***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Complications of axillary surgery occur due to severance of the intercostobrachial nerve ( ICBN ) . The feasibility and benefit of preserving the ICBN to prevent sensory loss was studied prospect ively Background The heterogeneity statistic I2 , interpreted as the percentage of variability due to heterogeneity between studies rather than sampling error , depends on precision , that is , the size of the studies included . Methods Based on a real meta- analysis , we simulate artificially ' inflating ' the sample size under the r and om effects model . For a given inflation factor M = 1 , 2 , 3 , ... and for each trial i , we create a M-inflated trial by drawing a treatment effect estimate from the r and om effects model , using si2MathType@MTEF@5@5@+=feaagaart1ev2aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacPC6xNi = xH8viVGI8Gi = hEeeu0xXdbba9frFj0xb9qqpG0dXdb9aspeI8k8fiI+fsY = rqGqVepae9pg0db9vqaiVgFr0xfr = xfr = xc9adbaqaaeGaciGaaiaabeqaaeqabiWaaaGcbaGaem4Cam3aa0baaSqaaiabdMgaPbqaaiabikdaYaaaaaa@2FBE@/M as within-trial sampling variance . Results As precision increases , while estimates of the heterogeneity variance τ2 remain unchanged on average , estimates of I2 increase rapidly to nearly 100 % . A similar phenomenon is apparent in a sample of 157 meta-analyses . Conclusion When deciding whether or not to pool treatment estimates in a meta- analysis , the yard-stick should be the clinical relevance of any heterogeneity present . τ2 , rather than I2 , is the appropriate measure for this purpose HYPOTHESIS Axillary relapse in node-negative patients staged with sentinel lymph node ( SLN ) biopsy alone is no more frequent than in patients treated with st and ard axillary dissection . Morbidity is less for patients who had SLN biopsy . DESIGN , SETTING , AND PATIENTS Between October 14 , 1997 , and August 31 , 2001 , 1253 consecutive women with primary invasive breast cancer were prospect ively entered into an SLN biopsy data base . Completion axillary dissection was performed in 164 patients after SLN biopsy as part of a training protocol . INTERVENTIONS Patients were contacted by question naire or telephone to determine breast cancer relapse ; presence of arm lymphedema , arm pain , axillary infection , or seroma formation ; and tumor recurrence or death . MAIN OUTCOME MEASURES chi2 or Fisher exact tests and Wilcoxon rank sum tests were used to analyze categorical and continuous variables . Logistic regression was used to analyze morbidity . RESULTS Of 1253 women , 894 ( 71 % ) were node negative by SLN biopsy alone ( n = 730 [ 82 % ] ) or SLN biopsy and completion axillary dissection ( n = 164 [ 18 % ] ) . Question naires were completed by 776 patients ( 87 % ) . Mean + /- SD follow-up was 2.4 + /- 0.9 years . Patients with axillary dissections reported a significantly higher occurrence of arm lymphedema ( 34 % ) , arm pain ( 38 % ) , seroma formation ( 24 % ) , and infection ( 9 % ) vs SLN biopsy-only patients ( 6 % , 14 % , 7 % , and 3 % , respectively ) . One axillary relapse ( 0.1 % ) occurred during follow-up of 685 women who underwent SLN biopsy only . CONCLUSIONS With intermediate-term follow-up , there was 1 axillary recurrence in 685 SLN node-negative women , supporting use of SLN biopsy as an accurate method for staging breast cancer . Biopsy of the SLN was associated with significantly less morbidity than completion axillary dissection BACKGROUND Sentinel lymph node biopsy in women with operable breast cancer is routinely used in some countries for staging the axilla despite limited data from r and omized trials on morbidity and mortality outcomes . We conducted a multicenter r and omized trial to compare quality -of-life outcomes between patients with clinical ly node-negative invasive breast cancer who received sentinel lymph node biopsy and patients who received st and ard axillary treatment .  METHODS The primary outcome measures were arm and shoulder morbidity and quality of life .  