SS 23 - Breast 3?- General
159 - Cancer-Specific Outcomes of Hypofractionated Locoregional Radiation Therapy for Patients With Stage I-III Breast Cancer
Tuesday, October 23
1:10 PM - 1:20 PM
Location: Room 303
Cancer-Specific Outcomes of Hypofractionated Locoregional Radiation Therapy for Patients With Stage I-III Breast Cancer
T. A. Koulis1, A. Nichol2, S. Tyldesley2, P. Truong3, L. Weir4, C. Speers2, G. Lovedeep2, and R. A. Olson5; 1BC Cancer Agency, Kelowna, BC, Canada, 2BC Cancer Agency, Vancouver, BC, Canada, 3British Columbia Cancer Agency, Victoria, BC, Canada, 4BC Cancer Vancouver, Vancouver, BC, Canada, 5BC Cancer, Prince George, BC, Canada
Purpose/Objective(s): Hypofractionated (HypoF) radiotherapy (RT) is well established following breast conserving surgery for breast cancer but many centers continue to use conventional fractionation (CF; ≤ 2Gy/day) if regional lymph nodes are included in the target volume. At our institution, HypoF regional nodal RT (15-16 fractions of >2Gy/day) has been used for over 30 years, with published data reporting no additional toxicity. This study evaluated long-term, population-based cancer-specific outcomes of HypoF vs CF for breast/chest wall plus regional nodal RT for patients with breast cancer.
Materials/Methods: A prospective provincial database was used to identify 6,247 newly diagnosed patients with Stage I-III breast cancer treated with curative intent breast/chest wall + regional nodal RT from 1998 to 2010. Loco-regional relapse free survival (LRRFS) and distant relapse free survival (DRFS) were compared using Kaplan Meier (KM) analyses of HypoF vs CF, for the entire cohort and for high-risk subgroups: grade 3, ER-negative, HER2+, and ≥4 positive nodes. Multivariable Cox regression analysis (MVA) was performed to assess the effect of RT fractionation on LRRFS.
Results: Overall, 70% (4384) received HypoF and 30% (1863) received CF. Median follow up was 12.2 years and was similar between the two groups (HypoF: 12.8 yrs vs CF: 11.2yrs). Patients treated with HypoF were significantly older, more likely to be post-menopausal, HER2+, not receive chemotherapy, and less likely to have Stage III disease. Ten-year outcomes in the HypoF vs CF cohorts were: LRRFS 94.5% vs 94.1% (p=0.91), and DRFS 73.5% vs 74.4%, p=0.31). On subgroup analysis, LRRFS and DRFS were not different between HypoF and CF cohorts with grade 3, ER- , or ≥4 positive nodes (all p>0.05). On MVA, HypoF was not associated with inferior LRRFS compared to CF (HR 1.0, 95% CI 0.9 – 1.1, p=0.996).
Conclusion: This large, population-based analysis with long-term follow-up demonstrates that modest hypofractionation provides similar local and distant control outcomes compared to conventional fractionation when the RT volume included the breast/chest wall plus regional lymph nodes. Hypofractionation is an effective alternative for patients with stage I-III breast cancer receiving nodal RT.
Author Disclosure: T.A. Koulis: None. A. Nichol: Research Grant; Varian Medical Systems. S. Tyldesley: None. P. Truong: None. L. Weir: None. R.A. Olson: None.