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BACKGROUND: Trials evaluating the omission of completion axillary-lymph-node dissection in patients with clinically node-negative breast cancer and sentinel-lymph-node metastases have been compromised by limited statistical power, uncertain nodal radiotherapy target volumes, and a scarcity of data on relevant clinical subgroups. METHODS: We conducted a noninferiority trial in which patients with clinically node-negative primary T1 to T3 breast cancer (tumor size, T1, ≤20 mm; T2, 21 to 50 mm; and T3, >50 mm in the largest dimension) with one or two sentinel-node macrometastases (metastasis size, >2 mm in the largest dimension) were randomly assigned in a 1:1 ratio to completion axillary-lymph-node dissection or its omission (sentinel-node biopsy only). Adjuvant treatment and radiation therapy were used in accordance with national guidelines. The primary end point was overall survival. We report here the per-protocol and modified intention-to-treat analyses of the prespecified secondary end point of recurrence-free survival. To show noninferiority of sentinel-node biopsy only, the upper boundary of the confidence interval for the hazard ratio for recurrence or death had to be below 1.44. RESULTS: Between January 2015 and December 2021, a total of 2766 patients were enrolled across five countries. The per-protocol population included 2540 patients, of whom 1335 were assigned to undergo sentinel-node biopsy only and 1205 to undergo completion axillary-lymph-node dissection (dissection group). Radiation therapy including nodal target volumes was administered to 1192 of 1326 patients (89.9%) in the sentinel-node biopsy-only group and to 1058 of 1197 (88.4%) in the dissection group. The median follow-up was 46.8 months (range, 1.5 to 94.5). Overall, 191 patients had recurrence or died. The estimated 5-year recurrence-free survival was 89.7% (95% confidence interval [CI], 87.5 to 91.9) in the sentinel-node biopsy-only group and 88.7% (95% CI, 86.3 to 91.1) in the dissection group, with a country-adjusted hazard ratio for recurrence or death of 0.89 (95% CI, 0.66 to 1.19), which was significantly (P<0.001) below the prespecified noninferiority margin. CONCLUSIONS: The omission of completion axillary-lymph-node dissection was noninferior to the more extensive surgery in patients with clinically node-negative breast cancer who had sentinel-node macrometastases, most of whom received nodal radiation therapy. (Funded by the Swedish Research Council and others; SENOMAC ClinicalTrials.gov number, NCT02240472.).
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Neoplasias da Mama , Excisão de Linfonodo , Linfadenopatia , Biópsia de Linfonodo Sentinela , Linfonodo Sentinela , Feminino , Humanos , Axila , Neoplasias da Mama/mortalidade , Neoplasias da Mama/patologia , Neoplasias da Mama/secundário , Neoplasias da Mama/terapia , Intervalo Livre de Doença , Excisão de Linfonodo/métodos , Linfonodos/patologia , Linfonodos/cirurgia , Linfadenopatia/patologia , Linfadenopatia/radioterapia , Linfadenopatia/cirurgia , Linfonodo Sentinela/patologia , Linfonodo Sentinela/cirurgia , Terapia Combinada , SeguimentosRESUMO
BACKGROUND: In luminal breast cancer, adjuvant CDK4/6 inhibitors (eg, abemaciclib) improve invasive disease-free survival. In patients with T1-2, grade 1-2 tumours, and one or two sentinel lymph node metastases, completion axillary lymph node dissection (cALND) is the only prognostic tool available that can reveal four or more nodal metastases (pN2-3), which is the only indication for adjuvant abemaciclib in this setting. However, this technique can lead to substantial arm morbidity in patients. We aimed to pragmatically describe the potential benefit and harm of this strategy on the individual patient level in patients from the ongoing SENOMAC trial. METHODS: In the randomised, phase 3, SENOMAC trial, patients aged 18 years or older, of any performance status, with clinically node-negative T1-T3 breast cancer and one or two sentinel node macrometastases from 67 sites in five European countries (Denmark, Germany, Greece, Italy, and Sweden) were randomly assigned (1:1), via permutated block randomisation (random block size of 2 and 4) stratified by country, to either cALND or its omission (ie, they had a sentinel lymph node biopsy only). The primary outcome is overall survival, which is yet to be reported. In