AbcApp: incidence of intra-abdominal ABsCesses following laparoscopic vs. open APPendectomy in complicated appendicitis.

BACKGROUND: Patients with complicated appendicitis are more at risk for the occurrence of postoperative intra-abdominal abscesses than patients with uncomplicated appendicitis. Studies comparing laparoscopic and open appendectomy showed limitations and contradictory findings on the incidence of intra-abdominal abscesses after appendicitis, as most of these studies analysed both uncomplicated and complicated appendicitis as one group. The aim of the present study is to investigate the incidence of intra-abdominal abscesses after laparoscopic versus open appendectomy for complicated appendicitis. METHODS: A retrospective cohort study was performed over the period January 2009 till May 2020. All patients who had an intra-operative diagnosis of complicated appendicitis (e.g. perforation, necrosis) were included. The outcome measure was the occurrence of intra-abdominal abscesses with a postoperative follow-up of 30 days. Multivariate logistic regression analysis was performed including adjustments for significant confounders. RESULTS: A total of 900 patients had undergone appendectomy for complicated appendicitis. The majority was operated laparoscopically (78%, n = 705). The incidence of postoperative intra-abdominal abscess was 12.3% in both laparoscopic and open appendectomy groups. On univariable analysis, the postoperative rates of intra-abdominal abscesses between laparoscopic and open appendectomy were not significantly different (odds ratio 1.11, 95% CI [0.67-1.84], p = 0.681). CONCLUSION: The present study provides evidence that, in current daily practice, intra-abdominal abscess formation remains a common postoperative complication for complicated appendicitis. Nonetheless, no significant difference was found with regard to intra-abdominal abscess formation when comparing laparoscopy with open surgery.

The effect of selective decontamination on the intestinal microbiota as measured with IS-pro: a taxonomic classification tool applicable for direct evaluation of intestinal microbiota in clinical routine.

Selective decontamination of the digestive tract (SDD) is aimed at elimination of potential pathogenic microorganisms. In this study, the effect of SDD on gut microbiota was evaluated in a large homogenous group of elective colorectal cancer surgery patients. Rectal swabs were taken from 118 patients undergoing colorectal surgery. These patients were randomly assigned to receive perioperative SDD or to the control group (no SDD). Rectal swabs were taken prior to surgery, 3 days after commencing administration of SDD. Gut microbial profiles were obtained with the IS-pro technique, a standardized microbiota profiling assay applicable in clinical routine. Differences in abundance for different taxonomical groups and diversity between the groups were assessed. Unsupervised and supervised classification techniques were used to assess microbial signatures, differentiating between the SDD group and the control group. Patients in the SDD group had different gut microbial signatures than in the control group, also in phyla that are not a target for SDD. Escherichia coli, Sutterella spp., Faecalibacterium prausnitzii, and Streptococcus spp. were the species that differed the most between the two groups. The SDD group showed clustering into two subgroups. In one subgroup, a decrease in Proteobacteria was observed, whereas the other subgroup showed a shift in Proteobacteria species. This study shows that SDD not only decreases colonization of the gastrointestinal tract with potential pathogenic Gram-negative microorganisms, but also reduces the abundance of normal colonizers of our gastrointestinal system and leads to a shift in total microbiota composition.

Locoregional recurrences after transanal total mesorectal excision of rectal cancer during implementation.

