Survival outcomes associated with fewer combination ipilimumab/nivolumab doses in advanced-stage melanoma

9549

Background: Standard combination ipilimumab/nivolumab (I/N) is given as 4 induction doses for advanced stage melanoma. While many patients receive less than 4 doses due to treatment-related toxicities, it is unclear if fewer doses of I/N may still provide long term clinical benefit. Our aim is to determine if response assessment after 1 or 2 doses of I/N can predict long-term survival and if fewer doses of I/N can achieve similar survival outcomes. Methods: We performed a single-center, retrospective analysis on a cohort of patients with metastatic or unresectable melanoma from 2012 to 2020 who were treated with standard I/N. Cox regression of progression free survival (PFS) and overall survival (OS) models were performed to assess the relationship between response assessment after 1 or 2 doses of I/N and risk of progression and/or death. Clinical benefit response (CBR) was assessed, defined as SD (stable disease) + PR (partial response) + CR (complete response) by imaging or physical examination. Among patients who achieved a CBR after 1 or 2 doses of I/N, a multivariable Cox regression of survival was used to compare 3 or 4 vs 1 or 2 doses of I/N adjusted by age, gender, pre-treatment LDH level, BRAF mutation status, primary melanoma site, time to initial assessment, brain metastasis, and liver metastasis. Results: 199 patients were identified and considered evaluable in our study. Median follow up was 28.8 months. Patients with CBR after 1 dose of I/N had improved PFS (HR: 0.23, 95% CI 0.14-0.39; p<0.001) and OS (HR: 0.19, 95% CI 0.10-0.38; p<0.001) compared to progressive disease (PD) [Table]. Patients with CBR (vs PD) after 2 doses of I/N also had improved PFS (HR: 0.17, 95% CI 0.11-0.26; p<0.001) and OS (HR: 0.13, 95% CI 0.07-0.23; p<0.001) [Table]. The survival risk comparing 3 or 4 vs 1 or 2 doses of I/N were HR 0.82 (95% CI 0.45-1.53; p=0.540) for PFS and HR 0.56 (95% CI 0.24-1.30; p=0.175) for OS. Conclusions: Clinical benefit response (CBR) after 1 or 2 doses of I/N may be predictive of long-term survival in advanced stage melanoma. Patients who have CBR after 1 or 2 doses of I/N may achieve a similar survival benefit with fewer doses of I/N. Longer follow up and prospective studies are warranted to validate our findings.[Table: see text]

Bone Metastases, Skeletal-Related Events, and Survival in Patients With Metastatic Non-Small Cell Lung Cancer Treated With Immune Checkpoint Inhibitors

BACKGROUND

Bone metastases and skeletal-related events (SREs) are a frequent cause of morbidity in patients with metastatic non-small cell lung cancer (mNSCLC). Data are limited on bone metastases and SREs in patients with mNSCLC treated using immune checkpoint inhibitors (ICIs), and on the efficacy of bone-modifying agents (BMAs) in this setting. Here we report the incidence, impact on survival, risk factors for bone metastases and SREs, and impact of BMAs in patients with mNSCLC treated with ICIs in a multi-institutional cohort.

PATIENTS AND METHODS

We conducted a retrospective study of patients with mNSCLC treated with ICIs at 2 tertiary care centers from 2014 through 2017. Overall survival (OS) was compared between patients with and without baseline bone metastases using a log-rank test. A Cox regression model was used to evaluate the association between OS and the presence of bone metastases at ICI initiation, controlling for other confounding factors.

RESULTS

We identified a cohort of 330 patients who had received ICIs for metastatic disease. Median patient age was 63 years, most patients were treated in the second line or beyond (n=259; 78%), and nivolumab was the most common ICI (n=211; 64%). Median OS was 10 months (95% CI, 8.4-12.0). In our cohort, 124 patients (38%) had baseline bone metastases, and 43 (13%) developed SREs during or after ICI treatment. Patients with bone metastases had a higher hazard of death after controlling for performance status, histology, line of therapy, and disease burden (hazard ratio, 1.57; 95% CI, 1.19-2.08; P=.001). Use of BMAs was not associated with OS or a decreased risk of SREs.

CONCLUSIONS

Presence of bone metastases at baseline was associated with a worse prognosis for patients with mNSCLC treated with ICI after controlling for multiple clinical characteristics. Use of BMAs was not associated with reduced SREs or a difference in survival.

Abstract 2578: An essential role for Argonaute 2 in HRAS and NRAS driven oncogenesis

The RAS gene family is among the most commonly mutated genes in cancer, and targeting the potential binding partners of mutated RAS may present a promising alternative therapeutic strategy. We recently identified Argonaute 2 (AGO2) of the RNA-induced silencing complex (RISC) as a novel partner of KRAS through its Switch II domain. Further, we demonstrated a role for AGO2 through the development of a KRASG12D driven mouse model of pancreatic cancer. Specifically, our findings revealed that AGO2 ablation drove early precursor pancreatic intraepithelial (PanIN) lesions to enter oncogene-induced senescence in lieu of progressing to late stage PanINs and pancreatic ductal adenocarcinoma. These studies suggested that AGO2 plays a key role in the development of mutant KRAS driven cancers.

