Contrast-Induced Acute Kidney Injury Among Patients With Chronic Kidney Disease Undergoing Imaging Studies: A Meta-Analysis.

OBJECTIVE. Contrast-induced nephropathy (CIN) generally is the main concern for patients with chronic kidney disease (CKD) undergoing contrast-enhanced imaging. To evaluate the risk of nephropathy induced by IV contrast medium (CM) in patients with CKD, we performed a meta-analysis. MATERIALS AND METHODS. We searched for PubMed and MEDLINE articles that were published up to October 3, 2018, contained the phrase "contrast medium" or "contrast media" and the word "renal," and included patients with CKD and a proper control group. The publications that were identified were reviewed, and only studies that used an IV route of CM administration were selected. Subgroup analysis was performed according to the estimated glomerular filtration rate. RESULTS. Six studies including 55,963 participants were selected. The Peto method and random-effects model were applied. IV infusion of CM did not lead to the deterioration of renal function in patients with CKD compared with those without CKD (odds ratio [OR], 1.07; 95% CI, 0.98-1.17; I2, 35.3%). As the estimated glomerular filtration rate decreased, fewer patients received IV CM. The ORs for CIN on the basis of CKD stage were as follows: 1.11 (95% CI, 0.95-1.30; I2, 4.0%) for stage 2 CKD, 1.05 (95% CI, 0.93-1.18, I2, 48.3%) for CKD lower than stage 3, 1.06 (95% CI, 0.94-1.19; I2, 32.0%) for stage 3 CKD, 1.08 (95% CI, 0.84-1.39; I2, 44.6%) for CKD lower than stage 4, 0.86 (95% CI, 0.37-2.00) for stage 4 CKD, and 0.26 (95% CI, 0.02-3.4) for stage 5 CKD in one study only. All analyses showed the lack of difference in the ORs for CIN between participants who received IV injection of CM and those who did not. CONCLUSION. Retrospective cohort studies of IV radiographic CM have failed to show renal damage in patients with CKD. This retrospective study is limited, and other risk factors for CIN might not be distributed evenly.

Insulin Receptor Substrate-1 (IRS-1) and IRS-2 expression levels are associated with prognosis in non-small cell lung cancer (NSCLC).

The insulin-like growth factor-1 (IGF-1) signaling pathway has been implicated in non-small cell lung cancer (NSCLC) outcomes and resistance to targeted therapies. However, little is known regarding the molecular mechanisms by which this pathway contributes to the biology of NSCLC. The insulin receptor substrate (IRS) proteins are cytoplasmic adaptor proteins that signal downstream of the IGF-1R and determine the functional outcomes of this signaling pathway. In this study, we assessed the expression patterns of IRS-1 and IRS-2 in NSCLC to identify associations between IRS-1 and IRS-2 expression levels and survival outcomes in the two major histological subtypes of NSCLC, adenocarcinoma (ADC) and squamous cell carcinoma (SCC). High IRS-2 expression was significantly associated with decreased overall survival in adenocarcinoma (ADC) patients, whereas low IRS-1 cytoplasmic expression showed a trend toward association with decreased overall survival in squamous cell carcinoma (SCC) patients. Tumors with low IRS-1 and high IRS-2 expression were found to be associated with poor outcomes in ADC and SCC, indicating a potential role for IRS-2 in the aggressive behavior of NSCLC. Our results suggest distinct contributions of IRS-1 and IRS-2 to the biology of ADC and SCC that impact disease progression.

Coffee Intake and Obesity: A Meta-Analysis.

Many studies have explored the relationship between coffee-one of the most commonly consumed beverages today-and obesity. Despite inconsistent results, the relationship has not been systematically summarized. Thus, we conducted a meta-analysis by compiling data from 12 epidemiologic studies identified from PubMed and Embase through February 2019. The included studies assessed obesity by body mass index (BMI, a measure of overall adiposity) or waist circumference (WC, a measure of central adiposity); analyzed the measure as a continuous outcome or binary outcome. Using random effects model, weighted mean difference (WMD) and 95% confidence interval (CI) were obtained for continuous outcomes; summary relative risk (RR) and 95% CI for the highest vs. lowest categories of coffee intake were estimated for binary outcome. For BMI, WMD was -0.08 (95% CI -0.14, -0.02); RR was 1.49 (95% CI 0.97, 2.29). For WC, WMD was -0.27 (95% CI -0.51, -0.02) and RR was 1.07 (95% CI 0.84, 1.36). In subgroup analysis by sex, evidence for an inverse association was more evident in men, specifically for continuous outcome, with WMD -0.05 (95% CI -0.09, -0.02) for BMI and -0.21 (95% CI -0.35, -0.08) for WC. Our meta-analysis suggests that higher coffee intake might be modestly associated with reduced adiposity, particularly in men.