BACKGROUND: Transanal total mesorectal excision (TaTME) has been proposed as an approach in patients with mid and low rectal cancer. The TaTME procedure has been introduced in the Netherlands in a structured training pathway, including proctoring. This study evaluated the local recurrence rate during the implementation phase of TaTME. METHODS: Oncological outcomes of the first ten TaTME procedures in each of 12 participating centres were collected as part of an external audit of procedure implementation. Data collected from a cohort of patients treated over a prolonged period in four centres were also collected to analyse learning curve effects. The primary outcome was the presence of locoregional recurrence. RESULTS: The implementation cohort of 120 patients had a median follow up of 21·9 months. Short-term outcomes included a positive circumferential resection margin rate of 5·0 per cent and anastomotic leakage rate of 17 per cent. The overall local recurrence rate in the implementation cohort was 10·0 per cent (12 of 120), with a mean(s.d.) interval to recurrence of 15·2(7·0) months. Multifocal local recurrence was present in eight of 12 patients. In the prolonged cohort (266 patients), the overall recurrence rate was 5·6 per cent (4·0 per cent after excluding the first 10 procedures at each centre). CONCLUSION: TaTME was associated with a multifocal local recurrence rate that may be related to suboptimal execution rather than the technique itself. Prolonged proctoring, optimization of the technique to avoid spillage, and quality control is recommended.

ANTECEDENTES: La escisión total del mesorrecto por vía transanal (Transanal Total Mesorectal Excision, TaTME) se ha propuesto como abordaje quirúrgico en pacientes con cáncer de recto medio e inferior. La técnica TaTME se ha introducido en los Países Bajos mediante un proceso de formación estructurado que incluye la supervisión. Este estudio evaluó el porcentaje de recidiva local durante la fase de implementación de TaTME. MÉTODOS: Se recogieron los resultados oncológicos de los primeros 10 procedimientos realizados mediante TaTME en cada uno de los 12 centros participantes como parte de una auditoría externa de implementación del procedimiento. Se reunió una cohorte más amplia de pacientes procedentes de 4 centros para analizar los efectos de la curva de aprendizaje. El criterio de valoración principal fue la presencia de recidiva locorregional. RESULTADOS: La cohorte de implementación de 120 pacientes tuvo una mediana de seguimiento de 21,9 meses. Los resultados a corto plazo incluyeron una tasa del margen de resección circunferencial positivo del 5% y una tasa de fuga anastomótica del 17,4%. La tasa global de recidiva local en la cohorte de implementación fue del 10% (12/120) con un intervalo medio de recidiva de 15,2 (DE 7) meses. El patrón de recidiva local fue multifocal en 8 de 12 casos (67%). En la cohorte ampliada (n = 266), la tasa global de recidiva fue del 5,6% (4,0%, excluyendo a los primeros 10 pacientes). CONCLUSIÓN: TaTME se asoció con un porcentaje de recidiva local multifocal que puede relacionarse con una ejecución subóptima, más que con la técnica en sí. Se recomienda una supervisión prolongada, la optimización de la técnica para evitar la diseminación tumoral, así como un control de calidad.

Volume-outcome relationship of liver surgery: a nationwide analysis.

BACKGROUND: Evidence for an association between hospital volume and outcomes for liver surgery is abundant. The current Dutch guideline requires a minimum volume of 20 annual procedures per centre. The aim of this study was to investigate the association between hospital volume and postoperative outcomes using data from the nationwide Dutch Hepato Biliary Audit. METHODS: This was a nationwide study in the Netherlands. All liver resections reported in the Dutch Hepato Biliary Audit between 2014 and 2017 were included. Annual centre volume was calculated and classified in categories of 20 procedures per year. Main outcomes were major morbidity (Clavien-Dindo grade IIIA or higher) and 30-day or in-hospital mortality. RESULTS: A total of 5590 liver resections were done across 34 centres with a median annual centre volume of 35 (i.q.r. 20-69) procedures. Overall major morbidity and mortality rates were 11·2 and 2·0 per cent respectively. The mortality rate was 1·9 per cent after resection for colorectal liver metastases (CRLMs), 1·2 per cent for non-CRLMs, 0·4 per cent for benign tumours, 4·9 per cent for hepatocellular carcinoma and 10·3 per cent for biliary tumours. Higher-volume centres performed more major liver resections, and more resections for hepatocellular carcinoma and biliary cancer. There was no association between hospital volume and either major morbidity or mortality in multivariable analysis, after adjustment for known risk factors for adverse events. CONCLUSION: Hospital volume and postoperative outcomes were not associated.

