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Aim: To assess the value of Post-mastectomy radiation therapy (PMRT) in breast cancer patients with no or minimal lymph nodes involvement. Materials and methods: We retrospectively analyzed a French multi-centric cohort of 4283 patients treated between 1980 and 2013, by mastectomy and axillary dissection with or without PMRT. Practices were analyzed according 3 treatment periods (1980-1999, 2000-2005; 2006-2013). The value of PMRT on loco-regional recurrence, disease-free survival, breast cancer specific survival and overall survival was assessed in pN0-1mi patients, using multivariate analyses (logistic regression and Cox model). It was subsequently assessed according to the number of clinicopathologic recurrence-risk factors, generating a prognostic index (f-PMRT index), in an attempt to isolate a pN0-1mi patients subgroup deriving benefit from PMRT. We tested the accuracy of the Cambridge-PMRT (c-PMRT) index in the discrimination of patients with significantly different outcomes, as well as the value of PMRT in each c-PMRT prognostic group. Results: PMRT was considered in more than half pN0-1mi patients of our cohort. Whereas matching pN0-1mi patients according to the number of clinicopathologic recurrence-risk factors led to isolate a higher-risk subpopulation (≥ 3 RR factors), PMRT had no significant impact on patients' outcomes, on multivariate analysis. Whereas the Cambridge-PMRT index had the potential to discriminate 3 patient populations with significantly different outcomes, its use did not help to the decision making for PMRT. Conclusion: Despite a large cohort, we failed to isolate a subgroup of early breast cancer patients suitable for PMRT, in the absence of lymph node involvement. Citation Format: Forissier V, Tallet A, Cohen M, Classe J-M, Reyal F, Chopin N, Mazouni C, Gimbergues P, Daraï E, Colombo PE, Azuar P, Lambaudie E, Houvenaeghel G. Is post mastectomy radiotherapy contributive in pN0-1mi breast cancers patients? Results of a French multi-centric cohort [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-11-17.

Aim To assess the value of post-mastectomy radiation therapy (PMRT) to breast cancer (BC) patients with no or minimal lymph node (LN) involvement. Materials and methods We retrospectively analysed a French multi-centric cohort of 4283 patients treated by mastectomy and axillary dissection, with or without PMRT, between 1980 and 2013. Practices were analysed for three treatment periods (1980–1999, 2000–2005 and 2006–2013). The impact of PMRT on loco-regional recurrence (LRR), disease-free survival (DFS), BC-specific survival and overall survival was assessed in pN0-1mi patients using multivariate analyses (logistic regression and Cox model). It was subsequently assessed based on the number of clinicopathological recurrence-risk factors, generating a prognostic index (French-PMRT index), to isolate a pN0-1mi patients subgroup that might derive a benefit from PMRT. We tested the accuracy of the Cambridge-PMRT (c-PMRT) index to discriminate between patients with significantly different outcomes and the value of PMRT in each c-PMRT prognostic group. Results More than half of the pN0-1mi patients of our cohort underwent PMRT, which almost significantly improved LRR-free survival and DFS. Matching pN0-1mi patients based on the number of clinicopathologic recurrence-risk factors identified a higher risk subpopulation (≥3 recurrence-risk factors), but PMRT did not improve patient outcomes. Although the c-PMRT index had the potential to predict patient outcomes, its use did not help in making the decision of whether or not to use PMRT. Conclusion We failed to isolate a subgroup of early BC patients without LN involvement suitable for PMRT, despite studying a large cohort.

