Radiotherapy to regional nodes in early breast cancer: an individual patient data meta-analysis of 14 324 women in 16 trials

BACKGROUND

Radiotherapy has become much better targeted since the 1980s, improving both safety and efficacy. In breast cancer, radiotherapy to regional lymph nodes aims to reduce risks of recurrence and death. Its effects have been studied in randomised trials, some before the 1980s and some after. We aimed to assess the effects of regional node radiotherapy in these two eras.

METHODS

In this meta-analysis of individual patient data, we sought data from all randomised trials of regional lymph node radiotherapy versus no regional lymph node radiotherapy in women with early breast cancer (including one study that irradiated lymph nodes only if the cancer was right-sided). Trials were identified through the EBCTCG's regular systematic searches of databases including MEDLINE, Embase, the Cochrane Library, and meeting abstracts. Trials were eligible if they began before Jan 1, 2009. The only systematic difference between treatment groups was in regional node radiotherapy (to the internal mammary chain, supraclavicular fossa, or axilla, or any combinations of these). Primary outcomes were recurrence at any site, breast cancer mortality, non-breast-cancer mortality, and all-cause mortality. Data were supplied by trialists and standardised into a format suitable for analysis. A summary of the formatted data was returned to trialists for verification. Log-rank analyses yielded first-event rate ratios (RRs) and confidence intervals.

FINDINGS

We found 17 eligible trials, 16 of which had available data (for 14 324 participants), and one of which (henceforth excluded), had unavailable data (for 165 participants). In the eight newer trials (12 167 patients), which started during 1989-2008, regional node radiotherapy significantly reduced recurrence (rate ratio 0·88, 95% CI 0·81-0·95; p=0·0008). The main effect was on distant recurrence as few regional node recurrences were reported. Radiotherapy significantly reduced breast cancer mortality (RR 0·87, 95% CI 0·80-0·94; p=0·0010), with no significant effect on non-breast-cancer mortality (0·97, 0·84-1·11; p=0·63), leading to significantly reduced all-cause mortality (0·90, 0·84-0·96; p=0·0022). In an illustrative calculation, estimated absolute reductions in 15-year breast cancer mortality were 1·6% for women with no positive axillary nodes, 2·7% for those with one to three positive axillary nodes, and 4·5% for those with four or more positive axillary nodes. In the eight older trials (2157 patients), which started during 1961-78, regional node radiotherapy had little effect on breast cancer mortality (RR 1·04, 95% CI 0·91-1·20; p=0·55), but significantly increased non-breast-cancer mortality (1·42, 1·18-1·71; p=0·00023), with risk mainly after year 20, and all-cause mortality (1·17, 1·04-1·31; p=0·0067).

INTERPRETATION

Regional node radiotherapy significantly reduced breast cancer mortality and all-cause mortality in trials done after the 1980s, but not in older trials. These contrasting findings could reflect radiotherapy improvements since the 1980s.

FUNDING

Cancer Research UK, Medical Research Council.

Abstract GS4-03: Validation of Profile for the Omission of Local Adjuvant Radiotherapy (POLAR) in a meta-analysis of three randomized controlled trials of breast conserving surgery +/- radiotherapy

Background: There are currently no commercially available tests to identify early stage breast cancer patients treated with breast conserving surgery (BCS) and systemic therapy at low risk of locoregional recurrence (LRR) for whom postoperative radiotherapy (RT) may be safely omitted. Profile for the Omission of Local Adjuvant Radiotherapy (POLAR) is a 16-gene molecular signature developed to identify invasive breast cancer patients who may be candidates for RT omission after BCS. In this work, we seek to validate POLAR in a meta-analysis of three RCTs of BCS +/- RT: SweBCG91RT, Scottish Conservation Trial (SCT) and Princess Margaret Hospital (PMH).

Methods: A patient-level meta-analysis was performed in 623 node-negative breast cancer patients with ER+/HER2-negative tumors who were enrolled in the three RCTs and for whom primary tumor material was available for analysis. Contributions from each cohort were as follows: SweBCG91RT N=354 (57%), SCT N=137 (22%), and PMH N=132 (21%). Numbers of LRR events in each cohort were as follows: SweBCG91RT N=72 (20%), SCT N=28 (20%), and PMH N=16 (12%). There was a mix of systemic therapy used (no systemic therapy for SweBCG91RT, chemotherapy or adjuvant endocrine therapy, but not both, in SCT, and tamoxifen but no chemotherapy for PMH). Median follow-up time for the patients who did not have LRR was 13.3 years for SweBCG91RT, 21.1 years for SCT, and 8.6 years for PMH. A multivariable Cox proportional hazards model on time to LRR, including the continuous standardized POLAR score, RT, and interaction, stratified by cohort, was used to test the interaction between the continuous POLAR score and RT. Additional Cox models tested the association between treatment arms separately for patients with a low and high POLAR score using a pre-specified cut point. Cumulative incidences were computed, with distant metastasis and death without recurrence considered as competing events.

Results: The test for interaction between RT treatment and POLAR was statistically significant (p = 0.022). Patients with a high POLAR score (N=429 [69%]) had a large benefit from RT (10-year cumulative incidence of LRR: 20% [15%-26%] for those not treated with RT vs 7% [4%-11%] for those treated with RT; hazard ratio for RT vs no RT: 0.37 [0.23-0.60], p < 0.001), whereas there was no evidence of benefit from RT for patients with a low POLAR score (N=194 [31%], 10-year cumulative incidence of LRR: 5% [2%-11%] for those not treated with RT vs 7% [3%-14%] for those treated with RT; hazard ratio for RT vs no RT: 0.92 [0.42-2.02], p = 0.832).

Conclusions: To our knowledge, POLAR is the first genomic classifier that is not only prognostic for LRR but also predictive, showing a significant interaction between RT and the classifier. Patients with a high POLAR score should be recommended radiotherapy while patients with a low score may be candidates for omission of radiotherapy after breast conserving surgery.

Citation Format: Per Karlsson, Anthony Fyles, S. Laura Chang, Bradley Arrick, Frederick Baehner, Per Malmström, Mårten Fernö, Erik Holmberg, Martin Sjöström, Fei-Fei Liu, David A. Cameron, Linda J. Williams, John MS Bartlett, Joanna Dunlop, Jacqueline Caldwell, Joseph F. Loane, Elizabeth Mallon, Tammy Piper, Wilma J. Jack, Ian Kunkler, Felix Y. Feng, Corey W. Speers, Lori Pierce, John Bennett, Karen J. Taylor. Validation of Profile for the Omission of Local Adjuvant Radiotherapy (POLAR) in a meta-analysis of three randomized controlled trials of breast conserving surgery +/- radiotherapy [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr GS4-03.

Abstract P4-02-12: Validation of Profile for the Omission of Local Adjuvant Radiotherapy (POLAR) in early-stage invasive breast cancer patients of the Scottish Conservation Trial

Background: Adjuvant whole breast radiotherapy (RT) is provided to almost all women with early-stage invasive breast cancer after breast conserving surgery and appropriate systemic therapy. While there is increasing interest to personalize the use of RT based on molecular profiling, to date, there is no molecular signature available to reliably assess the benefit of radiotherapy after surgical resection. Here we assess the ability of a 16-gene signature named Profile for the Omission of Local Adjuvant Radiotherapy (POLAR) to identify who may be suitable candidates for radiotherapy omission in patients of the Scottish Conservation Trial. Methods: The POLAR signature was applied to archival tissue from the Scottish Conservation Trial, which randomized 585 patients with stage I-II breast cancer, tumor size < 4 cm, and age ≤70 years old to receive RT or not. The archival tissue was measured for ER (ER+ >10%), PgR (PgR+ ≥20%), Ki67 (Ki67 high ≥14%), and HER2 (HER2+ defined as HER2 over-expressed or amplified). 26% received adjuvant chemotherapy, the remainder received tamoxifen 20 mg/daily for 5 years. Cox models for the locoregional recurrence (LRR) endpoint tested the association between treatment arms separately for patients with a low and high POLAR score using a pre-specified cut point. Cumulative incidences were computed, with distant metastasis and death without recurrence considered competing events. Results: 224 patients had tissue available and complete clinical data for analysis, 40 (18%) were node-positive. The distribution of clinicopathologic variables between the RT and no RT arms remained balanced. 43% were ER+/PgR+/Ki67 low/HER2-, 31% were ER+/HER2-/Ki67 high or PgR-, 5% were HER2+, and 13% were triple negative. The continuous standardized POLAR score was prognostic for LRR in the no RT arm after adjusting for relevant covariates (HR=1.78 [1.20-2.64], p=0.003). For patients with a POLAR-high score, the 10-year LRR rate was 31% [21%-42%] for patients not receiving RT and 8% [3%-15%] for patients receiving RT (HR 0.36 [0.19-0.69], p=0.0022). For patients with a POLAR low score, the 10-year LRR rates were 20% [10%-33%] for patients not receiving RT and 6% [1%-18%] for patients receiving RT; HR=0.28 [0.08-0.98], p=0.046). In the subgroup of node-negative patients with ER+/HER2-negative tumors (N=137), there was a statistically significant RT benefit for patients with a POLAR high score (HR=0.31 [0.11-0.88], p=0.028) but not for patients with a POLAR low score (HR=0.5 [0.1-2.4], p=0.39). Conclusions: For patients with early-stage invasive breast cancer treated with breast-conserving surgery without RT, POLAR is prognostic for LRR and may refine the selection of “low risk” for omission of RT.

