Background: The hypothesis that breast cancer (BC) susceptibility variants are linked to chemotherapy-induced toxicity has been previously explored. Here, we investigated the association between a validated 313-marker-based BC polygenic risk score (PRS) and chemotherapy-induced neutropenia without fever and febrile neutropenia (FNc) in Asian BC patients. Methods: This observational case-control study of Asian BC patients treated with chemotherapy included 161 FNc patients, 219 neutropenia patients, and 936 patients who did not develop neutropenia. A continuous PRS was calculated by summing weighted risk alleles associated with overall, estrogen receptor- (ER-) positive, and ER-negative BC risk. PRS distributions neutropenia or FNc cases were compared to controls who did not develop neutropenia using two-sample t-tests. Odds ratios (OR) and corresponding 95% confidence intervals were estimated for the associations between PRS (quartiles and per standard deviation (SD) increase) and neutropenia-related outcomes compared to controls. Results: PRS distributions were not significantly different in any of the comparisons. Higher PRS_overall quartiles were negatively correlated with neutropenia or FNc. However, the associations were not statistically significant (PRS per SD increase OR neutropenia: 0.91 [0.79–1.06]; FNc: 0.87 [0.73–1.03]). No dose-dependent trend was observed for the ER-positive weighted PRS (PRS_ER-pos) and ER-negative weighted PRS (PRS_ER-neg). Conclusion: BC PRS was not strongly associated with chemotherapy-induced neutropenia or FNc.

Introduction: Bilateral breast cancers (BBC) diagnosed at an interval apart are uncommon. While metastatic staging guidelines are established in patients with unilateral breast cancer, its role in BBC diagnosed at an interval apart is unclear. We aim to identify the subgroup who would benefit from metastatic staging at contralateral cancer diagnosis. Methods: Eligible patients were divided into three categories: (A) ipsilateral invasive cancer and contralateral ductal carcinoma in situ (DCIS), (B) bilateral invasive cancers and (C) ipsilateral DCIS and contralateral invasive cancer and reviewed retrospectively. We excluded patients with bilateral DCIS, synchronous BBC diagnosed within 6 months from first cancer, patients who were stage IV at first cancer diagnosis and patients with recurrence prior to contralateral cancer. Results: Of 4516 newly diagnosed breast cancer patients, 79 patients were included. Systemic metastasis occurred in 15.6% of patients in Group B. Having nodal positivity of either cancer which were diagnosed ≤30 months apart and nodal positivity of only the contralateral cancer when diagnosed >30 months apart was significantly associated with systemic metastasis (p = 0.0322). Conclusions: Both the nodal status and a 30 months cut-off time interval between the two cancers can be used to identify patients who will benefit from metastatic staging. This finding requires validation in larger studies.

Background: The management of the axilla in breast cancer patients with isolated chest wall recurrence (CWR) after mastectomy remains controversial. Although sentinel lymph node biopsy (SLNB) for restaging is feasible, its role is unclear. We aimed to determine if the omission of axillary restaging surgery in female patients with operable presumably isolated CWRs could result in an increased risk of second recurrences. Methods: In this retrospective multicentre study, patients who developed CWRs were reviewed. We excluded patients with suspected or concomitant regional/distant metastases, bilateral cancers and patients without CWR surgery. Patients’ demographics, pathological data and subsequent recurrences were collected from a prospective database and were compared between patients with axillary lymph node dissection (ALND) and/or SLNB versus no axillary operation at CWR. Findings: A total of 194 patients with CWRs were eligible. The median age at CWR was 56.0 (IQR 47.0–67.0) years old. At recurrence, 8 (4.1%), 5 (2.6%) and 181 (93.3%) patients had ALND, SLNB and no axillary operation, respectively. Patients with no axillary surgery during CWR were associated with, at primary cancer, a lower incidence of ductal carcinoma in situ as diagnosis (p = 0.007) and older age (p = 0.022). Subsequent ipsilateral axillary (p = 0.768) and second recurrences (p = 0.061) were not statistically different between patients with and without axillary surgery at CWR on median follow-up of 59.5 (IQR 27.3–105) months. Interpretation: In patients without evidence of concomitant regional or distant metastasis at CWR diagnosis, omission of axillary restaging surgery was not associated with an increased ipsilateral axillary or second recurrences on long-term follow-up.