Comparative analysis of various prognostic nodal factors, adjuvant chemotherapy and survival among stage III colon cancer patients over 65 years: an analysis using surveillance, epidemiology and end results (SEER)-Medicare data.

AIM: The prognostic effects of chemotherapy and various lymph node measures [positive nodes, total node count and the positive lymph node ratio (PLNR)] have been established. It is unknown whether the cancer-specific survival benefit of chemotherapy differs across these nodal prognostic categories. METHOD: This retrospective analysis of linked Surveillance, Epidemiology and End Results (SEER) data and Medicare data (SEER-Medicare)included patients ≥ 65 years of age with a diagnosis of stage III colon cancer between 1997 and 2002. We grouped patients according to the number of positive nodes (N1 and N2), total node count (≥ 12 and < 12 total nodes) and PLNR (below the 75th percentile and at least at the 75th percentile of the PLNR). The end point was colon cancer-specific mortality. RESULTS: Fifty-one per cent (3701) of the 7263 patients received adjuvant therapy during the time period 1997-2002. The mean (standard deviation) number of total nodes examined was 13 (9) and the number of positive nodes identified was 3 (3). Patients with N2 disease, < 12 total nodes examined and a high PLNR had a worse survival at 2, 3 and 5 years following colectomy. Utilization of chemotherapy demonstrated a colon cancer-specific survival benefit (hazard ratio at median follow up = 0.7; P < 0.001) that was consistent and statistically significant across the three nodal prognostic categories examined. CONCLUSION: The benefit of chemotherapy did not vary based on N stage, total node count or PLNR. The results favour a broad-based approach towards increasing the chemotherapy treatment rates in stage III patients of ≥ 65 years of age, rather than an approach that targets clinical subgroups.

Induction of donor-specific unresponsiveness by intrathymic islet transplantation.

The application of isolated pancreatic islet transplantation for treatment of diabetes mellitus has been hampered by the vulnerability of islet allografts to immunologic rejection. Rat islet allografts that were transplanted into the thymus of recipients treated with a single injection of anti-lymphocyte serum survived indefinitely. A state of donor-specific unresponsiveness was achieved that permitted survival of a second donor strain islet allograft transplanted to an extrathymic site. Maturation of T cell precursors in a thymic microenvironment that is harboring foreign alloantigen may induce the selective unresponsiveness. This model provides an approach for pancreatic islet transplantation and a potential strategy for specific modification of the peripheral immune repertoire.

A phosphatase associated with metastasis of colorectal cancer.

To gain insights into the molecular basis for metastasis, we compared the global gene expression profile of metastatic colorectal cancer with that of primary cancers, benign colorectal tumors, and normal colorectal epithelium. Among the genes identified, the PRL-3 protein tyrosine phosphatase gene was of particular interest. It was expressed at high levels in each of 18 cancer metastases studied but at lower levels in nonmetastatic tumors and normal colorectal epithelium. In 3 of 12 metastases examined, multiple copies of the PRL-3 gene were found within a small amplicon located at chromosome 8q24.3. These data suggest that the PRL-3 gene is important for colorectal cancer metastasis and provide a new therapeutic target for these intractable lesions.

Counting alleles reveals a connection between chromosome 18q loss and vascular invasion.

The analysis of loss of heterozygosity (LOH) is perhaps the most widely used technique in cancer genetics. In primary tumors, however, the analysis of LOH is fraught with technical problems that have limited its reproducibility and interpretation. In particular, tumors are mixtures of neoplastic and nonneoplastic cells, and the DNA from the nonneoplastic cells can mask LOH. We here describe a new experimental approach, involving two components, to overcome these problems. First, a form of digital PCR was employed to directly count, one by one, the number of each of the two alleles in tumor samples. Second, Bayesian-type likelihood methods were used to measure the strength of the evidence for the allele distribution being different from normal. This approach imparts a rigorous statistical basis to LOH analyses, and should be able to provide more reliable information than heretofore possible in LOH studies of diverse tumor types.

Vaccines for colorectal cancer.

Despite recent advances in the treatment of colorectal cancer, the overall survival rate for those patients with advanced locoregional disease remains less than 50%. Although adjuvant systemic chemotherapy has improved survival of these patients, more effective therapies are needed. Immunotherapy is an approach that could have a particular role in the adjuvant therapy of colorectal cancer. There is now convincing evidence that the immune system can specifically recognize and destroy malignant cells. Although both antibody- and T-cell-mediated anti-tumor responses have been documented, the cellular immune response with its direct cytotoxic mechanisms is felt to be the principal anti-tumor arm of the immune system. Analysis of the T cells that recognize tumors has led to the identification and characterization of many tumor-associated antigens including several colorectal antigens. Current approaches to developing a vaccine for colorectal cancer use our expanded understanding of these tumor-associated antigens and the conditions that allow development of an effective cellular immune response to them.