Citation Format: Karen J. Taylor, John MS Bartlett, John Bennett, S. Laura Chang, Bradley Arrick, Frederick Baehner, Joseph F. Loane, Tammy Piper, Elizabeth Mallon, Joanna Dunlop, Wilma J. Jack, Jacqueline Caldwell, Ian Kunkler, Linda J. Williams, Corey W. Speers, Felix Y. Feng, Lori Pierce, David A. Cameron. Validation of Profile for the Omission of Local Adjuvant Radiotherapy (POLAR) in early-stage invasive breast cancer patients of the Scottish Conservation Trial [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-02-12.

An Assessment of the Feasibility and Utility of an ACCC-ASCO Implicit Bias Training Program to Enhance Racial and Ethnic Diversity in Cancer Clinical Trials

PURPOSE

Cancer trial participants do not reflect the racial and ethnic diversity in the population of people with cancer in the United States. As a result of multiple system-, patient-, and provider-level factors, including implicit bias, cancer clinical trials are not consistently offered to all potentially eligible patients.

MATERIALS AND METHODS

ASCO and ACCC evaluated the utility (pre- and post-test knowledge changes) and feasibility (completion rates, curriculum satisfaction metrics, survey questions, and interviews) of a customized online training program combined with facilitated peer-to-peer discussion designed to help research teams identify their own implicit biases and develop strategies to mitigate them. Discussion focused on (1) specific elements of the training modules; (2) how to apply lessons learned; and (3) key considerations for developing a facilitation guide to support peer-to-peer discussions in cancer clinical research settings. We evaluated discussion via a qualitative assessment.

RESULTS

Participant completion rate was high: 49 of 50 participating cancer programs completed training; 126 of 129 participating individuals completed the training (98% response rate); and 119 completed the training and evaluations (92% response rate). Training increased the mean percentage change in knowledge scores by 19%-45% across key concepts (eg, causes of health disparities) and increased the mean percentage change in knowledge scores by 10%-31% about strategies/actions to address implicit bias and diversity concerns in cancer clinical trials. Knowledge increases were sustained at 6 weeks. Qualitative evaluation validated the utility and feasibility of facilitated peer-to-peer discussion.

CONCLUSION

The pilot implementation of the training program demonstrated excellent utility and feasibility. Our evaluation affirms that an online training designed to raise awareness about implicit bias and develop strategies to mitigate biases among cancer research teams is feasible and can be readily implemented in cancer research settings.

Mediators of Racial Disparities in Heart Dose Among Whole Breast Radiotherapy Patients

BACKGROUND

Racial disparities in survival of patients with cancer motivate research to quantify treatment disparities and evaluate multilevel determinants. Previous research has not evaluated cardiac radiation dose in large cohorts of breast cancer patients by race nor examined potential causes or implications of dose disparities.

METHODS

We used a statewide consortium database to consecutively sample 8750 women who received whole breast radiotherapy between 2012 and 2018. We generated laterality- and fractionation-specific models of mean heart dose. We generated patient- and facility-level models to estimate race-specific cardiac doses. We incorporated our data into models to estimate disparities in ischemic cardiac event development and death. All statistical tests were 2-sided.

RESULTS

Black and Asian race independently predicted higher mean heart dose for most laterality-fractionation groups, with disparities of up to 0.42 Gy for Black women and 0.32 Gy for Asian women (left-sided disease and conventional fractionation: 2.13 Gy for Black women vs 1.71 Gy for White women, P < .001, 2-sided; left-sided disease and accelerated fractionation: 1.59 Gy for Asian women vs 1.27 Gy for White women, P = .002). Patient clustering within facilities explained 22%-30% of the variability in heart dose. The cardiac dose disparities translated to estimated excesses of up to 2.6 cardiac events and 1.3 deaths per 1000 Black women and 0.7 cardiac events and 0.3 deaths per 1000 Asian women vs White women.

CONCLUSIONS

Depending on laterality and fractionation, Asian women and Black women experience higher cardiac doses than White women. This may translate into excess radiation-associated ischemic cardiac events and deaths. Solutions include addressing inequities in baseline cardiac risk factors and facility-level availability and use of radiation technologies.

Identifying Patients Whose Symptoms Are Underrecognized During Treatment With Breast Radiotherapy

Importance

Understanding whether physicians accurately detect symptoms in patients with breast cancer is important because recognition of symptoms facilitates supportive care, and clinical trials often rely on physician assessments using Common Toxicity Criteria for Adverse Events (CTCAE).

Objective

To compare the patient-reported outcomes (PROs) of patients with breast cancer who received radiotherapy from January 1, 2012, to March 31, 2020, with physicians' CTCAE assessments to assess underrecognition of symptoms.

Design, Setting, and Participants

This cohort study included a total of 29 practices enrolled in the Michigan Radiation Oncology Quality Consortium quality initiative. Of 13 725 patients with breast cancer who received treatment with radiotherapy after undergoing lumpectomy, 9941 patients (72.4%) completed at least 1 PRO questionnaire during treatment with radiotherapy and were evaluated for the study. Of these, 9868 patients (99.3%) were matched to physician CTCAE assessments that were completed within 3 days of the PRO questionnaires.

Exposures

Patient and physician ratings of 4 symptoms (pain, pruritus, edema, and fatigue) were compared.

Main Outcomes and Measures

We used multilevel multivariable logistic regression to evaluate factors associated with symptom underrecognition, hypothesizing that it would be more common in racial and ethnic minority groups.

Results

Of 9941 patients, all were female, 1655 (16.6%) were Black, 7925 (79.7%) were White, and 361 (3.6%) had Other race and ethnicity (including American Indian/Alaska Native, Arab/Middle Eastern, and Asian), either as self-reported or as indicated in the electronic medical record. A total of 1595 (16.0%) were younger than 50 years, 2874 (28.9%) were age 50 to 59 years, 3353 (33.7%) were age 60 to 69 years, and 2119 (21.3%) were 70 years or older. Underrecognition of symptoms existed in 2094 of 6781 (30.9%) observations of patient-reported moderate/severe pain, 748 of 2039 observations (36.7%) of patient-reported frequent pruritus, 2309 of 4492 observations (51.4%) of patient-reported frequent edema, and 390 of 2079 observations (18.8%) of patient-reported substantial fatigue. Underrecognition of at least 1 symptom occurred at least once for 2933 of 5510 (53.2%) of those who reported at least 1 substantial symptom. Factors independently associated with underrecognition were younger age (younger than 50 years compared with 60-69 years: odds ratio [OR], 1.35; 95% CI, 1.14-1.59; P < .001; age 50-59 years compared with 60-69 years: OR, 1.19; 95% CI, 1.03-1.37; P = .02), race (Black individuals compared with White individuals: OR, 1.56; 95% CI 1.30-1.88; P < .001; individuals with Other race or ethnicity compared with White individuals: OR, 1.52; 95% CI, 1.12-2.07; P = .01), conventional fractionation (OR, 1.26; 95% CI, 1.10-1.45; P = .002), male physician sex (OR, 1.54; 95% CI, 1.20-1.99; P = .002), and 2-field radiotherapy (without a supraclavicular field) (OR, 0.80; 95% CI, 0.67-0.97; P = .02).

Conclusions and Relevance

The results of this cohort study suggest that PRO collection may be essential for trials because relying on the CTCAE to detect adverse events may miss important symptoms. Moreover, since physicians in this study systematically missed substantial symptoms in certain patients, including younger patients and Black individuals or those of Other race and ethnicity, improving symptom detection may be a targetable mechanism to reduce disparities.

Strategies to Advance Equity in Cancer Clinical Trials

Cancer clinical trials are critical for testing new treatments, yet less than 5% of patients with cancer enroll in these trials. Minority groups, elderly individuals, and rural populations are particularly underrepresented in cancer treatment trials. Strategies for advancing equity in cancer clinical trials for these populations include (1) optimizing clinical trial matching by broadening eligibility criteria, screening all patients for trial eligibility, expanding the number of trials against which patients are screened, and following up on all patient matches with an enrollment invitation; (2) conducting site self-assessments to identify clinical-, patient-, provider-, and system-level barriers that contribute to low rates of clinical trial screening and enrollment; (3) creating a quality improvement plan that addresses the barriers to enrollment and incorporates the use of tools and strategies such as clinical trial checklists; workforce development and trainings to improve cultural competence and reduce unconscious bias; guides to promote community education, outreach and engagement with cancer clinical trials; screening and accrual logs designed to measure participation by demographics; models of informed consent that improve understanding; clinical trial designs that reduce accessibility barriers; use of cancer clinical trial patient navigators; and programs to eliminate barriers to participation and out-of-pocket expenses; and (4) working with stakeholders to develop both protocols that are inclusive of diverse populations' geographic locations, and strategies to access those trials. These actions will support greater access for populations that have remained underrepresented in cancer clinical trials and thereby increase the generalizability and efficiency of cancer research.

Aromatase inhibitors versus tamoxifen in premenopausal women with oestrogen receptor-positive early-stage breast cancer treated with ovarian suppression: a patient-level meta-analysis of 7030 women from four randomised trials

BACKGROUND

For women with early-stage oestrogen receptor (ER)-positive breast cancer, adjuvant tamoxifen reduces 15-year breast cancer mortality by a third. Aromatase inhibitors are more effective than tamoxifen in postmenopausal women but are ineffective in premenopausal women when used without ovarian suppression. We aimed to investigate whether premenopausal women treated with ovarian suppression benefit from aromatase inhibitors.