Which Should Be Used First for ALK-Positive Non-Small-Cell Lung Cancer: Chemotherapy or Targeted Therapy? A Meta-Analysis of Five Randomized Trials.

Background and objectives: Targeted therapy is widely used in the era of precision medicine. Whether the sequence in which targeted therapy and chemotherapy are performed matters, is however not known. We examined the impact of the sequential treatment of targeted therapy and chemotherapy among advanced anaplastic lymphoma kinase (ALK), non-small cell lung cancer (NSCLC) patients. Materials and Methods: Randomized controlled trials comparing the use of ALK inhibitors with chemotherapy were included in this meta-analysis. We estimated the hazard ratios (HRs) and 95% confidence intervals (CI), for progression-free survival (PFS) and overall survival (OS) from a random effects model. Two-sided statistical tests were used to determine the significance of these estimates. Results: In five eligible studies (1404 patients), ALK targeted therapy, in comparison with chemotherapy, had a significantly higher PFS (HR = 0.48; 95% CI, 0.42⁻0.55), but not significantly higher OS (HR = 0.88; 95% CI, 0.72⁻1.07). Crossover from chemotherapy to ALK inhibitors was allowed after progression in all trials. The sensitivity analysis of the use of ALK inhibitors as either the first- or second-line treatment, showed improvements in PFS but not in OS. Conclusions: Our results indicate that using targeted therapy first improved PFS, but that the sequence in which the treatments were performed did not cause a significant difference in overall survival.

Molecular Markers and Prognosis of Myelofibrosis in the Genomic Era: A Meta-analysis.

Molecular markers are important in guiding treatment and predicting outcome in the genomic era. Meta-analysis of molecular markers in myelofibrosis through a search of PubMed and Medline through October 31, 2017 was performed. Markers with more than 3 studies that compared overall survival (OS) and leukemia-free survival (LFS) were analyzed. A total of 16 studies were included. Hazard ratios (HRs) for OS were as follows: IDH 2.65 (95% confidence interval [CI], 1.66-4.21), SRSF2 2.12 (95% CI, 1.18-3.79), high-risk myeloma 2.11 (95% CI, 1.70-2.61), ASXL1 1.92 (95% CI, 1.60-2.32), EZH2 1.88 (95% CI, 1.32-2.67), JAK2 1.41 (95% CI, 1.04-1.93) in the univariate analysis and 1.49 (95% CI, 0.42-5.30) in the multivariate analysis. LFS of JAK2 and SRSF2 had HRs of 1.81 (95% CI, 0.42-5.30) and 0.36 (95% CI, 0.02-6.48), respectively. In conclusion, mutations in IDH, SRSF2, and ASXL1 had worse prognosis in OS with HRs around 2. JAK2 and SRSF2 mutation were not associated with increased leukemia transformation. The adverse effect of triple-negative, which was often compared with CALR mutation, needs to be explored.

IRS2 mutations linked to invasion in pleomorphic invasive lobular carcinoma.

Pleomorphic invasive lobular carcinoma (PILC) is an aggressive variant of invasive lobular breast cancer that is associated with poor clinical outcomes. Limited molecular data are available to explain the mechanistic basis for PILC behavior. To address this issue, targeted sequencing was performed to identify molecular alterations that define PILC. This sequencing analysis identified genes that distinguish PILC from classic ILC and invasive ductal carcinoma by the incidence of their genomic changes. In particular, insulin receptor substrate 2 (IRS2) is recurrently mutated in PILC, and pathway analysis reveals a role for the insulin receptor (IR)/insulin-like growth factor-1 receptor (IGF1R)/IRS2 signaling pathway in PILC. IRS2 mutations identified in PILC enhance invasion, revealing a role for this signaling adaptor in the aggressive nature of PILC.

Tumor characteristics and prognosis in women with pregnancy-associated breast cancer.