In order to assess the role of AGO2 in other mutant RAS driven cancers, we performed co-IP of purified AGO2 and purified NRAS/HRAS proteins using isoform specific antibodies. Both HRAS and NRAS bound AGO2, regardless of GDP or GTP nucleotide loading. Using a panel of cell lines (including T24 cells (HRASG12V) and Mel-Juso cells (NRASQ61L)), we observed that AGO2 interacted with both wild-type (WT) and mutant forms of HRAS and NRAS. Additionally, using a variety of cell line models, we observed that EGFR-mediated phosphorylation of AGO2Y393 disrupted the interaction between WT RAS and AGO2. However, the mutant NRAS-, HRAS-, and KRAS-AGO2 interactions were resistant to EGFR regulation.

Considering the strong role of AGO2 in mutant KRAS driven cancer, we next asked if loss of AGO2 could induce a similar inhibition of RAS driven disease in human cell line models. In a panel of mutant NRAS and HRAS driven cell lines, AGO2 knockdown led to a substantial decrease in cell proliferation; however, WT RAS expressing cells were unperturbed following loss of AGO2. Similar to the loss of AGO2 in the KRASG12D driven mouse model, knockdown of AGO2 led to increased beta-galactosidase staining in a panel of oncogenic NRAS/HRAS driven cells. Furthermore, knockdown of AGO2 was associated with an induction of multiple senescence pathways, including increased p53, p21, and p16 expression. These results suggest that decreased AGO2 expression is sufficient to induce senescence in mutant but not WT RAS driven cells. In these cell line models, AGO2 loss reduced not only the mutant RAS isoform expression but also the WT RAS isoforms. Finally, knockdown of AGO2 led to an inhibition of T24 and Mel-Juso cell migration and metastasis in a zebrafish xenograft model. Taken together, these results suggest that 1) AGO2 interactions with mutant HRAS and NRAS play a key role in mutant RAS driven oncogenesis and 2) both mutant HRAS and NRAS depend on AGO2 to overcome senescence.

Citation Format: Ronald F. Siebenaler, Jessica Waninger, Sunita Shankar, Seema Chugh, Shih-Chun Chu, Jean Tien, Vijaya L. Dommeti, Malay Mody, Anudeeta Gautam, Carson Kenum, Chandan Kumar-Sinha, Arul M. Chinnaiyan. An essential role for Argonaute 2 in HRAS and NRAS driven oncogenesis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2578.

An essential role for Argonaute 2 in EGFR-KRAS signaling in pancreatic cancer development

Both KRAS and EGFR are essential mediators of pancreatic cancer development and interact with Argonaute 2 (AGO2) to perturb its function. Here, in a mouse model of mutant KRAS-driven pancreatic cancer, loss of AGO2 allows precursor lesion (PanIN) formation yet prevents progression to pancreatic ductal adenocarcinoma (PDAC). Precursor lesions with AGO2 ablation undergo oncogene-induced senescence with altered microRNA expression and EGFR/RAS signaling, bypassed by loss of p53. In mouse and human pancreatic tissues, PDAC progression is associated with increased plasma membrane localization of RAS/AGO2. Furthermore, phosphorylation of AGO2Y393 disrupts both the wild-type and oncogenic KRAS-AGO2 interaction, albeit under different conditions. ARS-1620 (G12C-specific inhibitor) disrupts the KRASG12C-AGO2 interaction, suggesting that the interaction is targetable. Altogether, our study supports a biphasic model of pancreatic cancer development: an AGO2-independent early phase of PanIN formation reliant on EGFR-RAS signaling, and an AGO2-dependent phase wherein the mutant KRAS-AGO2 interaction is critical for PDAC progression.

The impact of BRAF mutation status on clinical outcomes with single-agent PD-1 inhibitor versus combination ipilimumab/nivolumab