METHODS

We did a meta-analysis of individual patient data from randomised trials comparing aromatase inhibitors (anastrozole, exemestane, or letrozole) versus tamoxifen for 3 or 5 years in premenopausal women with ER-positive breast cancer receiving ovarian suppression (goserelin or triptorelin) or ablation. We collected data on baseline characteristics, dates and sites of any breast cancer recurrence or second primary cancer, and dates and causes of death. Primary outcomes were breast cancer recurrence (distant, locoregional, or contralateral), breast cancer mortality, death without recurrence, and all-cause mortality. As distant recurrence invariably results in death from breast cancer several years after the occurrence, whereas locoregional recurrence and new contralateral breast cancer are not usually fatal, the distant recurrence analysis is shown separately. Standard intention-to-treat log-rank analyses estimated first-event rate ratios (RR) and their confidence intervals (CIs).

FINDINGS

We obtained data from all four identified trials (ABCSG XII, SOFT, TEXT, and HOBOE trials), which included 7030 women with ER-positive tumours enrolled between June 17, 1999, and Aug 4, 2015. Median follow-up was 8·0 years (IQR 6·1-9·3). The rate of breast cancer recurrence was lower for women allocated to an aromatase inhibitor than for women assigned to tamoxifen (RR 0·79, 95% CI 0·69-0·90, p=0·0005). The main benefit was seen in years 0-4 (RR 0·68, 99% CI 0·55-0·85; p<0·0001), the period when treatments differed, with a 3·2% (95% CI 1·8-4·5) absolute reduction in 5-year recurrence risk (6·9% vs 10·1%). There was no further benefit, or loss of benefit, in years 5-9 (RR 0·98, 99% CI 0·73-1·33, p=0·89) or beyond year 10. Distant recurrence was reduced with aromatase inhibitor (RR 0·83, 95% CI 0·71-0·97; p=0·018). No significant differences were observed between treatments for breast cancer mortality (RR 1·01, 95% CI 0·82-1·24; p=0·94), death without recurrence (1·30, 0·75-2·25; p=0·34), or all-cause mortality (1·04, 0·86-1·27; p=0·68). There were more bone fractures with aromatase inhibitor than with tamoxifen (227 [6·4%] of 3528 women allocated to an aromatase inhibitor vs 180 [5·1%] of 3502 women allocated to tamoxifen; RR 1·27 [95% CI 1·04-1·54]; p=0·017). Non-breast cancer deaths (30 [0·9%] vs 24 [0·7%]; 1·30 [0·75-2·25]; p=0·36) and endometrial cancer (seven [0·2%] vs 15 [0·3%]; 0·52 [0·22-1·23]; p=0·14) were rare.

INTERPRETATION

Using an aromatase inhibitor rather than tamoxifen in premenopausal women receiving ovarian suppression reduces the risk of breast cancer recurrence. Longer follow-up is needed to assess any impact on breast cancer mortality.

FUNDING

Cancer Research UK, UK Medical Research Council.

Abstract P2-08-01: Validation of a 16-gene genomic signature to identify early-stage invasive breast cancer patients who may omit radiotherapy

Background While whole breast radiotherapy has been standard of care for invasive breast cancer patients treated with breast conserving surgery, not all women may benefit from radiotherapy. Recently, we demonstrated that a 16-gene signature named Profile for the Omission of Local Adjuvant Radiotherapy (POLAR) could identify breast cancer patients with HR+, HER2- tumors treated with breast conserving surgery alone with a 10-year locoregional recurrence risk of less than 10%. Methods In this study, we apply the signature to patients enrolled in the Princess Margaret Trial, a randomized trial where patients age 50 years or older were randomized to radiotherapy and tamoxifen or tamoxifen alone after breast conserving surgery. Tissue from 132 patients with HR+, HER2- tumors were available for gene expression analysis. Results For women treated with tamoxifen alone after breast conserving surgery, POLAR identified low risk women with a 7% risk of locoregional recurrence at 10 years. Comparison to POLAR-low patients treated with adjuvant radiotherapy did not demonstrate a significant benefit from radiotherapy (HR=1.5[0.14-16], p=0.74). POLAR-high patients not treated with radiotherapy had a 22% risk of locoregional recurrence at 10 years. Comparison to POLAR-high patients treated with adjuvant radiotherapy demonstrated a significant benefit from standard radiotherapy (HR=0.25[0.07-0.92], p=0.038). Conclusions These data suggest that the POLAR genomic signature may be used to identify patients with a low risk of locoregional recurrence without significant benefit from adjuvant radiotherapy. Patients with low POLAR scores may potentially be candidates for radiation therapy omission when treated with breast conserving surgery and tamoxifen.

Citation Format: Anthony Fyles, S. Laura Chang, Katrina Rey-McIntyre, Wei Shi, Felix Feng, Corey Speers, Lori Pierce, David McCready, Fei-Fei Liu. Validation of a 16-gene genomic signature to identify early-stage invasive breast cancer patients who may omit radiotherapy [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-08-01.

The Michigan Radiation Oncology Quality Consortium: A Novel Initiative to Improve the Quality of Radiation Oncology Care

PURPOSE

Numerous quality measures have been proposed in radiation oncology, and initiatives to improve access to high-complexity care, quality, and equity are needed. We describe the design and evaluate impact of a voluntary statewide collaboration for quality improvement in radiation oncology initiated a decade ago.

METHODS AND MATERIALS

We evaluate compliance before and since implementation of annual metrics for quality improvement, using an observational dataset with information from over 20,000 patients treated in the 28 participating radiation oncology practices. At thrice-yearly meetings, experts have spoken regarding trends within the field and inspired discussions regarding potential targets for quality improvement. Blinded data on practices at various sites have been provided. Following Standards for Quality Improvement Reporting Excellence (SQUIRE) guidelines, we describe the approach and measures the program has implemented. To evaluate impact, we compare compliance at baseline and now with active measures using mixed effects regression models with site-level random effects.

RESULTS

Compliance has increased, including use of guideline-concordant hypofractionated radiotherapy, doses to targets/normal tissues, motion management, and consistency in delineating and naming contoured structures (a precondition for quality evaluation). For example, use of guideline-concordant hypofractionation for breast cancer increased from 47% to 97%, adherence to target coverage goals and heart dose limits for dose increased from 46% to 86%, motion assessment in patients with lung cancer increased from 52% to 94%, and use of standard nomenclature increased from 53% to 82% for lung patients and from 80% to 94% for breast patients (all p<0.001).

CONCLUSIONS

Although observational analysis cannot fully exclude secular trends, contextual data revealing slow uptake of best practices elsewhere in the US and qualitative feedback from participants suggests that this initiative has improved the consistency, efficiency, and quality of radiation oncology care in its member practices and may be a model for oncology quality improvement more generally.

Trastuzumab for early-stage, HER2-positive breast cancer: a meta-analysis of 13 864 women in seven randomised trials

BACKGROUND

Trastuzumab targets the extracellular domain of the HER2 protein. Adding trastuzumab to chemotherapy for patients with early-stage, HER2-positive breast cancer reduces the risk of recurrence and death, but is associated with cardiac toxicity. We investigated the long-term benefits and risks of adjuvant trastuzumab on breast cancer recurrence and cause-specific mortality.

METHODS

We did a collaborative meta-analysis of individual patient data from randomised trials assessing chemotherapy plus trastuzumab versus the same chemotherapy alone. Randomised trials that enrolled women with node-negative or node-positive, operable breast cancer were included. We collected individual patient-level data on baseline characteristics, dates and sites of first distant breast cancer recurrence and any previous local recurrence or second primary cancer, and the date and underlying cause of death. Primary outcomes were breast cancer recurrence, breast cancer mortality, death without recurrence, and all-cause mortality. Standard intention-to-treat log-rank analyses, stratified by age, nodal status, oestrogen receptor (ER) status, and trial yielded first-event rate ratios (RRs).

FINDINGS

Seven randomised trials met the inclusion criteria, and included 13 864 patients enrolled between February, 2000, and December, 2005. Mean scheduled treatment duration was 14·4 months and median follow-up was 10·7 years (IQR 9·5 to 11·9). The risks of breast cancer recurrence (RR 0·66, 95% CI 0·62 to 0·71; p<0·0001) and death from breast cancer (0·67, 0·61 to 0·73; p<0·0001) were lower with trastuzumab plus chemotherapy than with chemotherapy alone. Absolute 10-year recurrence risk was reduced by 9·0% (95% CI 7·4 to 10·7; p<0·0001) and 10-year breast cancer mortality was reduced by 6·4% (4·9 to 7·8; p<0·0001), with a 6·5% reduction (5·0 to 8·0; p<0·0001) in all-cause mortality, and no increase in death without recurrence (0·4%, -0·3 to 1·1; p=0·35). The proportional reduction in recurrence was largest in years 0-1 after randomisation (0·53, 99% CI 0·46 to 0·61), with benefits persisting through years 2-4 (0·73, 0·62 to 0·85) and 5-9 (0·80, 0·64 to 1·01), and little follow-up beyond year 10. Proportional recurrence reductions were similar irrespective of recorded patient and tumour characteristics, including ER status. The more high risk the tumour, the larger the absolute reductions in 5-year recurrence (eg, 5·7% [95% CI 3·1 to 8·3], 6·8% [4·7 to 9·0], and 10·7% [7·7 to 13·6] in N0, N1-3, and N4+ disease).

