Trends in the Delivery of Accelerated Partial Breast Irradiation Therapy

Abstract

<h3>Purpose/Objective(s)</h3> Accelerated partial breast irradiation (APBI) has been utilized as an alternative to whole breast irradiation (WBI) therapy for selected patients with early-stage breast cancer. The purpose of this investigation is to determine trends in the delivery of APBI based on racial and socioeconomic demographics. <h3>Materials/Methods</h3> The National Cancer Database (NCDB) was utilized to identify patients eligible for APBI based on consensus statements. Eligibility criteria included: ≥50 years old, stage I-II (T1-2N0, M0), tumor size ≤ 3 cm, ER+, LVSI-, invasive disease or DCIS, and receipt of radiation therapy (RT). For this analysis, partial breast irradiation (PBI) was defined as regimens with ≤10 fractions of external beam (EBRT), radioisotope, and brachytherapy, with an understanding that IMPORT LOW PBI would be excluded while 5 fraction WBI would be included. 2,981,732 breast cancer patients, diagnosed from 2004-2017, were initially identified in this analysis. Exclusion criteria include patients ≤49 years (n=635,461), tumors ≥3.1cm (n=875,558), LN+ (n=550,481), ER- (n=166,135), positive surgical margins (n=28,703), those with LVSI (n=369,236), those not receiving RT (n=147,543), those undergoing a mastectomy (n=3,139), those receiving neoadjuvant chemotherapy (n=32, 365), those without invasive disease or DCIS (n=11,727), and those with stage 3/4 disease (n=15,216). All patients with unknown data were excluded (n=39,863). Patients were separated by those who received APBI (n=16,200) and who received ≥11 fractions which were classified as WBI (n= 90,105). <h3>Results</h3> 106,305 (3.6%) patients were identified as APBI candidates. Of those, 15.2% (mean age 66, range 50-90) received APBI while 84.8% (mean age 65, range 50-90) patients received WBI. Black and Asian patients were significantly less likely to receive APBI (Black: 12.0% OR, 0.70 [95% CI, 0.64-0.77], p <.001]; Asian: 10.1% OR, 0.59 [95% CI, 0.52-0.68], p<.001]) compared to white patients (15.7 %). Similarly, Latinx/Hispanic patients were less likely to receive APBI [11.0% OR, 0.73 [95% CI, 0.65-0.83], p <.001] when compared to non-Hispanic individuals (15.4 %). Patients with Medicare/other government insurance (16.7%) were also more likely than those with Medicaid/ not insured (9.3% OR, 0.68 [95% CI, 0.61-0.77], p<.001]) to receive APBI. Compared to urban areas (13.7%), patients living in rural locations (19.5% OR, 1.37 [95% CI, 1.0-1.86], p<.05]) were more likely to receive APBI. On univariate analysis, zip codes with higher high school graduation rates, and incomes >$63,000 were also associated with increased receipt of APBI (p<.001). <h3>Conclusion</h3> Despite similar candidacy, minority patients and those with Medicaid/ uninsured are less likely to receive APBI; while, higher SES and high school graduation rates is associated with receipt of APBI. Further study is needed to identify methods to increase availability for all appropriate patients.