Breast Cancer

PV QA 4 - Poster Viewing Q&A 4

TU_4_3363 - Increasing use of hypofractionated whole breast irradiation: an analysis of practice patterns within a state-wide quality consortium

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Increasing use of hypofractionated whole breast irradiation: an analysis of practice patterns within a state-wide quality consortium
J. T. Dilworth1, K. Griffith2, F. A. Vicini3, J. A. Hayman4, J. M. Moran5, J. D. Radawski6, R. Jagsi5, G. S. Gustafson7, T. P. Boike8, E. M. Walker9, M. M. Dominello10, and L. J. Pierce4; 1Dept. of Radiation Oncology, Beaumont Health, Royal Oak, MI, 2Department of Biostatistics, University of Michigan, Ann Arbor, MI, 321st Century Oncology, Farmington Hills, MI, 4Michigan Medicine, Ann Arbor, MI, 5University of Michigan, Ann Arbor, MI, 6West Michigan Cancer Center, Rockford, MI, 7Beaumont Health System, Sterling Heights, MI, 8McLaren Northern Michigan, Petoskey, MI, 9Henry Ford Health System, Detroit, MI, 10Department of Oncology, Wayne State University School of Medicine, Detroit, MI

Purpose/Objective(s): Randomized clinical trials support the efficacy and safety of hypofractionated whole breast irradiation (H-WBI) in select patients with early stage breast cancer following breast conserving surgery. Existing 2011 ASTRO consensus guidelines suggest appropriateness criteria for the use of H-WBI based on subsets of patients well represented in these trials, including patients ≥50 years of age, pT1-2/pN0 disease, patients who did not receive systemic chemotherapy, and radiation treatment plans with dose heterogeneity within ~7%. This longitudinal study reports the use of H-WBI in patients treated in practices collaborating in a state-wide quality consortium.

Materials/Methods: We identified women in the consortium database who received whole breast irradiation between the years 2012 (11 participating institutions, 638 cases) and 2017 (22 institutions, 1295 cases). We determined the proportion of H-WBI cases (as a percentage ±95% CI) over time within various patient subgroups that satisfied all or some guideline criteria. We used separation (SEP) >25 cm along the central axis as a surrogate for dose heterogeneity.

Results: The most common H-WBI regimens utilized were 42.56 Gy/16 fractions (80% of cases) and 40 Gy/15 fractions (10% of cases). A boost of 10-10.64 Gy/4 fractions (51%), 10 Gy/5 fractions (31%), or 12 Gy/6 fractions (8%) was delivered to the surgical cavity in 88% (2012) and 81% (2017) of all cases. In the consortium as a whole, the use of H-WBI increased from 22%±3% to 61%±3% from 2012 to 2017. Among patients who met all consensus criteria, H-WBI use increased from 86%±14% to 99%±2% for patients who did not receive a boost and from 22%±7% to 85%±5% for those who received a boost. Similar increases in H-WBI use were observed independent of histology (IDC vs. ILC), receptor status (ER positive vs. ER negative vs. TNBC), or laterality (right vs. left). The use of H-WBI increased from 28%±10% to 76%±6% in patients with pure DCIS (otherwise guideline endorsed), from 33%±12% to 61%±9% in patients with a SEP >25 cm (otherwise guideline endorsed), and from 6%±11% to 40%±21% in patients who received systemic chemotherapy (otherwise guideline endorsed). However, the increase in H-WBI use was more modest for patients younger than 50 years but otherwise guideline endorsed (20%±35% to 38%±34%).

Conclusion: In this large, multi-center cohort, the use of H-WBI has increased over the last 5 years in all patient subsets, albeit with less frequency in those who did not meet all guideline criteria, particularly in patients who received chemotherapy and those <50 years of age. As updated guidelines for H-WBI are imminent, further examination of uptake in the use of H-WBI as well as the clinical outcomes and toxicities in these subgroups is warranted.

Author Disclosure: J.T. Dilworth: None. K. Griffith: None. F.A. Vicini: Member; ATIC. Co-Chair; NRG. PI; NSABP, RTOG. J.A. Hayman: Research Grant; Blue Cross Blue Shield of Michigan. J.M. Moran: Research Grant; Varian Medical Systems, Blue Cross Blue Shield of Michigan, NIH. We have a collaboration regarding the use of gel dosimetry. Modus Medical supplies gels for the research.; Modus Medical Devices. Consultant; Chartrounds, St. Jude Children's Research Hospital, VA National Center for Patient Safety. Travel Expenses; AAPM, St. Jude Children's Research Hospital. Chair; AAPM. J.D. Radawski: Executive Committee representative; Michigan Radiation Oncology Quality Consortium. R. Jagsi: Research Grant; American Cancer Society, NCCN, Breast Cancer Research Foundation, Abbott and Abbvie Pharmaceuticals. Advisory Board; Eviti. Research Committee Chair; Radiation Oncology Institute. Board of Directors; ASCO. G.S. Gustafson: None. T.P. Boike: Partner; Petoskey Radiation Oncology. Honoraria; ASTRO APEx Reviewer. Member; NCI Prostate Cancer Task Force. L.J. Pierce: Royalty; UpToDate.

Joshua Dilworth, MD, PhD

Beaumont Health System

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