Thermal ablation of hepatic malignancy: useful but still not optimal

The mortality associated with primary and metastatic hepatic malignancies remains high because few patients are candidates for hepatic resection or transplantation. Resection is the most effective treatment for liver tumors but may be contraindicated by factors such as the tumor's location; hepatic transplantation can cure primary hepatocellular carcinoma and underlying cirrhosis, but a donor may not be immediately available. When resection or transplantation is not possible, thermal ablation is a reasonable therapeutic option. Effective destruction of tumors can be achieved with low recurrence rates and minimal complications or risk of death. In patients with primary hepatic malignancy, ablation treatment does not preclude subsequent transplantation. Although radiofrequency ablation is currently the most widely used thermal ablative technique for hepatic malignancy, microwave ablation is gaining popularity and eventually may prove to be more effective.

Unfavourable prognosis associated with K-ras gene mutation in pancreatic cancer surgical margins

BACKGROUND

Despite intent to cure surgery with negative resection margins, locoregional recurrence is common in pancreatic cancer.

AIMS

To determine whether detection of K-ras gene mutation in the histologically negative surgical margins of pancreatic cancer reflects unrecognised disease.

PATIENTS

Seventy patients who underwent curative resection for pancreatic ductal adenocarcinoma were evaluated.

METHODS

All patients had surgical resection margins (pancreatic transection and retroperitoneal) that were histologically free of invasive cancer. DNA was extracted from these paraffin embedded surgical margins and assessed by quantitative real time polymerase chain reaction to detect the K-ras gene mutation at codon 12. Detection of K-ras mutation was correlated with standard clinicopathological factors.

RESULTS

K-ras mutation was detected in histologically negative surgical margins of 37 of 70 (53%) patients. A significant difference in overall survival was demonstrated between patients with margins that were K-ras mutation positive compared with negative (median 15 v 55 months, respectively; p = 0.0008). By univariate and multivariate analyses, detection of K-ras mutation in the margins was a significant prognostic factor for poor survival (hazard ratio (HR) 2.8 (95% confidence interval (CI) 1.5-5.3), p = 0.0009; and HR 2.8 (95% CI 1.4-5.5), p = 0.004, respectively).

CONCLUSIONS

Detection of cells harbouring K-ras mutation in histologically negative surgical margins of pancreatic cancer may represent unrecognised disease and correlates with poor disease outcome. The study demonstrates that molecular-genetic evaluation of surgical resection margins can improve pathological staging and prognostic evaluation of patients with pancreatic ductal adenocarcinoma.

Quality control issues in the management of colon cancer patients

Quality assurance in colon cancer demands a multidisciplinary effort involving general practitioners, surgeons, radiologists, gastroenterologists, medical oncologists, and pathologists, among others. Maximal improvements in survival will result when colon cancer screening, diagnosis, staging, treatment and surveillance are optimized. We seek to identify those issues most relevant to the quality of care we provide our colon cancer patients.

Ultrastaging of early colon cancer using lymphatic mapping and molecular analysis

Approximately one-third of node-negative colon cancers will recur, possibly due to understaging and inadequate pathological examination of lymph nodes (LNs). We evaluated the sensitivity, accuracy and feasibility of staging based on lymphatic mapping, focused examination, and molecular analysis of the sentinel node (SN) in patients with primary colorectal carcinoma. Between 1996 and 2000, 100 patients with colon carcinoma (CRC) underwent lymphatic mapping immediately after peritumoral injection of 1.0 cc of isosulphan blue dye. All LNs in the CRC specimen were examined by routine haematoxylin and eosin (H&E) staining. Sentinel nodes were examined by step serial sectioning, cytokeratin immunohistochemistry (CK-IHC) and/or reverse transcriptase-polymerase chain reaction (RT-PCR) analysis in an attempt to identify occult micrometastatic disease. Lymphatic mapping was successful in 97% of the cases. There were 5 false-negative cases, predominately associated with T3/T4 tumours. Aberrant lymphatic drainage was identified in 8 patients (8%) altering the operative approach. 26 patients had H&E-positive LNs. In 74 patients who were node-negative by routine H&E, 18 (24%) had occult nodal micrometastases missed on routine H&E examination, but detected by focused analysis of the SN. RT-PCR analysis of the SN was performed in 40 patients, 26 of which were negative by H&E and CK-IHC. In 12/26 (46%) of these patients, there was additional evidence of micrometastatic disease. In this study, focused examination of the SN in conjunction with RT-PCR analysis identified micrometastatic disease in a significant number of node-negative patients. This may have important implications when selecting patients for adjuvant treatment protocols.

Solid and papillary epithelial neoplasms of the pancreas: aggressive resection for cure

Solid and papillary epithelial neoplasms of the pancreas (SPENP) are extremely rare and usually affect young women. We retrospectively reviewed our experience with pancreatic neoplasms from 1986 to the present and identified nine patients with SPENP. All nine patients were female with a mean age of 32 years (range 16-66). All patients presented with gastrointestinal complaints including pain, mass, dyspepsia, or bloating and were subsequently diagnosed with a tumor of the pancreas by CT scan. All patients underwent surgical resection. Two patients had tumors located in the head of the pancreas and underwent a pancreaticoduodenectomy. The remainder had tumors located in the tail of the pancreas and underwent distal pancreatectomy. Pathology demonstrated solid and papillary or solid and cystic pseudopapillary neoplasm of the pancreas. Three tumors were positive for both vimentin and alpha-1 antitrypsin on immunohistochemical studies, and three were positive for neuron-specific enolase. All nine patients underwent curative resection and are alive without any evidence of recurrence with a mean follow-up of 5.4 years. SPENP is considered to be a low-grade malignancy with an excellent prognosis. Prompt diagnosis and surgical resection can result in cure.

Hepatic cytoreduction followed by a novel long-acting somatostatin analog: a paradigm for intractable neuroendocrine tumors metastatic to the liver

BACKGROUND

Optimal management of symptomatic neuroendocrine tumors that metastasize to the liver is controversial. We investigated aggressive hepatic cytoreduction and postoperative administration of octreotide long-acting release (LAR), a long-acting somatostatin analog.

METHODS

Between December 1992 and August 2000, 31 patients underwent hepatic surgical cytoreduction (20 carcinoid, 10 islet cell, and 1 medullary). All patients had progressive symptoms refractory to conventional therapy.

RESULTS

Hepatic cytoreduction (resection, cryosurgery, and/or radiofrequency ablation) eliminated symptoms in 27 patients (87%) and decreased secretion of hormones by an overall mean of 59%. When minor symptoms returned and/or hormonal levels increased during follow-up, adjuvant therapy was started. Ten patients received adjuvant octreotide LAR once a month, and 21 received other adjuvants. At a median postoperative follow-up of 26 months, 16 patients had progressive/recurrent disease, 13 had died of their disease, and 2 remained free of disease. Median symptom-free interval was 60 months (95% confidence interval, 48-72) with octreotide LAR and 16 months (95% confidence interval, 10-29) with other adjuvants (P = .0007). Two-year symptom-free survival rate was 100% with octreotide LAR and 33% with other adjuvants.

CONCLUSIONS

Hepatic surgical cytoreduction can palliate progressive symptoms associated with liver metastases from intractable neuroendocrine tumors. Postoperative adjuvant therapy with octreotide LAR can prolong symptom-free survival.

Aberrant drainage and missed micrometastases: the value of lymphatic mapping and focused analysis of sentinel lymph nodes in gastrointestinal neoplasms

Lymph node analysis is essential for staging gastrointestinal (GI) neoplasms. Our group has conducted several studies of intraoperative lymphatic mapping and sentinel lymphadenectomy (LM/SL) for the staging of GI neoplasms. LM is performed following injection of 0.5-1 ml of isosulfan blue dye, and blue-stained sentinel lymph nodes (SLNs) are analyzed by hematoxylin and eosin (H&E) staining, multiple sectioning, and cytokeratin immunohistochemistry. In feasibility trials, LM identified at least one SLN in 121 of 126 patients. Of the 58 cases with nodal metastasis, 50 (89%) had at least one positive SLN and 24 (42%) had nodal metastasis only in the SLN. In 25 cases, tumor deposits were identified by multiple sectioning (n = 8) or immunohistochemistry (n = 17) only. In 10 cases (8%), LM identified aberrant lymphatic drainage that altered the extent of the lymphadenectomy. Our cumulative experience indicates that focused analysis of the SLNs draining GI neoplasms can increase the detection of micrometastases and may improve selection of patients for adjuvant treatment.

Laparoscopic radiofrequency ablation of unresectable hepatic malignancies. A phase 2 trial

BACKGROUND

Radiofrequency ablation (RFA) of hepatic malignancies has been performed successfully via a percutaneous route or at laparotomy. We analyzed the efficacy and utility of laparoscopic intraoperative ultrasound and RFA in patients with unresectable hepatic malignancies.