Introduction The aim of this study was to examine changes in therapeutic practices for early breast cancer T0-2 N0 managed by upfront surgery and SLNB. Population Between 1999 and 2012, 15.508 patients were treated. Four periods were determined: 1999–2003, 2004–2006, 2007–2009 and > 2009. Five tumor subtypes were defined according to hormonal receptors (HR) and Her2: Luminal A (HR + Her2- Grade 1–2), Her2 (Her2+ HR-), Triple-negative (HR- Her2-), Luminal B Her2- (HR + Her2- Grade 3), Luminal B Her2+ (HR + HER2+). Methods Rates of axillary lymph node dissection (ALND), adjuvant chemotherapy ± trastuzumab, endocrine treatment, mastectomy and post mastectomy radiotherapy (PMRT) were analyzed according to treatment periods with univariate and multivariate analysis. Overall and disease-free survivals were analyzed according to treatment periods adjusted for HR and then for tumor subtypes. Results Rates of ALND, adjuvant chemotherapy and endocrine treatment varied significantly according to treatment periods, for HR positive and negative tumors. ALND rate decreased for all tumor subtypes with a decrease of adjuvant chemotherapy rate for Luminal A tumors and an increase for Luminal B Her2+ and Her2-tumors. Endocrine treatment rate decreased for Luminal A and increased for Luminal B Her2+ tumors. In multivariate analysis, these modifications with time remained significant. Mastectomy and PMRT rates increased. In multivariate analysis, overall and disease-free survivals increased during successive periods. Conclusion A global therapeutic de-escalation in ALND and adjuvant systemic treatment, combined with an actual escalation in some specific subsets was demonstrated, but without negative impact on survival.

Background Omission of completion axillary lymph node dissection (ALND) is a standard practice in patients with breast cancer (BC) and negative sentinel nodes (SNs) but has shown insufficient evidence to be recommended in those with SN invasion. Methods A retrospective analysis of a cohort of patients with BC and micrometastases (Mic) or isolated tumour cells (ITCs) in SN. Factors associated with ALND were identified, and patients with ALND were matched to patients without ALND. Overall survival (OS) and recurrence-free survival (RFS) were estimated in the overall population, in Mic and in ITC cohorts. Findings Among 2009 patients analysed, 1390 and 619 had Mic and ITC in SN, respectively. Factors significantly associated with ALND were SN status, histological type, age, number of SN harvested and absence of adjuvant chemotherapy. After a median follow-up of 60.4 months, ALND omission was independently associated with reduced OS (hazard ratio [HR] 2.41, 90 confidence interval [CI] 1.36–4.27, p = 0.0102), but not with increased RFS (HR 1.21, 90 CI 0.74–2.0, p = 0.52) in the overall population. In matched patients, the increased risk of death in case of ALND omission was found only in the Mic cohort (HR 2.88, 90 CI 1.46–5.69), not in the ITC cohort. The risk of recurrence was also significantly increased in the subgroup of matched Mic patients (HR 1.56, 90 CI 0.90–2.73). Interpretation A separate analysis of Mic and ITC groups, matched for the determinants of ALND, suggested that patients with Mic had increased recurrence rates and shorter OS when ALND was not performed. Our results are consistent with those of previous studies for patients with ITC but not for those with Mic. Randomised controlled clinical trials are still warranted to show with a high level of evidence if ALND can be safely omitted in patients with micrometastatic disease in SN.

