First-line real-world treatment patterns and survival outcomes in women younger or older than 40 years with metastatic breast cancer in the real-life multicenter French ESME cohort.

AIM: To describe first-line treatment patterns, overall survival (OS) and real-world progression-free survival (rwPFS) in young women (<40) with metastatic breast cancer (mBC), as compared to women aged 40-69. MATERIALS AND METHODS: Data on adult women diagnosed with mBC (2008-2017) were extracted from the ESME mBC database (NCT03275311) which includes consecutive patients starting first-line metastatic treatment in one of the 18 French Comprehensive cancer centers. We reported first-line therapeutic strategy and prognostic factors of OS and rwPFS for women aged < 40 and 40-69. RESULTS: In total, 14,897 mBC women were included (1512 aged <40). HR+ /HER2- mBC was the most frequent subtype. First-line treatment differed between young patients and older ones for HR+ /HER2- and Triple Negative (TN) mBC. Median OS for women aged < 40 and 40-69, respectively, was 46.9 and 46.2 months for HR+ /HER2- mBC; 13.5 and 15.2 for TN mBC; and, 60.7 and 55.1 for HER2 + mBC. Median rwPFS under first line treatment was 11.6 and 11.9 months for HR+ /HER2- in women aged < 40 and 40-69, respectively; 5.5 and 5.9 for TN, and, 13.3 and 12.9 for HER2 + . Factors associated with shorter OS and rwPFS were similar for both women aged < 40 and 40-69 and included ≥ 3 metastatic sites, visceral metastases, and longer MFI, with time-varying effects observed for several prognostic factors. CONCLUSION: Young women presented more frequently with TN and HER2 + subtypes and aggressive mBC than women aged 40-69 did. Prognostic factors of OS and rwPFS were quite similar between age groups and mBC subtypes.

Association between progression-free survival and overall survival in women receiving first-line treatment for metastatic breast cancer: evidence from the ESME real-world database.

BACKGROUND: Overall survival (OS) is the gold standard endpoint to assess treatment efficacy in cancer clinical trials. In metastatic breast cancer (mBC), progression-free survival (PFS) is commonly used as an intermediate endpoint. Evidence remains scarce regarding the degree of association between PFS and OS. Our study aimed to describe the individual-level association between real-world PFS (rwPFS) and OS according to first-line treatment in female patients with mBC managed in real-world setting for each BC subtype (defined by status for both hormone-receptor [HR] expression and HER2 protein expression/gene amplification). METHODS: We extracted data from the ESME mBC database (NCT03275311) which gathers deidentified data from consecutive patients managed in 18 French Comprehensive Cancer Centers. Adult women diagnosed with mBC between 2008 and 2017 were included. Endpoints (PFS, OS) were described using the Kaplan-Meier method. Individual-level associations between rwPFS and OS were estimated using the Spearman's correlation coefficient. Analyses were conducted by tumor subtype. RESULTS: 20,033 women were eligible. Median age was 60.0 years. Median follow-up duration was 62.3 months. Median rwPFS ranged from 6.0 months (95% CI 5.8-6.2) for HR-/HER2 - subtype to 13.3 months (36% CI 12.7-14.3) for HR + /HER2 + subtype. Correlation coefficients were highly variable across subtypes and first-line (L1) treatments. Among patients with HR - /HER2 - mBC, correlation coefficients ranged from 0.73 to 0.81, suggesting a strong rwPFS/OS association. For HR + /HER2 + mBC patients, the individual-level associations were weak to strong with coefficients ranging from 0.33 to 0.43 for monotherapy and from 0.67 to 0.78 for combined therapies. CONCLUSIONS: Our study provides comprehensive information on individual-level association between rwPFS and OS for L1 treatments in mBC women managed in real-life practice. Our results could be used as a basis for future research dedicated to surrogate endpoint candidates.

Real-World Data on Newly Diagnosed BRCA-Mutated High-Grade Epithelial Ovarian Cancers: The French National Multicenter ESME Database.