METHODS

Between November 1997 and November 1999, 27 patients with unresectable hepatic malignancies and no evidence of extrahepatic disease were entered in a phase 2 trial of laparoscopic intraoperative ultrasound and RFA. Real-time ultrasonography was used to guide RFA, and lesions were ablated at a temperature of 100 degrees C for 10 min. Overlapping ablations were performed for larger lesions.

RESULTS

Additional tumors were identified in 10 (37%) of the 27 study patients by laparoscopy and laparoscopic intraoperative ultrasound despite extensive preoperative imaging. Radiofrequency ablation of 85 hepatic tumors yielded no mortality and only one case of postoperative bleeding. During a mean follow-up period of 14 months, four tumors (4.7%) locally recurred. Of the 27 patients, 11 (41%) remain free of disease at this writing; (22%) are alive with disease; and 10 (37%) have died with disease.

CONCLUSION

Laparoscopic RFA and intraoperative ultrasound constitute a safe and accurate method for ablation of unresectable hepatic tumors.

Lymphatic mapping improves staging during laparoscopic colectomy for cancer

BACKGROUND

Recently, lymphatic mapping (LM) of the sentinel lymph node (SN) has been coupled with ultrastaging methods to diagnose nodal micrometastases from colorectal cancer (CRC). We have developed a technique for LM at the time of laparoscopic colon resection (LCR).

METHODS

Between August 1996 and February 2000, 11 patients with small early-stage CRC underwent laparoscopic LM and LCR. The primary tumor/polyp site was visualized through a colonoscope and either tattooed preoperatively with a carbon dye (India ink), or stained intraoperatively by peritumoral injection of isosulfan blue dye. Immediately after intraoperative injection of blue dye, efferent lymphatic channels were visualized through the laparoscope and followed to the SN. Each blue-stained SN was marked with a suture or clip.

RESULTS

In all 11 cases, laparoscopic LM identified between one and three SN draining the primary tumor. LM added ~15-20 min to the operating time. The SN correctly reflected the nodal status of the entire specimen in all cases. In the one node-positive case, micrometastases were found only in an SN and only after cytokeratin immunohistochemistry (CK-IHC). In four cases, LM demonstrated unexpected primary lymphatic drainage that prompted an increase in the margins of resection.

CONCLUSIONS

LM during laparoscopic colectomy for CRC may be useful to mark the primary tumor site and to demonstrate lymphatic drainage that can alter the margins of resection. Focused examination of SN identifies occult micrometastases that up-stage CRC.

Repeat hepatic cryotherapy for metastatic colorectal cancer

This study evaluated the risks and benefits of repeat hepatic cryotherapy for recurrent, unresectable hepatic metastases from colorectal carcinoma. Review of a prospective database identified 195 patients who underwent hepatic cryotherapy for metastatic colorectal carcinoma during a 7-year period. Of the 14 patients who underwent successful repeat cryotherapy for recurrences confined to the liver, 86% had Duke's stage D colorectal carcinoma at initial diagnosis. The median age of the 14 patients was 58 years (range 41 to 77 years). The median number of hepatic metastases was three at the first cryotherapy and two at the second cryotherapy. At a median follow-up of 71 months, the mean survival times from original diagnosis, first cryotherapy, and second cryotherapy were 53, 42, and 19 months, respectively. At the most recent follow-up, eight patients (57%) have died of their disease, four (29%) are alive with disease, and two (14%) have no evidence of disease. The mean interval between the first and second cryotherapies was 23 months. The complication rates after the first and second cryotherapies were 7% and 14%, respectively. One patient developed a wound dehiscence after the first cryotherapy. Following the second cryotherapy, one patient had a small bowel obstruction and another had a pleural effusion. There was no perioperative mortality. Repeat cryotherapy for recurrent, unresectable hepatic metastases from colorectal cancer is safe and improves survival. However, a prospective trial is needed to validate the efficacy of systemic therapy and to better define the indications for repeat hepatic cryotherapy.

CancerVax, an allogeneic tumor cell vaccine, induces specific humoral and cellular immune responses in advanced colon cancer

BACKGROUND

The immunogenicity of the polyvalent tumor cell vaccine CancerVax has been correlated with the survival of patients receiving active immunotherapy for melanoma. Because the various antigens expressed on the vaccine are common to colon adenocarcinoma cells, we examined the survival impact of immune responses elicited by CancerVax in patients with advanced colon cancer refractory to standard therapy.

METHODS

Twenty-seven patients with American Joint Committee on Cancer (AJCC) stage IV colorectal adenocarcinoma were entered prospectively into the study. CancerVax was coadministered with bacille Calmette-Guerin (BCG) for the first 2 weeks of vaccine treatment. Blood was drawn at the start of therapy and every 2 weeks thereafter to measure serum titers of immunoglobulin (Ig)G and IgM against TA90 (a 90-kD immunogen common to colon cancer and CancerVax cells) and against purified protein derivative (PPD), a nontumor control antigen. Cellular immune responses were evaluated by delayed-type hypersensitivity (DTH) reaction to vaccine cells and to PPD. Mean follow-up time was 17.5 months.

RESULTS

There was a significant (P = .0001) increase in anti-TA90 IgG and IgM titers and in DTH response to vaccine cells. Humoral and skin responses to TA90 did not correlate with responses to PPD (P = .199 for IgM, P = .958 for IgG, and P = .149 for DTH). This suggests that these responses are not a manifestation of general immune competence. The median overall survival (OS) was 21.9 months for the entire group. Overall survival was higher among patients whose IgMTA90 titer was >800 (P = .003) or whose disease-free interval exceeded 12 months (P = .031). Multivariate Cox regression analysis-using age, sex, disease-free interval, disease status, extent of metastasis, humoral responses, and DTH responses-found only peak IgMTA90 titer to be a significant predictor of overall survival (P = .0365).

CONCLUSIONS

CancerVax can induce measurable humoral and cellular immune responses to tumor-associated antigens in patients with advanced-stage colon cancer. These responses correlate with overall survival. This novel therapeutic regimen for patients with advanced colon cancer merits further investigation.

Systemic irinotecan or regional floxuridine chemotherapy prolongs survival after hepatic cryosurgery in patients with metastatic colon cancer refractory to 5-fluorouracil

Most colorectal cancers metastatic to the liver are resistant to chemotherapy and are not amenable to surgical resection. This study evaluated our 6-year experience (July 1992-July 1998) in treating patients with unresectable hepatic colorectal metastases refractory to systemic 5-fluorouracil (5-FU). One hundred fifty-three patients underwent cryosurgical ablation (CSA) of 5-FU-resistant hepatic metastases. The patients then received either hepatic arterial floxuridine (FUDR), systemic CPT-11, or no postoperative adjuvant chemotherapy. Number, size, and location of hepatic metastases, carcinoembryonic antigen (CEA) levels, and type of postoperative treatment were analyzed. One to 15 lesions were frozen (median number, 3; median size, 6 cm), for a total of 73 synchronous and 80 metachronous lesions. Overall median survival was 28.4 months from the date of diagnosis of liver metastases and 16.1 months from the time of CSA. After cryosurgery alone, median survival was 13 months, which was significantly shorter than the post-CSA survival of 23.6 months with adjuvant CPT-11 and 21.2 months with hepatic FUDR (P = 0.007). Predictors of survival included preoperative CEA, postoperative reduction in CEA, and adjuvant chemotherapy (P < 0.05). Neither size, number of lesions, nor tumor location impacted survival. At a median follow-up of 13 months, 67% of patients have recurred (35% hepatic, 16% extrahepatic, and 49% both). Twenty percent of the recurrences were in the lobe of the CSA site. The 25 patients who underwent a second CSA had a median survival of 28.4 months from CSA and 40 months from the date of diagnosis of liver metastases. These data indicate that CSA offers an effective alternative for unresectable patients resistant to 5-FU. Systemic CPT-11 or regional FUDR may further prolong survival after CSA.

Radiofrequency ablation of unresectable hepatic malignancies: lessons learned

Radiofrequency ablation (RFA) is increasingly used for the local destruction of unresectable hepatic malignancies. Relative contraindications include tumors in proximity to vital structures that may be injured by RFA and lesions whose size exceeds the ablation capabilities of the probe system employed. Given current technology, we believe that RFA should be cautiously utilized for lesions greater than 5 cm in diameter. Open (celiotomy) and laparoscopic approaches to RFA allow intraoperative ultrasonography, which may demonstrate occult hepatic disease. In addition, RFA performed via celiotomy can be accompanied by resection or cryosurgical ablation, and isolation of the liver from adjacent organs. Percutaneous RFA should be reserved for patients who cannot undergo general anesthesia, those with recurrent or progressive lesions, and those with smaller lesions sufficiently isolated from adjacent organs. Complications may be minimized when these approaches are selectively applied.

