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Purpose: Omitting sentinel lymph node biopsy (SLNB) in breast cancer treatment results in patients with unknown positive nodal status and potential risk for systemic undertreatment. This study aimed to investigate whether gene expression profiles (GEPs) can lower this risk in cT1-2N0 ER+ HER2- breast cancer patients treated with BCT., Methods: Patients were included if diagnosed between 2011 and 2017 with cT1-2N0 ER+ HER2- breast cancer, treated with BCT and SLNB, and in whom GEP was applied. Adjuvant chemotherapy recommendations based on clinical risk status (Dutch breast cancer guideline of 2020 versus PREDICT v2.1) with and without knowledge on SLNB outcome were compared to GEP outcome. We examined missing adjuvant chemotherapy indications, and the number of GEPs needed to identify one patient at risk for systemic undertreatment., Results: Of 3585 patients, 2863 (79.9%) had pN0 and 722 (20.1%) pN + disease. Chemotherapy was recommended in 1354 (37.8% guideline-2020) and 1888 patients (52.7% PREDICT). Eliminating SLNB outcome (n = 722) resulted in omission of chemotherapy recommendation in 475 (35.1% guideline-2020) and 412 patients (21.8% PREDICT). GEP revealed genomic high risk in 126 (26.5% guideline-2020) and 82 patients (19.9% PREDICT) in case of omitted chemotherapy recommendation in the absence of SLNB. Extrapolated to the whole group, this concerns 3.5% and 2.3%, respectively, resulting in the need for 28-44 GEPs to identify one patient at risk for systemic undertreatment., Conclusion: If no SLNB is performed, clinical risk status according to the guideline of 2020 and PREDICT predicts a very low risk for systemic undertreatment. The number of GEPs needed to identify one patient at risk for undertreatment does not justify its standard use., (© 2023. The Author(s).)

Background: After breast cancer treatment, follow-up consists of physical examination and mammography for at least 5 years, to detect local and regional recurrence. The risk of recurrence may decrease after event-free time. This study aims to determine the risk of local recurrence (LR) as a first event until 5 years after diagnosis, conditional on being event-free for 1, 2, 3 and 4 years., Methods: From the Netherlands Cancer Registry, all M0 breast cancers diagnosed between 2005 and 2008 were included. LR risk was calculated with Kaplan-Meier analysis, overall and for different subtypes. Conditional LR (assuming x event-free years) was determined by selecting event-free patients at x years, and calculating their LR risk within 5 years after diagnosis., Results: Five-year follow-up was available for 34,453 patients. Overall, five-year LR as a first event occurred in 3.0%. This risk varied for different subtypes and was highest for triple negative (6.8%) and lowest for ER+PR+Her2- (2.2%) tumors. After 1, 2, 3 and 4 event-free years, the average risk of LR before 5 years after diagnosis decreased from 3.0 to 2.4, 1.6, 1.0, and 0.6%. The risk decreased in all subtypes, the effect was most pronounced in subtypes with the highest baseline risk (ER-Her2+ and triple negative breast cancer). After three event-free years, LR risk in the next 2 years was 1% or less in all subtypes except triple negative (1.6%)., Conclusion: The risk of 5-year LR as a first event was low and decreased with the number of event-free years. After three event-free years, the overall risk was 1%. This is reassuring to patients and also suggests that follow-up beyond 3 years may produce low yield of LR, both for individual patients and studies using LR as primary outcome. This can be used as a starting point to tailor follow-up to individual needs.

Objective: This study aims to evaluate whether extracapsular extension (ECE) in the sentinel lymph node (SLN) is associated with involvement of ≥ 4 lymph node metastases at completion axillary lymph node dissection (ALND) and the effect on 5-year disease-free survival (DFS) and 10-year overall survival (OS). ECE in a SLN is usually a contraindication for omitting completion ALND in cT1-2N0 breast cancer patients treated with breast-conserving therapy and 1-2 positive SLN(s)., Methods: All cT1-2N0 breast cancer patients with 1-3 positive SLN(s) who underwent ALND between 2005 and 2008 were selected from the Netherlands Cancer Registry. Logistic regression analysis was used to determine the association between ECE and ≥ 4 lymph node metastases. Five-year DFS and 10-year OS were analyzed using Kaplan-Meier survival analysis. Cox regression analysis was performed to correct for other prognostic factors., Results: A total of 3502 patients were included. Information on ECE was available for 2111 (60.3%) patients, consisting of 741 (35.1%) patients with and 1370 (64.9%) without ECE. The incidence of ≥ 4 lymph node metastases was 116 (15.7%) in the ECE group vs. 80 (5.8%) in the group without ECE (p < 0.001). Five-year DFS rate was 86.4% in the ECE group compared to 88.8% in the group without ECE (p = 0.085). 10-year OS rate was 78.6% compared to 83.0% (p = 0.018), respectively. Cox regression analysis showed that ECE was not an independent prognostic factor for both DFS and OS., Conclusions: ECE was significantly associated with involvement of ≥ 4 lymph node metastases in the completion ALND group. ECE was not an independent prognostic factor for both DFS and OS.