Resume Objectifs L’objectif etait d’evaluer les facteurs pronostiques des carcinomes lobulaires infiltrants (CLI) T1 et T2 du sein et les facteurs predictifs de l’atteinte ganglionnaire axillaire. Methodes Etude retrospective multicentrique, menee de 1999 a 2008, parmi 13 centres francais. Les donnees concernant les patientes traitees d’un cancer du sein T1 ou T2 par une chirurgie premiere ont ete recueillies. Une mastectomie partielle ou totale etait realisee avec un curage axillaire systematique durant la periode de validation ou en cas d’envahissement des ganglions sentinelles. Parmi ces 8100 patients, 940 cas de CLI ont ete extraits. Apres analyse univariee identifiant les facteurs pronostiques significatifs, une regression logistique de Cox a ete appliquee. L’analyse a permis de determiner les facteurs pronostiques de survie sans recidive (SSR) et de survie globale (SG). Les differents facteurs correles a une atteinte des ganglions lymphatiques ont ete recherches en analyse univarie, puis multivarie, afin de determiner les facteurs predictifs d’envahissement ganglionnaire axillaire. Resultats L’âge median etait de 60 ans (27–89). La majorite des patientes presentaient une tumeur d’une taille superieure a 10 mm (n = 676 : 72 %), avec une minorite de lesions de haut grade SBR (n = 38 : 4 %) et une majorite de statut hormonal positif (n = 880 : 93,6 %). La duree mediane de suivi etait de 59 mois (1–131). Les facteurs significativement associes a une diminution de la SSR etaient le grade SBR 3 (hazard ratio [HR] : 3,85, IC 1,21–12,21), la taille tumorale superieure a 2 cm (HR : 2,85, IC : 1,43–5,68) et le statut ganglionnaire macrometastatique (HR : 3,11, IC : 1,47–6,58). L’analyse multivariee mettait en evidence un impact significatif sur la SG de l’âge de moins de 50 ans (HR : 5,2, IC : 1,39–19,49), du grade SBR 3 (HR : 5,03, IC : 1,19–21,25), de la taille tumorale superieure a 2 cm (HR : 2,53, IC : 1,13–5,69). Il n’a pas ete mis en evidence de correlation significative entre la prescription de chimiotherapie et la SSR (odds ratio [OR] 0,8, IC : 0,35–1,80) ou la SG (OR : 0,72, IC : 0,28–1,82). La SSR n’etait pas differente entre les pN0 (aucune invasion axillaire), les pNi+ (cellules tumorales isolees) ou les pNmic (micrometastase). Il n’y avait pas de difference entre un ou plus d’un ganglion lymphatique macromatastatique (pN1). Les SSR etaient statistiquement differentes entre les pN1 et les autres statuts ganglionnaires (pN0, pNi+ ou pNmic). Les facteurs associes a l’atteinte ganglionnaire en analyse multivariee etaient : l’âge entre 51 et 65 ans (OR : 2,1, IC 1,45–3,04), l’âge inferieur a 50 ans (OR 3,2, IC : 2,05–5,03), la taille tumorale superieure a 2 cm (OR 4,4, IC : 3,2–6,14), le grade SBR 2 (OR 1,9, IC : 1,30–2,90) et le grade SBR 3 (OR 3,5, IC : 1,61–7,75). Conclusion L’analyse de cette serie de 940 CLI de stade T1 et T2 apporte plusieurs informations : les facteurs associes a l’atteinte des ganglions lymphatiques axillaires sont l’âge de moins de 65 ans, la taille de la tumeur de plus de 20 mm et un grade SBR 2 ou 3. Les memes facteurs sont significativement correles aux taux de SSR et de SG. L’envahissement macrometastatique des ganglions axillaires a un impact significatif sur la SSR et la SG, contrairement aux pNi+ et aux pNmic, qui semblent avoir le meme pronostic que les pN0.

Sentinel lymph node biopsy (SLNB) remains under discussion for large size tumors. The aim of this work has been to study the false negative rate (FNR) of SLNB for large tumors and predictive factors of false negative (FN).A study of a multicentric cohort, involved patients presenting N0 breast cancer with a SLNB eventually completed by complementary axillary lymph node dissection (cALND). The main criteria were the FNR and the predictive factors of FN.12.415 patients were included: 748 with tumors ≥30 mm, 1101 with tumors20 and 30 mm and 10.566 with tumors ≤20 mm, with a cALND respectively for 501 patients (67%), 523 (62.1%) and 2775 (26.3%). The FNR were respectively: 3.05% (IC95%: 1.3-4.8) for tumors ≥30 mm*, 3.5% (1.8-5.2) for tumors20 and 30 mm*, 1.8% (1-2.4) for tumors ≤20 mm (p 0.05) (*Not significant). At multivariate analysis, SN number harvested ≤2 (OR:2.0, p = 0.023) and tumor size20 and 30 mm (OR:2.07, p = 0.017) were significant predictive factors of FN, without significant value for tumor size ≥30 mm (OR:1.83, p = 0.073).The FNR of SLNB was not higher amongst large size tumors compared to tumors of a smaller size. These results support the validation of SNLB for tumors up to 50 mm.