BACKGROUND: In spite of the frequency and clinical impact of BRCA1/2 alterations in high-grade epithelial ovarian cancer (HGEOC), real-world information based on robust data warehouse has been scarce to date. METHODS: Consecutive patients with BRCA-mutated HGEOC treated between 2011 and 2016 within French comprehensive cancer centers from the Unicancer network were extracted from the ESME database. The main objective of the study was the assessment of clinicopathological and treatments parameters. RESULTS: Out of the 8021 patients included in the ESME database, 266 patients matching the selection criteria were included. BRCA1 mutation was found in 191 (71.8%) patients, while 75 (28.2%) had a BRCA2 mutation only; 95.5% of patients received a cytoreductive surgery. All patients received a taxane/platinum-based chemotherapy (median = six cycles). Complete and partial response were obtained in 53.3% and 20.4% of the cases, respectively. Maintenance therapy was administered in 55.3% of the cases, bevacizumab being the most common agent. After a median follow up of 51.7 months, a median progression-free survival of 28.6 months (95% confidence interval (CI) [26.5; 32.7]) and an estimated 5-year median overall survival of 69.2% (95% CI [61.6; 70.3]) were reported. Notably, BRCA1- and BRCA2-mutated cases exhibited a trend towards different median progression-free survivals, with 28.0 (95% CI [24.4; 32.3]) and 33.3 months (95% CI [26.7; 46.1]), respectively (p-value = 0.053). Furthermore, five-year OS for BRCA1-mutated patients was 64.5% (95% CI [59.7; 69.2]), while it was 82.5% (95% CI [76.6; 88.5]) for BRCA2-mutated ones (p-value = 0.029). CONCLUSIONS: This study reports the largest French multicenter cohort of BRCA-mutated HGEOCs based on robust data from the ESME, exhibiting relevant real-world data regarding this specific population.

Neoadjuvant chemotherapy with FOLFIRINOX and preoperative chemoradiotherapy for patients with locally advanced rectal cancer (UNICANCER-PRODIGE 23): a multicentre, randomised, open-label, phase 3 trial.

BACKGROUND: Treatment of locally advanced rectal cancer with chemoradiotherapy, surgery, and adjuvant chemotherapy controls local disease, but distant metastases remain common. We aimed to assess whether administering neoadjuvant chemotherapy before preoperative chemoradiotherapy could reduce the risk of distant recurrences. METHODS: We did a phase 3, open-label, multicentre, randomised trial at 35 hospitals in France. Eligible patients were adults aged 18-75 years and had newly diagnosed, biopsy-proven, rectal adenocarcinoma staged cT3 or cT4 M0, with a WHO performance status of 0-1. Patients were randomly assigned (1:1) to either the neoadjuvant chemotherapy group or standard-of-care group, using an independent web-based system by minimisation method stratified by centre, extramural extension of the tumour into perirectal fat according to MRI, tumour location, and stage. Investigators and participants were not masked to treatment allocation. The neoadjuvant chemotherapy group received neoadjuvant chemotherapy with FOLFIRINOX (oxaliplatin 85 mg/m2, irinotecan 180 mg/m2, leucovorin 400 mg/m2, and fluorouracil 2400 mg/m2 intravenously every 14 days for 6 cycles), chemoradiotherapy (50 Gy during 5 weeks and 800 mg/m2 concurrent oral capecitabine twice daily for 5 days per week), total mesorectal excision, and adjuvant chemotherapy (3 months of modified FOLFOX6 [intravenous oxaliplatin 85 mg/m2 and leucovorin 400 mg/m2, followed by intravenous 400 mg/m2 fluorouracil bolus and then continuous infusion at a dose of 2400 mg/m2 over 46 h every 14 days for six cycles] or capecitabine [1250 mg/m2 orally twice daily on days 1-14 every 21 days]). The standard-of-care group received chemoradiotherapy, total mesorectal excision, and adjuvant chemotherapy (for 6 months). The primary endpoint was disease-free survival assessed in the intention-to-treat population at 3 years. Safety analyses were done on treated patients. This trial was registered with EudraCT (2011-004406-25) and ClinicalTrials.gov (NCT01804790) and is now complete. FINDINGS: Between June 5, 2012, and June 26, 2017, 461 patients were randomly assigned to either the neoadjuvant chemotherapy group (n=231) or the standard-of-care group (n=230). At a median follow-up of 46·5 months (IQR 35·4-61·6), 3-year disease-free survival rates were 76% (95% CI 69-81) in the neoadjuvant chemotherapy group and 69% (62-74) in the standard-of-care group (stratified hazard ratio 0·69, 95% CI 0·49-0·97; p=0·034). During neoadjuvant chemotherapy, the most common grade 3-4 adverse events were neutropenia (38 [17%] of 225 patients) and diarrhoea (25 [11%] of 226). During chemoradiotherapy, the most common grade 3-4 adverse event was lymphopenia (59 [28%] of 212 in the neoadjuvant chemotherapy group vs 67 [30%] of 226 patients in the standard-of-care group). During adjuvant chemotherapy, the most common grade 3-4 adverse events were lymphopenia (18 [11%] of 161 in the neoadjuvant chemotherapy group vs 42 [27%] of 155 in the standard-of-care group), neutropenia (nine [6%] of 161 vs 28 [18%] of 155), and peripheral sensory neuropathy (19 [12%] of 162 vs 32 [21%] of 155). Serious adverse events occurred in 63 (27%) of 231 participants in the neoadjuvant chemotherapy group and 50 (22%) of 230 patients in the standard-of-care group (p=0·167), during the whole treatment period. During adjuvant therapy, serious adverse events occurred in 18 (11%) of 163 participants in the neoadjuvant chemotherapy group and 36 (23%) of 158 patients in the standard-of-care group (p=0·0049). Treatment-related deaths occurred in one (<1%) of 226 patients in the neoadjuvant chemotherapy group (sudden death) and two (1%) of 227 patients in the standard-of-care group (one sudden death and one myocardial infarction). INTERPRETATION: Intensification of chemotherapy using FOLFIRINOX before preoperative chemoradiotherapy significantly improved outcomes compared with preoperative chemoradiotherapy in patients with cT3 or cT4 M0 rectal cancer. The significantly improved disease-free survival in the neoadjuvant chemotherapy group and the decreased neurotoxicity indicates that the perioperative approach is more efficient and better tolerated than adjuvant chemotherapy. Therefore, the PRODIGE 23 results might change clinical practice. FUNDING: Institut National du Cancer, Ligue Nationale Contre le Cancer, and R&D Unicancer.