INTERPRETATION

Adding trastuzumab to chemotherapy for early-stage, HER2-positive breast cancer reduces recurrence of, and mortality from, breast cancer by a third, with worthwhile proportional reductions irrespective of recorded patient and tumour characteristics.

FUNDING

Cancer Research UK, UK Medical Research Council.

Racial and Socioeconomic Disparities in Breast Cancer Outcomes within the AJCC Pathologic Prognostic Staging System

BACKGROUND

Non-Hispanic black (NHB) women and those of lower socioeconomic status (SES) have inferior breast cancer outcomes compared with non-Hispanic white (NHW) women and those of higher SES. We examined racial and SES disparities in breast cancer survival within the AJCC 8th edition pathologic prognostic staging system.

METHODS

Using the Surveillance, Epidemiology and End Results Program, we identified patients diagnosed with invasive breast cancer from 2010 to 2015, with follow-up through 2016. Census tract-level SES (cSES) data were available as a composite index and analyzed in quintiles. Cox proportional-hazards survival analyses adjusted for age, race, cSES, insurance, marital status, histology, pathologic prognostic stage, and treatment were used to estimate disease-specific survival (DSS).

RESULTS

A total of 259,852 patients were included: 176,369 (67.9%) NHW; 28,510 (11.0%) NHB; 29,737 (11.4%) Hispanic; and 22,887 (8.8%) Asian. NHB race and lower cSES were associated with increased incidence of triple-negative disease compared with NHW (p < 0.01). NHB race, lower cSES, public insurance, lower education, and increased poverty were associated with lower DSS. Survival analyses adjusting for cSES, tumor, and treatment characteristics demonstrated that NHB patients had inferior DSS within each AJCC pathologic prognostic stage (hazard ratio [HR] 1.25, 95% confidence interval [CI] 1.20-1.30) compared with NHW patients. Fully adjusted models also showed patients residing in lower SES counties had inferior DSS.

CONCLUSIONS

Racial and cSES disparities in breast cancer-specific mortality were evident across all stages, even within the pathologic prognostic staging system which incorporates tumor biology. Future efforts should assess the biological, behavioral, social, and environmental determinants that underlie racial and SES inequities in outcomes.

Predictors of Pneumonitis After Conventionally Fractionated Radiotherapy for Locally Advanced Lung Cancer

PURPOSE

Multiple factors influence the risk of developing pneumonitis after radiation therapy (RT) for lung cancer, but few resources exist to guide clinicians in predicting risk in an individual patient treated with modern techniques. We analyzed toxicity data from a state-wide consortium to develop an integrated pneumonitis risk model.

METHODS AND MATERIALS

All patients (N = 1302) received conventionally fractionated RT for stage II-III non-small cell lung cancer between April 2012 and July 2019. Pneumonitis occurring within 6 months of treatment was graded by local practitioners and collected prospectively from 27 academic and community clinics participating in a state-wide quality consortium. Pneumonitis was modeled as either grade ≥2 (G2+) or grade ≥3 (G3+). Logistic regression models were fit to quantify univariable associations with dose and clinical factors, and stepwise Akaike information criterion-based modeling was used to build multivariable prediction models.

RESULTS

The overall rate of pneumonitis of any grade in the 6 months following RT was 16% (208 cases). Seven percent of cases (n = 94) were G2+ and <1% (n = 11) were G3+. Adjusting for incomplete follow-up, estimated rates for G2+ and G3+ were 14% and 2%, respectively. In univariate analyses, gEUD, V5, V10, V20, V30, and mean lung dose (MLD) were positively associated with G2+ pneumonitis risk, whereas current smoking status was associated with lower odds of pneumonitis. G2+ pneumonitis risk of ≥22% was independently predicted by MLD of ≥20 Gy, V20 of ≥35%, and V5 of ≥75%. In multivariate analyses, the lung V5 metric remained a significant predictor of G2+ pneumonitis, even when controlling for MLD, despite their close correlation. For G3+ pneumonitis, MLD and V20 were statistically significant predictors. Number of patient comorbidities was an independent predictor of G3+, but not G2+ pneumonitis.

CONCLUSIONS

We present an analysis of pneumonitis risk after definitive RT for lung cancer using a large, prospective dataset. We incorporate comorbidity burden, smoking status, and dosimetric parameters in an integrated risk model. These data may guide clinicians in assessing pneumonitis risk in individual patients.

Abstract PD4-07: Contemporary practice patterns for the use of regional nodal irradiation during post-lumpectomy radiotherapy for patients with N0/N1 breast cancer

BACKGROUND: Current national guidelines encourage consideration for treating the at-risk regional nodes (axillary, supraclavicular, and/or internal mammary) with directed regional nodal irradiation (RNI) during post-lumpectomy radiotherapy for high risk N0 (node negative) and N1 (1-3 nodes positive) breast cancer patients. This recommendation is based on the results of several randomized trials published over the last decade. Evidence regarding translation of these trials into clinical practice in the United States has been limited to date. In this study, we sought to characterize the temporal changes in and clinical factors associated with the utilization of RNI during post-lumpectomy radiotherapy for N0-N1 breast cancer across a contemporary, statewide consortium of radiation oncology practices.

METHODS: Within a statewide radiation oncology quality consortium, 12,170 breast cancer patients were consecutively enrolled between 1/1/2013 and 10/31/2019 in both academic (teaching) and community (non-teaching) facilities. Data on receptor status, adjuvant systemic therapy, age, TNM stage, extent of axillary surgery, race, body mass index (BMI), type of treating facility, and year completing radiotherapy (RT) were collected. Eligibility for the present analysis was limited to patients with N0 and N1 disease not receiving neoadjuvant systemic therapy and receiving adjuvant radiotherapy after lumpectomy for non-metastatic breast cancer. Multiple variable logistic regression models were separately fit to explain the use of directed RNI (to the axilla, supraclavicular region, and/or internal mammary region) for the N0 and N1 populations separately and described using odds ratios (OR), with significant ORs (p&lt;0.05) reported.

RESULTS: A total of 8,468 patients from 29 treating facilities met the inclusion criteria: 6,929 (81.8%) with N0 and 1,539 (18.2%) N1 disease. RNI was performed in addition to whole breast radiation in 95 (1.4%) and 908 (59%) patients in the N0 and N1 cohorts respectively. For the N0 cohort, significant correlates of RNI on multivariable analysis (MVA) were receipt of adjuvant chemotherapy (OR 2.7), higher T-stage (OR 1.9 for T2 vs T1 and 27.3 for T3/T4 vs T1), axillary surgery [compared to sentinel node biopsy (SLN) alone : no axillary surgery (OR 14.5), axillary lymph node dissection (ALND) with 10+ nodes removed (OR 15.1) ALND after SLN (OR 2.7)], and underweight BMI (OR 4.9 compared to overweight, which was the reference as the largest BMI category). For the N1 cohort, MVA suggested adjuvant chemotherapy (OR 1.8) and larger tumors (OR 1.6 [T2 vs T1]) were significantly associated with use of RNI. The year completing RT was also significantly associated with RNI use, with 22% and 15% increases per year from 2013 to 2019 in the N0 and N1 cohorts, respectively. Lastly, receiving treatment in an academic facility compared to a community facility was significantly associated with receipt of RNI in both the N0 (OR 1.8) and N1 (OR 2.2) cohorts.

CONCLUSION: In this large cohort, selective use of RNI added to post-lumpectomy whole breast radiotherapy is estimated to have increased over time, suggesting growing implementation of recent trial data and current clinical practice guidelines. Patient, treatment, and tumor characteristics appear to factor into the decision to treat with RNI, but differences in use between academic and community practices suggest opportunities for improving the consistency of care across care delivery settings. Ongoing trials seeking to identify subgroups of N1 patients in whom RNI can safely be omitted may be especially important to inform decisions, given the almost even split (59% receiving, 41% not) in practice observed in this large American cohort.

Citation Format: Derek Bergsma, Kent Griffith, Reshma Jagsi, Michael Dominello, Thomas Boike, Joshua Dilworth, Amit Bhatt, Frank Vicini, Maggie Grubb, Jean Moran, James Hayman, Lori Pierce, on behalf of MROQC, the Michigan Radiation Oncology Quality Consortium. Contemporary practice patterns for the use of regional nodal irradiation during post-lumpectomy radiotherapy for patients with N0/N1 breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD4-07.

Delivering Cancer Care During the COVID-19 Pandemic: Recommendations and Lessons Learned From ASCO Global Webinars

PURPOSE

In response to the COVID-19 pandemic, the ASCO launched a Global Webinar Series to address various aspects of cancer care during the pandemic. Here we present the lessons learned and recommendations that have emerged from these webinars.

METHODS

Fifteen international health care experts from different global regions and oncology disciplines participated in one of the six 1-hour webinars to discuss the latest data, share their experiences, and provide recommendations to manage cancer care during the COVID-19 pandemic. These sessions include didactic presentations followed by a moderated discussion and questions from the audience. All recommendations have been transcribed, categorized, and reviewed by the experts, who have also approved the consensus recommendations.

RESULTS

The summary recommendations are divided into different categories, including risk minimization; care prioritization of patients; health care team management; virtual care; management of patients with cancer undergoing surgical, radiation, and systemic therapy; clinical research; and recovery plans. The recommendations emphasize the protection of patients and health care teams from infections, delivery of timely and appropriate care, reduction of harm from the interruption of care, and preparation to handle a surge of new COVID-19 cases, complications, or comorbidities thereof.

