Volumetric Modulated Arc Therapy Improves Outcomes in Definitive Radiochemotherapy for Anal Cancer Whilst Reducing Acute Toxicities and Increasing Treatment Compliance.

BACKGROUND: Intensity-modulated radiotherapy (IMRT) is the standard of care in chemoradiotherapy (CRT) for anal cancer. Until now, only a limited number of studies have analyzed the results with VMAT (volumetric modulated arc therapy). We conducted a retrospective study on patients treated at our institution. PATIENTS AND METHODS: We included patients who received curative CRT for anal cancer. We compared VMAT-treated and 3DCRT (3D conformal radiotherapy)-treated patients. We analyzed toxicities (acute: CTCAE criteria; late: LENT/SOMA criteria), treatment compliance, overall survival, cancer-specific survival (CSS), distant control (DC), and locoregional control. RESULTS: A total of 149 patients (3DCRT: n = 87, VMAT: n = 62) were included. The median follow-up was longer in 3DCRT-treated patients (3DCRT: 61.3 months; VMAT: 39.1 months; p < 0.05). VMAT-treated patients had more G3 tumors (3DCRT: 12/87 (13.8%); VMAT: 18/62 (29.0%), p < 0.001). VMAT reduced acute toxicities ≥grade 3 (3DCRT: n = 48/87 (55.2%); VMAT: n = 11/62 (17.7%), p < 0.001). VMAT improved treatment compliance (less interruptions/delays) (3DCRT: 37/87, 42.5%; VMAT: 4/62, 6.5%; p < 0.001), provided a shorter median overall treatment time (3DCRT: 41 days; VMAT: 38 days; p = 0.02), and gave a higher median absolute 5-fluorouracil dose (3DCRT: 13,700 mg; VMAT: 14,400 mg; p = 0.001). Finally, we found improved CSS (p = 0.02; 3DCRT: 81.9% at 3 years; VMAT: 94.1% at 3 years) and DC (p = 0.01; 3DCRT: 89.4% at 3 years; VMAT: 100.0% at 3 years) with VMAT. SUMMARY: Our study is the first to demonstrate improved treatment compliance and outcomes with VMAT for anal cancer. Previous studies have indicated that organs at risk sparing might be more improved with the use of VMAT vs. with conventional IMRT. Future studies should address whether these advantages lead to a further reduction in CRT-associated morbidity.

Supplementation and inhibition of nitric oxide synthesis influences bacterial transit time during bacterial translocation in rats.

In the obstructed gut, nitric oxide (NO) may influence intestinal barrier function and translocation of bacteria. By using a novel experimental approach, we investigated the effect of supplementation and inhibition of NO synthesis on the time interval necessary for translocation of green fluorescent protein-transfected Escherichia coli (GFP-uv E. coli) in a rat model of small bowel obstruction. In anesthetized Wistar rats, 4 x 10(8) GFP-uv E. coli were administered into a reservoir of terminal ileum formed by ligature. Animals were randomized to receive either i.v. arginine (10 mg/kg), aminoguanidine (300 mg/kg), L-NAME (25 mg/kg), or saline (control). Translocation of GFP-uv E. coli was assessed using intravital video microscopy. Minimal transit time of translocation was measured as time from injection of GFP-uv E. coli into the gut lumen until bacteria were observed in the lamina submucosa and as time from injection of bacteria into the gut lumen until bacteria were observed in the lamina muscularis propria. Minimal transit times were expressed as mean +/- SD. Bacterial translocation into the submucosa and muscularis propria took 36 +/- 7 min and 81 +/- 9 min, respectively in control animals receiving saline. Aminoguanidine and L-NAME caused a marked delay of minimal transit time into the submucosa (63 +/- 5 min and 61 +/- 7 min, respectively; P < 0.05). Arginine significantly accelerated bacterial translocation into the muscularis propria (61 +/- 9 min, P < 0.05). GFP-uv E. coli were detected on frozen sections of small bowel, mesentery, liver, and spleen 2 h after GFP-uv E. coli administration in all animals. A marked upregulation of inducible NO synthase (NOS) in the obstructed bowel segment was demonstrated on immunohistochemistry. The assessment of a newly defined parameter, minimal bacterial transit time, may serve as an additional functional aspect of intestinal barrier function for pathophysiological and pharmacological studies. Aminoguanidine, L-NAME, and arginine were effective in influencing minimal transit time of E. coli during small bowel obstruction.

The gut origin of bacterial pancreatic infection during acute experimental pancreatitis in rats.