10024

Background: Nearly half of all metastatic melanoma patients possess the BRAF V600 mutation. Several therapies are approved for BRAF mutant metastatic melanoma, but it is unclear if there is a differential outcome to various immunotherapy regimens. Our aim was to better assess if BRAF mutation status has any impact on survival to combination ipilimumab/nivolumab (I/N) versus single-agent PD-1 inhibitor (PD-1i). Methods: We performed a single center, retrospective analysis on a cohort of patients diagnosed with metastatic or unresectable melanoma from 2012 to 2019 at the University of Michigan who were treated with standard I/N or PD-1i (nivolumab or pembrolizumab). A univariate analysis of progression free survival (PFS) and overall survival (OS) was stratified by treatment type and BRAF mutation status. A multivariate Cox regression of survival was used to compare the effects of the treatment groups adjusted by BRAF status, age, gender, pre-treatment LDH level, prior treatment status, and brain metastases status. Results: 323 patients were identified. 132 had BRAF V600 mutation and 191 had BRAF wildtype (WT) status. 138 patients received I/N and 185 patients received PD-1i. In our univariate analysis, there was no difference in PFS [HR: 0.72, 95% CI, 0.46 – 1.13] or OS [HR: 0.78, 0.44 – 1.38] with I/N versus PD-1i in the BRAF mutant cohort, but there was improved PFS [HR: 0.55, 0.35 – 0.88) and OS [HR: 0.52, 0.28 – 0.95] with I/N compared to PD-1i in the BRAF WT group. In the multivariate analysis, the BRAF WT group continued to show PFS benefit with I/N compared to PD-1i [HR: 0.57, 95% CI, 0.35 – 0.95], but the OS benefit no longer achieved statistical significance [HR: 0.54, 0.28 – 1.03]. Conclusions: Our study results were discordant with the observation in the landmark CheckMate 067 trial, which noted improved PFS and OS with I/N compared to nivolumab alone in the BRAF mutant group and no difference in the BRAF WT group. In our real-world retrospective analysis, I/N over PD-1i should be considered as initial immunotherapy for metastatic melanoma patients regardless of BRAF mutation status, but even more favorably in BRAF WT.

Abstract A21: Loss of Argonaute 2 leads to oncogene-induced senescence in mutant RAS-driven cancer

The RAS gene family is among the most commonly mutated genes within cancer, but little progress has been made in successfully targeting RAS mutations. Targeting binding partners of mutated RAS, however, presents a promising alternative therapeutic strategy. With the goal of uncovering novel interactors of RAS, we recently identified Argonaute 2 (AGO2) of the RNA-induced silencing complex (RISC) as a novel partner of the Switch II domain of KRAS. In order to assess the role of AGO2 in KRAS-G12D driven disease, we developed a mouse model of pancreatic cancer with conditional loss of AGO2. While AGO2 knockout did not prevent development of early precursor pancreatic intraepithelial (PanIN) lesions, loss of AGO2 prevented progression to late-stage PanINs, pancreactic ductal adenocarcinoma (PDAC), and metastatic disease. AGO2 null lesions displayed increased activation of the EGFR-RAS signaling axis during PanIN development. This signaling resulted in an increase in WT RAS-GTP activation, pEGFR-Y1068, and pERK levels leading to the development of oncogene-induced senescence in these PanIN lesions. Furthermore, we observed that EGFR-mediated phosphorylation of AGO2-Y393 disrupted the interaction between WT RAS and AGO2. This regulation by EGFR, however, was blocked in cells expressing mutant KRAS. These results suggested that the interaction of mutant RAS and AGO2 was vital to tumor development. To better assess the role of AGO2 loss in mutant RAS driven cancer, we performed AGO2 knockdown in multiple cell lines expressing mutations in either NRAS or HRAS isoforms. In each cell line, AGO2 directly interacted with KRAS, NRAS, and KRAS. In addition to suppressing growth in mutant RAS-driven cells (T24: HRAS-G12V, SK-MEL-2: NRAS-Q61H), loss of AGO2 produced marked increases in beta-galactosidase and p16 expression, as well as a decrease in cyclin D1, suggesting development of oncogene-induced senescence. Interestingly, upon AGO2 loss, cells displayed induction of pEGFR and pERK similar to what was observed in our pancreatic mouse model, and despite decreased expression of mutant RAS, WT RAS-GTP loading upon AGO2 loss was strongly induced. Together these results suggest a unique EGFR-AGO2-RAS signaling axis that requires AGO2-RAS interaction to prevent induction of oncogene-induced senescence in mutant RAS-driven cancers.

Citation Format: Ronald F. Siebenaler, Sunita Shankar, Jean C. Tien, Vijaya L. Dommeti, Sylvia Zelenka-Wang, Jessica Waninger, Malay Mody, Seema Chugh, Chandan Kumar-Sinha, Arul M. Chinnaiyan. Loss of Argonaute 2 leads to oncogene-induced senescence in mutant RAS-driven cancer [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr A21.

Abstract A20: An essential role for Argonaute 2 in mouse models of KRAS driven cancers