CONCLUSION

The recommendations from the ASCO Global Webinar Series may guide practicing oncologists to manage their patients during the ongoing pandemic and help organizations recover from the crisis. Implementation of these recommendations may improve understanding of how COVID-19 has affected cancer care and increase readiness to manage the current and any future outbreaks effectively.

Abstract 6273: TTK inhibition radiosensitizes basal-like breast cancer through impaired homologous recombination

Background: Basal-like breast cancer (BC) has the highest rates of local recurrence despite the use of radiation therapy. Therefore, approaches for radiosensitization are critically needed for patients with this subtype of BC.

Methods: Four independent datasets were used to correlate gene expression with local recurrence (LR) and Kaplan-Meier analysis validated the impact of TTK expression on LR. The METABRIC dataset was used to determine TTK expression in BC subtypes. Clonogenic survival assays were used to determine the radiosensitization of cell lines after TTK inhibition (TTKi). Mouse models were used to assess TTKi in combination with RT in vivo. DNA damage was quantified using γH2AX staining. HR and NHEJ efficiency assays were performed using HR/NHEJ specific reporter systems. HR competency was also assessed using Rad51 foci formation assays. Rescue experiments were performed using wild-type (WT) and kinase-dead (KD) TTK plasmids in combination with siRNA targeting the UTR region of TTK.

Results: Ten genes were found to significantly correlate with early LR (≤3 years) after surgery and radiation across 4 independent datasets (N=896 pts), with TTK, a cell cycle kinase, ranked the highest. Kaplan-Meier survival analysis in multiple cohorts demonstrated that higher than median TTK expression correlates with decrease LR free survival after RT (HR 1.70-2.42, p&lt;0.01 for all 3 cohorts). Subtype association analysis demonstrated that TTK expression was most elevated in basal-like BC. Using inducible shRNA, the combination of TTK knockdown and RT increases radiosensitivity in multiple basal-like BC cell lines (rER 1.21-1.63). Additionally, TTKi using, Bayer 1161909 (B909), enhanced radiosensitivity in multiple cell lines (rER 1.10-2.27). In vivo, TTKi, using shRNA or B909, in combination with RT led to delayed tumor growth and a significant increase in time to tumor tripling (Placebo: 9 days vs. B909+RT: undefined [&gt;35 days], p&lt;0.0001) in both cell line and PDX models. Increased DNA damage was found after combination treatment of TTKi and RT compared to RT alone, indicating that DNA damage repair mechanisms may be compromised by TTKi. The efficiency of the double strand DNA damage repair mechanism, homologous recombination (HR), but not non-homologous end joining (NHEJ), was reduced upon TTKi in HR/NHEJ specific reporter systems. Additionally, Rad51 foci formation was reduced by TTKi after RT compared to RT alone. Reintroduction of WT TTK, after knockdown of endogenous TTK, rescued radioresistance and HR efficiency, however, reintroduction of kinase-dead (KD) TTK was unable to do so in multiple cell lines. WT TTK also rescued Rad51 foci formation after knockdown of endogenous TTK while KD TTK did not.

Conclusion: These data support TTKi as a radiosensitizing strategy for clinical development in basal-like BC patients and that radiosensitization is mediated, at least in part, through impaired HR repair.

Citation Format: Benjamin Chandler, Leah Moubadder, Cassandra Ritter, Meilan Liu, Meleah Cameron, Kari Wilder-Romans, Amanda Zhang, Andrea Pesch, Anna Michmerhuizen, Nicole Hirsh, Marlie Androsiglio, Tanner Ward, Eric Olsen, Yashar Niknafs, Sofia Merajver, Dafydd Thomas, Powel Brown, Theodore Lawrence, Shyam Nyati, Lori Pierce, Arul Chinnaiyan, Corey Speers. TTK inhibition radiosensitizes basal-like breast cancer through impaired homologous recombination [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6273.

Abstract PD6-6: Identifying patients at higher risk of toxicity after breast radiotherapy: Analysis of patient-reported outcomes in the Michigan Radiation Oncology Quality Consortium cohort

Objective: Patient-reported toxicities after breast radiotherapy merit understanding in order to inform decisions and target supportive care interventions.

Methods: As part of a collaborative quality improvement initiative, the Michigan Radiation Oncology Quality Consortium prospectively collects patient-reported outcomes data from women treated for breast cancer at 26 practices across the state. Of all 11,107 patients treated with lumpectomy and whole breast radiation therapy between 1/1/2012 and 12/31/2018, 2817 refused patient surveys. We describe here the maximal toxicity reported by the 7689 patients who provided survey responses within 7 days of end of treatment and for whom we had sufficient data to determine dose-fractionation and treatment fields. Multivariable logistic regression models separately identified the individual and treatment characteristics associated with 1) breast pain, 2) a bother scale (related to itching, stinging/burning, swelling, or hurting of the treated breast), and 3) fatigue. Breast pain was considered moderate or severe when score ≥4 on modified 10-point Brief Pain Inventory measure. Bother from multiple breast symptoms was considered frequent when score ≥3 on a scaled measure (range 0-4) averaging responses on four items derived from the Skindex. Fatigue was considered severe when rated as present “always” or “most of the time” over past four weeks.

Results: Moderate or severe breast pain was reported by 2882 (37.5%) overall: 1022 (28.3%) of those receiving hypofractionation (HF) and 1860 (45.7%) of those receiving conventional fractionation (CF). Frequent bother from multiple breast symptoms was reported by 1029 (13.4%) overall: 288 (8.0%) after HF and 741 (18.2%) after CF. Severe fatigue was reported by 1795 (23.4%) overall: 681 (18.8%) after HF and 1114 (27.4%) after CF. In addition to treatment fractionation (p&lt;0.001), younger age, higher BMI, and smoking were highly significant (p&lt;0.001) predictors of all three forms of toxicity, as detailed in the Table. Black race (p&lt;0.001) independently predicted greater breast pain (OR 1.9) and breast symptom bother (OR 1.6). Receipt of boost treatment also predicted greater breast pain (p=0.0006) and bother (p=0.04).

Conclusions: In this large observational dataset of patient-reported toxicities after whole breast radiotherapy, substantial differences existed by radiotherapy dose-fractionation. Race differences in breast pain and bother existed despite controlling for multiple other factors, including age, body habitus, comorbidities, and treatment characteristics; further research is needed to understand what drives these differences in order to target potentially modifiable factors. Intensification of supportive care may be appropriate for subgroups identified as being vulnerable to greater toxicity.

Multivariable Models of Patient-Reported Toxicity OutcomesIndependent VariableOdds Ratio (CI) [p value] in Model with Dependent Variable=Moderate or Severe Breast PainOdds Ratio (CI) [p value] in Model with Dependent Variable=Frequent Bother from Multiple Breast SymptomsOdds Ratio (CI) [p value] in Model with Dependent Variable=Severe FatigueAge 70+ vs 60-690.77 (0.67 - 0.89) [p&lt;0.001]0.63 (0.48 - 0.81) [p&lt;0.001]0.99 (0.84 - 1.16) [p&lt;0.001]Age 50-59 vs 60-691.49 (1.32 - 1.69)1.82 (1.52 - 2.17)1.34 (1.17 - 1.54)Age &lt;50 vs 60-691.90 (1.63 - 2.21)2.66 (2.17 - 3.25)1.44 (1.21 - 1.71)BMI: Normal 18.5-&lt;25 vs Overweight 25-&lt;300.78 (0.68 - 0.90) [p&lt;.0001]0.89 (0.72 - 1.09) [p&lt;.0001]0.74 (0.63 - 0.87) [p&lt;.0001]BMI: Obesity I 30-&lt;35 vs Overweight 25-&lt;301.32 (1.15 - 1.51)1.15 (0.94 - 1.40)1.22 (1.04 - 1.41)BMI: Obesity II 35-&lt;40 vs Overweight 25-&lt;301.50 (1.28 - 1.77)1.61 (1.29 - 2.01)1.34 (1.12 - 1.61)BMI: Obesity III &gt;40 vs Overweight 25-&lt;302.14 (1.79 - 2.57)1.86 (1.47 - 2.36)1.59 (1.31 - 1.94)BMI: Underweight &lt;18.5 vs Overweight 25-&lt;300.98 (0.68 - 1.42)0.82 (0.46 - 1.46)1.08 (0.72 - 1.62)Race: Black vs White1.94 (1.70 - 2.21) [p&lt;.0001]1.58 (1.33 - 1.87) [p&lt;.0001]0.96 (0.83 - 1.12) [p=0.88]Race: Asian vs White1.32 (0.89 - 1.96)0.84 (0.46 - 1.52)1.15 (0.74 - 1.80)Race: Other vs White1.74 (1.24 - 2.45)1.94 (1.31 - 2.90)1.01 (0.68 - 1.51)Hypertension: Yes vs No0.95 (0.84 - 1.06) [p=0.33]0.92 (0.78 - 1.08) [p=0.28]1.09 (0.96 - 1.24) [p=0.17]Diabetes: Yes vs No1.25 (1.08 - 1.44) [p=0.003]1.22 (1.00 - 1.49) [p=0.05]1.29 (1.10 - 1.51) [p=0.0015]Smoking Status: Former smoker vs Never smoker1.25 (1.12 - 1.39) [p&lt;.0001]1.33 (1.14 - 1.55) [p&lt;.0001]1.12 (0.99 - 1.27) [p&lt;.0001]Smoking Status: Current smoker vs Never smoker1.65 (1.41 - 1.93)2.02 (1.66 - 2.46)1.59 (1.34 - 1.89)Fractionation: Conventional vs Hypofractionation1.67 (1.49 - 1.86) [p&lt;.0001]1.85 (1.58 - 2.17) [p&lt;.0001]1.51 (1.34 - 1.71) [p&lt;.0001]Boost: Boost vs No boost1.30 (1.12 - 1.51) [p=0.0006]1.29 (1.01 - 1.65) [p=0.04]1.00 1.00 (0.84 - 1.18) [p=0.96]SCV Nodal field treatment: Yes vs No1.02 (0.87 - 1.20) [p=0.81]1.11 (0.91 - 1.36) [p=0.30]0.86 (0.71 - 1.03) [p=0.10]

Citation Format: Reshma Jagsi, Kent Griffith, Frank Vicini, Jay Burmeister, Michael Dominello, Inga Grills, James Hayman, Jean Moran, Peter Paximadis, Jeffrey Radawski, Eleanor Walker, Lori Pierce. Identifying patients at higher risk of toxicity after breast radiotherapy: Analysis of patient-reported outcomes in the Michigan Radiation Oncology Quality Consortium cohort [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr PD6-6.