To define the prognostic value of isolated tumor cells (ITC), micrometastases (pN1mi) and macrometastases in early stage breast cancer (ESBC). We conducted a retrospective multicenter cohort study at 13 French sites. All the eligible patients who underwent SLNB from January 1999 to December 2008 were identified, and appropriate data were extracted from medical records and analyzed. Among 8001 patients, including 70% node-negative (n = 5588), 4% ITC (n = 305), 10% pN1mi (n = 794) and 16% macrometastases (n = 1314) with a median follow-up of 61.3 months, overall survival (OS) and recurrence-free survival (RFS) rates at 84 months were not statistically different in ITC or pN1mi compared to tumor-free nodes. Axillary recurrence (AR) was significantly more frequent in ITC (1.7%) and pN1mi (1.5%) compared to negative nodes (0.6%). Survival and AR rates of single macrometastases were not different from those of ITC or pN1mi. In case of 2 macrometastases or more, survival rates decreased and recurrence rates increased significantly. Micrometastases and ITC do not have a negative prognostic value. Single macrometastases might have an intermediate prognostic value while 2 macrometastases or more are associated with poorer prognosis.

Controversy exists about the prognosis of breast cancer in young women. Our objective was to describe clinicopathological and prognostic features to improve adjuvant treatment indications.We conducted a retrospective multi centre study including fifteen French hospitals. Disease-free survival's data, clinical and pathological criteria were collected.5815 patients were included, 15.6% of them where between 35 and 40 years old and 8.7% below 35. In 94% of the cases, a palpable masse was found in patients ≤35 years old. Triple negative and HER2 tumors were predominantly found in patients ≤35 (22.2% and 22.1%, p 0.01). A young age ≤40 years (p 0.001; hazard ratio [HR]: 2.05; 95% confidence limit [CL]: 1.60-2.63) or ≤35 years (p 0.001; [HR]: 3.86; 95% [CL]: 2.69-5.53) impacted on the indication of chemotherapy. Age ≤35 (p 0.001; [HR]: 2.01; 95% [CL]: 1.36-2.95) was a significantly negative factor on disease-free survival. Chemotherapy (p 0.006; [HR]: 0.6; 95% [CL]: 0.40-0.86) and positive hormone receptor status (p 0.001; [HR]: 0.6; 95% [CL]: 0.54-0.79) appeared to be protector factors. Patients under 36, had a significantly higher rate of local recurrence and distant metastasis compared to patients35-40 (21.5 vs. 15.4% and 21.8 vs. 12.6%, p 0.01).Young women present a different distribution of molecular phenotypes with more luminal B and triple negative tumors with a higher grade and more lymph node involvement. A young age, must be taken as a pejorative prognostic factor and must play a part in indication of adjuvant therapy.