In 2016, we identified a direct interaction between RAS and Argonaute 2 (AGO2), a key mediator of RNA-mediated gene silencing that is required for KRAS-driven oncogenesis using pancreatic and lung cancer cell line models. Recently, we employed the genetically engineered mouse model of pancreatic cancer to define the effects of conditional loss of AGO2 in KRASG12D driven pancreatic cancer. Genetic ablation of AGO2 did not interfere with development of the normal pancreas or KRASG12D-driven early precursor pancreatic intraepithelial neoplasia (PanIN) lesions. However, AGO2 loss prevents progression from early to late PanIN lesions, development of pancreatic ductal adenocarcinoma (PDAC), and metastatic progression. This results in a dramatic increase in survival of KRASG12D mutant mice deficient in AGO2 expression. Using validated pan-RAS and AGO2 antibodies for immunofluorescence (IF) and proximity ligation assay (PLA), we observed increased RAS and AGO2 co-localization at the plasma membrane in mouse and human pancreatic tissues associated with PDAC progression. AGO2 ablation permits PanIN initiation driven by the EGFR-RAS axis; however rather than progressing to PDAC, these lesions undergo profound oncogene-induced senescence (OIS). Since PanIN development requires EGFR and is not AGO2 dependent, we probed the effects of EGF stimulation in cell lines expressing wild-type and mutant forms of KRAS (using co-IP and PLA analyses). In wild-type RAS expressing cells, grown in media containing serum, RAS-AGO2 co-localization was limited to the intracellular regions of the cells, which dramatically increased and shifted to the plasma membrane under conditions of stress (serum starvation). Interestingly, EGF stimulation disrupted this membrane RAS-AGO2 interaction and restored it to intracellular basal levels. Using phosphorylation-deficient AGO2 mutants, we demonstrate that the disruption of wild type-RAS-AGO2 interaction is due to AGO2Y393 phosphorylation, a target of EGFR. Interestingly, the mutant KRAS-AGO2 interaction is not subject to EGFR activation, suggesting that although both the wild-type and mutant RAS bind AGO2, they are differentially regulated through growth factor receptor activation. Taken together, our study supports a biphasic model of pancreatic cancer development: an AGO2-independent early phase of PanIN formation reliant on EGFR and wild-type RAS signaling, and an AGO2-dependent phase wherein the mutant KRAS-AGO2 interaction is critical for PDAC progression. In the lung cancer mouse model, we also observed a similar dependence of AGO2 in KRAS-driven lung adenocarcinoma. Along with related abstracts detailing the mechanisms of OIS mediated by AGO2 (Ronald Siebenaler) and evidence of direct interaction between oncogenic KRAS and AGO2 with an affinity of 200nM (Jessica Waninger), we present our latest studies related to the KRAS-AGO2 interaction.

Citation Format: Sunita Shankar, Jean Ching-Yi Tien, Ronald F. Siebenaler, Vijaya L. Dommeti, Sylvia Zelenka-Wang, Jessica Waninger, Xiao-Ming Wang, Kristin M. Juckette, Alice Xu, Seema Chugh, Malay Mody, Sanjana Eyunni, Andrew Goodrum, Grace Tsaloff, Yuping Zhang, Ingrid J. Apel, Lisha Wang, Javed Siddiqui, Richard D. Smith, Heather A. Carlson, John Tesmer, Xuhong Cao, Jiaqi Shi, Chandan Kumar-Sinha, Arul M. Chinnaiyan. An essential role for Argonaute 2 in mouse models of KRAS driven cancers [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr A20.

Abstract B39: Characterization of the interaction between KRAS and Argonaute 2

KRAS is one of three members of the RAS family of small GTPases, and nearly one third of all human cancers harbor mutations in the KRAS gene. These mutations lead to a constitutively active GTP-bound form of KRAS that results in aberrant activation of MAPK and PI3K pathways that control cell differentiation, growth, and survival. While much has been learned about the effectors of KRAS and its complex signaling network, little progress has been made in successfully targeting it in the treatment of cancer. Recently, we identified a functional protein-protein interaction between KRAS and Argonaute 2 (AGO2), a core component of the RNA-induced silencing complex (RISC). Investigation of this interaction revealed that the switch II domain of KRAS (both wild-type [WT] and mutant) binds to the N-terminal (Nt) domain of AGO2. Mutant KRAS-AGO2 binding results in attenuation of the RNAi function of AGO2 by preventing microRNA unwinding, a necessary step in the formation of the mature RISC complex (model 1). Analysis of this interaction revealed that KRAS-AGO2 binding is direct through Tyr64 of KRAS and Lys112/Glu114 of AGO2. Recently, using genetically engineered mouse models (GEMM), we showed that mutant KRAS is dependent on AGO2 for the development of pancreatic ductal adenocarcinoma (PDAC) from early precursor lesions in the pancreas, suggesting a critical role for the KRAS-AGO2 interaction in vivo. To further characterize KRAS-AGO2 binding, we purified recombinant proteins individually, isolated complex via size exclusion chromatography (SEC), performed differential scanning fluorimetry (DSF), isothermal titration calorimetry (ITC), and small angle x-ray scattering (SAXS). Additionally, in order to evaluate endogenous regulators of the KRAS-AGO2 interaction we investigated the role of the epidermal growth factor receptor (EGFR), which is known to regulate the RNAi function of AGO2 via phosphorylation at Tyr393. Interestingly, we observed that phosphorylation at this residue disrupts the interaction of AGO2 with WT but not mutant KRAS, providing a basis for differential regulation of the KRAS-AGO2 interaction through growth factor activation. Finally, to examine structural changes induced by EGFR phosphorylation of AGO2 at Tyr393 that may affect KRAS binding, we performed parallel molecular dynamics simulations (MDS) of nonphosphorylated and phospho-Tyr393 AGO2. These studies revealed immediate structural reorganization of the RAS binding site and an outward rotation of the entire Nt domain of AGO2. Taken together, these data shed light on a potential mechanism underlying the differential regulation of mutant vs. WT KRAS.