ANTECEDENTES: La asociación entre el volumen hospitalario y los resultados de la cirugía hepática no está clara. Según la recomendación actual de las guías holandesas se requiere un volumen mínimo de 20 procedimientos anuales por centro. El objetivo de este estudio fue analizar la asociación entre el volumen hospitalario con los resultados postoperatorios en la auditoría hepatobiliar obligatoria holandesa a nivel nacional. MÉTODOS: Se realizó un estudio a nivel nacional en los Países Bajos. Se incluyeron todas las resecciones hepáticas registradas en la auditoría hepatobiliar holandesa entre 2014 y 2017. El volumen anual del centro se calculó y se clasificó en categorías de 20 procedimientos por año. Los objetivos principales fueron la morbilidad de mayor grado (Clavien-Dindo grado IIIA o superior) y la mortalidad hospitalaria o la mortalidad a los 30 días. RESULTADOS: Se realizaron un total de 5.590 resecciones en 34 centros con una mediana (rango intercuartílico) de volumen anual de 35 procedimientos (20-69). La tasa global de morbilidad mayor fue del 11% y la mortalidad del 2%. La mortalidad fue de 1,9% después de la resección por metástasis hepáticas colorrectales (colorectal liver metastases, CRLM), 1,2% para no CRLM, 0,4% para tumores benignos, 4,9% para carcinoma hepatocelular, y 10,3% para tumores biliares. Los centros de mayor volumen realizaron más resecciones hepáticas mayores y más resecciones por carcinoma hepatocelular y cáncer biliar. En el análisis multivariable después de ajustar por factores de riesgo conocidos de eventos adversos, no se observó ninguna asociación entre el volumen hospitalario y la morbilidad o mortalidad mayor. CONCLUSIÓN: No hubo asociación entre el volumen hospitalario y los resultados postoperatorios de la cirugía hepática en los Países Bajos.

Structured training pathway and proctoring; multicenter results of the implementation of transanal total mesorectal excision (TaTME) in the Netherlands.

BACKGROUND: Transanal total mesorectal excision (TaTME) is a new complex technique with potential to improve the quality of surgical mesorectal excision for patients with mid and low rectal cancer. The procedure is technically challenging and has shown to be associated with a relative long learning curve which might hamper widespread adoption. Therefore, a national structured training pathway for TaTME has been set up in the Netherlands to allow safe implementation. The aim of this study was to monitor safety and efficacy of the training program with 12 centers. METHODS: Short-term outcomes of the first ten TaTME procedures were evaluated in 12 participating centers in the Netherlands within the national structured training pathway. Consecutive patients operated during and after the proctoring program for rectal carcinoma with curative intent were included. Primary outcome was the incidence of intraoperative complications, secondary outcomes included postoperative complications and pathological outcomes. RESULTS: In October 2018, 12 hospitals completed the training program and from each center the first 10 patients were included for evaluation. Intraoperative complications occurred in 4.9% of the cases. The clinicopathological outcome reported 100% for complete or nearly complete specimen, 100% negative distal resection margin, and the circumferential resection margin was positive in 5.0% of patients. Overall postoperative complication rate was 45.0%, with 19.2% Clavien-Dindo ≥ III and an anastomotic leak rate of 17.3%. CONCLUSIONS: This study shows that the nationwide structured training program for TaTME delivers safe implementation of TaTME in terms of intraoperative and pathology outcomes within the first ten consecutive cases in each center. However, postoperative morbidity is substantial even within a structured training pathway and surgeons should be aware of the learning curve of this new technique.

Randomized clinical trial of selective decontamination of the digestive tract in elective colorectal cancer surgery (SELECT trial).