this post-hoc analysis, patients from the SENOMAC per-protocol population, with luminal oestrogen-receptor positive, HER2-negative, T1-2, histological grade 1-2 breast cancer, with tumour size of 5 cm or smaller were selected to match the characteristics of cohort 1 of the monarchE trial who would only have an indication for adjuvant abemaciclib if found to have 4 or more nodal metastases. The primary study objective was to determine the number of patients who developed patient-reported severe or very severe impairment of physical arm function after cALND (as measured by the Lymphedema Functioning, Disability, and Health [Lymph-ICF] Questionnaire) 1 year after surgery to avoid one invasive disease-free survival event at 5 years with 2 years of adjuvant abemaciclib, using invasive disease-free survival event data from cohort 1 of the monarchE trial. The SENOMAC trial is registered with ClincialTrials.gov, NCT02240472, and is closed to accrual and ongoing. FINDINGS: Between Jan 31, 2015, and Dec 31, 2021, 2766 patients were enrolled in SENOMAC and randomly assigned to cALND (n=1384) or sentinel node biopsy only (n=1382), of whom 2540 were included in the per-protocol population. 1705 (67%) of 2540 patients met this post-hoc study's eligibility criteria, of whom 802 (47%) had a cALND and 903 (53%) had a sentinel lymph node biopsy only. Median age at randomisation was 62 years (IQR 52-71), 1699 (>99%) of 1705 patients were female, and six (<1%) were male. Among 1342 patients who responded to questionnaires, after a median follow-up of 45·2 months (IQR 25·6-59·8; data cutoff Nov 17, 2023), patient-reported severe or very severe impairment of physical arm function was reported in 84 (13%) of 634 patients who had cALND versus 30 (4%) of 708 who had sentinel lymph node biopsy only (χ2 test p<0·0001). To avoid one invasive disease-free survival event at 5 years with adjuvant abemaciclib, cALND would need to be performed in 104 patients, and would result in nine patients having severe or very severe impairment of physical arm function 1 year after surgery. INTERPRETATION: As a method to potentially identify an indication for abemaciclib, and subsequently avoid invasive disease-free survival events at 5 years with 2 years of adjuvant abemaciclib, cALND carries a substantial risk of severe or very severe arm morbidity and so cALND should be discouraged for this purpose. FUNDING: Swedish Research Council, the Swedish Cancer Society, the Nordic Cancer Union, and the Swedish Breast Cancer Association.
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BACKGROUND: Studies identifying risk factors for death from breast cancer after ductal carcinoma in situ (DCIS) are rare. In this retrospective nested case-control study, clinicopathological factors in women treated for DCIS and who died from breast cancer were compared with those of patients with DCIS who were free from metastatic disease. METHODS: The study included patients registered with DCIS without invasive carcinoma in Sweden between 1992 and 2012. This cohort was linked to the National Cause of Death Registry. Of 6964 women with DCIS, 96 were registered with breast cancer as cause of death (cases). For each case, up to four controls (318; women with DCIS, alive and without metastatic breast cancer at the time of death of the corresponding case) were selected randomly by incidence density sampling. Whole slides of tumour tissue were evaluated for DCIS grade, comedo necrosis, and intensity of periductal lymphocytic infiltrate. Composition of the immune cell infiltrate, expression of oestrogen receptor, progesterone receptor, human epidermal growth factor receptor 2, and proliferation marker Ki-67 were scored on tissue microarrays. Clinical information was obtained from medical records. Information on date, site, and histological characteristics of local and distant recurrences was obtained from medical records for both cases and controls. RESULTS: Tumour tissue was analysed from 65 cases and 195 controls. Intense periductal lymphocytic infiltrate around DCIS was associated with an increased risk of later dying from breast cancer (OR 2.21. 95% c.i. 1.01 to 4.84). Tumours with more intense lymphocytic infiltrate had a lower T cell/B cell ratio. None of the other biomarkers correlated with increased risk of breast cancer death. CONCLUSION: The immune response to DCIS may influence the risk of dying from breast cancer.