Validation of lymphatic mapping in colorectal cancer: in vivo, ex vivo, and laparoscopic techniques

BACKGROUND

The use of lymphatic mapping (LM) is being investigated to improve the staging of colorectal cancer (CRC) and thereby identify patients who might benefit from adjuvant chemotherapy. This study evaluated in vivo, laparoscopic, and ex vivo approaches for the ultrastaging of CRC.

METHODS

Seventy-five CRC patients were enrolled in a study of LM with peritumoral injection of isosulfan blue dye. LM was undertaken during open colon resection (OCR) in 64 patients, during laparoscopic colon resection (LCR) in 9 patients, and after specimen removal (ex vivo) in 2 patients. Ex vivo LM was also undertaken in 6 patients after unsuccessful in vivo LM. All nodes were examined by hematoxylin and eosin (H&E) staining; in addition, sentinel lymph nodes (SNs) were multisectioned and examined by immunohistochemical staining with cytokeratin (CK-IHC).

RESULTS

At least one SN was identified in 72 patients (96%). In vivo LM identified SNs in 56 of 64 (88%) patients undergoing OCR and in 9 of 9 (100%) patients undergoing LCR. Ex vivo LM was undertaken as the initial mapping procedure in 2 cases of intraperitoneal colon cancer and after in vivo LM had failed in 6 cases of extraperitoneal rectal carcinoma; an SN was identified in 7 of the 8 cases. Focused examination of the SN correctly predicted nodal status in 53 of 56 OCR cases, 9 of 9 LCR cases, and 6 of 7 ex vivo cases. Multiple sections and CK-IHC identified occult micrometastases in 13 patients (17%), representing 10 OCR, 1 LCR, and 2 ex vivo cases.

CONCLUSIONS

LM of drainage from a primary CRC can be accurately performed in vivo during OCR or LCR. Ex vivo LM can be applied when in vivo techniques are unsuccessful and may be useful for rectal tumors. During LCR, colonoscopic injection can be used to mark the primary tumor and define the lymphatic drainage so that adequate resection margins are obtained. These LM techniques improve staging accuracy in CRC.

Molecular staging of early colon cancer on the basis of sentinel node analysis: a multicenter phase II trial

PURPOSE

Approximately 30% of patients with American Joint Committee on Cancer stage I or II colorectal cancer (CRC) develop systemic disease. We hypothesized that multimarker reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of sentinel lymph nodes (SNs) draining a primary CRC could detect micrometastases not detected by conventional histopathologic analysis.

PATIENTS AND METHODS

In a multi-institutional study, 40 patients with primary CRC underwent dye-directed lymphatic mapping at the time of colon resection. Each dye-stained SN was tagged, and the tumor and regional nodes were resected en bloc. All lymph nodes were examined by conventional hematoxylin and eosin (HE) staining. In addition, each SN was cut into multiple sections for cytokeratin immunohistochemical (CK-IHC) staining and for RT-PCR and electrochemiluminescent detection of three markers: beta-chain human chorionic gonadotropin, hepatocyte growth factor receptor, and universal melanoma-associated antigen. Whenever possible, RT-PCR assay was also performed on primary tumor tissue. The detection sensitivity of individual markers was 10(-3) to 10(-4) microg of RNA and one to five tumor cells in 10(7) lymphocytes of healthy donors.

RESULTS

One to three SNs were identified in each patient. An average of 15 nodes were removed from each CRC specimen. No nonsentinel (untagged) node contained evidence of tumor if all tagged (sentinel) nodes in the same specimen were histopathology tumor-negative. HE staining of SNs identified tumor in 10 patients (25%), and CK-IHC of SNs identified occult micrometastases in four patients (10%) whose SNs were negative by HE. Of the remaining 26 patients with no evidence of SN involvement by HE or CK-IHC, 12 (46%) had positive RT-PCR results. The number of markers expressed in each SN correlated (P <.04) with the T stage of the primary tumor. There was 79% concordance in marker expression for the respective pairs (n = 38) of primary tumor and histopathologically positive SNs, and 86% (12 of 14) concordance between RT-PCR positive and histopathologically positive SNs.

CONCLUSION

Identification and focused examination of the SN is a novel method of staging CRC. CK-IHC and RT-PCR identified occult micrometastases in 53% of patients whose SNs were negative by conventional staging techniques. These ultrasensitive assays of the SN can identify patients who may be at high risk for recurrence of CRC and therefore are more likely to benefit from systemic adjuvant therapy.

Gastrointestinal carcinoid tumors and second primary malignancies

The development of second primary malignancies (SPM) in patients with gastrointestinal carcinoid tumors is a well-described phenomenon, with reported rates as high as 55%. There is a predilection for gastrointestinal and genitourinary adenocarcinomas, but a variety of other malignancies have been reported as well. The etiology of this malignant predisposition may be rooted in the tumorigenic properties of the various neuroendocrine peptides elaborated and secreted by neuroendocrine cells. Peptides such as secretin, gastrin, bombesin, cholecystokinin (CCK), and vasoactive intestinal peptide (VIP) are believed to promote the growth of tumor cells. As many as 30 peptides and amines identified in neuroendocrine cells may have similar properties. This review of the literature on carcinoid-associated second primary malignancies is accompanied by a case report of metastatic carcinoid identified during surgical exploration for a perforating colon adenocarcinoma.

Gastrointestinal carcinoid tumors and second primary malignancies

The development of second primary malignancies (SPM) in patients with gastrointestinal carcinoid tumors is a well-described phenomenon, with reported rates as high as 55%. There is a predilection for gastrointestinal and genitourinary adenocarcinomas, but a variety of other malignancies have been reported as well. The etiology of this malignant predisposition may be rooted in the tumorigenic properties of the various neuroendocrine peptides elaborated and secreted by neuroendocrine cells. Peptides such as secretin, gastrin, bombesin, cholecystokinin (CCK), and vasoactive intestinal peptide (VIP) are believed to promote the growth of tumor cells. As many as 30 peptides and amines identified in neuroendocrine cells may have similar properties. This review of the literature on carcinoid-associated second primary malignancies is accompanied by a case report of metastatic carcinoid identified during surgical exploration for a perforating colon adenocarcinoma.

Focused examination of sentinel lymph nodes upstages early colorectal carcinoma

Approximately 30 per cent of patients with early colorectal carcinoma (CRC) develop systemic disease. A subgroup of these patients may harbor occult micrometastatic disease and might benefit from adjuvant chemotherapy. We investigated sentinel lymph node (SLN) mapping and focused pathologic examination of the SLN as a means of detecting nodal micrometastases. Between 1996 and 2000 SLN mapping was performed in 50 consecutive patients undergoing colectomy for CRC. All lymph nodes in the resection specimen were examined via routine hematoxylin and eosin (H&E) staining. In addition multiple sections of each SLN were examined via both H&E and cytokeratin immunohistochemistry. At least one SLN was identified in 47 patients (94%). In seven patients (14%) SLN mapping identified aberrant drainage that altered the planned resection. The SLN(s) correctly predicted nodal basin status in 44 of 47 (94%) cases; there were three falsely negative SLNs. Sixteen cases had positive SLNs by conventional H&E staining. An additional 10 (20%) cases were upstaged by a focused examination of the SLNs. Micrometastases were identified in three cases by H&E staining of multiple sections of the SLN and in seven only by cytokeratin immunohistochemistry. In nine cases the SLN was the only node containing tumor cells. In this study, SLN mapping demonstrated aberrant nodal drainage patterns that altered the surgical resection in patients with CRC. Focused examination of SLNs may detect micrometastases missed by conventional techniques and thereby identify patients who might benefit from adjuvant therapy.

Radiofrequency ablation of 231 unresectable hepatic tumors: indications, limitations, and complications

BACKGROUND

Radiofrequency ablation (RFA) is increasingly used for the local destruction of unresectable hepatic malignancies. There is little information on its optimal approach or potential complications.

METHODS

Since late 1997, we have undertaken 91 RFA procedures to ablate 231 unresectable primary or metastatic liver tumors in 84 patients. RFA was performed via celiotomy (n = 39), laparoscopy (n = 27), or a percutaneous approach (n = 25). Patients were followed with spiral computed tomographic (CT) scans at 1 to 2 weeks postprocedure and then every 3 months for 2 years.