OSIRIS: A Minimum Data Set for Data Sharing and Interoperability in Oncology.

PURPOSE: Many institutions throughout the world have launched precision medicine initiatives in oncology, and a large amount of clinical and genomic data is being produced. Although there have been attempts at data sharing with the community, initiatives are still limited. In this context, a French task force composed of Integrated Cancer Research Sites (SIRICs), comprehensive cancer centers from the Unicancer network (one of Europe's largest cancer research organization), and university hospitals launched an initiative to improve and accelerate retrospective and prospective clinical and genomic data sharing in oncology. MATERIALS AND METHODS: For 5 years, the OSIRIS group has worked on structuring data and identifying technical solutions for collecting and sharing them. The group used a multidisciplinary approach that included weekly scientific and technical meetings over several months to foster a national consensus on a minimal data set. RESULTS: The resulting OSIRIS set and event-based data model, which is able to capture the disease course, was built with 67 clinical and 65 omics items. The group made it compatible with the HL7 Fast Healthcare Interoperability Resources (FHIR) format to maximize interoperability. The OSIRIS set was reviewed, approved by a National Plan Strategic Committee, and freely released to the community. A proof-of-concept study was carried out to put the OSIRIS set and Common Data Model into practice using a cohort of 300 patients. CONCLUSION: Using a national and bottom-up approach, the OSIRIS group has defined a model including a minimal set of clinical and genomic data that can be used to accelerate data sharing produced in oncology. The model relies on clear and formally defined terminologies and, as such, may also benefit the larger international community.

Management and outcome of male metastatic breast cancer in the national multicenter observational research program Epidemiological Strategy and Medical Economics (ESME).