BACKGROUND: Infectious complications and anastomotic leakage affect approximately 30 per cent of patients after colorectal cancer surgery. The aim of this multicentre randomized trial was to investigate whether selective decontamination of the digestive tract (SDD) reduces these complications of elective colorectal cancer surgery. METHODS: The effectiveness of SDD was evaluated in a multicentre, open-label RCT in six centres in the Netherlands. Patients with colorectal cancer scheduled for elective curative surgery with a primary anastomosis were eligible. Oral colistin, tobramycin and amphotericin B were administered to patients in the SDD group to decontaminate the digestive tract. Both treatment and control group received intravenous cefazolin and metronidazole for perioperative prophylaxis. Mechanical bowel preparation was given for left-sided colectomies, sigmoid and anterior resections. Anastomotic leakage was the primary outcome; infectious complications and mortality were secondary outcomes. RESULTS: The outcomes for 228 patients randomized to the SDD group and 227 randomized to the control group were analysed. The trial was stopped after interim analysis demonstrated that superiority was no longer attainable. Effective SDD was confirmed by interspace DNA profiling analysis of rectal swabs. Anastomotic leakage was observed in 14 patients (6·1 per cent) in the SDD group and in 22 patients (9·7 per cent) in the control group (odds ratio (OR) 0·61, 95 per cent c.i. 0·30 to 1·22). Fewer patients in the SDD group had one or more infectious complications than patients in the control group (14·9 versus 26·9 per cent respectively; OR 0·48, 0·30 to 0·76). Multivariable analysis indicated that SDD reduced the rate of infectious complications (OR 0·47, 0·29 to 0·76). CONCLUSION: SDD reduces infectious complications after colorectal cancer resection but did not significantly reduce anastomotic leakage in this trial. Registration number: NCT01740947 ( https://www.clinicaltrials.gov).

Training residents in laparoscopic colorectal surgery: is supervised surgery safe?

BACKGROUND: Colorectal resections are increasingly performed laparoscopically, and training in laparoscopic resections in the Netherlands has shifted from a post-residency fellowship to training in residency. The question remains if this supervised surgery affects short-term patient outcome. METHODS: Between January 2010 and July 2014, 523 consecutive patients, who underwent laparoscopic colorectal resection, were selected from a prospective single-center database. All data were obtained from the maintained database and retrospectively analyzed. We compared the short-term outcome of patients who underwent laparoscopic colorectal surgery by a supervised fifth- or sixth-year resident compared to patients who underwent laparoscopic colorectal surgery performed by a dedicated colorectal surgeon. Statistical analysis was performed using the Chi-square test for categorical variables and the t test for continuous variables. RESULTS: Almost 40 % of operations were performed by a resident with an even distribution in type of resection, except for the abdominal-perineal resection (residents vs. surgeon 3.57 vs. 8.26 %, p = 0.04) and the total number of patients who underwent preoperative chemoradiation (resident vs. surgeon 6.66 vs. 20.65 %, p = 0.04). No difference was found in operative time or per-operative blood loss. A higher conversion rate was found when surgery was performed by a supervised resident (residents vs. surgeon 17.34 vs. 9.17 %, p = 0.01), which could be attributed to case selection and one single year. No differences in major complications, oncological outcome and construction of a stoma were found. In the case of minor complications, a significantly increased percentage of bladder retention was found in the surgeon group (residents vs. surgeon 1 vs. 4.6 %, p = 0.03). CONCLUSIONS: In this study, we found that patient safety and short-term outcome are not adversely affected when laparoscopic colorectal surgery is performed by a supervised fifth- or sixth-year resident.

Selective Decontamination with Oral Antibiotics in Colorectal Surgery: 90-day Reintervention Rates and Long-term Oncological Follow-up.

