Relative dose intensity in early stage breast cancer chemotherapy: A retrospective analysis of incidence, risk factors and outcomes at a south-west Sydney cancer clinic.

AIM: In early stage breast cancer chemotherapy relative dose intensity (RDI) of <85% leads to poorer outcomes. This study assesses what proportion of such patients at a south-west Sydney cancer clinic received optimal RDI and the reasons and risk factors contributing to RDI reduction, as well as comparing survival outcomes.

METHODS: A retrospective analysis of 308 patients treated with adjuvant chemotherapy for early stage breast cancer at the Macarthur Cancer Centre was undertaken, with an overall RDI calculated for each patient. The study analysed reasons for reductions in RDI as well as predictive factors for reduced RDI and overall and disease-free survival.

RESULTS: Mean RDI was 92%. Of the participants, 17% had an RDI less than 85%, 55% received 100% RDI. Hematological toxicity, infection and patient choice were the most common reasons for RDI reduction. Body surface area capping (BSA) was the most common cause of initial dose reduction. Obesity, increasing body mass index and age ≥65 years were risk factors for RDI reduction. Disease-free and overall survival were reduced with RDI < 50%; overall survival decreased when RDI < 65%.

CONCLUSION: Most patients attained the RDI benchmark; however dose intensity reducing events occurred frequently. Despite contrary recommendations in the literature, BSA capping and dose reduction due to patient choice were common. Implementation of focused patient and physician education strategies may improve these results, as could measures directed as supporting those at risk (i.e. elderly or obese).