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Neoplasias da Mama , Carcinoma Ductal de Mama , Carcinoma Intraductal não Infiltrante , Feminino , Humanos , Neoplasias da Mama/patologia , Carcinoma Intraductal não Infiltrante/patologia , Estudos de Casos e Controles , Estudos Retrospectivos , Fatores de Risco , Inflamação , Carcinoma Ductal de Mama/patologiaRESUMO
BACKGROUND: Breast cancer is the most common cancer in women. Cancer cells can persist in a prolonged dormant state for years without any clinical evidence of disease creating an urgent need to better understand the molecular mechanisms leading to relapse. This study aimed to identify extracellular matrix (ECM) components associated with hypoxia-induced breast cancer dormancy. The effects of selected ECM proteins on breast cancer cell proliferation were analyzed, along with their correlation with established prognostic markers in human breast cancer tissue. MATERIALS AND METHODS: Screening of extracellular matrix proteins was performed in hypoxia-induced dormant MCF-7 breast cancer cells. Proliferation of MCF-7 cells in vitro was subsequently determined in the presence of recombinant ColVII. Adipose tissue-derived mesenchymal stem cells (AdMSCs) subpopulation overexpressing ColVII were indirectly isolated by ColVII receptor integrin-α6 specific antibodies. AdMSCs- MCF-7 3D spheroid cultures were generated to model solid tumour conditions. In addition, the association between ColVII and various prognostic markers was evaluated in clinical samples of human breast cancer tissue. RESULTS: Dormant MCF-7 cells showed an elevated expression of ColVII while MCF-7 cells cultured on ColVII exhibited reduced proliferation in vitro. In AdMSCs-MCF-7 3D spheroids, a reduced proliferation of MCF-7 cells was observed in Int-α6+/ ColVIIhigh compared with Int-α6-/ ColVIIlow AdMSCs spheroids. In human tissue, high ColVII expression correlated to several positive prognostic markers. Staining for Cytokeratin-5 revealed that ColVIIhigh-expressing cells were predominantly myoepithelial cells. CONCLUSION: ColVII is associated with reduced proliferation of breast cancer cells in vitro. ColVII is strongly expressed in myoepithelial cells and in breast cancer tissue the high ColVII expression correlates with several well-known positive prognostic markers, highlighting its potential as a prognostic marker in breast cancer.
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PURPOSE: Peritoneal infection, due to anastomotic leakage, after resection for colorectal cancer have been shown to associate with increased cancer recurrence and mortality, as well as cardiovascsular morbidity. Alterations in circulating protein levels could help shed light on the underlying mechanisms, prompting this exploratory study of 64 patients operated for colorectal cancer with anastomosis. METHODS: Thirty-two cases who suffered a postoperative peritoneal infection were matched with 32 controls who had a complication-free postoperative stay. Proteins in serum samples at their first postoperative visit and at one year after surgery were analysed using proximity extension assays and enzyme-linked immunosorbent assays. Multivariate projection methods, adjusted for multiple testing, were used to compare levels between groups, and enrichment and network analyses were performed. RESULTS: Seventy-seven proteins, out of 270 tested, were differentially expressed at a median sampling time of 41 days postoperatively. These proteins were all normalised one year after surgery. Many of the differentially expressed top hub proteins have known involvement in cancer progression, survival, invasiveness and metastasis. Over-represented pathways were related to cardiomyopathy, cell-adhesion, extracellular matrix, phosphatidylinositol-3-kinase/Akt (PI3K-Akt) and transforming growth factor beta (TGF-ß) signaling. CONCLUSION: These affected proteins and pathways could provide clues as to why patients with peritoneal infection might suffer increased cancer recurrence, mortality and cardiovascular morbidity.
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Neoplasias Colorretais , Humanos , Masculino , Feminino , Neoplasias Colorretais/cirurgia , Neoplasias Colorretais/sangue , Neoplasias Colorretais/patologia , Idoso , Pessoa de Meia-Idade , Peritonite/sangue , Peritonite/cirurgia , Peritonite/etiologia , Estudos de Casos e Controles , Fístula Anastomótica/sangue , Fístula Anastomótica/etiologia , Complicações Pós-Operatórias/sangue , Complicações Pós-Operatórias/etiologia , Colectomia/efeitos adversosRESUMO
Screening of the general population for cancer is a matter of primary prevention reducing the burden of disease. Whilst this is successful for several cancers including breast, colon and prostate, the situation to screen and hence prevent pancreatic cancer is different. The organ is not as accessible to simple physical exam or biological samples (fecal or blood test). Neither exists a blood test such as PSA that is cost-effective. Reviewing the evidence from screening risk groups for pancreatic cancer, one must conclude that there is no rational at present to screen the general population, for a lack of appropriate tests.
