Is a 3-mm intrafractional margin sufficient for daily image-guided intensity-modulated radiation therapy of prostate cancer?

PURPOSE: To determine whether a 3-mm isotropic target margin adequately covers the prostate and seminal vesicles (SVs) during administration of an intensity-modulated radiation therapy (IMRT) treatment fraction, assuming that daily image-guided setup is performed just before each fraction. MATERIALS AND METHODS: In-room computed tomographic (CT) scans were acquired immediately before and after a daily treatment fraction in 46 patients with prostate cancer. An eight-field IMRT plan was designed using the pre-fraction CT with a 3-mm margin and subsequently recalculated on the post-fraction CT. For convenience of comparison, dose plans were scaled to full course of treatment (75.6 Gy). Dose coverage was assessed on the post-treatment CT image set. RESULTS: During one treatment fraction (21.4+/-5.5 min), there were reductions in the volumes of the prostate and SVs receiving the prescribed dose (median reduction 0.1% and 1.0%, respectively, p<0.001) and in the minimum dose to 0.1 cm(3) of their volumes (median reduction 0.5 and 1.5 Gy, p<0.001). Of the 46 patients, three patients' prostates and eight patients' SVs did not maintain dose coverage above 70 Gy. Rectal filling correlated with decreased percentage-volume of SV receiving 75.6, 70, and 60 Gy (p<0.02). CONCLUSIONS: The 3-mm intrafractional margin was adequate for prostate dose coverage. However, a significant subset of patients lost SV dose coverage. The rectal volume change significantly affected SV dose coverage. For advanced-stage prostate cancers, we recommend to use larger margins or improve organ immobilization (such as with a rectal balloon) to ensure SV coverage.

Is H. pylori infection associated with diarrhea in a cohort of 3- to 8-year-old Colombian children?

The Estudio Comunitario sobre la Salud del Niño cohort study followed 326 3- to 8-year-old Colombian children for 4 years to observe the natural history of Helicobacter pylori infection and identify risk factors for acquisition, recurrence and persistence. Acute H. pylori infection during childhood may predispose to other enteric infections and therefore increase the risk of diarrheal disease. This dissertation aimed to estimate the effect of H. pylori infection on the occurrence of diarrhea and parasitic co-infections. The analysis used Generalized Estimating Equations to obtain odds ratios to estimate relative risks for diarrhea and the Zhang-Yu algorithm to estimate relative risks for on parasitic infections. Andersen-Gill models were used to estimate rate ratios for the effect of H. pylori status on the recurrence of parasitic infections. H. pylori status was classified for the entire follow-up duration in 1 of 3 categories: persistently positive, intermittently positive, and persistently negative. Multivariable models included child’s sex, age, symptoms, medication use, and socio-environmental factors. H. pylori infection was weakly and imprecisely associated with diarrheal disease, which occurred at an unexpectedly low frequency in this study. Persistently H. pylori-positive children had a somewhat higher incidence of reported diarrhea than intermittently positive or persistently negative children. Stratified analysis revealed that the presence of specific helminthes modified the effect of persistent H. pylori infection on diarrhea. The incidence of any parasitic infections was higher in children with persistent H. pylori infection relative to those with intermittent or persistently negative status, but this association did not hold when adjusted for the full set of selected covariates. The effects of H. pylori persistent status were similar for the occurrence or recurrence of Giardia duodenalis, Entamoeba histolytica, and Ascaris lumbricoides. These results show that H. pylori frequently co-exists with other parasites in Andean children and suggest that intermittently H. pylori–positive children might be at a lower risk of parasitic infections than persistently positive children. The relationship of H. pylori infection, helminthic infection and diarrheal disease should be further explored in studies that devote more intensive resources to accurate ascertainment of diarrhea.^