There is evidence of poor prognosis in women with pregnancy-associated breast cancer (PABC) diagnosed during pregnancy or within 2 years of delivery. Using a large, population-based cohort, we examined clinicopathologic features and survival in women with PABC. A cohort of women diagnosed with invasive breast cancer between 1992 and 2009 at ages 15-44 years was identified in the Swedish Cancer Register and the Breast Cancer Quality Registers. Dates of childbirths for each woman were retrieved from the Swedish Multi-Generation Register. Age-standardized distributions of tumor stage (tumor size, nodal status, metastasis), Elston grade and ER/PR/HER2 status were compared between nulliparous women and women with breast cancer during pregnancy and up to 10 years postdelivery. Adjusted hazard ratios for all-cause mortality rates among patients were estimated using Cox regression. We identified 1,661 nulliparous women with breast cancer, 778 women with PABC (97 during pregnancy, 270 within first and 411 within second year postdelivery) and 3,598 during 2-10 years postdelivery. Compared to nulliparous women, women with PABC, and especially women diagnosed 0-12 months after delivery, had more advanced T and N stage, and higher proportions of ER/PR negative, HER2 positive and triple-negative tumors. Increased hazard ratios were observed in women diagnosed within 5 years of delivery after adjustment for age, year, education and region. Following additional adjustment for tumor characteristics, the hazard ratios were attenuated and nonsignificant. The poorer prognosis observed in women with PABC appears to be largely explained by more adverse tumor characteristics at diagnosis.

The necessity of intrathecal chemotherapy for the treatment of breast cancer patients with leptomeningeal metastasis: A systematic review and pooled analysis.

Leptomeningeal carcinomatosis is a devastating disease. Despite its numerous complications, intrathecal (IT) chemotherapy remains a longstanding treatment for leptomeningeal carcinomatosis. Using case studies with internationally reported results, we attempted to determine the necessity of IT chemotherapy in treating leptomeningeal carcinomatosis. We conducted a systematic review and pooled analysis to compare hormone therapy, chemotherapy, and IT therapy. We excluded articles on IT trastuzumab therapy. We performed our literature search without language restriction. We retrieved articles that were published by as late as July 19, 2016. The present study was performed in accordance with the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analysis. The Cox proportional hazard regression model was performed to examine the effects of prognostic variables. A total of 34 patients from 32 studies were considered eligible. The median age of the patients in the hormone treatment, chemotherapy, and IT therapy groups was 46, 51.5, and 51 years, respectively. The median overall survival (OS) of the patients in the hormone treatment, chemotherapy, and IT therapy groups was 65, 52, and 41 weeks, respectively. One patient who received hormone therapy exhibited the longest survival of approximately 8.5 years. Only magnetic resonance imaging response was associated with OS (hazard ratio = 0.05, 95% confidence interval 0.00-0.74; p = 0.03). Hormone status, HER2 status, age, central nervous system radiation therapy, IT therapy, metastasis sites (central nervous system only vs. others), and cerebrospinal fluid responses were all not associated with OS. Given its obvious side effects and lack of evidence of effectiveness from prospective randomized clinical trials, IT chemotherapy should be used with caution in the treatment of leptomeningeal metastasis breast cancer patients.

Prenatal Maternal Physical Activity and Stem Cells in Umbilical Cord Blood.

PURPOSE: Early life processes, through influence on fetal stem cells, affect postnatal and adult health outcomes. This study examines the effects of physical activity before and during pregnancy on stem cell counts in umbilical cord blood. METHODS: We isolated mononuclear cells from umbilical cord blood samples from 373 singleton full-term pregnancies and quantified hematopoietic (CD34(+), CD34(+)CD38(-), and CD34(+) c-kit(+)), endothelial (CD34(+)CD133(+), CD34(+)CD133(+)VEGFR2(+), CD34(+)VEGFR2(+), and CD133(+)VEGFR2(+)), and putative breast (EpCAM(+), EpCAM(+)CD49f(+), EpCAM(+)CD49f(+)CD117(+), CD49f(+)CD24(+), CD24(+)CD29(+), and CD24(+)CD29(+)CD49f(+)) stem/progenitor cell subpopulations by flow cytometry. Information on physical activities before and during pregnancy was obtained from questionnaires. Weekly energy expenditure was estimated based on metabolic equivalent task values. RESULTS: Prepregnancy vigorous exercise was associated positively with levels of endothelial CD34(+)CD133(+), CD34(+)CD133(+)VEGFR2(+), CD34(+)VEGFR2(+), and CD133(+)VEGFR2(+ )progenitor cell populations (P = 0.02, P = 0.01, P = 0.001, and P = 0.003, respectively); positive associations were observed in samples from the first births and those from the second or later births. Prepregnancy moderate and light exercises and light exercise during the first trimester were not significantly associated with any stem/progenitor cell population. Light exercise during the second trimester was positively associated with CD34(+)VEGFR2(+) endothelial progenitor cells (P = 0.03). In addition, levels of EpCAM(+)CD49f(+) and CD49f(+)CD24(+) breast stem cells were significantly lower among pregnant women who engaged in vigorous/moderate exercise during pregnancy (P = 0.05 and P = 0.02, respectively). CONCLUSIONS: Vigorous exercise before pregnancy increases the number of endothelial progenitor cells in umbilical cord blood and thus could potentially enhance endothelial function and improve cardiovascular fitness in the offspring. Findings of lower levels of putative breast stem cell subpopulations could have implications on exercise and breast cancer prevention. Prenatal effects of exercise on fetal stem cells warrant further studies.

