METHODS

Two time periods were evaluated, 2006 through 2008 and 2011 through 2013, defined by date of lumpectomy. The time periods were selected to assess 3 years before and 3 years after publication of the START trials and the long-term follow-up of the OCOG trial.

Patients were identified from a prospective breast cancer database which along with this study, was approved by the Mayo Clinic Institutional Review Board, and written informed consent was obtained from all participants for the use of the data for research purposes. Inclusion criteria were completion of BCT at our institution, age ≥50 years, histologic findings of invasive ductal carcinoma, stage T1-T2N0M0, ER+, and HER2 normal. These inclusion criteria were chosen to match the ASTRO recommended guidelines for shorter whole-breast radiation schedules.18 Patients receiving brachytherapy on clinical trial were excluded. We collected additional data from our institutional electronic medical record. Cases were categorized by RT modality (3DCRT, IMRT) and fractionation schedule (traditional >23 fractions vs hypofractionated <17 fractions, excluding boost).


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Continuous variables were compared using the t test. Categorical variables were compared using the chi-squared test. A P value <0.05 was considered statistically significant. Cases were analyzed on an intent-to-treat basis.

Direct medical costs were estimated for 15- and 25-fraction WBRT using 3DCRT or IMRT, based on the Current Procedural Terminology, Fourth Edition, coding system. Payment rates are national average payments under the 2016 Hospital Outpatient Prospective Payment System (technical fees) and Medicare Physician Fee Schedule (professional fees).19,20

RESULTS

From 2006 to 2008, 55 patients met the inclusion criteria (mean [SD] age, 72.1 [9.0] years; range 51–89 years). WBRT was given on a traditional schedule for 69% of patients and was hypofractionated for 11%. RT was omitted in 20% of all patients (mean [SD] age, 80.6 [6.3] years; range, 67–89 years). For patients aged >70 years, RT was omitted in 29%.

From 2011 to 2013, 83 patients met the inclusion criteria (mean [SD] age, 70.7 [8.9] years; range, 51–97 years). WBRT was given on a traditional schedule for 19% of patients and was hypofractionated for 54%. RT was omitted for 27% of all patients (mean [SD] age, 78.5 [7.6] years; range, 61–97 years). For patients aged >70 years, RT was omitted in 48%.

Between the two time periods, no significant differences were seen in patient age (P=0.37), proportion of patients aged >70 years (P=0.22), or disease stage (P=0.95). The change in radiation therapy practice patterns between the two time periods was statistically significant (P<0.001) (Table 1). When only WBRT patients were considered, the hypofractionation rate increased from 14% in 2006–2008 to 74% in 2011–2013 (P<0.001) (Figure 1). For patients aged >70 years, the RT omission rate increased from 29% in 2006–2008 to 48% in 2011–2013; however, it did not reach statistical significance (P=0.11) (Table 1; Figure 1).


The rationale for the treatment using a traditional rather than a hypofractionated schedule was documented in medical records in 11 of 16 traditional schedule cases from 2011 to 2013. In six cases, patient preference led to using the traditional schedule. In five cases, the treating physician recommended a traditional schedule because of a large breast separation. Of the five remaining cases in which the rationale for choosing a traditional schedule was not clear, one patient had breast implants and two patients were initially planned for hypofractionation but were ultimately treated with a traditional schedule.

All WBRT was delivered using 3DCRT. No cases used an IMRT technique. WBRT was delivered in 2.66 or 2.67 Gy/fraction for the hypofractionated regimen and 2 Gy/fraction for the traditional regimen.

Direct medical cost estimates were as follows: 15 fractions of 3DCRT, $7,197.87; 15 fractions of IMRT, $11,232.33; 25 fractions of 3DCRT, $9,731.39; and 25 fractions of IMRT, $16,877.45 (Table 2).

(To view a larger version of Table 2, click here.)