Do women younger than 40 treated in the hormone-therapy era benefit from a radiotherapy boost as a part of adjuvant breast radiotherapy?

Abstract

72 Background: The EORTC 22881 trial showed a 10% reduction in local relapse with a radiotherapy boost (RTB) after breast conserving therapy (BCT) among women ≤40 years old. However no premenopausal patients received hormone therapy (HT) in this study. A policy change in December 1998 recommended the use of HT after chemotherapy for premenopausal ER positive women. A second policy change in December 2001 recommended an RTB after BCT for women ≤40 years old. The purpose of our study was to describe: 1)how the use of HT and RTB after BCT changed after practice guidelines were implemented in a population-based cancer care program; and 2) how local relapse rates (LRR) changed after these policy changes. Methods: A provincial database was used to analyse all women ≤ 40 years old referred for consideration of radiotherapy with margin negative stage 1 and 2 (≤3 nodes positive) breast cancer, treated with lumpectomy and whole breast radiotherapy. Cases were grouped into three eras according to policy transition with 3 month gaps: 1) Jan 1996-Sep 1998, 2) Jan 1999-Sep 2001, 3) Jan 2002 to Sep 2004. Changes in the use of HT and RTB over these eras were assessed. Eight year LR-free survival was calculated using the Kaplan-Meier method and the three eras compared using log rank tests. Multivariable analysis (MVA) was performed including era, size of tumour, nodal status (0 vs 1-3), grade, lymphovascular space invasion (LVI), and use of chemotherapy. Results: There were 130 eligible patients from Era 1, 145 patients from Era 2, and 140 patients from Era 3. ER status did not differ across eras. HT was used for ER positive patients in 13% of Era 1, 68% of Era 2, and 83% of Era 3 cases (p<0.001). RTB was used in 40% of Era 1, 28% of Era 2, and 77% of Era 3 patients (p<0.001). LRR at 8 years were 87.3% Era 1, 94.8 % Era 2, and 94.5% Era 3 (p=0.03). Era (used as surrogate for transitions in the use of HT and RTB) remained significant on MVA (0=0.008). Conclusions: Patterns of use of HT and RTB changed after policy changes. The benefit of adding a boost in women ≤40 years old shown by the EORTC was not observed after the introduction of routine HT at a population level.