Secondary Cancers After Radiation Therapy for Primary Prostate or Rectal Cancer.

Literature about the risk of secondary cancer after radiation therapy (RT) of prostate and rectal cancer reveals contradictory results. We conducted a meta-analysis to examine whether the RT induces secondary rectal or prostate cancer in patients, respectively, with prostate or rectal cancer. All studies published in Medline or Pubmed up to March 3, 2015, containing RT of primary rectal or prostate cancer, and providing risk estimates of secondary prostate or rectal cancer were considered as eligible. Relative risk (RR) and standardized incidence ratios (SIR) were calculated using the random-effects model. Twenty studies met the inclusion criteria. 12 of them were from the Surveillance, Epidemiology, and End Results (SEER) database. For prostate cancer patients, pooled adjusted RRs or SIRs did not show an effect on the risk of secondary rectal cancer. However, notwithstanding the limitations of SEER-based studies, the subgroup of prostate cancer patients receiving external beam radiation therapy (EBRT) showed an increased risk of rectal cancer. For rectal cancer patients, pooled adjusted RR of prostate cancer was 1.12 (95 % CI, 0.44-2.8) and SIR was 0.40 (95 % CI, 0.29-0.55). All studies included in the SIR analysis of rectal cancer were derived from the SEER data source. Based on current evidence, RT for prostate cancer patients had no effect on rectal cancer incidence, except for patients who received EBRT therapy. However, compared with the general population, RT for rectal cancer is associated with a decreased prostate cancer risk as found in SEER-based studies.

Family history and risk of pregnancy-associated breast cancer (PABC).

The risk of breast cancer is at least two-fold increased in young women with a family history of breast cancer. Pregnancy has a dual effect on breast cancer risk; a short-term increase followed by a long-term protection. We investigated if the risk of breast cancer during and within 10 years following pregnancy is affected by a family history of breast cancer. We followed a cohort of women aged 15-44 years between 1963 and 2009 identified in Swedish population-based registers. Family history was defined as having a mother or sister with breast cancer. We estimated incidence rate ratios of breast cancer during pregnancy and time intervals up to 10 years post-delivery, with a focus on pregnancy-associated breast cancer (PABC), defined as breast cancer during pregnancy or within 2 years post-delivery. In 3,452,506 women, there were 15,548 cases of breast cancer (1208 were PABC). Compared to nulliparous women, the risk of breast cancer was decreased during pregnancy, similar during first year and increased during second year post-delivery. The pattern was similar in women with or without family history of breast cancer. A peak in risk was observed 5-6 years following the first birth regardless of family history. After a second birth, this peak was only present in women with a family history. Our results indicate that women with a family history of breast cancer do not have a different breast cancer risk during and within 10 years following pregnancy compared to women without a family history.

Effect of preeclampsia on umbilical cord blood stem cells in relation to breast cancer susceptibility in the offspring.

