[Locoregional control and patterns of locoregional failure in women with breast cancer treated by highly conformal electron beam irradiation]. / Caractérisation des rechutes locorégionales chez des patientes atteintes d'un cancer du sein traité par irradiation pariétale par électrons : expérience monocentrique de l'institut Curie.

PURPOSE: The purpose of this study was to evaluate locoregional control and describe the patterns of locoregional failure in women with breast cancer irradiated by a previously described post-mastectomy highly conformal electron beam radiotherapy technique. MATERIAL AND METHODS: We included all women irradiated by post-mastectomy highly conformal electron beam radiotherapy technique for non-metastatic breast cancer between 2007 and 2011 in our department. All cases of bilateral breast cancer were excluded. All patients who experienced locoregional recurrence have been studied. Mapping patterns of regional recurrences was also performed and compared with the European Society for Radiotherapy and Oncology (ESTRO) and Radiotherapy Oncology Group (RTOG) guidelines of volume definition and delineation guidelines. RESULTS: With a median follow-up of 64 months (range: 6-102 months), 5-year locoregional recurrence-free and overall survival probabilities were 90 % (95 % confidence interval [95 %CI]: 88.1-92.4) and 90.9 % (95 %CI: 88.9-93), respectively. Among the 796 patients included in the study, 23 patients (2.9 %) presented locoregional recurrences of them only 13 (1.6%) were presented with local recurrence. The majority of them presented aggressive biological features with grade III tumours in 17 patients (74 %) with high mitotic index in 16 cases (70 %) and triple negative tumours in 12 (52 %). Lymphovascular invasion was observed in 11 cases (48 %). In 14 cases the locoregional recurrences were diagnosed at the same time as the metastatic disease whereas 4 patients presented distant metastases secondarily. Locoregional recurrences occurred in 11 cases "in field" although adequate doses and volumes were used and in 12 cases "outfield", out of irradiated volume. Local recurrences occurred in 13 patients with 12 recurrences within the irradiated volumes. Regional recurrences occurred in 13 patients with 15 lymph nodes metastases identified. Four nodal recurrences occurred outside the ESTRO clinical target volume and within the RTOG clinical target volume and two occurred outside both RTOG and ESTRO clinical target volumes. CONCLUSION: In presented series, the local recurrence resulted mostly from of biologic radio resistance whereas regional recurrences were caused by geographical miss. A number of nodal recurrences could occur outside the target volumes defined by ESTRO and RTOG.

Outcome of postmastectomy radiotherapy after primary systemic treatment in patients with clinical T1-2N1 breast cancer.

PURPOSE: The role of postmastectomy radiotherapy following primary systemic treatment in patients with clinical T1-2N1 breast cancer remains a controversial issue. The purpose of this study was to evaluate the benefit of postmastectomy radiotherapy following primary systemic treatment. PATIENTS AND METHODS: Between 2005 and 2012, in two independent institutions, female patients with T1-2N1 breast cancer receiving primary systemic treatment followed by mastectomy and lymph node dissection because bad response, then treated with or without chest wall and regional lymph node irradiation have been studied retrospectively. The patients received normofractionated radiotherapy using 3D conformal photons or electron techniques. Locoregional recurrence-free survival, distant metastasis-free survival and disease-free survival were calculated using Kaplan-Meier method. Univariate analysis of potential prognostic factors was performed using log-rank test. RESULTS: Eighty-eight patients have been studied. Of them, 75 patients received postmastectomy radiotherapy. At surgery, 53 patients achieved ypN0. Median follow-up was 67 months. Postmastectomy radiotherapy significantly improved locoregional recurrence-free survival, with a 5-year rate of 96.9% versus 78.6% in the group that did not have postmastectomy radiotherapy. In the subgroup of 53 patients achieving ypN0, postmastectomy radiotherapy improved locoregional recurrence-free survival (a 5-year rate of 94.7% vs. 72.9%), distant metastasis-free survival (a 5-year rate of 92.8% vs. 75%) and disease-free survival (a 5-year rate of 92.9% vs. 62.5%). By univariate analysis, postmastectomy radiotherapy was the only significant prognostic factor affecting locoregional recurrence-free survival. CONCLUSIONS: For patients with clinical T1-2N1 disease, postmastectomy radiotherapy could significantly improve locoregional recurrence-free survival after primary systemic treatment and be even more therapeutic in the subgroup of patients with good response for primary systemic treatment by improving locoregional recurrence-free, distant metastasis-free and disease-free survival. Larger prospective studies are needed to confirm our findings.