In utero exposure to environmental chemicals can result in reproductive toxicity via endocrine disruption mechanisms. Whether some of those contaminants also have an impact on fetal thyroid function or pathways, and, thus, potentially on neuropsychological development, is still debated.We used samples from a cord blood (CB) and milk bank, established for a research on cryptorchidism and xenobiotic exposure to compounds known for their anti-androgenic and/or estrogenic activity, to study CB thyroid tests and their correlation with CB and milk xenobiotics concentrations in boys born in Nice area.No difference was found in thyroid tests between 60 cryptorchid boys and 76 matched controls (median thyroid stimulating hormone 5.97 vs. 6.55 mUI/L, free thyroxine [fT4] 13.1 vs. 12.9 pmol/L, free triiodothyronine [fT3] 1.9 vs. 2.1 pmol/L), with no influence of season of birth, gestational age, maternal smoking, or mode of delivery (except for higher fT4 in control boys born vaginally). FT4 was correlated with fetal growth only in cryptorchid boys. Since we had previously shown differences between cryptorchid and controls exposure, we studied correlations of thyroid tests with xenobiotics in control boys only. All tested CB or maternal milk was contaminated by one or more selected xenobiotics, mainly polychlorinated biphenyls (PCBs), dichloro diphenyl dichloroethylène (DDE), dibutylphthalate, hexachlorobenzene, and bisphenol A. We found a significant negative correlation between fT4 and concentrations of PCB118, PC180, and DDE in milk (respectively r = -0.342, p0.03, r = -0.296, p = 0.031, r = -0.315, p = 0.016), persisting after adjustment for mode of delivery. There was a significant positive correlation of fT3 with milk concentrations of PCB138, PCB153, ΣPCB, and dibutylphthalate (respectively r = 0.31, p = 0.016, r = 0.28, p = 0.029; r = 0.34, p = 0.0079 and r = 0.272, p = 0.0295), with a trend for PCB180 (r = 0.259, p = 0.061). There was no correlation of thyroid stimulating hormone with any of the measured xenobiotics, except for a weak negative trend with CB bisphenol A (r = -0.25, p = 0.077).CB thyroid tests are within normal range in cryptorchid boys, similar to controls. Our data in controls suggest a possible weak correlation between in utero exposure to some xenobiotics (PCBs, DDE) and fT3 and fT4 CB concentrations, with usually negative correlations with fT4 and positive with fT3 concentrations, which we speculate could suggest an impact on deiodinases.

Struma ovarii (SO) is extremely rare, with less than 200 reported cases in the medical literature. SO is defined by the presence of an ovarian tumor containing thyroid tissue as the predominant cell type. Malignant transformation is rare and lethal cases of SO are even rarer. We report on a patient presenting with left ovarian cystic SO and lethal outcome.A 45-year-old woman was diagnosed with a follicular variant of papillary carcinoma on laparotomy and left salpingo-oophorectomy. She had persistently elevated serum thyroglobulin following total thyroidectomy + radioiodine and second-look surgery. Imaging scan analysis showed pelvic tumor recurrence and hypervascular liver metastases during follow-up as well as peritoneal carcinomatosis in the pelvis, right abdominal wall, and malignant ascites. The patient died from cachexia at 37 months after diagnosis.Such an aggressive malignant disease and lethal course of SO is rare. Total thyroidectomy is mandatory to exclude a primary thyroid neoplasm and for radioiodine therapy and follow-up. SO may spread to contralateral ovary, pelvic nodes, peritoneum, liver, lungs, and bones through hematogeneous spread, which is different from the dissemination pattern of papillary thyroid carcinomas. Imaging highlights the mixed behavior of this ovarian tumor.

Key points Neoadjuvant chemotherapy and oncoplastic surgery have reduced the indications for mastectomy without compromising either overall or relapse-free survival. Conservative surgery is appropriate, but not when it produces poor esthetic results that are difficult to correct after radiotherapy. The permanent goal of better esthetic results after conservative surgery must never compromise effective cancer management, which is the principal factor to consider. We must, above all, aim at in sano surgery, that is, tumor-free resection margins. Oncoplastic surgery makes it possible to enlarge the indications for conservative treatment to indications previously treated by mastectomy, without increasing adverse cosmetic effects or jeopardizing cancer management and the likelihood of cure. While some authors use the term “oncoplastic surgery” to describe conservative surgical management, other teams define it as oncology surgery plus plastic surgery. Reconstructive surgery of the breast is an integral part of breast cancer treatment. Multidisciplinary decision-making and honest information to patients are essential before any reconstructive surgery.

