Background In metastatic breast cancer (MBC), there is no consensus regarding the optimal regimen sequence and whether adults >65 years old (OA) are at increased risk from chemotherapy toxicity. Treatment decisions are often driven by the ability to tolerate treatment and maintain the quality of life. This study was designed to assess current practice in an oncology hospital in the UK. Methods Retrospective data were collected about treatments used for 87 OA with MBC in a single centre between 2009 and 2016 to assess the tolerability and efficacy of first-line chemotherapy. Student’s T-tests and Kaplan-Meier statistical methods were applied. Results 70% of patients were commenced on standard dose (SD) of chemotherapy; 84% (21/25) of the anthracycline group (AG), 65% (20/31) of the capecitabine group (CG), 48% (10/21) of the taxane group (TG) and 100% (10/10) of other agents. 32% of patients had dose reductions; 16% in AG, 19% in TG and 58% in CG. Overall 30% of patients received six cycles of SD of chemotherapy; 36% in AG, 29% in CG and 14% in TG. 23% of patients suffered ≥grade 3 toxicity; 28% in AG, 29% in CG and 10% in TG. There were four treatment-related deaths; two in AG and one in both CG and TG. 61% of the CG received 6+ cycles with a mean on treatment time of 445 days (1–2,150). There was no statistical significance in progression- free survival (PFS) between groups. The median PFS for all patients was 244 days (87–381). Performance status, haemoglobin and estimated glomerular filtration rates prior to starting chemotherapy were all useful in predicting PFS. Conclusions A relevant number of patients required dose reduction but dose-reduced chemotherapy was tolerated well. Anthracycline-based regimens were used in patients who had not received adjuvant chemotherapy. Capecitabine required the most dose reductions. Taxanes were generally started at reduced doses, resulting in fewer grade 3+ toxicities. As well as age, underlying physiological reserve, current performance status and co-morbidities should guide physicians who should consider lower starting doses in OA and recognise that dose reductions may be required to improve tolerability. The PFS of all regimens were similar in this study. This study highlights the need for further research to define the optimal first-line chemotherapy and starting dose in OA with MBC.

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