BACKGROUND AND AIMS: Because of its low prevalence, metastatic breast cancer (MBC) in males is managed based on clinical experience with women. Using a real-life database, we aim to provide a comprehensive analysis of male MBC characteristics, management and outcome. METHODS: The Epidemiological Strategy and Medical Economics Data Platform collected data for all men and women ⩾18 years with MBC in 18 participating French Comprehensive Cancer Centers from January 2008 to November 2016. Demographic, clinical, and pathological characteristics were retrieved, as was treatment modality. Men were matched 1:1 to women with similar characteristics. RESULTS: Of 16,701 evaluable patients, 149 (0.89%) men were identified. These men were older (median age 69 years) and predominantly had hormone receptor HR+/HER2- disease (78.3%). Median overall survival (OS) was 41.8 months [95% confidence interval (CI: 26.9-49.7)] and similar to women. Median progression-free survival (PFS) with first-line therapy was 9.3 months [95% CI (7.4-11.5)]. In the HR+/HER2- subpopulation, endocrine therapy (ET) alone was the frontline treatment for 43% of patients, including antiestrogens (n = 19), aromatase inhibitors (n = 15) with luteinizing hormone-releasing hormone (LHRH) analogs (n = 3), and various sequential treatments. Median PFS achieved by frontline ET alone was similar in men [9.8 months, 95% CI (6.9-17.4)] and in women [13 months, 95% CI (8.4-30.9)] (p = 0.80). PFS was similar for HR+/HER2- men receiving upfront ET or chemotherapy: 9.8 months [95% CI (6.9-17.4)] versus 9.5 months [95% CI (7.4-11.7)] (p = 0.22), respectively. CONCLUSION: MBC management in men and women leads to similar outcomes, especially in HR+/HER2- patients for whom ET should also be a cornerstone. Unsolved questions remain and successfully recruiting trials for men are still lacking.

Short- and long-term impact of adapted physical activity and diet counseling during adjuvant breast cancer therapy: the "APAD1" randomized controlled trial.

BACKGROUND: Patients with breast cancer undergoing chemotherapy and radiotherapy experience fatigue and other treatment side effects. Integrative therapies combining physical activity and dietary counseling are recommended; however to date no large randomized controlled trial has been conducted during adjuvant therapy. The Adapted Physical Activity and Diet (APAD) intervention was evaluated for its ability to decrease fatigue (primary outcome), anxiety, depression, body mass index (BMI), and fat mass, and enhance muscular and cognitive performances, and quality-of-life (QoL). METHODS: Women diagnosed with early breast cancer (N = 143, mean age = 52 ± 10 years) were randomized to APAD or usual care (UC). APAD included thrice-weekly moderate-intensity mixed aerobic and resistance exercise sessions and 9 dietetic consultations. Patient-reported outcomes (PROs) and anthropometric, muscular, and cognitive variables were measured at baseline, 18 weeks (end of chemotherapy), and 26 weeks (end of radiotherapy and intervention), and at 6- and 12-month post-intervention follow-ups. Multi-adjusted linear mixed-effects models were used to compare groups over time. RESULTS: Significant beneficial effects of the APAD intervention were observed on all PROs (i.e., fatigue, QoL, anxiety, depression) at 18 and 26 weeks. The significant effect on fatigue and QoL persisted up to 12-month follow-up. Significant decreases in BMI, fat mass, and increased muscle endurance and cognitive flexibility were observed at 26 weeks, but did not persist afterward. Leisure physical activity was enhanced in the APAD group vs UC group at 18 and 26 weeks. No significant effect of the intervention was found on major macronutrients intake. CONCLUSIONS: A combined diet and exercise intervention during chemotherapy and radiotherapy in patients with early breast cancer led to positive changes in a range of psychological, physiological and behavioral outcomes at the end of intervention. A beneficial effect persisted on fatigue and QoL at long term, i.e., 1 year post-intervention. Diet-exercise supportive care should be integrated into the management of early breast cancer patients. TRIAL REGISTRATION: The APAD study was prospectively registered on ClinicalTrials.gov (NCT01495650; date of registration: December 20, 2011).

The ongoing French metastatic breast cancer (MBC) cohort: the example-based methodology of the Epidemiological Strategy and Medical Economics (ESME).

PURPOSE: The currently ongoing Epidemiological Strategy and Medical Economics (ESME) research programme aims at centralising real-life data on oncology care for epidemiological research purposes. We draw on results from the metastatic breast cancer (MBC) cohort to illustrate the methodology used for data collection in the ESME research programme. PARTICIPANTS: All consecutive ≥18 years patients with MBC treatment initiated between 2008 and 2014 in one of the 18 French Comprehensive Cancer Centres were selected. Diagnostic, therapeutic and follow-up data (demographics, primary tumour, metastatic disease, treatment patterns and vital status) were collected through the course of the disease. Data collection is updated annually. FINDING TO DATE: With a recruitment target of 30 000 patients with MBC by 2019, we currently screened a total of 45 329 patients, and >16 700 patients with a metastatic disease treatment initiated after 2008 have been selected. 20.7% of patients had an hormone receptor (HR)-negative MBC, 73.7% had a HER2-negative MBC and 13.9% were classified as triple-negative BC (ie, HER2 and HR status both negative). Median follow-up duration from MBC diagnosis was 48.55 months for the whole cohort. FUTURE PLANS: These real-world data will help standardise the management of MBC and improve patient care. A dozen of ancillary research projects have been conducted and some of them are already accepted for publication or ready to be issued. The ESME research programme is expanding to ovarian cancer and advanced/metastatic lung cancer. Our ultimate goal is to achieve a continuous link to the data of the cohort to the French national Health Data System for centralising data on healthcare reimbursement (drugs, medical procedures), inpatient/outpatient stays and visits in primary/secondary care settings. TRIAL REGISTRATION NUMBER: NCT03275311; Pre-results.