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Detecção Precoce de Câncer , Neoplasias Pancreáticas , Humanos , Neoplasias Pancreáticas/genética , Neoplasias Pancreáticas/diagnóstico , Neoplasias Pancreáticas/prevenção & controle , Detecção Precoce de Câncer/métodos , Predisposição Genética para Doença , Vigilância da População/métodos , Programas de Rastreamento/métodos , Masculino , FemininoRESUMO
OBJECTIVES: Pancreatic ductal adenocarcinoma (PDAC) is characterized by poor prognosis and lack of effective diagnostic and prognostic biomarkers. A rich and activated desmoplastic tumor stroma is considered a hallmark of PDAC, and therefore stromal components could be a source of possible new prognostic biomarkers. Expression of collagen VI (COL6) has been found to associate with prognosis in many forms of cancer but has been less extensively studied in PDAC. Some previous studies indicate that COL6 expression is upregulated in PDAC, and it could have prognostic value. METHODS: In this study the expression of COL6 was analyzed by immunohistochemistry in tissue microarrays (TMAs) containing tumor tissue samples from 164 (n = 164) PDAC patients who had undergone surgical resection. Scoring results were combined with clinical data, and the prognostic significance of COL6 was estimated with Kaplan-Meier survival estimates and multivariable Cox regression analysis. COL6 protein expression patterns were further investigated in The Cancer Proteome Atlas (TCPA) dataset (n = 103) and in the Clinical Proteomic Tumor Analysis Consortium (CPTAC) dataset (n = 138). COL6 mRNA expression in PDAC tissue was investigated using The Cancer Genome Atlas (TCGA) by forming a dataset containing gene expression data and corresponding clinical variables of 168 (n = 168) PDAC patients. RESULTS: In this large PDAC TMA cohort we could not find statistically significant (p < 0.05) differences in survival when comparing patients with high and low protein expression of any of the analyzed COL6 α-chains (α1(VI): HR 0.90, 95% CI 0.64-1.28; α2(VI): HR 1.28, 95% CI 0.86-1.89; α3(VI): HR 0.91, 95%CI 0.64-1.29). Similar results were obtained when assessing expression of COL6 in public data from TCPA, CPTAC and TCGA. CONCLUSIONS: In contrast with previous studies and some other cancer forms, we did not find any association of COL6 tissue expression and PDAC survival on protein or mRNA level.
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BACKGROUND: The Swedish Breast Reconstruction Outcome Study (SweBRO) initiative is a nationwide study with the primary aim of assessing long-term outcomes after mastectomy with and without breast reconstruction (BR). The current part (SweBRO 2) is designed to evaluate health-related quality of life (HRQoL), with the hypothesis that BR has a positive impact on patient-reported HRQoL in the long-term. METHODS: Women who underwent mastectomy in Sweden in 2000, 2005, or 2010 and were alive at the time of the survey were identified through the National Breast Cancer Registry. Eligible participants received formal invitation letters to take part in a survey evaluating their HRQoL at 5 , 10, or 15 years post-mastectomy. The EORTC QLQ-C30, EORTC QLQ-BR23, and EQ-5D-3L questionnaires were employed. RESULTS: Of 2904 respondents (50% of 5853 invited), 895 (31%) had received BR. Among them, 516 (58%) were reconstructed with implants and 281 (31%) with autologous tissue. Women with BR scored significantly better in the EORCT QLQ-C30 physical functioning domain (mean 90 versus 81 points), fatigue (mean 21 versus 25), and dyspnoea (mean 16 versus 22) compared to non-reconstructed women. The EORTC QLQ-BR23 revealed that women with BR experienced favourable sexual functioning compared with non-reconstructed women (mean 26 versus 14). The EQ-5D-3L visual analogue scale score was similar between groups. CONCLUSION: The current study underscores the benefits of BR for long-term well-being, for example, in terms of physical and sexual functioning. These underline the importance of informing women undergoing mastectomy about BR alternatives and its potential benefits in enhancing long-term well-being.
