Observational study of axilla treatment for breast cancer patients with 1 to 3 positive micrometastases or macrometastases in sentinel lymph nodes.

Abstract

e12576 Background: From the results of ACOSOG Z0011, IBCSG23-01 and AMAROS trials, axilla surgery in node-positive breast cancer (BC) tends to be less invasive with sentinel node biopsy (SNB) followed by adjuvant therapy and regional node irradiation (RNI). However, optimized axilla treatment including SNB without RNI is still debated. The Japanese Society for Sentinel Node Navigation Surgery conducted a multi-institutional prospective cohort study to compare SNB with SNB followed by axillary lymph node dissection (ALND) in cases with positive-sentinel lymph nodes (SLN)(UMIN No. 000011782, Jpn J Clin Oncol, p.876-9, 2014). Methods: Female BC patients with cT1-3N0-1M0 were eligible. When 1 to 3 positive micrometastases or macrometastases in SLN were confirmed by histological or molecular diagnosis, SNB alone or additional ALND had been decided by physician’s discretion. Primary chemotherapy before or after SNB was acceptable for registration. Lymph node sampling was also allowed in the SNB group. Cases with bilateral BC, isolated tumor cells only in SLN, past history of invasive cancer within 5 years at the registration were ineligible. The primary endpoint was the 5-year recurrence rate of regional node (RN) in the SNB group. The secondary endpoint was overall survival (OS). We planned to collect 240 patients to reject that the 5-year recurrence rate of RN was more than 10% assuming the rate 5%. To compare the SNB group and ALND group, the propensity score matching (PSM) was performed. Matching variables were initial treatment, metastatic size and numbers of SLN, clinical stage, age, body mass index, menopausal status, family history, past history of invasive cancer, breast surgery. Results: Eight-hundred eighty cases had been registered between 2013 and 2016. In the 871 eligible cases, 308 cases were the SNB group. At the median follow-up of 6.3 years, 5-year recurrence rate of RN was 2.7% [95% confidence interval, 1.4% to 5.4%] and 5-year OS was 97.6% [94.9% to 98.8%]. After PSM, 209 cases were matched in the SNB and ALND group. Among them, 343 cases (82%) received operation at initial treatment. Partial and total mastectomy was performed in 225 (54%) and 193 cases (46%), respectively. One-positive SLN was recorded in 366 cases (88%), 2 in 48 (11%) and 3 in 4 (1%). Macrometastases and micrometastases in SLN were diagnosed in 271 (65%) and 147 cases (35%), respectively. Three-hundred seventy-six cases (90%) belonged to luminal-like subtype. RNI was underwent in 42 cases (20%) of the SNB group and 13 cases (6%) of the ALND group. Five-year recurrence rate of RN was 2.1% [0.8% to 5.5%] and 2.0% [0.8% to 5.3%] for the SNB and ALND group, respectively. Conclusions: Our series suggests that RNI is not necessary for regional control in cases with 1 to 3 positive SLN. In conclusion, SNB alone is acceptable in cases with fewer metastatic SLN. Clinical trial information: UMIN No. 000011782.