BACKGROUND: Infections are frequent complications and determine clinical course and outcome in severe pancreatitis. A novel animal model was used to assess minimal transit time of bacterial translocation (BT) across the gut mucosa in vivo using green fluorescent protein-transfected Escherichia coli and intravital video microscopy. METHODS: Three hours after induction of acute pancreatitis by i.p. injection of 40 microg/kg cerulein, 0.5 ml of a suspension of green fluorescent protein-transfected E. coli were injected into the lumen of a small bowel reservoir formed by ligature in anesthetized Wistar rats. Translocation of E. coli was assessed by intravital microscopy. Animals were sacrificed 5 h after induction of pancreatitis. RESULTS: BT across the mucosa and into the muscularis propria took a mean +/- SD of 36.4 +/- 8 min and 80.9 +/- 9.5 min, respectively, in sham animals. Pancreatitis resulted in a significantly shorter minimal transit time across the mucosa (16.4 +/- 4.9 min, p = 0.007) and into the muscularis propria (47.7 +/- 2.5 min, p = 0.001). E. coli were detected on frozen cross-sections and on bacteriological examination of pancreatic tissue in animals with acute pancreatitis but not in controls. DISCUSSION: Intravital microscopy of fluorescent bacteria is a new approach towards studying BT in vivo. Minimal transit time of BT serves as a novel functional aspect of mucosal barrier function during acute pancreatitis. The observation of fluorescent bacteria translocating from the small bowel lumen into the pancreas provides substantial experimental proof for the gut-origin-hypothesis of infectious complications in pancreatitis.

Microscopy of bacterial translocation during small bowel obstruction and ischemia in vivo--a new animal model.

BACKGROUND: Existing animal models provide only indirect information about the pathogenesis of infections caused by indigenous gastrointestinal microflora and the kinetics of bacterial translocation. The aim of this study was to develop a novel animal model to assess bacterial translocation and intestinal barrier function in vivo. METHODS: In anaesthetized male Wistar rats, 0.5 ml of a suspension of green fluorescent protein-transfected E. coli was administered by intraluminal injection in a model of small bowel obstruction. Animals were randomly subjected to non-ischemic or ischemic bowel obstruction. Ischemia was induced by selective clamping of the terminal mesenteric vessels feeding the obstructed bowel loop. Time intervals necessary for translocation of E. coli into the submucosal stroma and the muscularis propria was assessed using intravital microscopy. RESULTS: Bacterial translocation into the submucosa and muscularis propria took a mean of 36 +/- 8 min and 80 +/- 10 min, respectively, in small bowel obstruction. Intestinal ischemia significantly accelerated bacterial translocation into the submucosa (11 +/- 5 min, p < 0.0001) and muscularis (66 +/- 7 min; p = 0.004). Green fluorescent protein-transfected E. coli were visible in frozen sections of small bowel, mesentery, liver and spleen taken two hours after E. coli administration. CONCLUSIONS: Intravital microscopy of fluorescent bacteria is a novel approach to study bacterial translocation in vivo. We have applied this technique to define minimal bacterial transit time as a functional parameter of intestinal barrier function.

A new abdominal cavity chamber to study the impact of increased intra-abdominal pressure on microcirculation of gut mucosa by using video microscopy in rats.

OBJECTIVE: In experimental studies of capillary blood flow that use intravital video microscopy, organs are exposed in observation chambers implanted into the animal. In this article we describe an abdominal cavity chamber for intravital video microscopy of gut mucosa microcirculation during increased intra-abdominal pressure. DESIGN: Prospective, experimental animal study. SETTING: Research laboratory at a university hospital. SUBJECTS: Male Wistar rats. INTERVENTIONS: The abdominal cavity chamber was designed for implantation into the abdominal wall of rats after laparotomy, thus creating an expanded hermetic, abdominal cavity volume. Animals were assigned to three levels of intra-abdominal pressure: controls (group 1), 10 mm Hg (group 2), and 15 mm Hg (group 3). Intra-abdominal pressure was increased by intra-abdominal insufflation of gas. By using a fluorescent marker, we quantitatively assessed mucosa perfusion index, functional capillary density, red blood cell velocity, capillary diameters, and flow motion during increased intra-abdominal pressure by intravital video microscopy. Results were expressed as mean +/- SEM. Significance of differences was determined by analysis of variance and multiple comparison of means with post hoc test (*p <.05 groups vs. control;p <.05 group 3 vs. group 2). MEASUREMENTS AND MAIN RESULTS: When compared with controls, animals subjected to an intra-abdominal pressure of 10 and 15 mm Hg showed a significant stepwise decrease in mucosa perfusion index (88%, 71%*, 22%*), functional capillary density (665.4 +/- 71.7, 461.6 +/- 71.9*, 375.1 +/- 2.0*cm(-1)), and red blood cell velocity (0.50 +/- 0.04, 0.33 +/- 0.03*, 0.04 +/- 0.06*mm/sec), indicating a stepwise impairment of mucosal microcirculation. Capillary diameters and flow motion did not change with respect to intra-abdominal pressure. CONCLUSIONS: This novel animal model of intravital intestinal video microscopy that uses an abdominal cavity chamber is a feasible and sensitive experimental tool to study intestinal microcirculation during increased intra-abdominal pressure. Intra-abdominal pressure likely results in a severe impairment of mucosal microcirculation.