RESULTS

Intraoperative ultrasound (IOUS) detected intrahepatic disease not evident on the preoperative scans of 25 of 66 patients (38%) undergoing RFA via celiotomy or laparoscopy. In 38 of 84 patients (45%), RFA was combined with resection or cryosurgical ablation (CSA), or both. RFA was used to treat an average of 2.8 lesions per patient, and the median size of treated lesions was 2 cm (range, 0.3-9 cm). The average hospital stay was 3.6 days overall (1.8 days for percutaneous and laparoscopic cases). Ten patients underwent a second RFA procedure (sequential ablations) and, in one case, a third RFA procedure for large (one patient), progressive (seven patients), and/or recurrent (three patients) lesions. Seven (8%) patients had complications: one skin burn; one postoperative hemorrhage; two simple hepatic abscesses; one hepatic abscess associated with diaphragmatic heat necrosis following sequential percutaneous ablations of a large lesion; one postoperative myocardial infarction; and one liver failure. There were three deaths, one (1%) of which was directly related to the RFA procedure. Three of the complications, including one RFA-related death, occurred after percutaneous RFA. At a median follow-up of 9 months (range, 1-27 months), 15 patients (18%) had recurrences at an RFA site, and 36 patients (43%) remained clinically free of disease.

CONCLUSIONS

Celiotomy or laparoscopic approaches are preferred for RFA because they allow IOUS, which may demonstrate occult hepatic disease. Operative RFA also allows concomitant resection, CSA, or placement of a hepatic artery infusion pump, and isolation of the liver from adjacent organs. Percutaneous RFA should be reserved for patients at high risk for anesthesia, those with recurrent or progressive lesions, and those with smaller lesions sufficiently isolated from adjacent organs. Complications may be minimized when these approaches are applied selectively.

Lymphatic mapping and focused analysis of sentinel lymph nodes upstage gastrointestinal neoplasms

BACKGROUND

Lymph node analysis is essential for staging gastrointestinal (GI) neoplasms. Intraoperative lymphatic mapping and sentinel lymphadenectomy were originally described for melanoma but have not yet been investigated for most GI neoplasms.

HYPOTHESES

(1) Lymphatic mapping and sentinel lymphadenectomy is feasible in GI neoplasms, (2) the sentinel node (SN) status reflects the regional node status, and (3) focused analysis of the SN improves staging accuracy.

DESIGN

Prospective patient series.

PATIENTS AND METHODS

Lymphatic mapping was performed in 65 patients with GI neoplasms by injecting 0.5 to 1 mL of isosulfan blue dye around the periphery of the neoplasm. Blue-stained SNs were analyzed by hematoxylin-eosin staining, multiple sectioning, and cytokeratin immunohistochemistry.

RESULTS

Lymphatic mapping identified at least 1 SN in 62 patients (95%). Of the 36 cases with nodal metastasis, 32 (89%) had at least 1 positive SN and 15 (42%) had nodal metastasis only in the SN. In 11 cases, tumor deposits were identified by multiple sectioning (n = 2) or immunohistochemistry (n = 9) only. In 5 cases (8%), lymphatic mapping identified aberrant lymphatic drainage that altered the extent of the lymphadenectomy.

CONCLUSIONS

Lymphatic mapping and sentinel lymphadenectomy are feasible in GI neoplasms and identify aberrant lymphatic drainage. The SN status accurately reflects the regional node status. Focused analysis of the SN increases the detection of micrometastases and may improve selection of patients for adjuvant treatment.

Cryosurgical ablation and radiofrequency ablation for unresectable hepatic malignant neoplasms: a proposed algorithm

BACKGROUND

Thermal ablation of unresectable hepatic tumors can be achieved by cryosurgical ablation (CSA) or radiofrequency ablation (RFA). The relative advantages and disadvantages of each technique have not yet been determined.

HYPOTHESIS

Radiofrequency ablation of malignant hepatic neoplasms can be performed safely, but is currently limited by size. Cryosurgical ablation, while associated with higher morbidity, is more effective for larger unresectable hepatic malignant neoplasms.

DESIGN

Retrospective analysis of prospective patient database.

PATIENTS AND METHODS

Between July 1992 and September 1999, 308 patients with liver tumors not amenable to curative surgical resection were treated with CSA and/or RFA (percutaneous, laparoscopic, celiotomy). No patient had preoperative evidence of extrahepatic disease. All patients underwent laparoscopy with intraoperative ultrasound if technically possible. Both RFA and CSA were performed under ultrasound guidance. Resection, as an adjunctive procedure, was combined with ablation in certain patients.

RESULTS

Laparoscopy identified extrahepatic disease in 12% of patients, and intraoperative hepatic ultrasound identified additional lesions in 33% of patients, despite extensive preoperative imaging. Radiofrequency ablation alone or combined with resection or CSA resulted in reduced blood loss (P<.05), thrombocytopenia (P<.05), and shorter hospital stay compared with CSA alone (P<.05). Median ablation times for lesions greater than 3 cm were 60 minutes with RFA and 15 minutes with CSA (P<.001). Local recurrence rates for lesions greater than 3 cm were also greater with RFA (38% vs 17%).

CONCLUSIONS

Laparoscopy and intraoperative ultrasound are essential in staging patients with hepatic malignant neoplasms. Radiofrequency ablation when combined with CSA reduces the morbidity of multiple freezes. Although RFA is safer than CSA and can be performed via different approaches (percutaneously, laparoscopically, or at celiotomy), it is limited by tumor size (<3 cm). Percutaneous RFA should be considered in high-risk patients or those with small local recurrences.

TA90-IC, a new marker for advanced colon cancer

BACKGROUND

Although carcinoembryonic antigen (CEA) is the most frequently used marker for colon cancer, it is elevated in only 70% of patients with advanced disease and in even fewer patients with earlier stages of disease. We previously identified a 90-kDa glycoprotein, TA90, which is present in serum in the form of circulating immune complexes. TA90 is found in a variety of solid neoplasms but rarely in healthy controls (3.2%). We hypothesized that this new tumor-associated antigen may be a useful marker for colon cancer.

METHODS

Serum samples from 59 patients with known colon adenocarcinoma were analyzed for the presence of CEA and TA90. Fifty-one (86%) patients had distant metastases; the remaining patients had clinically localized primary colon cancer. A murine monoclonal antibody-based enzyme-linked immunosorbent assay was used to measure concentrations of TA90-specific circulating immune complexes (TA90-IC). A positive value was defined as an optical density of more than 0.410 at 405 nm. Forty-seven (80%) of the 59 patients had serum samples for TA90 and CEA drawn at the same time.

RESULTS

TA90-IC concentrations were elevated more frequently than CEA concentrations (82.9% vs. 70.2%; P = .134). The combination of both markers identified more patients with colon carcinoma than did either marker alone (93.6%; P < .001).

CONCLUSIONS

Concomitant use of TA90-IC and CEA identified 93.6% of patients with advanced colon cancer. The role of TA90-IC in screening and monitoring progression of earlier disease deserves further investigation.

Role of Na+-glucose cotransport in jejunal meal-induced absorption

In awake dogs, meal ingestion stimulates the absorption of water and electrolytes from neurovascularly intact jejunal Thiry-Vella loops, even though these loops are isolated from the remainder of the gut. This study was designed to investigate the role of Na+-glucose cotransport in mediating this event. Meal ingestion enhanced absorption when the jejunal lumen was perfused with an isotonic solution containing D-glucose, D-galactose, or 3-O-methylglucose. This response was absent when the perfusate contained mannitol or when phlorizin was added to the D-glucose solution. Mucosa from the jejunal loops was serially biopsied and assayed for brush-border Na+-glucose cotransporter (SGLT1) mRNA and protein expression. Although no changes in SGLT1 mRNA levels were observed, protein levels significantly increased within 30 min following meal ingestion. The time course of SGLT1 protein expression corresponded with that of increased Na+ and water absorption. These results suggest that meal-stimulated jejunal absorption may be mediated through an induction of mucosal SGLT1.

Radiofrequency ablation: a minimally invasive technique with multiple applications

PURPOSE

Radiofrequency ablation (RFA) of soft tissue, which has recently been approved by the United States Food and Drug Administration, destroys tumor cells by delivering an electrical current through a 15-gauge needle. This study evaluated RFA for patients with hepatic malignancies considered unresectable because of their distribution, their number, and/or the presence of liver dysfunction.

PATIENTS AND METHODS

Between November 1997 and February 1999, 50 patients with 132 unresectable hepatic metastases underwent RFA of tumors from 0.5 to 9 cm in diameter. There were 41 colorectal metastases in 22 patients, 13 hepatomas in seven patients, 37 neuroendocrine metastases in six patients, and 41 noncolorectal metastases in 15 patients. Real-time ultrasonography was used to guide RFA, and lesions were ablated by applying temperatures of approximately 100 degrees C for 8 minutes. Overlapping ablations were used for larger lesions. In patients with multiple lesions, RFA was performed simultaneously with cryosurgery, resection, and/or hepatic arterial infusion.