Women born from a preeclamptic (PE) pregnancy are associated with a lower risk of breast cancer. Prenatal and early-life exposures are hypothesized to influence breast cancer susceptibility through their effect on stem cells. We examined stem cell populations in umbilical cord blood from PE pregnancies and compared with those from pregnancies without this condition. We isolated mononuclear cells from 58 PE and 197 normotensive (non-PE) umbilical cord blood samples and examined the different stem cell populations. Hematopoietic (CD34(+) and CD34(+)CD38(-)), endothelial (CD34(+)CD133(+), CD34(+)VEGFR2(+), CD133(+)VEGFR2(+) and CD34(+)CD133(+)VEGFR2(+)), and putative breast (EpCAM(+), EpCAM(+)CD49f(+), EpCAM(+)CD49f(+)CD117(+), CD49f(+)CD24(+), CD24(+)CD29(+) and CD24(+)CD29(+)CD49f(+)) stem/progenitor cell subpopulations were quantified by flow cytometry and compared between PE and non-PE samples. Hematopoietic CD34(+) cell counts were significantly lowered in PE compared with non-PE samples (P = 0.039, Kruskal-Wallis test). Levels of CD34(+)CD133(+) endothelial progenitor cells were also lower in PE samples (P = 0.032, multiple regression analysis). EpCAM(+) and EpCAM(+)CD49f(+) putative breast stem cell levels were significantly lowered in PE subjects (multiple regression analysis: P = 0.038 and 0.007, respectively). Stratifying by newborn gender, EpCAM(+) and EpCAM(+)CD49f(+) stem cells were significantly lowered in PE samples of female, but not male, newborns. Umbilical cord blood samples from pregnancies complicated by preeclampsia thus had significantly lower levels of hematopoietic, endothelial, and putative breast stem cells than non-PE controls. With a lowered breast cancer risk for offspring of a PE pregnancy, our findings provide support to the hypothesis that susceptibility to breast oncogenesis may be affected by conditions and processes during the prenatal period.

Maternal and cord blood hormones in relation to birth size.

Birth size has been associated with adult life diseases, but the endocrine factors that are likely involved are not established. We evaluated the associations of maternal and cord blood hormones with birth size in normal pregnancies, and examined possible effect modification by maternal height, on the basis of prior suggestive evidence. In a prospective study of normal singleton pregnancies in Boston, USA and Shanghai, China, maternal hormone levels at the 27th gestational week were available for 225 pregnancies in Boston and 281 in Shanghai and cord blood measurements for 92 pregnancies in Boston and 110 in Shanghai. Pearson partial correlation coefficients of log-transformed hormone levels with birth weight and length were calculated. Overall, positive correlations with birth weight were found for maternal estriol (r = 0.19; p < 0.001) and progesterone (r = 0.15; p < 0.001) and these associations were more evident among taller mothers. There was an inverse association of cord blood progesterone (r = -0.16; p < 0.03) with birth weight. In Boston, cord blood IGF-1 was positively associated with birth weight (r = 0.22; p < 0.04) and length (r = 0.25; p < 0.02), particularly among taller mothers (r = 0.43 and 0.38, respectively; p < 0.02), whereas among taller mothers in Shanghai the associations of IGF-2 with birth size appeared to be at least as strong as those of IGF-1. In conclusion, maternal estriol and progesterone, and cord blood IGF-1 were positively correlated with birth size. All correlations tended to be more pronounced among offspring of taller mothers. Among taller mothers in Shanghai, IGF-2 appeared to be at least as strongly associated with birth size as IGF-1.

Birth size in the most recent pregnancy and maternal mortality in premenopausal breast cancer by tumor characteristics.

The main aim of this study was to investigate possible associations between measures of offspring size at birth in the most recent pregnancy before premenopausal breast cancer diagnosis and the risks of maternal breast cancer mortality, taking tumor characteristics into account. We also aimed to investigate if these associations are modified by age at childbirth, time since childbirth, parity, and age at diagnosis. We followed 6,019 women from their date of premenopausal breast cancer (diagnosed from 1992 to 2008) until emigration, death or December 31st, 2009, whichever occurred first. We used Cox proportional hazard regression models, adjusted for parity, age at diagnosis, and education level, to estimate associations between women pregnancy, cancer characteristics and offspring birth characteristics, and mothers' mortality risk. In stratified analyses, mortality risks were estimated by tumor stage, ER or PR status. There was no association between offspring birth weight (HR = 1.00, 95 % CI 0.99-1.01, when used as a continuous variable), birth weight for gestational age or ponderal index, and premenopausal breast cancer mortality. Similarly, in analyses stratified by tumor stage, receptor status, and time difference between last pregnancy and date of diagnosis, we found no associations between birth size and breast cancer mortality. Our findings suggest that the hypothesis that "premenopausal breast cancer mortality is associated with offspring birth characteristics in the most recent pregnancy before the diagnosis" may not be valid. In addition, these associations are not modified by tumor characteristics.

Screening preeclamptic cord plasma for proteins associated with decreased breast cancer susceptibility.

