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Background: Whole breast irradiation delivered once per day over 3-5 weeks after breast conserving surgery reduces local recurrence with good cosmetic results. Accelerated partial breast irradiation (APBI) delivered over 1 week to the tumour bed was developed to provide a more convenient treatment. In this trial, we investigated if external beam APBI was non-inferior to whole breast irradiation., Methods: We did this multicentre, randomised, non-inferiority trial in 33 cancer centres in Canada, Australia and New Zealand. Women aged 40 years or older with ductal carcinoma in situ or node-negative breast cancer treated by breast conserving surgery were randomly assigned (1:1) to receive either external beam APBI (38·5 Gy in ten fractions delivered twice per day over 5-8 days) or whole breast irradiation (42·5 Gy in 16 fractions once per day over 21 days, or 50 Gy in 25 fractions once per day over 35 days). Patients and clinicans were not masked to treatment assignment. The primary outcome was ipsilateral breast tumour recurrence (IBTR), analysed by intention to treat. The trial was designed on the basis of an expected 5 year IBTR rate of 1·5% in the whole breast irradiation group with 85% power to exclude a 1·5% increase in the APBI group; non-inferiority was shown if the upper limit of the two-sided 90% CI for the IBTR hazard ratio (HR) was less than 2·02. This trial is registered with ClinicalTrials.gov, NCT00282035., Findings: Between Feb 7, 2006, and July 15, 2011, we enrolled 2135 women. 1070 were randomly assigned to receive APBI and 1065 were assigned to receive whole breast irradiation. Six patients in the APBI group withdrew before treatment, four more did not receive radiotherapy, and 16 patients received whole breast irradiation. In the whole breast irradiation group, 16 patients withdrew, and two more did not receive radiotherapy. In the APBI group, a further 14 patients were lost to follow-up and nine patients withdrew during the follow-up period. In the whole breast irradiation group, 20 patients were lost to follow-up and 35 withdrew during follow-up. Median follow-up was 8·6 years (IQR 7·3-9·9). The 8-year cumulative rates of IBTR were 3·0% (95% CI 1·9-4·0) in the APBI group and 2·8% (1·8-3·9) in the whole breast irradiation group. The HR for APBI versus whole breast radiation was 1·27 (90% CI 0·84-1·91). Acute radiation toxicity (grade ≥2, within 3 months of radiotherapy start) occurred less frequently in patients treated with APBI (300 [28%] of 1070 patients) than whole breast irradiation (484 [45%] of 1065 patients, p<0·0001). Late radiation toxicity (grade ≥2, later than 3 months) was more common in patients treated with APBI (346 [32%] of 1070 patients) than whole breast irradiation (142 [13%] of 1065 patients; p<0·0001). Adverse cosmesis (defined as fair or poor) was more common in patients treated with APBI than in those treated by whole breast irradiation at 3 years (absolute difference, 11·3%, 95% CI 7·5-15·0), 5 years (16·5%, 12·5-20·4), and 7 years (17·7%, 12·9-22·3)., Interpretation: External beam APBI was non-inferior to whole breast irradiation in preventing IBTR. Although less acute toxicity was observed, the regimen used was associated with an increase in moderate late toxicity and adverse cosmesis, which might be related to the twice per day treatment. Other approaches, such as treatment once per day, might not adversely affect cosmesis and should be studied., Funding: Canadian Institutes for Health Research and Canadian Breast Cancer Research Alliance., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Background: Two new cancer centers providing radiation therapy opened in Alberta, Canada, in 2010 and 2013, respectively. We aimed to assess whether opening the new RT centers influenced mastectomy rates for breast cancer., Method: Breast cancer patients who underwent surgery from 2004 through 2015 were identified from the Alberta Cancer Registry. Mastectomy rates for 64 predefined health status areas (HSAs) were calculated after adjusting for patient and system factors. Variations in mastectomy rates among the HSAs were quantified using weighted coefficient of variation (CV). Multivariable logistic regressions were performed to determine associations between driving time and mastectomy use in the entire cohort and in subgroups., Results: Of the 21,872 patients, the proportion of patients who lived a ≤ 60 min drive from the nearest RT center significantly increased from 68.8% (95% CI 67.7-69.9%) to 80.7% (95% CI 79.5-81.9%) during the study period. Concurrently, the crude provincial mastectomy rate decreased from 56.2% (95% CI 55.3-57.1%) to 45.3% (95% CI 44.1-46.5%). However, variation in adjusted mastectomy rates (weighted CV) across the 64 HSAs increased from 9.5 to 14.6. Factors associated with mastectomy included age, larger tumor size, lymph node involvement, higher tumor grade, molecular subtype, lobular histology type, more comorbidities, academic institution, region, earlier period of diagnosis, and longer driving time to the nearest RT center., Conclusions: Opening new RT centers in previously underserved regions reduced driving times to the nearest center, and was associated with a reduction in mastectomy rates; however, these reductions among regions across the province were not uniform.