RESULTS

RFA was undertaken percutaneously on an outpatient basis in 13 patients (25 lesions). The remaining patients underwent RFA via laparoscopy (21 patients; 58 lesions) or celiotomy (16 patients; 49 lesions); mean hospital stay was 1 and 5 days, respectively. RFA was the sole therapy in 28 patients and was additional therapy in 22 patients. At a median follow-up of 6 months, 27 patients were free of disease, 17 were alive with disease, and six had died of their disease (three colon, three melanoma). Three patients whose disease recurred at a prior RFA site underwent successful percutaneous RFA. Overall, there was a significant postoperative reduction in levels of carcinoembryonic antigen, alpha-fetoprotein, serotonin, and 5-hydroxyindoleacetic acid. Intraoperative ultrasonography identified unrecognized hepatic lesions in 12 of 37 patients (32%); these lesions were successfully ablated. When performed with cryosurgery, RFA reduced the morbidity of multiple freezes.

DISCUSSION

RFA is a safe and effective alternative for the ablation of unresectable hepatic malignancies and when used adjunctively can reduce the morbidity of cryosurgery. Percutaneous and laparoscopic RFA can be performed effectively with less than 24 hours of hospitalization. Intraoperative ultrasonography is essential for accurate staging.

Radiofrequency ablation: a novel primary and adjunctive ablative technique for hepatic malignancies

The majority of primary and metastatic tumors of the liver are not amenable to surgical resection at presentation. Radiofrequency ablation (RFA) is a new modality for local tumor destruction with minimal local and systemic complications. We prospectively reviewed the experience with RFA at a single institute as a primary or adjunctive ablative technique in the treatment of hepatic malignancies. Between November 1997 and December 1998, 30 patients with primary or metastatic hepatic lesions were treated with RFA at the John Wayne Cancer Institute and the Cancer Center at Century City Hospital. Pathology of the treated lesions included colorectal metastases (29 in 14 patients), neuroendocrine metastases (29 in 4 patients), noncolorectal metastases (29 in 9 patients), and hepatocellular carcinoma (6 in 3 patients). Twelve patients underwent RFA laparoscopically, 12 at celiotomy, and the remaining 6 patients had percutaneous ablation. RFA was the only procedure in 17 patients, whereas the remainder underwent a combination of RFA and other procedures including resection, cryosurgical ablation, and hepatic artery infusion pump placement. Median length of stay for all patients was 6 days (2 days for laparoscopic patients). A single complication of a delayed intrahepatic abscess was noted in this series (3%). There have been no deaths associated with RFA. At a median follow-up of 5 months, 16 patients remain disease free, and 10 are alive with disease. RFA is a safe and effective method of tumor ablation for hepatic malignancies. This technique can be performed laparoscopically, at celiotomy, or percutaneously and can be used as a primary technique or in conjunction with other interventional procedures.

Universal application of intraoperative lymphatic mapping and sentinel lymphadenectomy in solid neoplasms

PURPOSE

Regional lymph node involvement is the most important prognostic indicator in patients with solid tumors. Conventional lymph node dissection has not been shown to affect survival and is often associated with considerable morbidity. Intraoperative lymphatic mapping and sentinel lymph node dissection were therefore designed as a minimally invasive alternative to routine elective lymph node dissection in patients with primary cutaneous melanoma. This study examined whether introperative lymphatic mapping and sentinel lymph node dissection were accurate in staging patients with other solid malignancies.

PATIENTS AND METHODS

Between 1985 and 1998, 107 patients with breast cancer, 17 with thyroid tumors, 14 with gastrointestinal/gynecologic cancers, six with Merkel cell cancers, and five with squamous cell carcinomas of the head and neck have undergone mapping and sentinel lymph node dissection at the John Wayne Cancer Institute.

RESULTS

The sentinel node was identified in 96% of patients (98% melanoma). In 36% of patients the sentinel node was the only tumor-positive node (71% melanoma). Eighteen percent of sentinel nodes were negative by hematoxylin and eosin staining but were positive by immunohistochemical staining (15% melanoma).

CONCLUSION

These data suggest that many solid neoplasms have a primary lymphatic channel and lymph node to which it drains. Although sentinel lymph node dissection has been popularized in melanoma therapy, we have found it feasible for treatment of other solid malignancies. This technique may ultimately replace conventional dissection with more accurate staging.

Cryosurgical palliation of metastatic neuroendocrine tumors resistant to conventional therapy

BACKGROUND

Hepatic cryosurgery is a well-recognized modality for hepatic colon metastases. We examined its potential use for refractory neuroendocrine tumors causing progressive symptoms.

METHODS

Between July 1992 and February 1997, 19 patients (with islet cell, 7; carcinoid, 8; vasoactive intestinal peptide, 1; gastrinoma, 3) underwent cryosurgery with ultrasonography. The number of lesions frozen ranged from 1 to 16 (median, 8), and their diameters ranged from 2 to 15 cm with an average of 4 cm. Patients underwent resection of the primary tumor either before (37%) or concurrent with (32%) cryosurgery, and half underwent excision of metastases with cryosurgery. Before cryosurgery, patients received chemotherapy (63%), somatostatin (47%), interferon (10%), hepatic artery ligation (5%), radiation (10%), and/or omeprazole (16%).

RESULTS

The reduction in tumor markers reached 90% (5-hydroxyindoleacetic acid), 80% (vasoactive intestinal peptide), 90% (gastrin), 90% (pancreatic polypeptide), and 80% (serotonin). At a median follow-up of 17 months, the metastases had progressed in 11 patients (two underwent a second cryosurgical procedure that eliminated symptoms) and five had died. Subsequently an additional five patients received chemotherapy and three somatostatin. Median symptom-free and overall survival were 10 months and more than 49 months, respectively.

CONCLUSIONS

Cryosurgery dramatically relieved symptoms with significant reduction in tumor markers. The reduced tumor burden may explain the subsequent response to systemic therapy. Cryosurgery is a useful adjuvant in symptomatic patients with refractory hepatic neuroendocrine metastases.

Cryosurgery causes a profound reduction in tumor markers in hepatoma and noncolorectal hepatic metastases

Cryosurgical ablation of hepatic metastases from colon carcinoma has become a useful adjunct in the management of patients whose tumors are not amenable to surgical resection. We evaluated cryoablation of hepatoma and noncolorectal hepatic metastases by examining its effect on serum levels of tumor markers in 20 patients with primary liver cancer (N = 5) or liver metastases (N = 15) from breast cancer, neuroendocrine tumors, ovarian cancer, and thyroid cancer. All patients had failed conventional therapy and had no evidence of extrahepatic spread. After cryosurgery, 17 patients had a significant decrease in tumor marker levels (median 77%) and a significant improvement in symptoms. One patient died of nontumor causes, and five patients died of recurrent disease. Median interval to death or last follow-up was 28.3 months overall (range, 2-45 months), 17.9 months for nonsurvivors (range, 2-44 months), and 35.2 months for survivors (range, 26-45 months). Median survival was 32 months following curative surgery (range, 16-45 months) and 25 months following palliative surgery (range, 2-42 months). Cryosurgical ablation of noncolorectal hepatic metastases and primary hepatomas produces a profound reduction in serum levels of tumor markers. It is safe, provides excellent palliation of symptoms, and in selected patients can be performed with curative intent.

Antisecretory mechanisms of peptide YY in rat distal colon

Peptide YY (PYY) is a potent regulator of intestinal secretion. These studies investigated the role of Y1 and Y2 receptor subtypes in mediating the antisecretory effects of PYY on mucosa-submucosa preparations of rat distal colon. Addition of vasoactive intestinal peptide (VIP) to these tissues resulted in a 140 +/- 18% increase in basal short-circuit current (Isc) and the induction of Cl- secretion. VIP-stimulated increases in Isc were abolished by the addition of each of PYY, (Pro34)-PYY, a Y1 receptor-selective agonist, and PYY-(3-36), an endogenous Y2 receptor-selective ligand. However, when tissue neural transmission was blocked with tetrodotoxin, neither PYY nor its receptor subtype-selective analogs were able to inhibit VIP-stimulated increases in Isc. These results suggest that in the rat distal colon, the antisecretory actions of PYY are mediated through a combination of Y1 and Y2 receptor subtypes or through a novel receptor subtype that is unable to discriminate between (Pro34)-PYY and PYY-(3-36).

Peptide YY: a potential proabsorptive hormone for the treatment of malabsorptive disorders

Peptide YY (PYY) is a 36 amino acid peptide that is released from the endocrine cells of the distal ileum, colon, and rectum following a meal. PYY is strongly proabsorptive in the small intestine. We studied the effects of intravenous PYY on colonic water and electrolyte transport in awake dogs. Dogs had 20 cm neurovascularly intact colon Thiry-Vella fistulas (TVS) surgically constructed. Colonic transport was studied in three experimental groups. Group 1 animals received a standard mixed meal. Group 2 animals were unfed and received intravenous PYY and 100 pmol/kg/hr for two hours. This dose of PYY has previously been shown to simulate the plasma levels of PYY normally seen after a meal. Group 3 received intravenous PYY at the same dose in addition to a mixed meal. Our study shows an increase in colonic water, Na+, and Cl- absorption after a meal (P < 0.05). Infusion of PYY at a 100 pmol/kg/hr was significantly proabsorptive beginning at 60 minutes (P < 0.01). Infusion of PYY in addition to a meal further increased absorption (P < 0.05). PYY is a potent proabsorptive agent in the colon of the conscious dog. PYY, or its analogs, may be useful clinical agents in intestinal malabsorptive disorders or after bowel resection.

