Why is renal impairment associated with poorer cancer specific survival in breast cancer patients?: a comparison with patients with other comorbidities

BACKGROUND: Our aim is to assess whether the poor breast cancer specific survival (BCSS) seen in women with breast cancer and impaired renal function can be explained by associations with other prognostic factors. METHODS: The study group was a consecutive series of patients undergoing breast ultrasound (US) who had invasive breast cancer (n = 1171). All women had their US diameter and mean stiffness (kPa) at shear wave elastography (SWE) recorded. The core biopsy grade and receptor status were noted. Core biopsy of abnormal axillary nodes and the patient referral source was also noted. Survival including cause of death was ascertained. Comorbidities at diagnosis were recorded. Patients were divided into those with a GFR<60 (“renal group”), those with other comorbidities and those with none. BCSS was assessed using Kaplan–Meier survival curves and Cox proportional hazards regression. RESULTS: One thousand, one hundred and forty-one patients constituted the study group. 107 (9%) patients had impaired renal function, 182 (16%) had other comorbidities while 852 (75%) had no comorbidities. Mean follow-up was 5.8 years. 109 breast cancer and 122 non-breast cancer deaths occurred. BCSS in the renal group was significantly worse than the other groups. Women with renal comorbidity were older, more likely to present symptomatically, have a pre-operative diagnosis of axillary metastases, and have larger and stiffer cancers. Cox proportional hazards regression showed that renal impairment maintained independent significance. CONCLUSION: The poor BCSS in women with impaired renal function is partially explained by advanced tumour stage at presentation. However, impaired renal function maintains an independent prognostic effect.