From November 1999 to October 2003 , 1031 patients were r and omly assigned to undergo sentinel lymph node biopsy ( n = 515 ) or st and ard axillary surgery ( n = 516 ) . Patients with sentinel lymph node metastases proceeded to delayed axillary clearance or received axillary radiotherapy ( depending on the protocol at the treating institution ) . Intention-to-treat analyses of data at 1 , 3 , 6 , and 12 months after surgery are presented . All statistical tests were two-sided . RESULTS The relative risks of any lymphedema and sensory loss for the sentinel lymph node biopsy group compared with the st and ard axillary treatment group at 12 months were 0.37 ( 95 % confidence interval [ CI ] = 0.23 to 0.60 ; absolute rates : 5 % versus 13 % ) and 0.37 ( 95 % CI = 0.27 to 0.50 ; absolute rates : 11 % versus 31 % ) , respectively . Drain usage , length of hospital stay , and time to resumption of normal day-to-day activities after surgery were statistically significantly lower in the sentinel lymph node biopsy group ( all P < .001 ) , and axillary operative time was reduced ( P = .055 ) . Overall patient-recorded quality of life and arm functioning scores were statistically significantly better in the sentinel lymph node biopsy group throughout ( all P < or = .003 ) . These benefits were seen with no increase in anxiety levels in the sentinel lymph node biopsy group ( P > .05 ) . CONCLUSION Sentinel lymph node biopsy is associated with reduced arm morbidity and better quality of life than st and ard axillary treatment and should be the treatment of choice for patients who have early-stage breast cancer with clinical ly negative nodes PURPOSE To provide evidence -based recommendations to practicing oncologists , surgeons , and radiation therapy clinicians to up date the 2005 clinical practice guideline on the use of sentinel node biopsy ( SNB ) for patients with early-stage breast cancer . METHODS The American Society of Clinical Oncology convened an Up date Committee of experts in medical oncology , pathology , radiation oncology , surgical oncology , guideline implementation , and advocacy . A systematic review of the literature was conducted from February 2004 to January 2013 in Medline . Guideline recommendations were based on the review of the evidence by Up date Committee . RESULTS This guideline up date reflects changes in practice since the 2005 guideline . Nine r and omized clinical trials ( RCTs ) met systematic review criteria for clinical questions 1 and 2 ; 13 cohort studies informed clinical question 3 . RECOMMENDATIONS Women without sentinel lymph node ( SLN ) metastases should not receive axillary lymph node dissection ( ALND ) .  Women with one to two metastatic SLNs planning to undergo breast-conserving surgery with whole-breast radiotherapy should not undergo ALND ( in most cases ) . Women with SLN metastases who will undergo mastectomy should be offered ALND . These three recommendation are based on RCTs . Women with operable breast cancer and multicentric tumors , with ductal carcinoma in situ ( DCIS ) who will undergo mastectomy , who previously underwent breast and /or axillary surgery , or who received preoperative/neoadjuvant systemic therapy may be offered SNB . Women who have large or locally advanced invasive breast cancer ( tumor size T3/T4 ) , inflammatory breast cancer , or DCIS ( when breast-conserving surgery is planned ) or are pregnant should not undergo SNB . These recommendations are based on cohort studies and /or informal consensus . In some cases , up date d evidence was insufficient to up date previous recommendations UNLABELLED Chronic pain following breast cancer surgery is associated with decreased health-related quality of life and is a source of additional psychosocial distress in women who are already confronting the multiple stresses of cancer . Few prospect i ve studies have identified risk factors for chronic pain following breast cancer surgery . Putative demographic , clinical , and psychosocial risk factors for chronic pain were evaluated prospect ively in 95 women scheduled for breast cancer surgery . In a multivariate analysis of the presence of chronic pain , only younger age was associated with a significantly increased risk of developing chronic pain 3 months after surgery . In an analysis of the intensity of chronic pain , however , more invasive surgery , radiation therapy after surgery , and clinical ly meaningful acute postoperative pain each independently predicted more intense chronic pain 3 months after surgery . Preoperative emotional functioning variables did not independently contribute to the prediction of either the presence or the intensity of chronic pain after breast cancer surgery . These findings not only increase underst and ing of risk factors for chronic pain following breast cancer surgery and the processes that may contribute to its development but also provide a basis