ESTRO 2022 - Abstract Book

S657

Abstract book

ESTRO 2022

In the past, axillary dissection (ALND) was performed for tumour staging and to improve local control (LC). Axillary management in cN0 breast cancer (BC) patients with positive sentinel lymph node (SLN) is unclear in case of ALND omission. The ACOSOG Z0011, comparing cN0 patients and positive SLN treated with or without ALND, demonstrated ALND safety omission; this study was although criticized for adjuvant radiotherapy (RT) non uniformity. We conducted the LISEN trial with ALND omission in cN0 and positive SLN patients who met the ACOSOG Z0011 criteria. These patients were treated with whole breast radiotherapy (WBRT) without high tangent or nodal irradiation. Subsequently, we compared LISEN patients with a retrospective group with similar pathological characteristics who underwent ALND and same RT fields. In LISEN trial we analysed female patients with histologically confirmed invasive BC at biopsy, cT1-2cN0, submitted to conservative surgery with SLN biopsy. Adjuvant systemic therapy was prescribed according to staging and tumor biology. Tangential fields WBRT was planned without high tangent or nodal irradiation.We search in our database patients with similar characteristics who underwent ALND and WBRT without nodal irradiation (group 1) and compared with LISEN patients (group 2). Clinical outcomes, local recurrence (LR), regional recurrence (RR), loco-regional recurrence (LRR), distant metastases (DM), disease-free survival (DFS) and overall survival (OS), were analyzed, measured from surgery until first event. Two hundreds and nine patients were analysed (76 in group 1 and 133 in group 2). Patients, tumor and treatment characteristics are reported in Table 1.The median number of removed nodes was 12 for group 1 and 2 for group 2. The median number of histologically positive nodes was 1 in both groups. In group 1, all patients (100%) underwent WBRT with conventional fractionation (50 Gy in 25 fraction). In group 2, 126 (94.7%) received a conventional fractionation and 7 (5.3%) hypofractionation (from 40 to 40.05 Gy in 16-15 fraction). The median follow-up was 92 months (range= 21-131) for group 1 and 50 months (range= 5-91) for group 2. In group 1, the 9-year LR was 2.6%, RR: 1.3%, LRR: 0%, DM: 2.6%. In group 2, the 5-year LR was 3.2%, RR: 1.5%, LRR: 1.5% and DM: 6.7%. OS and DFS were 94.7 and 94.7 in group 1 and 93.6 and 96 in group 2 respectively. Comparing the two groups, LR occurred in 2 and 4 patients, RR in 1 and 1, DM in 2 and 5 and death in 4 and 1, in group 1 and 2 respectively. Materials and Methods Results

Conclusion

Similar outcomes were reported in both groups. Although the longer follow up for group 1 and the greater number of patients in group 2, ALND seems to improve LC and DM although its omission seems to have not a worse impact on DFS and OS, sparing axillary morbidities. A longer follow-up is necessary to confirm these results.