Na+/H+ exchange mediates postprandial ileal water and electrolyte transport

Feeding stimulates fluid and electrolyte absorption in the small intestine. Previous studies have suggested that Na+/glucose cotransport is important in initiating this response in the jejunum. The purpose of this study was to determine whether Na+/H+ exchange plays a role in meal-induced absorption. Exteriorized, neurovascularly intact jejunal and ileal loops (25 cm) were constructed in dogs. Following a two-week period of postoperative recovery, the loops of awake dogs were perfused with standard buffer alone or with increasing concentrations of amiloride, a Na+/H+ exchange inhibitor. Water, sodium, and chloride fluxes were calculated following a meal using [14C]PEG as a volume marker. The meal significantly increased absorption in both the jejunum (P < 0.001) and ileum (P < 0.01) in those animals perfused with buffer alone. More significantly, amiloride suppressed the increased absorption seen following a meal in the ileum (P < 0.001) but not the jejunum. The response in the ileum was dose dependent. These findings suggest that a major mediator of postprandial sodium and water absorption in the ileum is the Na+/H+ exchanger.

Early regional expression and secretion of peptide YY and enteroglucagon after massive resection of small bowel

BACKGROUND

Previous studies suggest that peptide YY (PYY) and enteroglucagon have an important role in intestinal adaptation after massive small bowel resection. This study was done to define the mechanisms, timing, and anatomic distribution of the PYY and enteroglucagon response.

STUDY DESIGN

Lewis rats underwent resection of 70 percent of the small bowel (leaving equal segments of jejunum and ileum), transection, or laparotomy alone. Jejunum, ileum, and colon were compared in resected, transected, and control bowel six hours, 24 hours, one week, and two weeks postoperatively.

RESULTS

Analysis of DNA, RNA, and protein per cm of bowel demonstrated hyperplastic changes. Radioimmunoassay revealed plasma PYY and enteroglucagon to be significantly elevated 24 hours after resection and they remained so through week two. In contrast, tissue PYY and enteroglucagon content decreased significantly in all tissues (p < 0.05) after resection. Reverse transcriptase polymerase chain reaction and Southern blot analysis demonstrated an immediate and sustained increase in PYY messenger RNA (mRNA) in both the ileum (fourfold) and in the colon (2.5-fold) at six hours (p < 0.05). A gradual increase in PYY mRNA was also demonstrated in the jejunum with significance at two weeks (p < 0.05). Proglucagon mRNA was significantly higher in the jejunum, compared with the ileum and colon, at 24 hours, one week, and two weeks postresection.

CONCLUSIONS

Alterations in PYY and enteroglucagon synthesis occur early in the ileum and colon after massive small bowel resection. The residual jejunum, however, is primarily responsible for the adaptive hyperenteroglucagonemia. These findings suggest that although PYY and enteroglucagon are colocalized to the same cell type, there is a gene-specific response for these two peptides after resection.

Amino acids mediate postprandial jejunal proabsorption

Ingestion of a meal stimulates small intestinal ion and water transport. Current evidence suggests that this response, termed proabsorption, is primarily mediated by the apical Na+/glucose cotransporter. Like glucose, the majority of amino acid absorption occurs by Na(+)-dependent, secondary active transport. The purpose of this study was to determine the role of amino acid transport in meal-induced jejunal ion and water absorption in vivo. Exteriorized, neurovascularly intact jejunal loops measuring 25 cm were created in six female mongrel dogs, and the dogs were allowed to recover for 2 weeks. After an overnight fast, the loops were perfused with a standard buffer containing 10 mM aspartate, leucine, glycine, or lysine. Net water and electrolyte absorption before and after a mixed meal was calculated using [14C]polyethylene glycol as a volume marker. Aspartic acid, leucine, glycine, and lysine are each transported by a separate transporter system. Except for lysine, each amino acid significantly (P < 0.05) potentiated sodium and water absorption after a meal. In addition, this effect was at least as great as that seen with 10 mM glucose. These results demonstrate that amino acid transporter, like the Na+/glucose cotransporter, mediates meal-induced jejunal sodium and water absorption and may be as important in the proabsorptive response.

Peptide YY immunoneutralization inhibits meal-induced absorption in vivo

BACKGROUND

Plasma peptide YY (PYY) levels rise after a meal and have recently been shown to increase small bowel-absorption. The purpose of this study was to determine whether immunoneutralization of PYY would block postprandial absorption in vivo.

METHODS

Exteriorized, neurovascularly intact jejunal and ileal segments (25 cm) were created in six mongrel dogs. After a 2-week recovery luminal perfusion with an isotonic buffer, containing [14C]-polyethylene glycol as a volume marker, was used to analyze water and sodium flux after an oral meal. Each meal was accompanied by either intravenous anti-PYY (0.5 mg.kg-1.h-1) or nonspecific immunoglobulin IG (control). PYY antibody binding was determined by radioimmunoassay.

RESULTS

Displacement studies showed complete PYY neutralization. In control experiments feeding increased absorption of sodium and water in both segments. PYY immunoneutralization had no effect on jejunal absorption but significantly diminished ileal absorption (p < 0.05).

CONCLUSIONS

These results suggest that PYY acts selectively in the ileum to increase postprandial fluid and electrolyte absorption after a meal. Agents directed at PYY-stimulated absorption may prove to be of therapeutic benefit in patients with malabsorptive conditions.

Up-regulation of Na+,K+ adenosine triphosphatase after massive intestinal resection

BACKGROUND

The mechanisms of intestinal adaptation after resection are not completely defined. The purpose of this study was to examine the changes after resection in the enterocyte basolateral Na+,K+ adenosine triphosphatase (ATPase) known to play a critical role in epithelial transport and homeostasis.

METHODS

Lewis rats underwent 70% small bowel resection or transection. At 6 hours, 24 hours, 1 week, and 2 weeks, jejunum and ileum were harvested for analysis of Na+,K+ ATPase activity, kinetic analysis, and alpha 1-ATPase messenger RNA and protein levels.

RESULTS

Na+,K+ ATPase activity increased (p < 0.05) in both the jejunum and ileum by 2 weeks after resection. This rise in activity correlated with an increase in the maximal activity of ATPase, from 20.8 to 101.01 mumol inorganic phosphate.mg-1.hr-1. ATPase messenger RNA levels increased sixfold in the jejunum and tenfold in the ileum by 2 weeks after resection (p < 0.05). Protein levels rose at 6 hours and remained elevated in both tissues.

CONCLUSIONS

After intestinal resection, enterocyte Na+,K+ ATPase activity rises as a result of an increase in the number of transporters per cell. This occurs through both transcriptional and translational mechanisms. It appears that intestinal adaptation after resection involves not only an increase in absorptive surface area but also functional adaptation by the individual enterocyte.

Effects of raw soya diet and cholecystokinin receptor blockade on pancreatic growth and tumor initiation in the hamster

Raw soya diet in the hamster had short-term trophic effects on the pancreas, causing significant increases in pancreatic weight, DNA, RNA, and protein. These changes appear to be mediated by cholecystokinin (CCK) because the increases were blocked by infusion of the CCKA receptor antagonist, MK329. Raw soya diet significantly increased plasma levels of CCK in both the short-term and long-term studies. However, raw soya did not potentiate pancreatic cancer in hamsters treated with N-nitrosobis(2-oxopropyl)amine (BOP). Infusion of MK329 during the initiation period of carcinogenesis did not change tumor incidence or yield, suggesting that endogenous CCK does not influence tumor induction during the initiation period in the hamster.