Citation Format: Jessica Waninger, Sunita Shankar, Ronald Siebenaler, Malay Mody, Jean Tien, Vijaya Dommeti, Tyler Beyett, Richard Smith, Chandan Kumar-Sinha, Heather Carlson, John Tesmer, Arul Chinnaiyan. Characterization of the interaction between KRAS and Argonaute 2 [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr B39.

Abstract 957: An essential role for Argonaute 2 in mouse models of KRAS-driven cancers

In 2016, we identified a direct interaction between RAS and Argonaute 2 (AGO2), a key mediator of RNA-mediated gene silencing, that is essential for KRAS-driven oncogenesis using pancreatic and lung cancer cell line models. Recently, we employed a genetically engineered mouse model of pancreatic cancer to define the effects of conditional loss of AGO2 in KRASG12D-driven pancreatic cancer (KC model). Genetic ablation of AGO2 did not interfere with development of the normal pancreas or KRASG12D-driven early precursor pancreatic intraepithelial neoplasia (PanIN) lesions. However, AGO2 loss prevents progression from early to late PanIN lesions, development of pancreatic ductal adenocarcinoma (PDAC), and metastatic progression. This results in a dramatic increase in the survival of KRASG12D mutant mice deficient in AGO2 expression. Mechanistically, lack of PanIN to PDAC progression was due to oncogene-induced senescence (OIS) through activation of EGFR-wild type RAS-phosphoERK signaling in the absence of AGO2.

Using validated pan-RAS and AGO2 antibodies for immunofluorescence (IF) and proximity ligation assay (PLA), we observed increased RAS and AGO2 co-localization at the plasma membrane in mouse and human pancreatic tissues associated with PDAC progression. While AGO2 ablation permits PanIN initiation driven by the EGFR-RAS axis, these lesions undergo OIS rather than progressing to PDAC. Further, we used co-IP and PLA analyses to probe the effects of EGF stimulation in cell lines expressing wild-type and mutant forms of KRAS. In wild-type RAS expressing cells, RAS-AGO2 co-localization and interaction were limited to the intracellular regions of the cells, and dramatically increased and shifted to the plasma membrane under conditions of stress (serum starvation). Interestingly, EGF stimulation disrupted this membrane RAS-AGO2 interaction and restored it to intracellular levels. Using phosphorylation-deficient AGO2 mutants, we further demonstrate that the disruption of wild-type RAS-AGO2 interaction is due to EGFR-mediated AGO2Y393 phosphorylation. Interestingly, mutant KRAS-AGO2 interaction is not subject to EGFR activation, suggesting that although both the wild type and mutant RAS bind AGO2, they are differentially regulated through growth factor receptor activation.

We will discuss our ongoing studies evaluating the effects of AGO2 ablation in the KRASG12Ddriven lung cancer mouse model and PDAC progression with p53 loss (KPC model). Our recent in vivo work supports a biphasic model of pancreatic cancer development: an AGO2-independent early phase of PanIN formation reliant on EGFR and wild-type RAS signaling, and an AGO2-dependent phase wherein the mutant KRAS-AGO2 interaction is critical for PDAC progression.

Citation Format: Sunita Shankar, Jean Ching-Yi Tien, Ronald F. Siebenaler, Vijaya L. Dommeti, Sylvia Zelenka-Wang, Jessica Waninger, Kristin M. Juckette, Alice Xu, Xiao-Ming Wang, Seema Chugh, Malay Mody, Sanjana Eyunni, Andrew Goodrum, Grace Tsaloff, Yuping Zhang, Ingrid J. Apel, Javed Siddiqui, Richard D. Smith, Heather A. Carlson, John Tesmer, Xuhong Cao, Jiaqi Shi, Chandan Kumar-Sinha, Arul M. Chinnaiyan. An essential role for Argonaute 2 in mouse models of KRAS-driven cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 957.

[Acute cholecystitis. Do you send the patient to the operating room or to bed?]

Acute cholecystitis is increasingly becoming a disease of the elderly. The condition begins with colic-like pain in the upper abdomen radiating to the right shoulder, and is accompanied by fever, nausea and vomiting. The diagnosis is confirmed by tenderness and palpable resistance in the right upper abdomen. Ultrasound detects the stone in 95% of cases, and confirms the diagnosis. Differential diagnostic considerations include appendicitis, duodenal or gastric ulcer, and myocardial infarction. Early cholecystectomy is associated with a low complication rate which, however, increases, the longer the intervention is delayed. Laparoscopic cholecystectomy has a lower complication rate and a reduced hospital stay; the reported mortality rate is between 0% and 3.5%. Conventional cholecystectomy is recommended when there is concomitant choledocholithiasis and no possibility of carrying out ERCP, and in patients with previous upper abdominal surgery. Conservative treatment is applied when the patient refuses surgery or is at high risk from anaesthesia.