for the development of preventive interventions . PERSPECTIVE Clinical variables and severe acute pain were risk factors for chronic pain following breast cancer surgery , but psychosocial distress was not , which provides a basis for hypothesizing that aggressive management of acute postoperative pain may reduce chronic pain BACKGROUND Post-mastectomy pain syndrome is defined as a chronic pain that persists beyond the normal healing time of 3 months . It is considered a neuropathic condition that arises after surgery for breast cancer . AIM To evaluate the incidence and risk factors of pain syndromes in patients undergoing surgical treatment of breast cancer in the National Cancer Institute . METHODS This study is a prospect i ve cohort of women undergoing surgical treatment for breast cancer from September 2008 to June 2009 , followed up until 6 months postoperatively . RESULTS AND CONCLUSIONS One hundred seventy-four women were examined . The mean age was 58 years . The incidence of pain syndrome was 52 % . Younger women ( < 40 years ) and those who were su bmi tted to axillary lymph node dissection ( with more than 15 lymph nodes excised ) have shown a significantly increased risk of pain syndrome after surgery for breast cancer ( relative risk ( RR ) = 5.23 95 % confidence interval ( CI ) : 1.11 - 24.64 ) and ( RR=2.01 95 % CI : 1.08 - 3.75 ) Background A sound underst and ing of the benefits of different treatment options and their health-related quality of life ( HRQoL ) impacts is required for optimal breast cancer care . Methods A cross-sectional cohort study was conducted to determine the prevalence and severity of persistent functional decrements and symptoms and identify demographic , clinical and treatment variables associated with poorer outcomes . Four hundred English-speaking women treated for ductal carcinoma-in-situ or stage I to III breast cancer between 1999 and 2009 , at least 12 months after surgery and currently disease free , were r and omly selected and invited to complete ( 1 ) the Breast Cancer Treatment Outcome Scale and ( 2 ) the EORTC core Quality of Life Question naire , version 3 . Results The response rate was 85.60 % . Many participants reported moderate to severe decrements in a number of HRQoL domains , including functional well-being ( 15 % ) , cosmetic status ( 32 % ) and overall quality of life ( 21 % ) . There were significant associations ( p < .05 ) between younger age and poorer HRQoL but none between time since surgery and morbidity ( p > .05 ) . Different treatments were associated with different HRQoL impacts . Poorer functional status was predicted by axillary dissection ( p = .011 ) , and adjuvant radiotherapy was a significant predictor of breast-specific pain ( p < .05 ) . Conclusions Many breast cancer survivors report long-term morbidity that is unaffected by time since surgery . The significant associations between the extent of locoregional therapies and poorer HRQoL outcomes emphasize the importance of the safe tailoring of these treatments PURPOSE To evaluate toxicity and cosmetic outcome ( CO ) in breast cancer survivors treated with three-dimensional conformal radiotherapy with a hypofractionated , simultaneous integrated boost ( 3D-CRT-SIB )  and to identify risk factors for toxicity , with special focus on the impact of age . METHODS AND MATERIAL S Included were 940 consecutive disease-free patients treated for breast cancer ( Stage 0-III ) with 3D-CRT-SIB , after breast-conserving surgery , from 2005 to 2010 .  Physician-rated toxicity ( Common Terminology Criteria for Adverse Events version 3.0 ) and CO were prospect ively assessed during yearly follow-up , up to 5 years after radiotherapy . Multivariate logistic regression analyses using a bootstrapping method were performed . RESULTS At 3 years , toxicity scores of 436 patients were available . Grade ≥ 2 fibrosis in the boost area was observed in 8.5 % , non-boost fibrosis 
    Output:
    
High- quality evidence showed no association with body mass index , type of breast surgery , chemotherapy or endocrine therapy .
INTERPRETATION Development of persistent pain after breast cancer surgery was associated with younger age , radiotherapy , axillary lymph node dissection , greater acute postoperative pain and preoperative pain .
Axillary lymph node dissection provides the only high-yield target for a modifiable risk factor to prevent the development of persistent pain after breast cancer surgery