Comment on "Acute lymphoblastic leukemia and adiponcosis" by M. Bifulco and AM MalfitanoWe read with interest the letter by Bifulco and Malfitano 1 that argues that adiposity may be an underlying cause of cancer, and of acute lymphoblastic leukemia (ALL) in particular. Based on our recently published paper "The negative impact of underweight and weight loss on survival of children with acute lymphoblastic leukemia" 2 and other studies, the authors suggest that the use of the entity "adiponcosis", derived from the fusion of "adiposis" and "oncosis", may be appropriate to support the hypothesis that adiposity increases the risk of ALL.Although we appreciate existing knowledge that high body mass index may in part enhance cancer risk (either by 'nature' or by 'nurture'), 3 this particular issue was not the focus of our study. As stated in a letter by Renehan,4 it is important to differentiate between studies examining the link between excess weight and incidence of cancer and those that examine being overweight and cancer survival. We examined the influence of being underweight on relapse risk and survival in children with ALL, and did not address the influence of weight on ALL risk. Most studies that Bifulco and Malfitano refer to in order to support their hypothesis of "adiponcosis" with respect to "ALL" addressed excess weight as an accelerator of ALL progression, rather than oncogenetic aspects of the question. [5][6][7][8][9][10] Nevertheless, there are many epidemiological studies that now show that excess weight is associated with increased risk for several common cancer types in adults, including breast cancer, cancer of the esophagus and ovaria. 3 These studies suggest that hormonal influences have a substantial influence; however, such studies have not yet been performed in children.In our Dutch national study, 2 including over 700 children, we have now analyzed the prevalence of being overweight and obese and compared this to healthy Dutch peers. The results show that the frequency of being overweight and obese [defined by a body mass index (BMI) of 20-25 kg/m 2 and >30 kg/m 2 , respectively] at diagnosis was 6% and 1%, respectively (Table 1). BMI data standardized for sex and age [BMI standard deviation score (SDS)] were available for 738 patients, of whom 104 (14%) were overweight (11%) and 3% obese (Table 2). By way of comparison, according to the standard normal distribution, 16% of the matched healthy Dutch population has a BMI over 1 SDS and 2% has a BMI over 2 SDS. These results did not show that being overweight and obesity are more prevalent in children with ALL in the diagnostic phase, hence our data do not support the hypothesis that overweight children have an increased risk of developing ALL.Although, epidemiological studies may give further insight into the existence of a link between adiposity and ALL, a direct causal relationship may be hard to show. We feel the suggested potential causative relationship of adiposity and ALL occurence, and consequently the true existence of the entity "ad...