Purpose: This analysis compares the efficacy of a common clinical decision regarding selection of an abbreviated course of adjuvant radiotherapy for early-stage breast cancer: brachytherapy-based accelerated partial breast irradiation (APBI) vs. whole breast Canadian hypofractionated external beam radiation therapy. Materials and Methods: Patients were treated between November 1993 and November 2010 with APBI at 340 cGy BID for five days or Canadian Hypofractionation [CHfx] to the whole breast delivering 266 cGy per day for 16 fractions. The brachytherapy CTV was a 1cm expansion from the applicator surface for balloon devices and 1.5 to 2 cm from implanted interstitial catheters. For CHfx, the CTV was whole breast without boost irradiation. To compare efficacy between the two treatment groups, a matched-pair analysis was performed using a 1:1 ratio which paired 59 brachytherapy APBI patients with 59 patients treated via the CHfx dose scheme. Match criteria included minimal followup (FU) O1.0 yr, clinical stage, age (þ/3 yrs), and ER status. Clinical outcomes analyzed included freedom from local-regional recurrence [FRLR, FRRR], freedom from distant metastases (FRDM), disease-free, causespecific and overall survival [DFS, CSS, & OS]. Results: Matched exactly for stage and ER, no significant differences were noted for age (p50.775), nodal stage (p50.638), use of chemotherapy (p50.205) or endocrine therapy (p50.072) in the matched population. With a mean FU of 4.0 yrs (5.2 yrs for APBI vs. 2.8 yrs for CHfx, p! 0.001), no differences were seen in the 3-year actuarial rates of FRLR (98.3% vs. 100%, p50.317), DFS (98.3% vs. 100%, p50.317), or OS (91.0% vs. 100 %, p50.142); the 5-yr figures for these endpoints were likewise not statistically different. As well, no differences were seen in the 3and 5actuarial rates of FRRR, FRDM [both 100% at 3 & 5 yrs], or CSS [100% at 3& 5-yr intervals] between the APBI and CHfx groups, respectively. Conclusions: With a mean followup of 4 years, brachytherapy APBI offers similar treatment efficacy in a more time-compressed treatment course versus Canadian Hypofractionation while sparing dose to the remainder of the breast. Further FU and more patients will be needed to substantiate equivalence of brachytherapy-based APBI compared with whole breast CHfx, as well as the need for irradiation delivered to a volume beyond that prescribed for APBI in selected early-stage breast cancer patients.