FOLFIRINOX or Gemcitabine as Adjuvant Therapy for Pancreatic Cancer.

BACKGROUND: Among patients with metastatic pancreatic cancer, combination chemotherapy with fluorouracil, leucovorin, irinotecan, and oxaliplatin (FOLFIRINOX) leads to longer overall survival than gemcitabine therapy. We compared the efficacy and safety of a modified FOLFIRINOX regimen with gemcitabine as adjuvant therapy in patients with resected pancreatic cancer. METHODS: We randomly assigned 493 patients with resected pancreatic ductal adenocarcinoma to receive a modified FOLFIRINOX regimen (oxaliplatin [85 mg per square meter of body-surface area], irinotecan [180 mg per square meter, reduced to 150 mg per square meter after a protocol-specified safety analysis], leucovorin [400 mg per square meter], and fluorouracil [2400 mg per square meter] every 2 weeks) or gemcitabine (1000 mg per square meter on days 1, 8, and 15 every 4 weeks) for 24 weeks. The primary end point was disease-free survival. Secondary end points included overall survival and safety. RESULTS: At a median follow-up of 33.6 months, the median disease-free survival was 21.6 months in the modified-FOLFIRINOX group and 12.8 months in the gemcitabine group (stratified hazard ratio for cancer-related event, second cancer, or death, 0.58; 95% confidence interval [CI], 0.46 to 0.73; P<0.001). The disease-free survival rate at 3 years was 39.7% in the modified-FOLFIRINOX group and 21.4% in the gemcitabine group. The median overall survival was 54.4 months in the modified-FOLFIRINOX group and 35.0 months in the gemcitabine group (stratified hazard ratio for death, 0.64; 95% CI, 0.48 to 0.86; P=0.003). The overall survival rate at 3 years was 63.4% in the modified-FOLFIRINOX group and 48.6% in the gemcitabine group. Adverse events of grade 3 or 4 occurred in 75.9% of the patients in the modified-FOLFIRINOX group and in 52.9% of those in the gemcitabine group. One patient in the gemcitabine group died from toxic effects (interstitial pneumonitis). CONCLUSIONS: Adjuvant therapy with a modified FOLFIRINOX regimen led to significantly longer survival than gemcitabine among patients with resected pancreatic cancer, at the expense of a higher incidence of toxic effects. (Funded by R&D Unicancer and others; ClinicalTrials.gov number, NCT01526135 ; EudraCT number, 2011-002026-52 .).

Radiocurability by targeting tumor necrosis factor-alpha using a bispecific antibody in carcinoembryonic antigen transgenic mice.

