Fractionation trends in breast cancer and implications in partial breast irradiation

Abstract

Purpose/objectives

The aim of this study is to analyze the national trends in breast radiotherapy fractionation over the past decade.

Methods/materials

The National Cancer Database was queried for women with pTis-pT3pN0, cM0 breast carcinoma (ductal or lobular) treated with breast conserving surgery and radiotherapy (RT) from 1998 to 2012. Patients were grouped by number of radiotherapy fractions into four groups: conventional fractionation (ConvFx, 25–33 fractions), hypofractionation (HypoFx, 15–24 fractions), accelerated partial breast RT (APBI, 10 fractions), and intraoperative RT (IORT, 1 fraction on the day of surgery). Patients with alternative schedules were excluded. Trends were analyzed graphically, and univariable and multivariable (MVA) analyses were performed to investigate factors associated with the receipt of APBI or IORT.

Results

A total of 371,145 patients met inclusion criteria. Trends analysis demonstrates a clear increase in APBI from 1998 to 2008, at which point hypofractionation became increasingly popular and APBI stabilized. Among APBI patients (n = 5787), the predominant RT modality was HDR brachytherapy (71%). On MVA, several factors were associated with APBI over other fractionations (all p < 0.001): later year of diagnosis, older age, ductal histology, smaller tumors, estrogen receptor positivity, lower grade, and increased patient distance from treating facility (OR 2.16 if over 100 mi). Similar factors were associated with the receipt of IORT, including patients living a further distance from the hospital (OR 8.18 if over 100 mi).

Conclusions

While APBI utilization increased sharply from 2000 to 2008, the use of APBI has stabilized since 2008 with a concomitant increase in use of hypofractionation. The causes of these trends are unknown but should be the focus of future research.

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