Adaptation of the Na+/glucose cotransporter following intestinal resection

Following massive small bowel resection, the remaining intestine adapts to compensate for lost absorptive capacity. Although the Na+/glucose cotransporter plays a critical role in nutrient, fluid, and electrolyte transport in the small intestine, its role in adaptation following resection has not been defined. To examine this, we sought to determine whether there were changes in the expression of the Na+/glucose cotransporter, SGTL1, at the messenger RNA level. Lewis rats underwent either transection or 70% small bowel resection and reanastomosis. The animals were sacrificed at intervals following operation. Jejunum proximal to the anastomosis and ileum and colon distal to the anastomosis were harvested and analyzed for Na+/glucose mRNA by reverse transcriptase-polymerase chain reaction and Southern blot. Blots were semiquantitated by 32P labeling and standardized to beta-actin. Histologic sections and analysis of DNA, RNA, and protein content revealed hyperplastic changes. Following resection, mRNA for the Na+/glucose cotransporter in the jejunum increased significantly (P < 0.05) by 1 week and remained elevated. In the ileum, an almost fivefold increase occurred at 6 hr and persisted throughout the study (P < 0.05). The early response was greater in the ileum, distal to the reanastomosis, than that in the jejunum (P < 0.05). In contrast, there was no change in the small amount of transporter mRNA detected in the colon. These results suggest that, in addition to mucosal hyperplasia, the intestinal response to resection involves upregulation of transporter mRNA by the individual enterocyte. This transcriptional increase in the Na+/glucose cotransporter appears to be an early response by the intestine and may be important in maintaining overall intestinal transport capacity following resection.

Peptide YY augments postprandial small intestinal absorption in the conscious dog

Since feeding increases intestinal fluid and electrolyte losses in short bowel syndrome, an agent increasing postprandial small bowel absorption might have a therapeutic role. Peptide YY (PYY) has recently been shown to increase net small bowel absorption under basal conditions. The aim of this study was to determine whether PYY can also augment postprandial absorption. Exteriorized, neurovascularly intact jejunal and ileal segments (25 cm Thiry-Vella loops) were created in dogs (n = 6) and gastrointestinal continuity was restored. Luminal perfusion with [14C]polyethylene glycol was used to calculate the change in water (H2O) and sodium (Na+) and chlorine (Cl-) ion fluxes after an oral meal. Changes in fluxes were also determined after a 2-hour infusion of a physiological dose of PYY (100 pmol/kg per hour). In a third series of experiments, fluxes were measured after a meal, during PYY infusion. Feeding increased small bowel absorption of fluid and electrolytes independent of the luminal content. This effect persisted for 2 hours after the meal. PYY infusion significantly augmented this proabsorptive response in both jejunum and ileum. These results suggest that PYY-agonists may have a therapeutic role in conditions such as short bowel syndrome where postprandial absorption is reduced.

Peptide YY is a physiological regulator of water and electrolyte absorption in the canine small bowel in vivo

BACKGROUND

Peptide YY (PYY), a hormone released following a meal, is one potential mediator of intestinal absorption. Although PYY inhibits 5'-cyclic adenosine monophosphate (cAMP)-stimulated small intestinal secretion in vitro, its effects on fluid and electrolyte transport in vivo are unknown.

METHODS

This study examines the effects of physiological doses of PYY in dogs (n = 6) with jejunal and ileal exteriorized, neurovascularly intact intestinal loops (Thiry-Vella fistulas).

RESULTS

Plasma PYY levels increased after a meal from 155 +/- 15 to 324 +/- 26 pmol/L at 30 minutes and remained elevated for 2 hours. PYY infused intravenously in unfed animals at 25, 50, 100, and 200 pmol.kg-1.h-1, produced a dose-dependent increase in plasma PYY levels. At 100 pmol.kg-1.h-1, PYY plasma concentrations were similar to those of fed animals (317 +/- 39 pmol/L). PYY infusion resulted in a dose-dependent increase in water and electrolyte absorption at all doses in both the jejunum and ileum. Although the relative increase in absorption was similar, the magnitude was greater in the ileum.

CONCLUSIONS

Physiological concentrations of PYY produced an increase in small bowel absorption of water and electrolytes in vivo. The postprandial release of PYY may mediate the increase in absorption following a meal. Such a proabsorptive agent may have considerable potential for clinical use in malabsorptive states.

Cyclic AMP-mediated release of peptide YY (PYY) from the isolated perfused rabbit distal colon

We have investigated the role of the colonic nervous system in regulating the release of peptide YY (PYY) from the isolated perfused rabbit distal colon. In addition, we have studied the role of cAMP- and Ca(2+)-dependent mechanisms in mediating the release of PYY. We investigated three agents which stimulate increases in intracellular cAMP (vasoactive intestinal polypeptide (VIP), cholera toxin, and forskolin) and three agents which raise intracellular Ca2+ concentrations (substance P, carbachol, and the calcium ionophore A23187). The three cAMP-dependent agents, VIP (10(-7) M and 3 x 10(-7) M), cholera toxin (100 micrograms), and forskolin (10(-6) M and 10(-5) M) significantly stimulated release of PYY (P < 0.05). Tetrodotoxin (3 x 10(-6) M) did not alter forskolin (10(-5) M) stimulated release of PYY. Substance P (10(-9) M and 10(-8) M), carbachol (10(-5) M), and A23187 (10(-6) M) failed to stimulate the release of PYY. These results suggest that the colonic neurotransmitter VIP participates in the modulation of PYY release from rabbit distal colons. Further, these studies suggest that release of PYY is mediated by cAMP-dependent pathways.

Deoxycholate is an important releaser of peptide YY and enteroglucagon from the human colon

Peptide YY (PYY) and enteroglucagon are hormonal peptides found in endocrine cells of the distal intestinal mucosa. Although it is known that plasma concentrations of both peptides increase in response to feeding, the mechanism by which ingested food causes release of colonic hormones is not understood. The release of PYY and enteroglucagon was measured in response to intraluminal stimuli in 176 patients having investigative colonoscopy. Introduction of air, saline (isotonic and hypertonic), glucose (isotonic and hypertonic), oleic acid (without bile salts), and casein hydrolysate all failed to release PYY but glucose caused a small but significant increase in enteroglucagon concentrations. In contrast with the lack of effect of nutrients, infusion of deoxycholic acid produced a rapid and marked dose responsive increase in plasma PYY concentrations when introduced into the sigmoid colon. PYY release was statistically significant at doses between 3.3 mM to 30 mM; for example 10 mM deoxycholate caused a sixfold increase in plasma PYY concentrations. Infusion of 10 mM deoxycholate into the transverse colon or caecum produced an increase of PYY that was similar to the responses in the sigmoid colon. There was also a significant release of enteroglucagon in response to infusion of this bile salt into the sigmoid colon at doses between 3.3 mM and 30 mM. The enteroglucagon response to 10 mM deoxycholate was similar in all three colonic regions. When oleic acid was added to deoxycholate as an emulsion, the release of PYY and enteroglucagon was similar to that seen with the bile salt alone. These findings suggest that bile salts may play an important part in the control of colonic endocrine function and may explain the increased circulating concentrations of colonic regulatory peptides that are seen in malabsorption states and after small bowel resection in humans.

Management of unresectable malignant endocrine tumors of the pancreas

Malignant endocrine tumors of the pancreas are a heterogenous group of tumors with a multipotential secretory capacity. The lesions are generally slow growing with a relatively long life expectancy from the time of diagnosis. Death results from a combination of local and metastatic disease and the sequelae of excess hormone secretion. While potentially successful curative resections are rare, long term survival is frequently possible based on the rate of growth and the inhibition of the bioactive effects of the secretory products of the tumor. Regional control with palliative surgical debulking and transcatheter arterial embolization of hepatic metastases has an important role in terms of symptomatic relief and long term survival. These tumors respond frequently to chemotherapy. Combination chemotherapy is more effective than single agent treatment. Preliminary information suggests that leukocyte interferon is useful in treatment, but this agent still requires careful prospective evaluation. While current data do not support the use of octreotide for an antitumor effect, it is capable of producing prompt and substantial symptomatic relief with minimal side effects in a large proportion of patients with functional malignant endocrine tumors of the pancreas. Many advances have been made in the recognition, diagnosis and management of patients with malignant endocrine tumors of the pancreas. Additional basic cellular research is necessary to define the molecular and cell biologic factors of these tumor cells. Particular facets that require further understanding include their basic cytogenetic abnormality, regulation of peptide production and the role of peptides and other growth factors in endocrine, paracrine and autocrine regulatory relationships. The answers to these questions will hopefully promulgate the discovery of improved cytotoxic agents, better peptide pharmacotherapeutic agents and improve the overall management of patients with unresectable malignant endocrine tumors of the pancreas.