BACKGROUND: Oral antibiotics (OAB) in colorectal surgery have been shown to reduce surgical site infections (SSIs) and possibly anastomotic leakage. However, evidence on long-term follow-up, reintervention rates and 5-year oncological follow-up is lacking. The current study aims at elucidating this knowledge gap. METHODS: This study evaluated the long-term effectiveness of perioperative 'Selective decontamination of the digestive tract' (SDD) in colorectal cancer surgery. The primary outcome was anastomotic leakage within 90 days, secondary outcomes included infectious complications, reinterventions, readmission, hospital stay, and 5-year overall and disease-free-survival. Statistical analysis including univariate and multivariate analysis was performed to identify predictors of 90-day outcomes, and Kaplan-Meier survival analysis was used for the 5-year survival outcomes. RESULTS: In total 455 patients were analyzed, 228 participants in the SDD group and 227 in the control group. Anastomotic leakage rate was not statistically different between the SDD and control group (6.6% versus 9.7%). One or more infectious complications occurred in 15.4% of patients in the SDD group and in 28.2% in the control group (OR 0.46, 95% C.I. 0.29 - 0.73). In the SDD group 8,8% of patients required a reintervention compared to 16,3% of patients in the control group (OR 0.47, 95% C.I. 0.26 - 0.84). After multivariable analysis SDD remained significant in reducing both infectious complications and reinterventions after 90-days follow-up. There was no difference between SDD and control group in 5-year overall survival and disease-free-survival. CONCLUSION: SDD as OAB is effective in reducing 90-days postoperative infectious complications and reinterventions. As such, SDD as standard OAB in elective colorectal surgery is highly recommended.

Cost-effectiveness of selective decontamination of the digestive tract to decrease infectious complications in colorectal cancer surgery: An analysis of the SELECT trial.

INTRODUCTION: Selective decontamination of the digestive tract (SDD) is effective in reducing infectious complications in elective colorectal cancer (CRC) surgery. However, it is unclear whether SDD is cost-effective compared to standard antibiotic prophylaxis. MATERIAL & METHODS: Economic evaluation alongside multicenter randomized controlled trial, the SELECT-trial, from a healthcare perspective. Patients included underwent elective surgery for non-metastatic CRC. The intervention group received oral non-absorbable colistin, tobramycin and amphotericin B (SDD) next to standard antibiotic prophylaxis. Both groups received a single shot intravenous cefazolin and metronidazole preoperatively as standard prophylaxis. Occurrence of postoperative infectious complication in the first 30 postoperative days was extracted from medical records, Quality-Adjusted Life-Years (QALYs) based on the ED-5D-3L, and healthcare costs collected from the hospital's financial administration. RESULTS: Of the 455 patients, 228 were randomly assigned to intervention group and 227 patients to the control group. SDD significantly reduced the number of infectious complications compared to control (difference = -0.13, 95 % CI -0.05 to -0.20). No difference was found for QALYs (difference = 0.002, 95 % CI -0.002 to 0.005). Healthcare costs were statistically significantly lower in the intervention group (difference = -€1258, 95 % CI -2751 to -166). The ICER was -9872 €/infectious complication prevented and -820,380 €/QALY gained. For all willingness-to-pay thresholds, the probability that prophylactic SDD was cost-effective compared to standard prophylactic practice alone was 1.0. CONCLUSION: The addition of SDD to the standard preoperative intravenous antibiotic prophylaxis is cost-effective compared to standard prophylactic practice from a healthcare perspective and should be considered as the standard of care.

Surgical trauma and peritoneal recurrence of colorectal carcinoma.

BACKGROUND: Local peritoneal recurrence is a relatively common complication after intentionally curative surgery for colorectal cancer and has unfavourable prognosis. METHODS: This manuscript reviews the relevant experimental and clinical literature on surgical trauma and development of local recurrences, which was obtained by extensive search in the PubMed database. RESULTS AND CONCLUSION: Although surgery is required as the only option for treatment, operative trauma and subsequent wound healing promote development of local recurrences. Minimizing peritoneal trauma reduces local tumour outgrowth in animal models, but clinical trials have not been conclusive so far. Recognition of the increased susceptibility to tumour establishment in the early post-operative phase challenges the aim for further research, targeting at strategies that obstruct local tumour implantation or outgrowth and/or improve (local) anti-tumour response.

Peri-operative bowel perforation in early stage colon cancer is associated with an adverse oncological outcome.