The rate of axillary recurrence (AR) after sentinel lymph node biopsy is usually low but few studies investigated its impact on survival. Our aim was to determine the rate and predictive factors of AR in a large cohort of breast cancer patients and its impact on survival.From 1999 to 2013, 14,095 patients who underwent surgery for clinically N0 previously untreated breast cancer and had sentinel lymph node biopsy were analysed. A simplified score predictive of AR was established.Median follow-up was 55.2 months. AR was observed in 0.51% of cases, with a median time to onset of 43.4 months. In multivariate analysis, the occurrence of AR was significantly correlated with grade 2 or 3 disease, absence of radiotherapy and tumour subtype (hormonal receptor [HR]- / human estrogen receptor [HER]+). AR rates were 1% for triple-negative tumours, 2.8% for HER2-positive tumours, 0.4% for luminal A tumours, 0.9% for HER2-negative luminal B tumours, and 0.5% for HER2-positive luminal B tumours. A simplified score predictive of the occurrence of AR was established. Patients could be divided into three different score groups (p0.0001). In multivariate analysis, overall survival was significantly lower in cases of AR (p0.0001), age50, lymphovascular invasion, grade 3 disease, sentinel node (SN) macrometastases, tumour size20 mm, absence of chemotherapy and triple-negative phenotype. Survival in patients with AR was significantly lower in case of early-onset (2 years) AR (p = 0.017).Isolated AR is more common in Her2-positive/HR-negative triple-negative tumours with a more severe prognosis in triple-negative and Her2-positive/HR-negative tumours, and represents an independent adverse factor justifying an indication for systemic treatment for AR treatment. However, the benefit of any systemic treatment remains to be proven.

Background A subgroup of T1N0M0 breast cancer (BC) carries a high potential of relapse, and thus may require adjuvant systemic therapy (AST). Patients and methods Retrospective analysis of all patients with T1 BC, who underwent surgery from January 1999 to December 2009 at 13 French sites. AST was not standardized. Results Among 8100 women operated, 5423 had T1 tumors (708 T1a, 2208 T1b and 2508 T1c 11–15 mm). T1a differed significantly from T1b tumors with respect to several parameters (lower age, more frequent negative hormonal status and positive HER2 status, less frequent lymphovascular invasion), exhibiting a mix of favorable and poor prognosis factors. Overall survival was not different between T1a, b or c tumors but recurrence-free survival was significantly higher in T1b than in T1a tumors (P = 0.001). In multivariate analysis, tumor grade, hormone therapy and lymphovascular invasion were independent prognostic factors. Conclusion Relatively poor outcome of patients with T1a tumors might be explained by a high frequency of risk factors in this subgroup (frequent negative hormone receptors and HER2 overexpression) and by a less frequent administration of AST (endocrine treatment and chemotherapy). Tumor size might not be the main determinant of prognosis in T1 BC.

La valeur pronostique des micrometastases (pN1mi) et des cellules isolees (pN0i+) reste tres debattue compte tenu de resultats divergents de la litterature selon les etudes et selon les modalites d’analyse ganglionnaire. Il s’agit pourtant d’un element important pour decider des therapeutiques adjuvantes lorsque la decision repose principalement sur ce facteur. L’objectif principal de cette etude est de preciser la valeur pronostique de ces atteintes des ganglions sentinelles (GS) en reference aux atteintes par une macrometastase et a l’absence d’envahissement.