[A retaining dam against reflux. Laparoscopic fundoplication helps even in stubborn cases]

The introduction of proton pump inhibitors (PPI) and laparoscopic fundoplication in the treatment of gastroesophageal reflux disease offered an opportunity for definitive healing. The indication for surgery is the failure of medical treatment, recurrence of symptoms following conservative treatment, severe side effects of the medication, and the patient's wish to stop taking drugs. The laparoscopic treatment has a low rate of complications. Apart from temporary dysphagia (30%), rapid satiety, increased flatulence and suppressed eructation are possible undesirable sequelae. Intra-operative bleeding and organ perforation (1%) are major feared occurrences. The rate of conversion to open surgery is 5.8%, and the mortality rate is 0.1%. Persistent dysphagia in 3.4% may be caused by a slipped cuff. A revision procedure is necessary in 0.7% of the patients. Patient satisfaction with the results of the operation ranges between 87 and 100%.

[Cost data of standard surgical interventions]

Personnel and nonpersonnel costs of seven surgical standard procedures were calculated related to the patient. Nonpersonnel costs were up to 57% below to the figures of the Ministry of Health. Personnel costs ranged from 3.2% to 30% less. The result of a patient related calculation will lead to more efficiency by changing a faulty organisation, the management of the personnel, the indication for surgical procedures and the surgical technique.

[Inguinal hernia--which method leads to the goal? Endoscopic and open surgical procedures are available]

In recent years, the methods available for repair of inguinal hernia have greatly expanding, resulting in confusion as to what constitutes a suitable choice. Is it to be laparoscopy or open surgery, plastic mesh yes or no, general anesthesia or local anesthesia? Bassini's operation has now been ousted by the Shouldice procedure, which is suitable for all primary forms of hernia. The Lichtenstein procedure is readily and rapidly carried out under local anesthesia, making it suitable for use in multimorbid and old patients; the recurrence rate is low. The laparoscopic approach can be recommended for patients who, for private or occupational reasons need to be up and about again as soon as possible. It is also particularly suitable for the treatment of recurrent hernias or for the simultaneous repair of bilateral hernias. Disadvantages are the high costs, a lack of long-term results and unusual complications that are not seen in open surgery.

Comparison of laparoscopic handsewn suture techniques for experimental small-bowel anastomoses

Laparoscopic techniques have only rarely been applied to procedures on the small bowel. A comparison of three handsewn intracorporeal anastomoses was carried out. Thirty pigs were divided into three groups, and a different technique was used in each group (SK, single knot; RS, running suture; CL, clip suture). Half of the animals had a relaparoscopy on day 4. The duration of the procedure was recorded, and the quality of anastomotic healing was assessed by morphological, radiological, mechanical, and biochemical examinations. The animals were sacrificed on postoperative day 14. The anastomoses in the SK group took significantly longer than in the RS or CL groups. The mean duration of relaparoscopy was 28 min. Bursting pressure values and hydroxyproline concentrations were without any significant difference. The SK and CL groups showed a good alignment of the layers and the RS showed necrosis and overlying mucosa. Most complications were noted in RS. The results demonstrate that manual small-bowel anastomoses can be performed laparoscopically. Single-knot and clip sutures are reliable techniques. The ongoing development of new instruments and the three-dimensional technique will basically improve the construction of intracorporeal anastomoses.

Effects of the Pringle maneuver on hemodynamics during laparoscopic liver resection in the pig

The Pringle maneuver (PM) is recognized in conventional liver surgery as a method of controlling bleeding. To determine the hemodynamic effects of the PM during pneumoperitoneum (PP) for laparoscopic liver resection, we measure hemodynamic and blood gas changes in 7 healthy pigs. All variables were recorded 5 min before and 10 and 30 min after employing PP or PM and 10 min after discontinuation of PM. After the induction of PP, cardiac index and arterial carbon dioxide tension significantly increased, accompanied by a significant decrease in pH. After the beginning of PM, cardiac index and mean arterial and central venous pressures decreased significantly, whereas the heart rate rose markedly. After discontinuation of the PM, the systemic vascular resistance index decreased, and the heart rate remained elevated. These results demonstrate severe hemodynamic deterioration with PP and a subsequent PM. The latter should, therefore, be considered only as a last resort for the control of bleeding during laparoscopic liver surgery.