Increasing the dose intensity of chemotherapy by more frequent administration or sequential scheduling: a patient-level meta-analysis of 37 298 women with early breast cancer in 26 randomised trials

BACKGROUND

Increasing the dose intensity of cytotoxic therapy by shortening the intervals between cycles, or by giving individual drugs sequentially at full dose rather than in lower-dose concurrent treatment schedules, might enhance efficacy.

METHODS

To clarify the relative benefits and risks of dose-intense and standard-schedule chemotherapy in early breast cancer, we did an individual patient-level meta-analysis of trials comparing 2-weekly versus standard 3-weekly schedules, and of trials comparing sequential versus concurrent administration of anthracycline and taxane chemotherapy. The primary outcomes were recurrence and breast cancer mortality. Standard intention-to-treat log-rank analyses, stratified by age, nodal status, and trial, yielded dose-intense versus standard-schedule first-event rate ratios (RRs).

FINDINGS

Individual patient data were provided for 26 of 33 relevant trials identified, comprising 37 298 (93%) of 40 070 women randomised. Most women were aged younger than 70 years and had node-positive disease. Total cytotoxic drug usage was broadly comparable in the two treatment arms; colony-stimulating factor was generally used in the more dose-intense arm. Combining data from all 26 trials, fewer breast cancer recurrences were seen with dose-intense than with standard-schedule chemotherapy (10-year recurrence risk 28·0% vs 31·4%; RR 0·86, 95% CI 0·82-0·89; p<0·0001). 10-year breast cancer mortality was similarly reduced (18·9% vs 21·3%; RR 0·87, 95% CI 0·83-0·92; p<0·0001), as was all-cause mortality (22·1% vs 24·8%; RR 0·87, 95% CI 0·83-0·91; p<0·0001). Death without recurrence was, if anything, lower with dose-intense than with standard-schedule chemotherapy (10-year risk 4·1% vs 4·6%; RR 0·88, 95% CI 0·78-0·99; p=0·034). Recurrence reductions were similar in the seven trials (n=10 004) that compared 2-weekly chemotherapy with the same chemotherapy given 3-weekly (10-year risk 24·0% vs 28·3%; RR 0·83, 95% CI 0·76-0·91; p<0·0001), in the six trials (n=11 028) of sequential versus concurrent anthracycline plus taxane chemotherapy (28·1% vs 31·3%; RR 0·87, 95% CI 0·80-0·94; p=0·0006), and in the six trials (n=6532) testing both shorter intervals and sequential administration (30·4% vs 35·0%; RR 0·82, 95% CI 0·74-0·90; p<0·0001). The proportional reductions in recurrence with dose-intense chemotherapy were similar and highly significant (p<0·0001) in oestrogen receptor (ER)-positive and ER-negative disease and did not differ significantly by other patient or tumour characteristics.

INTERPRETATION

Increasing the dose intensity of adjuvant chemotherapy by shortening the interval between treatment cycles, or by giving individual drugs sequentially rather than giving the same drugs concurrently, moderately reduces the 10-year risk of recurrence and death from breast cancer without increasing mortality from other causes.

FUNDING

Cancer Research UK, Medical Research Council.

Abstract P5-15-02: Evaluating the cost of endocrine therapy vs. radiation therapy alone for low risk hormone positive early stage breast cancer in elderly patients

Objective: Elderly patients with low-risk hormone-positive breast cancer are at risk of over treatment. Avoidance of radiation therapy (RT) in favor of endocrine therapy alone was first heralded as the optimal conservative strategy due to logistical simplicity, low acute sequelae and a reduction of contralateral cancers not seen with RT. However, long-term use of aromatase inhibitors (AI) is not without costs and morbidity, often leading to low compliance and notable late effects. We therefore performed a cost-effectiveness analysis to compare the outcomes and costs between AI for five years without RT versus hypofractionated RT alone without endocrine therapy.

Materials and Methods: Using data from available phase III trials and meta-analyses, we constructed a patient-level microsimulation Markov decision model to replicate the comparative outcomes between the strategies above from the societal perspective among 200,000 simulated patients. Five years of anastrozole was compared to a 15-fraction hypofractionated whole breast RT course without boost in a cohort of patients with low-risk disease as defined by CALGB 9343 entry criteria. Noncompliance with AI was modeled from recent population-based data. Relative effectiveness on ipsilateral breast tumor recurrence and contralateral breast cancers were based off the NSABP B-21 trial, adjusted to match the modern outcomes demonstrated in CALGB 9343 and PRIME II with further adjustment for AI over tamoxifen (ATAC, EBCTCG meta-analysis). Indirect costs of travel were accounted for, as were the costs of common and serious side-effects from RT (dermatitis, fibrosis, second malignancy, heart disease) and AI (arthralgia, hot flashes, osteopenia, fracture, thrombosis). A 1-year cycle time and lifetime horizon were used, with all costs adjusted to 2018 US dollars and extracted primarily from Medicare reimbursement data. The primary measure of efficacy was the quality-adjusted life-year (QALY) with age-adjusted utilities extracted from the literature. Half-cycle correction and a 3% discount rate were applied. Probabilistic sensitivity analysis was used to vary all parameters simultaneously.

Results: On average, RT was approximately $3,981 more expensive than endocrine therapy over the lifetime horizon. Under a number of assumptions, RT appeared similar in long-term effectiveness to AI therapy, with a difference of less than 0.03 quality-adjusted life years. Given the low value of the denominator in the incremental cost-effectiveness ratio (ICER), RT did not meet the formally defined $100,000/QALY threshold. On one-way sensitivity analysis, the ICER was particularly sensitive to the incidence and impact of salvage strategies for recurrence, treatment of contralateral breast cancers, cardiac events and fracture rates.

Conclusions: Modeling with the available evidence suggests it is likely that quality-of-life after RT-alone is nearly identical to an AI-alone strategy but associated with a small increase in cost. These results suggest select patients at risk of noncompliance can safely be treated with RT-alone rather than AI alone. Given the relative pros and cons of each strategy, RT-alone should be considered for select elderly low-risk breast patients.

Citation Format: Ward MC, Vicini F, Chadha M, Pierce L, Recht A, Hayman J, Thaker N, Khan A, Keisch M, Shah C. Evaluating the cost of endocrine therapy vs. radiation therapy alone for low risk hormone positive early stage breast cancer in elderly patients [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-15-02.

A Randomized Comparison of Radiation Therapy Techniques in the Management of Node-Positive Breast Cancer: Primary Outcomes Analysis

PURPOSE

Although inverse-planned intensity modulated radiotherapy (IMRT) and deep inspiration breath hold (DIBH) may allow for more conformal dose distributions, it is unknown whether using these technologies reduces cardiac or pulmonary toxicity of breast radiotherapy.

METHODS AND MATERIALS

A randomized controlled trial compared IMRT-DIBH versus standard, free-breathing, forward-planned, three-dimensional conformal radiotherapy in patients with left-sided, node-positive breast cancer in whom the internal mammary nodal region was targeted. Endpoints included dosimetric parameters and changes in pulmonary and cardiac perfusion and function, measured by single photon emission computed tomography (SPECT) scans and pulmonary function testing performed at baseline and 1 year post treatment.

RESULTS

Of 62 patients randomized, 54 who completed all follow-up procedures were analyzed. Mean doses to the ipsilateral lung, left ventricle, whole heart, and left anterior descending coronary artery were lower with IMRT-DIBH; the percent of left ventricle receiving ≥5 Gy averaged 15.8% with standard radiotherapy and 5.6% with IMRT-DIBH (P < .001). SPECT revealed no differences in perfusion defects in the left anterior descending coronary artery territory, the study's primary endpoint, but did reveal statistically significant differences (P = .02) in left ventricular ejection fraction (LVEF), a secondary endpoint. No differences were found for lung perfusion or function.

CONCLUSION

The small but statistically significant benefit in preservation of cardiac LVEF observed here should motivate future studies that include LVEF as a potentially meaningful endpoint. Future studies should disaggregate the impact of IMRT from that of DIBH. Clinical practice should recognize the importance of minimizing cardiac dose, even when already low in comparison to historical levels.