In utero and lactational exposure to endocrine disruptors is thought to be potentially harmful on fetal and infant development. Data of exposure in France is scarce. This is a prospective study with (1) collection of 84 cord bloods (CB) and 69 milks from 86 mothers delivering healthy boys (gestational age >or= 34 weeks) at two maternity wards in Southern France, between 2002 and 2005 and (2) screening for 15 xenobiotics with anti-androgenic and/or estrogenic effects: DDE, 7 PCBs, dibutylphthalate and its metabolite mBP, HCB, lindane, linuron, procymidone and vinclozoline. Correlations were made with delivery and neonatal outcomes. All CB and milks were contaminated by one or more xenobiotics (mainly PCBs, DDE, HCB, and phthalates) with good correlation between CB and milk concentrations. Compared to other geographical areas, exposure was usually in the lower bracket. Milk [PCB180] was associated with lower birth weight. Infant head circumference correlated negatively with [HCB] and positively with [mBP] in CB. There was a similar but not significant trend for birth weight and length. [DDE] in milk was higher in older mothers and in women born in Africa. In utero and lactational exposure is ubiquitous in our area. Contamination of milk with HCB, mBP, and PCB 180 showed weak correlations with infant growth. This snapshot of exposure in an area with no major industry will serve for further monitoring.

Neoadjuvant chemotherapy and oncoplastic surgery have reduced the indications for mastectomy without compromising either overall or relapse-free survival. Conservative surgery is appropriate, but not when it produces poor esthetic results that are difficult to correct after radiotherapy. The permanent goal of better esthetic results after conservative surgery must never compromise effective cancer management, which is the principal factor to consider. We must, above all, aim at in sano surgery, that is, tumor-free resection margins. Oncoplastic surgery makes it possible to enlarge the indications for conservative treatment to indications previously treated by mastectomy, without increasing adverse cosmetic effects or jeopardizing cancer management and the likelihood of cure. While some authors use the term "oncoplastic surgery" to describe conservative surgical management, other teams define it as oncology surgery plus plastic surgery. Reconstructive surgery of the breast is an integral part of breast cancer treatment. Multidisciplinary decision-making and honest information to patients are essential before any reconstructive surgery.

566 Background: T1N0M0 breast cancer (BC) are generally considered as carrying good prognosis and cancer-specific survival rates after 5 to 10 years are as high as 90 or 95% in many studies. However, they constitute a heterogeneous group and many studies identified biologically-defined at-risk patients within T1 BC. The objectives of our study were to describe the main characteristics of T1a, b, and c (11-15mm) BC and to identify prognostic factors for survival. Methods: We retrospectively collected the medical files of all patients diagnosed with BC who underwent sentinel lymph node biopsy (SLNB) between January 1999 and December 2008 in 13 French sites and examined overall survival (OS) and Relapse-free survival (RFS) in T1a, T1b and T1c 11-15 mm. Results: Among 8,100 women operated, 5,423 had T1 tumors (708 T1a, 2,208 T1b and 2,508 T1c 11-15mm). T1a differed significantly from T1b tumors with respect to several parameters : younger age, more frequent negative hormonal status and positive HER2 status, less frequent lymphovascular invasion (LVI), exhibiting a mix of favorable and poor prognosis factors. After a median follow-up of 60.5 months, OS rate was 97.6% (95CI: 97.1-98) at 60 months, 95.4%(94.5-96.4) at 84 months and 90.7% (85.2-96.4) at 120 months. No significant difference was observed between T1a, T1b and T1c tumors (p=0.335). RFS rates were 94% (95CI: 93.8-95.2), 92.1% [91.1-93.2] and 83.8% (77.6-90.5) at 60, 84 and 120 months respectively. RFS was significantly higher in T1b tumors (95.9%, 95CI: 95-96.9) as compared to T1a (93.2%, 91-95.4) or T1c tumors (93.8%, 92.8-94.9), p=0.0099. In multivariate analysis, SBR tumor grade, hormone therapy and LVI were independent prognostic factors for RFS, while hormone therapy and SBR grade were independently associated with OS. Conclusions: Relatively poor outcome of patients with T1a tumors might be explained by a high frequency of risk factors in this subgroup (frequent negative hormone receptors and HER2 overexpression) and by a less frequent administration of adjuvant systemic therapy (endocrine treatment and chemotherapy). Tumor size might not be the main determinant of prognosis in T1 breast cancer.