Abstract P1-15-02: Utilization of hypofractionated radiation therapy for early stage breast cancer in women over 50 years of age
Authors: Rajagopalan Malolan S , Lehocky Craig , Flickinger John C , Heron Dwight E , Sukumvanich Paniti , Kelley Joseph L , Ahrendt Gretchen M , Beriwal Sushil 
Published: May 2015

Purpose: Hypofractionated whole breast irradiation (HF-WBI) following breast conserving surgery for early stage breast cancer is now recommended for women over 50 years of age by the American Society for Radiation Oncology (ASTRO). Herein, we explored the rate of HF-WBI utilization and its associated patterns of care using the National Cancer Data Base (NCDB), a comprehensive oncology outcomes database which captures 70% of all newly diagnosed cancer patients in the US.

Methods: We utilized NCDB to identify women aged ≥50 diagnosed with T1N0/T1Nx invasive breast cancer or Tis (DCIS) who underwent breast conserving surgery and adjuvant whole breast external beam radiation therapy. HF-WBI was defined when a definitive radiation dose (≥40 Gy) was delivered in ≤23 fractions. We evaluated factors associated with the use of HF-WBI through exploratory univariate and multivariable analyses.

Results: A total of 311,071 patients from 1998-2011 met inclusion criteria. The commonest HF-WBI regimen was 42.56 Gy in 16 fractions. The rate of HF-WBI utilization increased over time from 0.4% in 1998 to 16.5% in 2011 (p&lt;0.001). HF-WBI was delivered more often for women of advancing age. In 2011, HF-WBI was delivered in 10.0%, 14.2%, 24.2% and 35.6% of women in their 50’s, 60’s, 70’s and 80+ (p&lt;0.001). Multivariable analysis correlated significantly increased use of HF-WBI with (in order of association): later year of diagnosis, advancing age (decade), treatment in academic center, regional location in US, lower grade of disease, white race, residence in a higher income area (p&lt;0.001), greater comorbidity score (p&lt;0.03), presence of invasive cancer (p&lt;0.01), right-sided disease (p&lt;0.01), and greater distance from reporting facility (p&lt;0.001).

Factors Associated with Increased Use of HF-WBIAssociation with HF-WBIOdds Ratio of HF-WBI Use (95% confidence interval)Year of Diagnosis (2011 vs. prior to 2009)7.14 (6.85-7.52)Age (Decade, 80+ years)6.45 (6.06-6.90)Facility Type: Academic4.00 (3.69-4.33)Location (Mountain Region)1.82 (1.68-1.97)Grade 11.40 (1.33-1.47)Race: White1.38 (1.25-1.53)Income Quartile 4 (&gt;$46K/year)1.30 (1.21-1.40)Comorbidity Index (High, 2)1.15 (1.02-1.31)Invasive Cancer1.09 (1.04-1.14)Laterality (Right Side)1.05 (1.02-1.09)Distance from Treatment Facility1.002 per mile (1.002-1.002)

Conclusions: This comprehensive patterns of care study of HF-WBI in women ≥50 years old with early stage breast cancer from a national database identified a substantial increase in the utilization of this technique with time. Advancing patient age and treatment at academic facility were also strong predictors of delivery of HF-WBI. Disparities in utilization of HF-WBI and overall employment of this technique, even in later years, remain suboptimal. Strategies to identify and break barriers to the adoption of HF-WBI should be explored.

Citation Format: Malolan S Rajagopalan, Craig Lehocky, John C Flickinger, Dwight E Heron, Paniti Sukumvanich, Joseph L Kelley, Gretchen M Ahrendt, Sushil Beriwal. Utilization of hypofractionated radiation therapy for early stage breast cancer in women over 50 years of age [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-15-02.