Breastfeeding and the risk of childhood Hodgkin lymphoma: a systematic review and meta-analysis

Classic Hodgkin lymphoma in young people

Classic Hodgkin lymphoma (CHL) is a unique form of lymphoid cancer featuring a heterogeneous tumor microenvironment and a relative paucity of malignant Hodgkin and Reed-Sternberg (HRS) cells with characteristic phenotype. Younger individuals (children, adolescents and young adults) are affected as often as the elderly, producing a peculiar bimodal age-incidence profile that has generated immense interest in this disease and its origins. Decades of epidemiological investigations have documented the populations most susceptible and identified multiple risk factors that can be broadly categorized as either biological or environmental in nature. Most risk factors result in overt immunodeficiency or confer more subtle alterations to baseline health, physiology or immune function. Epstein Barr virus, however, is both a risk factor and well-established driver of lymphomagenesis in a significant subset of cases. Epigenetic changes, along with the accumulation of somatic driver mutations and cytogenetic abnormalities are required for the malignant transformation of germinal center-experienced HRS cell precursors. Chromosomal instability and the influence of endogenous mutational processes are critical in this regard, by impacting genes involved in key signaling pathways that promote the survival and proliferation of HRS cells and their escape from immune destruction. Here we review the principal features, known risk factors and lymphomagenic mechanisms relevant to newly diagnosed CHL, with an emphasis on those most applicable to young people.

Breastfeeding and the risk of childhood cancer: a systematic review and dose-response meta-analysis

BACKGROUND

The aim of this study was to quantitatively summarize the available evidence on the association of breastfeeding with the risk of childhood cancer.

METHODS

A literature search of PubMed and Embase databases was performed to identify eligible observational studies published from inception to July 17, 2020. The categorical and dose-response meta-analysis was conducted by pooling relative risk (RR) or odds ratio (OR) estimates with 95% confidence intervals (CIs). Potential sources of heterogeneity were detected by meta-regression and stratification analysis. Sensitivity analysis and publication bias test were also carried out.

RESULTS

Forty-five articles involving 475,579 individuals were included in the meta-analysis. Among the thirty-three studies on the association between breastfeeding and risk of childhood leukemia, the pooled risk estimates were 0.77 (95% CI, 0.65-0.91) and 0.77 (95% CI 0.63-0.94) for ever versus non/occasional breastfeeding and longest versus shortest breastfeeding duration group, respectively. There was clear indication for non-linear dose-response relationship between breastfeeding duration and the risk of childhood leukemia (P non-linear < 0.001). The most protective effect (OR, 0.66, 95% CI 0.62-0.70) was observed at a breastfeeding duration of 9.6 months. Four studies examined, the association between breastfeeding and risk of childhood neuroblastoma, and significant inverse associations were consistently observed in both the comparisons of ever breastfeeding versus non/occasional breastfeeding (OR = 0.59, 95% CI 0.44-0.81) and longest versus shortest breastfeeding (OR = 0.61, 95% CI 0.44-0.83). However, no associations of breastfeeding with risk of other cancers were found.

CONCLUSIONS

Our study supports a protective role of breastfeeding on the risk of childhood leukemia, also suggesting a non-linear dose-response relationship. Further studies are warranted to confirm the association between breastfeeding and risk of childhood neuroblastoma.

[Analysis of small areas of pediatric cancer in the municipality of Murcia (Spain)]

INTRODUCTION

Occasionally, primary care pediatricians notice the presence of small clusters of pediatric cancer (PC), but are often frustrated by the findings after statistical analysis. The study of small areas in spatial epidemiology has led to advances in identifying clusters and the environmental risk factors involved. The purpose of this study was to describe the PC incidence and the spatial distribution at the minimum level of disaggregation possible in Murcia, presenting the first urban municipality map of PC in Spain.

MATERIALS AND METHODS

A population-based descriptive study was conducted on the PC cases diagnosed in children younger than 15 years, between 1998 and 2013 in the municipality of Murcia. Cases were classified by sex, age group, and tumor type. Coordinates of home addresses at the time of diagnosis were assigned to each case, and spatial and spatio-temporal analyses were carried out at the level of census tracts, using FleXScan and SatScan.

RESULTS

A total of 155 cases of PC were diagnosed during this period. The overall incidence of PC (138/10(6) of children under the age of 15) and the incidence for individual tumor types were within the expected ranges for Europe. A spatio-temporal cluster of Hodgkin lymphoma was identified.

CONCLUSIONS

Small area analysis of PC cases may be a useful tool for the identification of PC clusters, which would allow for the generation of hypotheses regarding disease etiology, as well as developing urban models for environmental surveillance of PC.

Breastfeeding and ovarian cancer risk: a systematic review and meta-analysis of 40 epidemiological studies

The present systematic review and meta-analysis was conducted to assess any association between breastfeeding and the risk of ovarian cancer. A systematic search of published studies was performed in PUBMED and EMBASE and by reviewing reference lists from retrieved articles through March 2013. Data extraction was conducted independently by two authors. Pooled relative risk ratios were calculated using random-effect models. Totals of 5 cohort studies and 35 case-control studies including 17,139 women with ovarian cancer showed a 30% reduced risk of ovarian cancer when comparing the women who had breastfed with those who had never breastfed (pooled RR = 0.70, 95% CI: 0.64-0.76; p = 0.00), with significant heterogeneity in the studies (p = 0.00; I2 = 76.29%). A significant decreasd in risk of epithelial ovarian cancer was also observed (pooled RR = 0.68, 95% CI: 0.61-0.76). When the participants were restricted to only parous women, there was a slightly attenuated but still significant risk reduction of ovarian cancer (pooled RR = 0.76, 95% CI: 0.69-0.83). For total breastfeeding duration, the pooled RRs in the < 6 months, 6-12 months and > 12 months of breastfeeding subgroups were 0.85 (95% CI: 0.77-0.93), 0.73 (95% CI: 0.65-0.82) and 0.64 (95%CI: 0.56-0.73), respectively. Meta-regression of total breastfeeding duration indicated an increasing linear trend of risk reduction of ovarian cancer with the increasing total breastfeeding duration (p = 0.00). Breastfeeding was inversely associated with the risk of ovarian cancer, especially long-term breastfeeding duration that demonstrated a stronger protective effect.