Dosimetric predictors for acute esophagitis during radiation therapy for lung cancer: Results of a large statewide observational study

PURPOSE

The purpose of this study is to identify dosimetric variables that best predict for acute esophagitis in patients treated for locally advanced non-small cell lung cancer in a prospectively accrued statewide consortium.

METHODS AND MATERIALS

Patients receiving definitive radiation therapy for stage II-III non-small cell lung cancer within the Michigan Radiation Oncology Quality Consortium were included in the analysis. Dose-volume histogram data were analyzed to determine absolute volumes (cc) receiving doses from 10 to 60 Gy (V10, V20, V30, V40, V50, and V60), as well as maximum dose to 2 cc (D2cc), mean dose (MD), and generalized equivalent uniform dose (gEUD). Logistic regression models were used to characterize the risk of toxicity as a function of dose and other covariates. The ability of each variable to predict esophagitis, individually or in a multivariate model, was quantified by receiver operating characteristic analysis.

RESULTS

There were 533 patients who met study criteria and were included; 437 (81.9%) developed any grade of esophagitis. Significant variables on univariate analysis for grade ≥2 esophagitis were concurrent chemotherapy, V20, V30, V40, V50, V60, MD, D2cc, and gEUD. For grade ≥3 esophagitis, the predictive variables were: V30, V40, V50, V60, MD, D2cc, and gEUD. In multivariable modeling, gEUD was the most significant predictor of both grade ≥2 and grade ≥3 esophagitis. When gEUD was excluded from the model, D2cc was selected as the most predictive variable for grade ≥3 esophagitis. For an estimated risk of grade ≥3 esophagitis of 5%, the threshold values for gEUD and D2cc were 59.3 Gy and 68 Gy, respectively.

CONCLUSIONS

In this study, we report the novel finding that gEUD and D2cc, rather than MD, were the most predictive dose metrics for severe esophagitis. To limit the estimated risk of grade ≥3 esophagitis to <5%, thresholds of 59.3 Gy and 68 Gy were identified for gEUD and D2cc, respectively.

Concurrent Veliparib With Chest Wall and Nodal Radiotherapy in Patients With Inflammatory or Locoregionally Recurrent Breast Cancer: The TBCRC 024 Phase I Multicenter Study

Purpose Locoregional control for inflammatory breast cancers and chest wall recurrences is suboptimal, which has motivated interest in radiosensitization to intensify therapy. Preclinical studies have suggested a favorable therapeutic index when poly (ADP-ribose) polymerase inhibitors are used as radiosensitizers; clinical investigation is necessary to establish appropriate dosing and confirm safety. Patients and Methods We conducted a multi-institutional phase I study of veliparib and concurrent radiotherapy (RT) to the chest wall and regional lymph nodes in 30 patients with inflammatory or locally recurrent breast cancer after complete surgical resection. RT consisted of 50 Gy to the chest wall and regional lymph nodes plus a 10-Gy boost. A Bayesian time-to-event continual reassessment method escalated dose through four levels, with a 30% targeted rate of dose-limiting toxicity (DLT) measured during the 6 weeks of treatment plus 4 weeks of follow-up. DLTs were defined as confluent moist desquamation > 100 cm², nonhematologic toxicity grade ≥ 3, toxicity that requires an RT dose delay > 1 week, absolute neutrophil count < 1,000/mm³, platelet count < 50,000/mm³, or hemoglobin < 8.0 g/dL if possibly, probably, or definitely related to study treatment. Results Five DLTs occurred: Four were moist desquamation (two each at 100 and 150 mg twice a day), and one was neutropenia (at 200 mg twice a day). The crude rate of any grade 3 toxicity (regardless of attribution) was 10% at year 1, 16.7% at year 2, and 46.7% at year 3. At year 3, six of 15 surviving patients had severe fibrosis in the treatment field. Conclusion Although severe acute toxicity did not exceed 30% even at the highest tested dose, nearly half of surviving patients demonstrated grade 3 adverse events at 3 years, which underscores the importance of long-term monitoring of toxicity in trials of radiosensitizing agents.

Long-term outcomes for neoadjuvant versus adjuvant chemotherapy in early breast cancer: meta-analysis of individual patient data from ten randomised trials

BACKGROUND

Neoadjuvant chemotherapy (NACT) for early breast cancer can make breast-conserving surgery more feasible and might be more likely to eradicate micrometastatic disease than might the same chemotherapy given after surgery. We investigated the long-term benefits and risks of NACT and the influence of tumour characteristics on outcome with a collaborative meta-analysis of individual patient data from relevant randomised trials.

METHODS

We obtained information about prerandomisation tumour characteristics, clinical tumour response, surgery, recurrence, and mortality for 4756 women in ten randomised trials in early breast cancer that began before 2005 and compared NACT with the same chemotherapy given postoperatively. Primary outcomes were tumour response, extent of local therapy, local and distant recurrence, breast cancer death, and overall mortality. Analyses by intention-to-treat used standard regression (for response and frequency of breast-conserving therapy) and log-rank methods (for recurrence and mortality).

FINDINGS

Patients entered the trials from 1983 to 2002 and median follow-up was 9 years (IQR 5-14), with the last follow-up in 2013. Most chemotherapy was anthracycline based (3838 [81%] of 4756 women). More than two thirds (1349 [69%] of 1947) of women allocated NACT had a complete or partial clinical response. Patients allocated NACT had an increased frequency of breast-conserving therapy (1504 [65%] of 2320 treated with NACT vs 1135 [49%] of 2318 treated with adjuvant chemotherapy). NACT was associated with more frequent local recurrence than was adjuvant chemotherapy: the 15 year local recurrence was 21·4% for NACT versus 15·9% for adjuvant chemotherapy (5·5% increase [95% CI 2·4-8·6]; rate ratio 1·37 [95% CI 1·17-1·61]; p=0·0001). No significant difference between NACT and adjuvant chemotherapy was noted for distant recurrence (15 year risk 38·2% for NACT vs 38·0% for adjuvant chemotherapy; rate ratio 1·02 [95% CI 0·92-1·14]; p=0·66), breast cancer mortality (34·4% vs 33·7%; 1·06 [0·95-1·18]; p=0·31), or death from any cause (40·9% vs 41·2%; 1·04 [0·94-1·15]; p=0·45).

INTERPRETATION

Tumours downsized by NACT might have higher local recurrence after breast-conserving therapy than might tumours of the same dimensions in women who have not received NACT. Strategies to mitigate the increased local recurrence after breast-conserving therapy in tumours downsized by NACT should be considered-eg, careful tumour localisation, detailed pathological assessment, and appropriate radiotherapy.

FUNDING

Cancer Research UK, British Heart Foundation, UK Medical Research Council, and UK Department of Health.

Estimating the Risks of Breast Cancer Radiotherapy: Evidence From Modern Radiation Doses to the Lungs and Heart and From Previous Randomized Trials

Purpose Radiotherapy reduces the absolute risk of breast cancer mortality by a few percentage points in suitable women but can cause a second cancer or heart disease decades later. We estimated the absolute long-term risks of modern breast cancer radiotherapy. Methods First, a systematic literature review was performed of lung and heart doses in breast cancer regimens published during 2010 to 2015. Second, individual patient data meta-analyses of 40,781 women randomly assigned to breast cancer radiotherapy versus no radiotherapy in 75 trials yielded rate ratios (RRs) for second primary cancers and cause-specific mortality and excess RRs (ERRs) per Gy for incident lung cancer and cardiac mortality. Smoking status was unavailable. Third, the lung or heart ERRs per Gy in the trials and the 2010 to 2015 doses were combined and applied to current smoker and nonsmoker lung cancer and cardiac mortality rates in population-based data. Results Average doses from 647 regimens published during 2010 to 2015 were 5.7 Gy for whole lung and 4.4 Gy for whole heart. The median year of irradiation was 2010 (interquartile range [IQR], 2008 to 2011). Meta-analyses yielded lung cancer incidence ≥ 10 years after radiotherapy RR of 2.10 (95% CI, 1.48 to 2.98; P < .001) on the basis of 134 cancers, indicating 0.11 (95% CI, 0.05 to 0.20) ERR per Gy whole-lung dose. For cardiac mortality, RR was 1.30 (95% CI, 1.15 to 1.46; P < .001) on the basis of 1,253 cardiac deaths. Detailed analyses indicated 0.04 (95% CI, 0.02 to 0.06) ERR per Gy whole-heart dose. Estimated absolute risks from modern radiotherapy were as follows: lung cancer, approximately 4% for long-term continuing smokers and 0.3% for nonsmokers; and cardiac mortality, approximately 1% for smokers and 0.3% for nonsmokers. Conclusion For long-term smokers, the absolute risks of modern radiotherapy may outweigh the benefits, yet for most nonsmokers (and ex-smokers), the benefits of radiotherapy far outweigh the risks. Hence, smoking can determine the net effect of radiotherapy on mortality, but smoking cessation substantially reduces radiotherapy risk.

American Society of Clinical Oncology Strategic Plan for Increasing Racial and Ethnic Diversity in the Oncology Workforce

In December 2016, the American Society of Clinical Oncology (ASCO) Board of Directors approved the ASCO Strategic Plan to Increase Racial and Ethnic Diversity in the Oncology Workforce. Developed through a multistakeholder effort led by the ASCO Health Disparities Committee, the purpose of the plan is to guide the formal efforts of ASCO in this area over the next three years (2017 to 2020). There are three primary goals: (1) to establish a longitudinal pathway for increasing workforce diversity, (2) to enhance ASCO leadership diversity, and (3) to integrate a focus on diversity across ASCO programs and policies. Improving quality cancer care in the United States requires the recruitment of oncology professionals from diverse backgrounds. The ASCO Strategic Plan to Increase Racial and Ethnic Diversity in the Oncology Workforce is designed to enhance existing programs and create new opportunities that will move us closer to the vision of achieving an oncology workforce that reflects the demographics of the US population it serves.