Background: Most women with ductal carcinoma in situ (DCIS) will receive breast-conserving surgery (BCS) and radiation (RT). RT can be omitted for women at low risk of local recurrence (LR). The Oncotype DX DCIS score (DS) predicts LR risk after BCS alone. This study assesses the impact of RT and DS on LR risk., Methods: Population-based cohort analysis of individuals with DCIS treated by BCS ± RT from 1994-2003. Treatment and outcomes were determined by linkage and chart review. We used a propensity score-adjusted multivariable model to examine associations between DS and LR and evaluate the impact of RT. All statistical tests were two-sided., Results: The cohort includes 571 individuals treated by BCS alone, 689 cases treated with BCS + RT. Median follow-up was 9.4 years. On multivariable analysis, factors associated with LR include RT, age at diagnosis, tumor size, and multifocality. Adjusting for these factors, the DS risk group was statistically significantly associated with LR risk (hazard ratio high/intermediate = 1.75, 95% confidence interval = 1.28 to 2.41, P < .001). Women with a low-risk DS treated by BCS alone had an LR risk of 10.6% at 10 years and a small benefit from RT, while those with a high DS had a higher risk of LR (25.4%) after BCS alone and greater benefit from RT. A subgroup of patients with favorable clinicopathological features had a high-risk DS; these patients had a higher than expected risk of LR after BCS alone and a greater benefit with RT., Conclusions: The DS molecular assay improves risk stratification and estimates of RT benefit in individuals with DCIS treated with breast-conserving therapy.

Background: The utility of post mastectomy radiotherapy in very young women is understudied. The objective of this study was to evaluate the use of PMRT in very young women to determine the effect on recurrence and survival., Methods: All women aged ≤35 years diagnosed with invasive breast cancer from 1994 to 2003 were identified from the Ontario Cancer Registry. Patient, tumour, treatment and outcome data were abstracted from primary chart review. Local or regional recurrence was the primary endpoint with contralateral, distant recurrence/death treated as competing risks. Propensity score methods were incorporated into multivariable Cox proportional hazards models to evaluate the effect of radiation therapy on the time to local/regional, distant recurrence or death., Results: 588 patients were identified during the study period, of which 382 were eligible for analysis. Overall, 182 (48%) of patients sustained a recurrence after a median follow-up of 2.72 years. The use of PMRT significantly reduced locoregional recurrence (HR 0.54, 95% CI 0.29-0.996) compared with those who did not receive PMRT. There was no significant effect of PMRT on contralateral, distant recurrences, or death without recurrence (HR 0.98, 95% CI 0.66-1.47). Of the patients with known node status (N = 451), isolated local recurrence occurred in 5, 2.5, and 8.5% in patients with N0, N1-3, and N4 positive nodes respectively., Conclusions: We have found a significant reduction in locoregional recurrence with PMRT but no survival benefit in very young women with breast cancer.

Aims: Post-lumpectomy breast radiation is the standard of care for all patient subgroups. However, elderly women with stage I breast cancer on adjuvant tamoxifen therapy have a 4% risk of local recurrence after lumpectomy without adjuvant breast radiation. The purpose of this study was to explore the attitudes of Canadian radiation oncologists who treat breast cancer with respect to their use of adjuvant post-lumpectomy radiotherapy, and their willingness to implement a decision aid for this patient population., Materials and Methods: The questionnaire was mailed to 141 Canadian radiation oncologists who treat breast cancer. The respondents were asked to complete an online survey consisting of four parts: (1) demographic information; (2) factors determining post-lumpectomy radiation treatment decisions; (3) hypothetical case scenarios; (4) interest in using a decision aid in their practice., Results: Among the 61 (43%) physicians who completed the survey, there was substantial response variation. After contraindications to radiotherapy, patient overall health and patient preference had the greatest influence on their decision to offer radiotherapy to this patient subgroup. Margin status and use of hormonal therapy were given less importance. For each of the case scenarios, 60-83% of physicians (depending on the case scenario) would offer the patient a choice; far fewer (12-57%) would be comfortable not irradiating. Sixty-four per cent of respondents welcomed the concept of a decision aid for this population., Conclusions: Although there is significant variation in practice patterns and attitudes among radiation oncologists regarding post-lumpectomy radiotherapy for elderly, low-risk breast cancer patients, the vast majority value patient choice and would be willing to use a decision aid designed for this population in their practice., (2009 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.)