[Laparoscopic techniques in therapy of choledocholithiasis]

Several methods for therapy of common bile duct stones (CBDS) during laparoscopic cholecystectomy are available. After intraoperative cholangiography laparoscopic removal of CBDS can be achieved via the cystic duct or a choledochotomy using a thin cholangioscope, balloon catheters and Dormia baskets. Lithotripsy (electrohydraulic or laser) is necessary in presence of larger stones. Also combined procedures with intraoperative antegrade or retrograde papillotomy have been described. Published studies show that laparoscopic common bile duct exploration can be performed successfully by experienced surgeons. However, these procedures are demanding and time-consuming. Further evaluation is essential.

[Microbiological and economic studies of abbreviated procedures for surgical hand disinfection]

An investigation was performed of whether shortened procedures for surgical hand disinfection (2 and 3 min, respectively) are equally effective as the usual German standard procedure of 5 min duration and, in addition, which saving of working time and costs would be achievable if shorter procedures were employed. The shortened procedures were: 1) 3 min alcoholic disinfectant (1 min prior handwashing) and 2) 1 min chlorhexidine detergent (Hibiscrub), 2 min 0.5% chlorhexidine in 70% isopropanol (Hibisol). The two shortened procedures were equally effective as the standard procedure (test of equivalence, p < 0.05). The savings of working time and costs calculated for 17708 operations were 1) 2360 h or 79768 German marks and 2) 3540 h or 119652 German marks, respectively.

[Abdominal surgery in advanced age. Indications and prognosis exemplified by stomach, bile duct, colon and hernia surgery]

The increased risk of morbidity and mortality associated with abdominal surgery in the aged is determined by the number and severity of accompanying diseases and the emergency situation. Age per se is not a risk factor. Limitation of the risk requires an age-oriented treatment plan, which must take account of the specific problems of the geriatric patient in the pre-, intra-, and postoperative phases. Emergency operations should be avoided as far as possible. The aim of geriatric surgery is not merely to prolong life, but also to secure adequate quality of life. To accomplish this, it may occasionally be necessary to forgo surgical radicality in favor of a palliative procedure. The results of abdominal surgery in the elderly are presented on the basis of exemplary cases of stomach, biliary, colonic and hernial surgery.

[Ambulatory follow-up care in laparoscopic cholecystectomy]

FUNDAMENTAL CONSIDERATIONS: With increasing frequency, laparoscopic procedures are now replacing conventional cholecystectomy. Given the choice, patients with cholecystolithiasis almost always opt for the former procedure.

MAJOR POINTS

Because the laparoscopic procedure offers considerable advantages as compared with open surgery, the increased risk of local complications associated with it tends to be ignored. For example, injuries to the biliary ducts are about ten times as common as in the case of conventional cholecystectomy. Injuries to the bowel, previously unknown, are increasingly being observed. Symptoms associated with undetected injuries usually do not occur until the patient has been discharged.

CONCLUSIONS

Ambulatory aftercare is particularly important following laparoscopic cholecystectomy. Complications need to be detected in good time in order to be able to institute appropriate counter-measures.

Laparoscopic cholecystectomy after unsuccessful shock-wave therapy

Extracorporeal shock-wave therapy of gallstones was begun at the Surgical Department of the University of Freiburg, Germany, in March 1988; 85 patients were treated up to September 1991. The stone-free rate differed with the gallstone group. Patients with solitary stones less than 20 mm in diameter showed a significantly higher rate after 18 months of lithotripsy and dissolution therapy than patients with multiple stones (p < 0.01), that is, 83% and 49%, respectively. Open cholecystectomy was necessary for seven patients with complications following fragmentation. After starting laparoscopic cholecystectomy, eight patients decided in favor of this procedure because of constant biliary symptoms. These patients had a mean duration of dissolution therapy of 19 months. The minimal invasive procedure is an alternative for patients with unsuccessful lithotripsy and lysis who initially demanded conservative treatment. Indication for shock-wave therapy is limited to only a small group of patients with solitary cholesterol gallstones less than 20 mm who reject laparoscopic surgery.

Influence of the distance between interrupted sutures and the tension of sutures on the healing of experimental colonic anastomoses

Certain technical factors determine the success of the creation of intestinal anastomoses. The influence of the distance between interrupted sutures and the suture tension on wound healing was investigated in an experimental study using a specially designed suture model. The combination of a long suture distance (group A, 2.5 mm) and a short suture distance (group B, 1.5 mm) with three different suture tensions, i.e., (1) no tension; (2) moderate tension; and (3) high tension, resulted in six different techniques. Tension was created by means of a spring balance. The anastomoses were examined macroscopically, histologically by microangiography, and by bursting pressure. Apposition of the bowel wall between the interrupted sutures was inappropriate due to prolapse of the mucosa in 7.9% of the patients in group A but did not occur in groups B2 and B3. The leakage rate was 4.6% in group A and 1.3% in group B. Early healing of the mucosa was noted in group B2. Bursting pressure was significantly higher on day 2 and 4 in groups B2 and B3. The results demonstrate the influence of suture technique on the wound healing of intestinal anastomoses. The best healing pattern was achieved by a small distance between the sutures and a moderate suture tension.