BACKGROUND: The presence of an inflammatory response resulting from bowel perforation or anastomotic leakage has been suggested to enhance recurrence rates in colorectal cancer patients. Currently, it is unknown if bowel perforation or anastomotic leakage has prognostic significance in early stage colon cancer patients. In this study, the impact of peri-operative bowel perforation including anastomotic leakage on disease-free survival of stage I/II colon cancer patients was investigated. METHODS: Prospective follow up data of 448 patients with stages I/II colon cancer that underwent resection were included. Patients who died within 3 months after initial surgery were excluded. RESULTS: Median follow up was 56.0 months. Patients with peri-operative bowel perforation (n = 25) had a higher recurrence rate compared to patients without perforation (n = 423), 36.0 % vs. 16.1 % (p = 0.01). Disease-free survival was significantly worse for the perforation group compared to patients without perforation (p = 0.004). Multivariate analysis including T-stage, histological grade, and adjuvant chemotherapy showed peri-operative bowel perforation to be an independent factor significantly associated with disease recurrence (odds ratio, 2.7; 95 % CI, 1.1-6.7). CONCLUSION: Peri-operative bowel perforation is associated with increased recurrence rates and impaired disease-free survival in early-stage colon cancer patients.

Insufficient ability of omental milky spots to prevent peritoneal tumor outgrowth supports omentectomy in minimal residual disease.

BACKGROUND: The greater omentum is frequently involved in the course of gastrointestinal and ovarian tumors. Therefore, common practice in surgical treatment for especially gastric and ovarian cancer includes removal of the greater omentum. Paradoxically, many immune cells, such as macrophages that accumulate in so-called milky spots, reside within the omentum and are cytotoxic against tumor cells ex vivo. Consequently, omental macrophages might play an important role in killing tumor cells, and may hereby prevent development into local peritoneal recurrences. In the present study, we therefore evaluated the role of the omentum and the clinical relevance of omentectomy in minimal residual disease (MRD). METHODS: Tumor cell dissemination patterns on the omentum in a rat model were examined using DiI-labelled CC531s tumor cells. Additionally, intra peritoneal (i.p.) tumor load was investigated in rats that underwent omentectomy or sham laparotomy followed by i.p. injection of CC531s cells on day 21, which represented MRD. RESULTS: At 4 h post injection, tumor cells predominantly adhered on milky spots. Number of cells thereafter declined rapidly suggesting initial tumor killing functions in these specific immune aggregates. Despite initial reduction observed in milky spots, numbers of tumor cells however increased at fatty tissue stripes that border the omentum. This indicated proliferation at these locations, which corresponded to macroscopic observations of the omenta on day 21 after tumor cell injection. Omentectomy resulted in reduced intra-abdominal tumor load, which was completely attributable to the absence of the omentum, as tumor development did not differ on other sites. Even in the MRD group microscopic clusters of tumor cells located in the omentum eventually developed into macroscopic nodules. CONCLUSION: Since the ability of omental milky spots is, even in MRD, insufficient to prevent intra abdominal tumor outgrowth, omentectomy, which reduces tumor load, is recommended in surgical treatment of intra abdominal tumors that are prone to disseminate intraperitoneally.

Perioperative IFN-alpha to avoid surgically induced immune suppression in colorectal cancer patients.

Surgical treatment of colorectal cancer is associated with postoperative immunosuppression, which might facilitate dissemination of tumor cells and outgrowth of minimal residual disease/(micro) metastases. Minimal residual disease has been shown to be of prognostic relevance in colorectal cancer. Therefore, stimulation of (anti-tumor) immune responses may be beneficial in the prevention of metastases formation. Important anti-tumor effector cells, which serve this function, are natural killer (NK) cells, CD8+ lymphocytes (CTL), dendritic cells (DC) and macrophages. In this review the immunomodulating properties of IFN-alpha are discussed, with a particular focus on perioperative stimulation of immune function in cancer patients. IFN-alpha is known to enhance innate immune functions such as stimulation of NK cells, transition from innate to adaptive responses (activation of DC) and regulating of CD8+ CTL activity and memory. Moreover, it exerts direct antitumor effects by regulating apoptosis and cell cycle. In several clinical trials, perioperative administration of IFN-alpha has indeed been shown to improve T cell responsiveness, prevent impairment of NK cell cytotoxicity and increase expression of activation markers on NK, T and NKT cells. In a clinical pilot study we showed in colorectal cancer patients that received perioperative IFN-alpha enhanced activation markers on T cells and NK cells, combined with better-preserved T cell function as indicated by phytohemaggluttinin skin tests. In the liver of these patients significantly more CD8+ T cells were found. In conclusion, IFN-alpha provides an effective adjuvant in several forms of cancer and improves several postoperative immune functions in perioperative administration. However, larger clinical trials are necessary to investigate effects on disease-free and overall survival.