PURPOSE: Tumor necrosis factor-alpha (TNF-alpha) enhances radiotherapy (RT) killing of tumor cells in vitro and in vivo. To overcome systemic side effects, we used a bispecific antibody (BsAb) directed against carcinoembryonic antigen (CEA) and TNF-alpha to target this cytokine in a CEA-expressing colon carcinoma. We report the evaluation of this strategy in immunocompetent CEA-transgenic mice. METHODS AND MATERIALS: The murine CEA-transfected colon carcinoma MC-38 was used for all experiments. In vitro, clonogenic assays were performed after RT alone, TNF-alpha alone, and RT plus TNF-alpha. In vivo, the mice were randomly assigned to treatment groups: control, TNF-alpha, BsAb, BsAb plus TNF-alpha, RT, RT plus TNF-alpha, and RT plus BsAb plus TNF-alpha. Measurements of endogenous TNF-alpha mRNA levels and evaluation of necrosis (histologic evaluation) were assessed per treatment group. RESULTS: In vitro, combined RT plus TNF-alpha resulted in a significant decrease in the survival fraction at 2 Gy compared with RT alone (p < 0.00001). In vivo, we observed a complete response in 5 (50%) of 10, 2 (20%) of 10, 2 (18.2%) of 11, and 0 (0%) of 12 treated mice in the RT plus BsAb plus TNF-alpha, RT plus TNF-alpha, RT alone, and control groups, respectively. This difference was statistically significant when TNF-alpha was targeted with the BsAb (p = 0.03). The addition of exogenous TNF-alpha to RT significantly increased the endogenous TNF-alpha mRNA level, particularly when TNF-alpha was targeted with BsAb (p < 0.01). The percentages of necrotic area were significantly augmented in the RT plus BsAb plus TNF-alpha group. CONCLUSION: These results suggest that targeting TNF-alpha with the BsAb provokes RT curability in a CEA-expressing digestive tumor syngenic model and could be considered as a solid rationale for clinical trials.

Multicentre phase II study using increasing doses of irinotecan combined with a simplified LV5FU2 regimen in metastatic colorectal cancer.

PURPOSE: Irinotecan at 180 mg/m2 combined with an infusional 5-fluorouracil/leucovorin (5-FU/LV) regimen (FOLFIRI) is a standard first line therapy for metastatic colorectal cancer (mCRC). This phase II study aimed to assess whether increasing the irinotecan dose in the first line FOLFIRI regimen would benefit mCRC patients. PATIENTS AND METHODS: Patients received FOLFIRI every 2 weeks for up to six cycles, comprising a 5-FU/LV regimen combined with irinotecan at 180 mg/m2 (cycle 1), increasing to 220 mg/m2 (cycle 2) and 260 mg/m2 (cycle 3 and subsequent cycles) dependent on toxicity. Efficacy and safety were determined in the intention to treat (ITT) population and in patients able to receive irinotecan at 260 mg/m2 for at least four cycles [high-dose (HD) population]. RESULTS: Fifty-four eligible patients were included. Among them, 44 (81.5%) formed the HD population. The ITT objective response rate was 48% (90%CI: 36-60) with 25/26 of the responses in the HD population. The disease control rate was 76% (90%CI: 65-85) and median overall survival was 20.4 months (90%CI: 6.4-27.1). The main grade 3/4 toxicities (ITT/HD populations) were neutropenia (61%/59%), and diarrhoea (18%/11%), respectively. CONCLUSIONS: This study confirms the feasibility of increasing the standard dose of the irinotecan component of FOLFIRI to 260 mg/m2, for more than 80% of patients but does not support a clear advantage of this strategy on unselected mCRC patients.

Letrozole sensitizes breast cancer cells to ionizing radiation.

INTRODUCTION: Radiotherapy (RT) is considered a standard treatment option after surgery for breast cancer. Letrozole, an aromatase inhibitor, is being evaluated in the adjuvant setting. We determined the effects of the combination of RT and letrozole in the aromatase-expressing breast tumour cell line MCF-7CA, stably transfected with the CYP19 gene. METHODS: Irradiations were performed using a cobalt-60 source with doses ranging from 0 to 4 Gy. Cells were incubated with androstenedione in the presence or absence of letrozole. Effects of treatment were evaluated using clonogenic assays, tetrazolium salt colorimetric (MTT) assays, and cell number determinations. Cell-cycle analyses were conducted using flow cytometry. RESULTS: The survival fraction at 2 Gy was 0.66 for RT alone and was 0.44 for RT plus letrozole (P = 0.02). Growth of MCF-7CA cells as measured by the cell number 6 days after radiotherapy (2 and 4 Gy) was decreased by 76% in those cells treated additionally with letrozole (0.7 microM) compared with those receiving radiotherapy alone (P = 0.009). Growth inhibition, assessed either by cell number (P = 0.009) or by the MTT assay (P = 0.02), was increased after 12 days of the combination treatment. Compared with radiation alone, the combination of radiation and letrozole produced a significant decrease in radiation-induced G2 phase arrest and a decrease of cells in the S phase, with cell redistribution in the G1 phase. CONCLUSIONS: These radiobiological results may form the basis for concurrent use of letrozole and radiation as postsurgical adjuvant therapy for breast cancer.