conclusions Application of the ESTRO-CTV in early-stage disease seems justified.