Isolated lung perfusion with melphalan: pharmacokinetics and toxicity in a pig model.

BACKGROUND: In patients with unresectable lung cancer or pulmonary metastases, isolated lung perfusion (ILP) has been described as an alternative method to deliver high-dose chemotherapy to the lungs, thereby minimizing systemic toxicity. Pharmacokinetics of ILP have not been extensively investigated. Therefore, we studied the feasibility of ILP with melphalan in a pig model with emphasis on pharmacokinetics and acute lung damage. METHODS: Five pigs underwent ILP with melphalan. Blood and tissue samples were obtained for determination of melphalan levels. Tissue biopsies were taken for microscopic evaluation of lung damage. RESULTS: During ILP, no hemodynamic effects of importance were noted. No systemic leakage of melphalan was observed in any of the animals. Compared with normal lung tissue, microscopic examination of lung tissue after perfusion without melphalan showed pulmonary edema. Directly after melphalan perfusion additional hemorrhagic areas were seen; however, electron microscopy displayed no irreversible endothelial damage. CONCLUSION: This study on pigs proved to be a well reproducible model for ILP with melphalan. Pharmacokinetics show a safety profile with no systemic toxicity, which could justify further patient studies, necessary to determine its effect on pulmonary metastases in humans, especially in case of adjuvant therapy after surgical resection or in unresectable disease.

Surgery promotes implantation of disseminated tumor cells, but does not increase growth of tumor cell clusters.

INTRODUCTION: Local recurrence and peritoneal dissemination is common after intentionally curative resection of colorectal carcinoma. It is not yet clear which mechanisms stimulate post-operative intra-abdominal tumor development. Enhanced adhesion or growth of tumor cells and/or post-operative immuno suppression may influence tumor recurrence. AIMS OF THE STUDY: In the present study, we evaluated effects of local and remote surgery on intra-abdominal tumor development. MATERIALS AND METHODS: A standardized intra-abdominal trauma was inflicted by rubbing both uterus horns in laparotomy groups, while a dorsolateral thoracotomy was performed in thoracotomy groups (on day -1, 0, or +3). To induce tumor development rats were injected intra-peritoneally with the coloncarcinoma cell line CC531s on day 0 and evaluated after 21 days. RESULTS: Rats undergoing laparotomy and injection on day 0 showed significantly higher tumorload than control rats (195 +/- 20 vs. 47 +/- 29, P < 0.001). When a laparotomy was performed, the day before tumor inoculation even higher tumorload was seen (245 +/- 37 vs. 195 +/- 20, P < 0.01). Strikingly, performing a thoracotomy on the day before or on the same day as tumor inoculation resulted in enhanced tumorload compared to controls as well (135 +/- 84 vs. 47 +/- 29; P < 0.001 and 88 +/- 38 vs. 47 +/- 29; P < 0.02, respectively). Either laparotomy or thoracotomy 3 days after tumor cell inoculation did not affect growth of pre-existing tumor cell clusters. CONCLUSIONS: The (post) surgical intra-peritoneal microenvironment enhances successful implantation of spilled tumor cells, whereas growth of adhered tumor cell clusters is not affected. The inflammatory response as a result of remote surgery promotes successful tumor development as well.