Abstract P6-06-05: RadiotypeDx: Identification and validation of a radiation sensitivity signature in human breast cancer

Purpose: An unmet clinical need in breast cancer (BC) management is the identification of which patients will respond to radiation therapy (RT). We hypothesized that the integration of post-RT clonogenic survival data with gene expression data across a large spectrum of BC cell lines would generate a BC-specific RT sensitivity signature predictive for RT response in BC patients and allow identification of patients with tumors refractive to conventional therapy.

Methods: Using clonogenic survival assays, we identified the range of surviving fraction (SF) after 2 Gy of RT across 21 BC cell lines. Using SF as a continuous variable, the RT sensitivity score (RSS) was correlated to gene expression using a Spearman correlation method on an individual gene basis. Genes were selected for the signature based on positive or negative correlation with a p-value &lt;0.05 and FDR of &lt;0.01. Unsupervised hierarchical clustering identified differences in gene expression across resistant and sensitive cell lines to generate a radiation sensitivity (RS) signature. This signature was trained and validated in a separate human breast tumor dataset (185 pts) containing early stage, node-negative patients treated with surgery and RT alone without adjuvant chemotherapy to assess the predictive effect of RS signature on recurrence risk after RT. Gene function and potentially actionable targets from the signature were validated using clongenic survival and DNA damage assays.

Results: Clonogenic survival identifies a range of radiation sensitivity in human BCC lines (SF 77%-17%) with no significant correlation (r value &lt;0.3) to the intrinsic BC subtype. Using Spearmans correlation method, a total of 126 genes were identified as being associated with radiation sensitivity (72 positively correlated, 54 negatively correlated). Unsupervised hierarchical expression discriminates gene expression patterns in the RT resistant and RT sensitive cell lines and is enriched for genes involved in cell cycle arrest and DNA damage response (enrichment p-value 5.0 E-22). Knockdown of genes associated with the radioresistance signature identifies previously unreported radiation resistance genes, including TACC1 and RND3 with enhancement ratios of 1.25 and 1.37 in BCC lines. Application of this RS signature to an independent breast cancer dataset with clinical outcomes validates the signature and accurately identifies patients with decreased rates of recurrence compared to patients with high expression of the radioresistant signature (p-value &lt;0.0001, misclassification error rate .31, 12/13 patients with locoregional recurrence accurately identified).

Conclusion: In this study, we derive a human BC-specific RT sensitivity signature (RadiotypeDx) with biologic relevance from preclinical studies and validate this signature for prediction of recurrence in an independent clinical dataset. The signature is not correlated to the intrinsic subtypes of human breast cancer and thus provides useful information beyond traditional breast cancer subtyping. By identifying patients with tumors refractory to standard RT, this signature has the potential to allow for personalization of radiotherapy, particularly in patients for whom treatment intensification is needed.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-06-05.

Abstract P6-04-04: Maternal embryonic leucine zipper kinase (MELK) is a novel radiosensitizing and therapeutic target and is independently prognostic in triple-negative breast cancer

Background: While effective targeted therapies exist for estrogen receptor (ER)-positive and HER2/neu-positive breast cancer, no such effective therapies exist for ER-negative, PR-negative, and HER2-negative (“triple negative”) cancers. Given the lack of targeted agents for triple negative (TN) disease and their relative radiation insensitivity, it is clear that additional targets for treatment are critically needed.

Our previous work identified one such novel molecular target as maternal embryonic leucine zipper kinase (MELK), and we sought to investigate the impact of MELK expression on radiation response and patient outcomes.

Methods: Using gene expression arrays, we interrogated the expression of MELK in 2,061 breast tumor samples as well as a panel of 51 breast cancer cell lines. We measured protein expression in TN cancers with western blotting and used clonogenic survival assays to quantitate radiosensitivity of BCC lines at baseline and after MELK inhibition. Multiple datasets were used to evaluate the prognostic import of MELK. Kaplan-Meier analysis using local control and survival data was performed. Chi squared scores were calculated to determine significance and hazard ratios (HR) and 95% confidence intervals (CI) were calculated. A Cox proportional hazards model was constructed to identify potential factors of survival.

Results: We demonstrate that MELK expression is significantly elevated in human TN breast cancers, including chemoradiation resistant tumors (305 tumors compared to 1756 non-TN breast tumors; p-value 7.5 e-21). MELK protein and RNA expression is induced by ionizing radiation (5.6-7.5 fold at 72 hours, p-value &lt;0.01). We characterized the radiation sensitivity of BCC lines and demonstrated that MELK expression is significantly correlated with radioresistance (as measured by clonogenic survival) in 21 breast cancer cell lines (R: 0.62, p-value 0.003). Inhibition of MELK using both siRNA and small molecule inhibitors induces radiation sensitivity in vitro with and enhancement ratio (ER) of 1.5-1.6. We demonstrate that high MELK expression is strongly correlated with p53 mutation positive status (p-value &lt;0.001). Finally, local control and survival analyses of patients with BC showed that those patients whose tumors have high expression of MELK have significantly higher rates of LR after radiation and an overall poorer prognosis than patients with low expression of MELK (HR for LR 1.89-2.23, p-value 0.001; HR for overall survival 1.46-3.3; p-value &lt;0.001 in 3 independent datasets). In multivariate analysis of all patients, only MELK expression and grade were significantly associated with worse local recurrence free (LRF) survival with a HR of 1.35 (95% CI 1.05-1.72, p-value &lt; 0.01).

Conclusion: Here, we identify MELK as a potential biomarker of radioresistance and target for radiosensitization in triple negative breast cancers. MELK overexpression was associated with local failure across multiple data sets. MVA identified MELK as the strongest factor associated with poor local control. Our results support the rationale for developing clinical strategies to inhibit MELK as a novel target in triple-negative breast cancer.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-04-04.

Effect of radiotherapy after breast-conserving surgery on 10-year recurrence and 15-year breast cancer death: meta-analysis of individual patient data for 10,801 women in 17 randomised trials

BACKGROUND

After breast-conserving surgery, radiotherapy reduces recurrence and breast cancer death, but it may do so more for some groups of women than for others. We describe the absolute magnitude of these reductions according to various prognostic and other patient characteristics, and relate the absolute reduction in 15-year risk of breast cancer death to the absolute reduction in 10-year recurrence risk.

METHODS

We undertook a meta-analysis of individual patient data for 10,801 women in 17 randomised trials of radiotherapy versus no radiotherapy after breast-conserving surgery, 8337 of whom had pathologically confirmed node-negative (pN0) or node-positive (pN+) disease.

FINDINGS

Overall, radiotherapy reduced the 10-year risk of any (ie, locoregional or distant) first recurrence from 35·0% to 19·3% (absolute reduction 15·7%, 95% CI 13·7-17·7, 2p<0·00001) and reduced the 15-year risk of breast cancer death from 25·2% to 21·4% (absolute reduction 3·8%, 1·6-6·0, 2p=0·00005). In women with pN0 disease (n=7287), radiotherapy reduced these risks from 31·0% to 15·6% (absolute recurrence reduction 15·4%, 13·2-17·6, 2p<0·00001) and from 20·5% to 17·2% (absolute mortality reduction 3·3%, 0·8-5·8, 2p=0·005), respectively. In these women with pN0 disease, the absolute recurrence reduction varied according to age, grade, oestrogen-receptor status, tamoxifen use, and extent of surgery, and these characteristics were used to predict large (≥20%), intermediate (10-19%), or lower (<10%) absolute reductions in the 10-year recurrence risk. Absolute reductions in 15-year risk of breast cancer death in these three prediction categories were 7·8% (95% CI 3·1-12·5), 1·1% (-2·0 to 4·2), and 0·1% (-7·5 to 7·7) respectively (trend in absolute mortality reduction 2p=0·03). In the few women with pN+ disease (n=1050), radiotherapy reduced the 10-year recurrence risk from 63·7% to 42·5% (absolute reduction 21·2%, 95% CI 14·5-27·9, 2p<0·00001) and the 15-year risk of breast cancer death from 51·3% to 42·8% (absolute reduction 8·5%, 1·8-15·2, 2p=0·01). Overall, about one breast cancer death was avoided by year 15 for every four recurrences avoided by year 10, and the mortality reduction did not differ significantly from this overall relationship in any of the three prediction categories for pN0 disease or for pN+ disease.

INTERPRETATION

After breast-conserving surgery, radiotherapy to the conserved breast halves the rate at which the disease recurs and reduces the breast cancer death rate by about a sixth. These proportional benefits vary little between different groups of women. By contrast, the absolute benefits from radiotherapy vary substantially according to the characteristics of the patient and they can be predicted at the time when treatment decisions need to be made.

FUNDING

Cancer Research UK, British Heart Foundation, and UK Medical Research Council.

Electron imaging of pyrrhotite superstructures

Natural pyrrhotites, when studied by high resolution electron microscopy, yield crystallographic information on a unit cell scale. Structural heterogeneity is prominent. The many reported superstructures are interpretable through an antiphase model. The 5C pyrrhotite superstructure results from an ordered sequence of antiphase domains while the higher temperature NC type results from a disordered sequence.