Effects of high fat diet and cholecystokinin receptor blockade on pancreatic growth and tumor initiation in the hamster

The mechanism by which high-fat diet potentiates pancreatic cancer is not known, but trophic hormones may be involved. In preliminary growth studies, hamsters fed a high fat diet (17.5% lard, 17.5% corn oil) for 14 days showed a 16.3% increase (P < 0.01) in pancreatic weight compared to controls on low fat diet (2.5% lard, 2.5% corn oil). A significant increase was also seen at 28 days. Similar increases were seen in pancreatic DNA (29%, P < 0.01) and pancreatic RNA (22%, P < 0.05) at 14 days. Plasma cholecystokinin (CCK) levels at 14 days were 2.5 fold higher in the animals fed high fat (P < 0.01). Infusion of the CCK antagonist MK329 (25 nmol/kg/h) completely abolished the increase in pancreatic weight, pancreatic DNA and pancreatic RNA. The effect of CCK receptor blockade during the initiation period of carcinogenesis was investigated in hamsters fed the same diets used in the growth studies. One hundred animals received a single injection of N-nitrosobis(2-oxopropyl)amine, (BOP, 20 mg/kg). Half of the hamsters in each diet group received a 2 week infusion of MK329 (25 nmol/kg/h), beginning 8 days before carcinogen administration. At the time of death, 55 weeks after carcinogen administration, non-fasting plasma CCK levels were 31% higher in the high fat fed hamsters than in the low fat fed animals (P < 0.01). The high-fat diet group had a 3-fold increase in total cancer incidence and a 5-fold increase in advanced lesions (adenocarcinomas). Tumor incidence and yield were not changed in either diet group by CCK-receptor blockade during the initiation period. Cholecystokinin appears to mediate the short-term trophic effect that high-fat feeding has on the pancreas. However, potentiation of pancreatic cancer by high-fat diet in the hamster cancer model does not appear to be influenced by endogenous cholecystokinin at the time of tumor induction.

Influence of chloroquine on diet-induced pancreatitis

Recent investigations have suggested that digestive zymogens may become activated within the acinar cell during acute pancreatitis. While the molecular events responsible for intracellular zymogen activation remain unknown, several potential enzymatic pathways require an acidic pH to optimally proceed. We therefore proposed that manipulation of subcellular pH might alter the course of experimental pancreatitis. Chloroquine, a weak base that raises the pH of acidic subcellular compartments, was administered to young female mice in which pancreatitis was induced by a choline-deficient, ethionine-supplemented (CDE) diet. Control animals were maintained on regular laboratory chow. Examination of isolated pancreatic acini using acridine orange cytofluorescence demonstrated expansion of acidic subcellular compartments in animals fed the CDE diet. These compartments were effectively neutralized in animals receiving chloroquine. Animals receiving continuous infusions of high-dose chloroquine demonstrated a significant (p < 0.05) decrease in free pancreatic tryptic activity as well as improved survival. These changes were also associated with decreased trypsinogen content in animals treated with high-dose chloroquine, suggesting an additional potential effect of chloroquine on zymogen synthesis and accumulation. One explanation of these findings is that a low-pH compartment may be important in the pathogenesis of diet-induced pancreatitis.

Plasma and tissue alterations of peptide YY and enteroglucagon in rats after colectomy

Peptide YY (PYY) and enteroglucagon are produced by endocrine cells of the colonic mucosa. PYY inhibits upper gastrointestinal motility, and enteroglucagon is trophic for small bowel mucosa. Adaptive increase in the production and release of these peptides may improve functional results after colorectal resections. We hypothesized that if segments of the colon were resected, then production and release of PYY and enteroglucagon would increase in the remaining segments of bowel. Animals which underwent colonic transections and partial resections had transient elevations of PYY up to 250 +/- 80 pmol/L, which dropped to control group levels in the second week following surgery. Rats with an abdominal colectomy had significantly greater PYY levels than all other groups from the third (208 +/- 30 pmol/L) to the thirty-eighth (100 +/- 16 pmol/L) week of the study. Circulating levels of enteroglucagon were elevated to 156 +/- 35 pmol/L in rats with a right hemicolectomy during the first week following surgery. Enteroglucagon levels did not significantly vary in the other groups studied. Both tissue PYY (413 +/- 33 pmol/gram) and tissue enteroglucagon (171 +/- 17 pmol/gram) were significantly elevated in the rectums of the rats with an abdominal colectomy, as compared to all other groups. The elevated tissue levels may thus account for the ability to maintain elevated plasma PYY. Double immunogold labeling of endocrine cells in the colorectal tissue for PYY and enteroglucagon revealed both peptides within the same endocrine cells and secretory granules. These studies support the hypothesis that circulating levels of PYY are elevated after major colonic resections and suggest that L-type endocrine cells may participate in adaptive responses which improve intestinal function following colonic surgery.

Distribution and immunocytochemical colocalization of peptide YY and enteroglucagon in endocrine cells of the rabbit colon

Peptide YY (PYY) is 36 amino acid peptide hormone present in high concentrations in the colon where it is colocalized with enteroglucagon in L cells. A selective release of PYY and enteroglucagon from the rabbit colon has been described, raising the question of the exact localization of the two hormones in the rabbit colon. We have therefore examined the distribution of PYY and enteroglucagon as well as somatostatin in the rabbit colon using RIA and electron microscopic immunocytochemistry. PYY and enteroglucagon were present in high concentrations in the colorectal mucosa with peak concentrations in the left colon (PYY 544 +/- 87 pmol/g, enteroglucagon 152 +/- 10 pmol/g). Electron microscopic examination of the colonic mucosa demonstrated a large population (65%) of EC cells, a moderate population (30%) of L cells, and a small population (5%) of D cells. By immunogold labeling serotonin was localized to EC cells, PYY and enteroglucagon to L cells, and somatostatin to the D cell. Double immunogold labeling revealed PYY and enteroglucagon in all L cells examined (93 cells). A majority of the secretory granules (83%) were labeled by both PYY and glucagon antibodies, whereas a significant portion of granules (15%) was labeled by the PYY antibodies alone. The results demonstrate that L cells are the sole source of PYY and enteroglucagon in the rabbit colon and that L cells contain different populations of secretory granules. The existence of different secretory granules in L cells may explain the selective release of PYY and enteroglucagon observed in the rabbit colon.

Short-chain fatty acid release of peptide YY in the isolated rabbit distal colon

Short-chain fatty acids (SCFAs) form the major ionic fraction of stool, provide the major metabolic substrate for colonic epithelium, and promote mucosal ion transport. Despite this prominent role of SCFAs in metabolism of the colon, their effect on colonic endocrine cell function has not been studied. Consequently, we hypothesized that SCFAs might modulate release of peptide YY (PYY) from colonic type-L endocrine cells. The specific aims of this study were to measure release of PYY from the isolated perfused rabbit distal colon stimulated by intraluminal infusion of 0.9% saline, acetate (10 mM), acetoacetate (10 mM), n-butyrate (1, 3.3, 10, 100 mM), and pyruvate (10 mM). PYY levels were measured by radioimmunoassay in the venous effluent of the rabbit colon. All four SCFAs (10 mM) caused at least a twofold increase in integrated release of PYY from the isolated perfused rabbit colon. Graded concentrations of n-butyrate caused a stepwise release of PYY. This study suggests that SCFAs may modulate the release of colonic PYY in rabbits.

Amelioration of cholinergic-induced pancreatitis with a selective cholecystokinin receptor antagonist

Acute edematous pancreatitis follows excessive cholinergic stimulation in patients exposed to anticholinesterase-containing insecticides. We describe the role of cholecystokinin and the benefits of cholecystokinin receptor blockade in this form of pancreatitis. A cholinergic mimetic (carbachol) was administered to rats weighing 300 to 350 g and produced a form of edematous pancreatitis that mimics that seen in humans. Animals received carbachol intraperitoneally, either alone (250 micrograms/kg of body weight) or with cholecystokinin-receptor antagonist devazepide (3 mg/kg of body weight) and were killed 4 hours later. Carbachol administration resulted in a 19% increase in pancreatic weight, a fourfold increase in serum amylase levels, and a 14-fold increase in serum lipase levels. Plasma cholecystokinin levels, however, were not altered. Devazepide administered prior to cholinergic hyperstimulation blocked pancreatic weight increase and reduced elevations in serum amylase levels twofold and lipase levels fourfold. Although cholecystokinin levels are not elevated in this model of pancreatitis, blockade of even low, background concentrations of this regulatory peptide is beneficial.

Experimental models of acute pancreatitis

Acute pancreatitis remains a disease of uncertain pathogenesis and nonspecific therapy. Because of the practical problems plaguing investigation of pancreatitis in man, investigators have developed various experimental animal models of pancreatitis in order to develop rationale concepts regarding pathogenesis and therapy. Despite numerous investigations over the past century, the events involved in the initiation and progression of pancreatitis remain obscure. Indeed, identification of the cellular mechanisms responsible for the initiation of this disease may allow for significant advances in therapy. Previous studies have largely focused on the mechanism of pancreatitis at the organ level. It is now apparent that the early initiating events in acute pancreatitis probably occur at a membrane or intracellular level. The resolution of the cellular events which underlie the development of pancreatitis in combination with the introduction of new therapeutic agents may enable a rational and safe protocol to be developed for the support of patients with pancreatitis. In this review different experimental models of acute pancreatitis are discussed. Emphasis is placed on the relevance of various models to clinical pancreatitis.