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Neoplasias da Mama , Mamoplastia , Feminino , Humanos , Mastectomia/efeitos adversos , Suécia/epidemiologia , Neoplasias da Mama/cirurgia , Qualidade de Vida , Medidas de Resultados Relatados pelo PacienteRESUMO
INTRODUCTION: Fibrillar collagens accumulate in the breast cancer stroma and appear as poorly defined spiculated masses in mammography imaging. The prognostic value of tissue type I collagen remains elusive in treatment-naïve and chemotherapy-treated breast cancer patients. Here, type I collagen mRNA and protein expression were analysed in 2 large independent breast cancer cohorts. Levels were related to clinicopathological parameters, prognostic biomarkers, and outcome. METHOD: COL1A1 mRNA expression was analysed in 2509 patients with breast cancer obtained from the cBioPortal database. Type I collagen protein expression was studied by immunohistochemistry in 1395 women diagnosed with early invasive breast cancer. RESULTS: Low COL1A1 mRNA and protein levels correlated with poor prognosis features, such as hormone receptor negativity, high histological grade, triple-negative subtype, node positivity, and tumour size. In unadjusted analysis, high stromal type I collagen protein expression was associated with improved overall survival (OS) (HR = 0.78, 95% CI = 0.61-0.99, p = .043) and trended towards improved breast cancer-specific survival (BCSS) (HR = 0.65, 95% CI = 0.42-1.01, P = 0.053), although these findings were lost after adjustment for other clinical variables. In unadjusted analysis, high expression of type I collagen was associated with better OS (HR = 0.70, 95% CI = 0.55-0.90, P = .006) and BCSS (HR = 0.55, 95% CI = 0.34-0.88, P = .014) among patients not receiving chemotherapy. Strikingly, the opposite was observed among patients receiving chemotherapy. There, high expression of type I collagen was instead associated with worse OS (HR = 1.83, 95% CI = 0.65-5.14, P = .25) and BCSS (HR = 1.72, 95% CI = 0.54-5.50, P = .357). CONCLUSION: Low stromal type I collagen mRNA and protein expression are associated with unfavourable tumour characteristics in breast cancer. Stromal type I collagen might predict chemotherapy response.
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Biomarcadores Tumorais , Neoplasias da Mama , Colágeno Tipo I , Humanos , Feminino , Neoplasias da Mama/patologia , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/metabolismo , Neoplasias da Mama/mortalidade , Biomarcadores Tumorais/metabolismo , Biomarcadores Tumorais/análise , Colágeno Tipo I/metabolismo , Prognóstico , Pessoa de Meia-Idade , Cadeia alfa 1 do Colágeno Tipo I , Idoso , Adulto , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Células Estromais/metabolismo , Células Estromais/patologiaRESUMO
Background: Pancreatic ductal adenocarcinoma (pancreatic cancer) is often detected at late stages resulting in poor overall survival. To improve survival, more patients need to be diagnosed early when curative surgery is feasible. We aimed to identify circulating metabolites that could be used as early pancreatic cancer biomarkers. Methods: We performed metabolomics by liquid and gas chromatography-mass spectrometry in plasma samples from 82 future pancreatic cancer patients and 82 matched healthy controls within the Northern Sweden Health and Disease Study (NSHDS). Logistic regression was used to assess univariate associations between metabolites and pancreatic cancer risk. Least absolute shrinkage and selection operator (LASSO) logistic regression was used to design a metabolite-based risk score. We used receiver operating characteristic (ROC) analyses to assess the discriminative performance of the metabolite-based risk score. Results: Among twelve risk-associated metabolites with a nominal P value <0.05, we defined a risk score of three metabolites [indoleacetate, 3-hydroxydecanoate (10:0-OH), and retention index (RI): 2,745.4] using LASSO. A logistic regression model containing these three metabolites, age, sex, body mass index (BMI), smoking status, sample date, fasting status, and carbohydrate antigen 19-9 (CA 19-9) yielded an internal area under curve (AUC) of 0.784 [95% confidence interval (CI): 0.714-0.854] compared to 0.681 (95% CI: 0.597-0.764) for a model without these metabolites (P value =0.007). Seventeen metabolites were significantly associated with pancreatic cancer survival [false discovery rate (FDR) <0.1]. Conclusions: Indoleacetate, 3-hydroxydecanoate (10:0-OH), and RI: 2,745.4 were identified as the top candidate biomarkers for early detection. However, continued efforts are warranted to determine the usefulness of these metabolites as early pancreatic cancer biomarkers.
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Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with poor survival. Novel biomarkers are urgently needed to improve the outcome through early detection. Here, we aimed to discover novel biomarkers for early PDAC detection using multi-omics profiling in pre-diagnostic plasma samples biobanked after routine health examinations. A nested case-control study within the Northern Sweden Health and Disease Study was designed. Pre-diagnostic plasma samples from 37 future PDAC patients collected within 2.3 years before diagnosis and 37 matched healthy controls were included. We analyzed metabolites using liquid chromatography mass spectrometry and gas chromatography mass spectrometry, microRNAs by HTG edgeseq, proteins by multiplex proximity extension assays, as well as three clinical biomarkers using milliplex technology. Supervised and unsupervised multi-omics integration were performed as well as univariate analyses for the different omics types and clinical biomarkers. Multiple hypothesis testing was corrected using Benjamini-Hochberg's method and a false discovery rate (FDR) below 0.1 was considered statistically significant. Carbohydrate antigen (CA) 19-9 was associated with PDAC risk (OR [95 % CI] = 3.09 [1.31-7.29], FDR = 0.03) and increased closer to PDAC diagnosis. Supervised multi-omics models resulted in poor discrimination between future PDAC cases and healthy controls with obtained accuracies between 0.429-0.500. No single metabolite, microRNA, or protein was differentially altered (FDR < 0.1) between future PDAC cases and healthy controls. CA 19-9 levels increase up to two years prior to PDAC diagnosis but extensive multi-omics analysis including metabolomics, microRNAomics and proteomics in this cohort did not identify novel early biomarkers for PDAC.