[Laparoscopic cholecystectomy]

In a short space of time, laparoscopic cholecystectomy has become the operative treatment of choice in cholecystolithiasis. The performance of the operation, however, requires complex equipment, and became at all possible only with the aid of video technology. The indication depends both on the patient's symptoms and the experience of the operator. Prior surgery in the upper abdomen and complications of gallstones are considered relative contraindications, and portal hypertension an absolute contraindication. The advantages of this minimally invasive operative procedure are the minimal traumatization and improved postoperative well-being. The need for pain-killer is low, gastric tube and selective drainage are not required. Dietary build-up and mobilization are possible early on. Postoperative hospitalization is 2 to 3 days. The future will bring further developments in the field of laparoscopic operative interventions.

[Surgical techniques in Crohn disease and ulcerative colitis]

The usefulness of surgical treatment of inflammatory bowel disease is determined by the results that can be achieved. In Crohn's disease, in addition to minimal resections, non-resective procedures such as stricturoplasty, are also available for the treatment of acute and chronic complications. The operative treatment of peri-anal Crohn's lesions is determined by the acute or chronic complications that develop. Ulcerative colitis can be cured by complete removal of the colorectal mucosa, and malignant degeneration thus avoided. Continence-preserving colectomy with proctomucosectomy and ileo-anal pouch anastomosis obviates the need for a permanent ileostomy.

[Extracorporeal piezoelectric gallstone lithotripsy: initial surgical experience with a new treatment. Technique and indications]

The extracorporeal piezoelectric lithotripsy (EPL) is a new method for non-operative therapy of symptomatic gallbladder and problematic bile duct stones. The rare intrahepatic calculi were similarly disintegrated. Best results were reached with EPL as adjuvant measure or combined with oral cheno- and ursodeoxycholic acid therapy. EPL compared to other lithotripsy techniques is performed without any analgesia. That means advantage and patient's benefit.

Large-bile-duct stones--extracorporeal piezoelectric lithotripsy as adjuvant measure for endoscopic basket extraction

Extracorporeal piezoelectric lithotripsy (EPL) was performed in 12 patients with large-bile-duct stones and intrahepatic stones. The Piezolith 2300 lithotripter (Wolf, Knittlingen, FRG) was used in all patients in whom routine endoscopic approaches for removal of the calculi had failed or were considered inappropriate because of large stone size or difficult localization. In 9 of the 12 patients the stones were fragmented. Complete stone clearance from the bile ducts was obtained in 8 of 10 patients by EPL alone or combined with one of the following: endoscopic extraction, mechanical lithotripsy or installation of solvents. Adjuvant EPL in conjunction with endoscopic therapy increased the success rate of nonsurgical treatment for bile duct stones from 73% to 95%. No clinically significant side effects or complications were noted.

[Non-Hodgkin's lymphoma of the descending colon in a 6-year-old girl]

The most common site of non-Hodgkin lymphoma of the intestinal tract in children is the terminal ileum and the ileocecal region; boys are 5- to 10 times more frequently affected than girls, peak incidence is between 5 and 8 years of age. We present a 6-year-old girl with non-Hodgkin lymphoma of the descending colon.

[Ultrasound diagnosis following blunt abdominal trauma. Sonography in acute and follow-up diagnosis]

Experience with ultrasonography as a non-invasive imaging procedure for acute and follow-up diagnostic evaluation of blunt abdominal trauma was analysed in a retrospective study. Between 1980 and 1988, more than 2,000 ultrasonographic investigations were performed for blunt abdominal trauma; 246 patients were laparotomized. Retrospectively, false results based on ultrasonography were less than 1% of all cases, so that the sole use of ultrasonographic diagnosis and the non-use of peritoneal lavage seems justified in cases of blunt abdominal trauma. A number of figures illustrate typical cases.

[Microangiographic findings in experimental intestinal anastomoses]

Microangiography of anastomosis at the rat colon and the pig jejunum did reveal the postoperative state of vessel regeneration. Findings for evaluation were avascular areas, dislocation and dilatation of vessels, vessel break, vessel-anastomosis to the opposite site and to adhesions as well as the complete regeneration of the vessel architecture. A suture technique leading to correct apposition of the wound edges without destroying the circulation will be followed by an almost complete regeneration of the vessel architecture.

[The hemorrhagic infarction of the cecum. A complication after the intake of potassium-chloride tablets (author's transl)]

Case report of a 28 year old female patient who had a localized gangrene of the cecum after the intake of Kalinor-Dragées an enteric-coated potassium tablet. It is emphasized that the enteric-coated potassium-tablets have a higher complication rate of stenosis, ulceration and spontaneous perforation of the small bowel, than the slow-release tablets. One should remember potassium-chloride tablet as a possible cause of unexplained stenosis, localized gangrene, ulceration or perforation of the small bowel.