Preeclampsia, a complication of pregnancy characterized by hypertension and proteinuria, has been found to reduce the subsequent risk for breast cancer in female offspring. As this protective effect could be due to exposure to preeclampsia-specific proteins during intrauterine life, the proteomic profiles of umbilical cord blood plasma between preeclamptic and normotensive pregnancies were compared. Umbilical cord plasma samples, depleted of 14 abundant proteins, were subjected to proteomic analysis using the quantitative method of nanoACQUITY ultra performance liquid chromatography-mass spectrometry with elevated energy mode of acquisition(E) (NanoUPLC-MS(E)). Sixty-nine differentially expressed proteins were identified, of which 15 and 6 proteins were only detected in preeclamptic and normotensive pregnancies, respectively. Additionally, expression of 8 proteins (gelsolin, complement C5, keratin type I cytoskeletal 10, pigment epithelium-derived factor, complement factor B, complement component C7, hemoglobin subunit gamma-2 and alpha-fetoprotein) were up-regulated in preeclampsia with a fold change of ≥2.0 when compared to normotensive pregnancies. The identification of alpha-fetoprotein in preeclamptic umbilical cord blood plasma supported the validity of this screen as alpha-fetoprotein has anti-estrogenic properties and has previously been linked to preeclampsia as well as a reduced breast cancer risk. The findings of this pilot study may provide new insights into the mechanistic link between preeclampsia and potentially reduced breast cancer susceptibility in adult life.

Associations of placental weight with maternal and cord blood hormones.

PURPOSE: Placental weight has been associated with mammographic pattern and coronary heart disease in the adult offspring, but the mechanisms are unknown. We evaluated the associations of maternal and cord blood hormones with placental weight in normal pregnancies. METHODS: Prospective study of 167 normal singleton pregnancies in Boston, USA and 256 in Shanghai, China. Maternal hormone levels at the 27th gestational week were available for all pregnancies. Cord blood measurements were available for 86 pregnancies in Boston and 104 in Shanghai. Pearson partial correlation coefficients of log-transformed hormone levels with placental weight were calculated. RESULTS: Maternal levels of estriol, testosterone, and progesterone (P < .05) were positively associated with placental weight. There was no such evidence for adiponectin, prolactin, and insulin-like growth factor (IGF)-I. Cord blood steroids tended to be inversely associated with placental weight, the results being statistically significant for testosterone (P < .05). There was a marginally significant positive association of cord blood IGF-I with placental weight. Reported results were adjusted for study center. CONCLUSIONS: Placental weight appears to be positively correlated with maternal steroids. Its correlation with cord blood steroids, however, appears inverse, compatible with negative feedback mechanisms. There is also a suggestion for placental weight to be positively associated with cord blood IGF-I.

Is maternal height a risk factor for breast cancer?

We hypothesize that the link between height and the risk of breast cancer may, to some extent, be accounted for by an association between maternal height and the risk of breast cancer. Unlike mothers of smaller stature, among taller mothers, maternal size does not impose constraints on fetal growth, thus allowing growth-enhancing pregnancy hormones, including estriol and insulin-like growth factors, to exercise their growth potential and be positively associated with birth size and, thus, the risk of breast cancer.

Prognostic significance of partial tumor regression after preoperative chemoradiotherapy for rectal cancer: a meta-analysis.

BACKGROUND: Complete tumor regression after preoperative chemoradiotherapy for rectal cancer has been associated with better disease-free and overall survival. The survival experience for patients with partial tumor regression is less clear. OBJECTIVE: The aim of this meta-analysis was to evaluate the prognostic significance of partial response after preoperative chemotherapy on disease-free survival in rectal cancer patients. DATA SOURCES: Relevant studies were identified by a search of MEDLINE and EMBASE databases with no restrictions to October 31, 2012. STUDY SELECTION: We included long-course radiotherapy that reported the association between degree of tumor regression and disease-free survival of rectal cancer. INTERVENTIONS: Direct, indirect, and graph methods were used to extract HRs. MAIN OUTCOME MEASURES: Study-specific HRs on the disease-free survival were pooled using a random-effects model. Eleven articles in total were selected. Analysis was performed first among the 6 studies that separated partial response from the complete response and later among all 11 of the studies. RESULTS: Pooled HR was 0.49 (95% CI, 0.28-0.85) for the 6 studies that compared partial response with poor response. It was 0.41 (95% CI, 0.25-0.67) when all 11 of the studies were analyzed together. LIMITATIONS: The studies were limited by not being prospective, randomized trials, and the tumor regression grades were not uniform. CONCLUSIONS: Partial tumor response is associated with a 50% improvement in disease-free survival and should be considered as a favorable prognostic factor.