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BACKGROUND AND PURPOSE: Recommendations for regional radiotherapy (RT) of sentinel lymph node (SLN)-positive breast cancer are debated. We here report a RT quality assessment of the SENOMAC trial. MATERIALS AND METHODS: The SENOMAC trial randomized clinically node-negative breast cancer patients with 1-2 SLN macrometastases to completion axillary lymph node dissection (cALND) or SLN biopsy only between 2015-2021. Adjuvant RT followed national guidelines. RT plans for patients included in Sweden and Denmark until June 2019 were collected (N = 1176) and compared to case report forms (CRF). Dose to level I (N = 270) and the humeral head (N = 321) was analyzed in detail. RESULTS: CRF-data and RT plans agreed in 99.3 % (breast/chest wall) and in 96.6 % of patients (regional RT). Congruence for whether level I was an intended RT target was lower (78 %). In accordance with Danish national guidelines, level I was more often an intended target in the SLN biopsy only arm (N = 334/611, 55 %,) than in the cALND arm (N = 174/565, 31 %,). When an intended target, level I received prescribed dose to 100 % (IQR 98-100 %) of the volume. However, even when not an intended target, full dose was delivered to > 80 % of level I (IQR 75-90 %). The intentional inclusion of level I in the target volume more than doubled the dose received by ≥ 50 % of the humeral head. CONCLUSION: Congruence between CRF data and RT plans was excellent. Level I received a high dose coverage even when not intentionally included in the target. Including level I in target significantly increased dose to the humeral head.
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Neoplasias da Mama , Humanos , Feminino , Neoplasias da Mama/radioterapia , Neoplasias da Mama/patologia , Estudos Prospectivos , Biópsia de Linfonodo Sentinela , Excisão de Linfonodo , Dosagem Radioterapêutica , Suécia , Radioterapia Adjuvante , Axila , Garantia da Qualidade dos Cuidados de Saúde , Dinamarca , Planejamento da Radioterapia Assistida por Computador/métodos , Linfonodo Sentinela/patologia , Metástase Linfática/radioterapia , Pessoa de Meia-Idade , IdosoRESUMO
BACKGROUND: A high body mass index (BMI, kg/m2) is associated with decreased risk of breast cancer before menopause, but increased risk after menopause. Exactly when this reversal occurs in relation to menopause is unclear. Locating that change point could provide insight into the role of adiposity in breast cancer etiology. METHODS: We examined the association between BMI and breast cancer risk in the Premenopausal Breast Cancer Collaborative Group, from age 45 up to breast cancer diagnosis, loss to follow-up, death, or age 55, whichever came first. Analyses included 609,880 women in 16 prospective studies, including 9956 who developed breast cancer before age 55. We fitted three BMI hazard ratio (HR) models over age-time: constant, linear, or nonlinear (via splines), applying piecewise exponential additive mixed models, with age as the primary time scale. We divided person-time into four strata: premenopause; postmenopause due to natural menopause; postmenopause because of interventional loss of ovarian function (bilateral oophorectomy (BO) or chemotherapy); postmenopause due to hysterectomy without BO. Sensitivity analyses included stratifying by BMI in young adulthood, or excluding women using menopausal hormone therapy. RESULTS: The constant BMI HR model provided the best fit for all four menopausal status groups. Under this model, the estimated association between a five-unit increment in BMI and breast cancer risk was HR=0.87 (95% CI: 0.85, 0.89) before menopause, HR=1.00 (95% CI: 0.96, 1.04) after natural menopause, HR=0.99 (95% CI: 0.93, 1.05) after interventional loss of ovarian function, and HR=0.88 (95% CI: 0.76, 1.02) after hysterectomy without BO. CONCLUSION: The BMI breast cancer HRs remained less than or near one during the 45-55 year age range indicating that the transition to a positive association between BMI and risk occurs after age 55.