K-ras oncogene mutations in osteoclast-like giant cell tumors of the pancreas and liver: genetic evidence to support origin from the duct epithelium.

Osteoclast-like giant cell tumors (OCGTs) of the pancreas and liver are enigmatic tumors. Despite their striking morphologic resemblance to certain mesenchymal tumors of bone and tendon sheath, it has been suggested that these tumors may, in fact, arise from epithelial precursors. It is also unclear whether the osteoclast-like giant cells in OCGTs are neoplastic or nonneoplastic. We identified OCGTs of the pancreas and liver that were associated with atypical intraductal epithelial proliferations or mucinous cystic neoplasms. To determine the relationship between the noninvasive epithelial proliferations and the infiltrating OCGTs, each individual component was analyzed for mutations at codon 12 of the K-ras oncogene. Four of the five-duct epithelial lesions harbored activating mutations of the K-ras oncogene. In each case, the same K-ras mutation was also present in the mononuclear cells from the paired OCGT. Moreover, these same mutations were detected when the osteoclast-like giant cells were individually microdissected and analyzed. A panel of immunohistochemical stains was performed, and the osteoclast-like giant cells demonstrated macrophage differentiation. These cells were consistently reactive for the monocyte/macrophage marker KP1, but showed absent staining for a panel of epithelial markers. The infiltrating mononuclear cells lacked strong staining for epithelial markers and monocyte/macrophage markers. These findings suggest that OCGTs of the pancreas and liver are undifferentiated carcinomas that arise directly from intraductal epithelial precursors. The finding of K-ras mutations in the osteoclast-like giant cells may reflect their propensity to phagocytize tumor cells.

Modulation of the major histocompatibility complex antigen and the immunogenicity of islet allografts.

Modulation of major histocompatibility complex (MHC) antigen by parenchymal cells and "passenger leukocytes" is a common feature of allograft rejection. To assess its significance we have examined the fate of antigen-presenting cell (APC)-depleted pancreatic islet allografts subsequent to increasing their expression of MHC antigens by in vitro exposure to the lymphokine interferon-gamma (gIFN). While most untreated grafts survived indefinitely, gIFN-exposed grafts were acutely rejected. Using in vitro islet cell-lymphocyte coculture assays, we attempted to dissect the underlying mechanism of enhanced islet cell immunogenicity resulting from gIFN treatment. We determined that gIFN exposure did not affect the capacity of islet cells to serve as APC for T lymphocytes, however islet cell exposure to gIFN was associated with enhanced vulnerability to allogeneic cytotoxic T lymphocyte (CTL) lysis in vitro by an CD5+ (OX-19+), CD8+ (OX-8+), CD4- (W3/25-), class I-restricted CTL. On the basis of these findings, we conclude that antigenic modulation can be a decisive factor in the survival of engrafted tissues by augmenting the interaction of the graft antigens with cytolytic effector T lymphocytes.

Isolated liver metastases from neuroendocrine tumors: does resection prolong survival?

BACKGROUND: Neuroendocrine tumors commonly metastasize to the liver. Although surgical resection is considered a treatment option for patients with localized metastases confined to the liver, the longterm survival benefit of liver resection has not been clearly demonstrated. We examined the survival of patients undergoing liver resection for this disease. STUDY DESIGN: Between 1984 and 1995, we evaluated 38 patients with liver-only metastases from neuroendocrine tumors, including 21 carcinoid, 13 islet cell, and 4 atypical neuroendocrine neoplasms. Data from a combined prospective and retrospective database and a tumor registry were analyzed. Of these patients, 15 underwent complete resection of all known disease. The remaining 23 patients, who also had disease confined to the liver, had comparable tumor burden but were believed to be unresectable. The longterm survival rates of these two groups were compared. RESULTS: Patients who underwent liver resection did not differ from those who were unresectable with regard to age, pathology, primary tumor site, serum alkaline phosphatase levels, or percentage of the liver involved. All resections were complete, leaving no residual disease, and consisted of lobectomy (n = 3), segmentectomy (n = 1), and wedge resections (n = 11). There were no operative deaths. Patients who underwent hepatic resection had a significantly longer survival than unresected patients. Although median survival had not been reached in resected patients, the median survival in the unresectable group was 27 months. Patients who underwent liver resection had a higher 5-year actuarial survival (73% versus 29%). CONCLUSIONS: Hepatic resection in selected patients with isolated liver metastases from neuroendocrine tumors may prolong survival. This conclusion was reached by comparing our resected group with an unresectable group with similar tumor burden.

Focal hepatic ablation using interstitial photon radiation energy.

BACKGROUND: Intratumoral ablative therapy is being used increasingly for the treatment of primary and secondary hepatic malignancies. The interstitial point-source photon radiosurgery system (PRS) is a novel ablative technique that uses radiation therapy similar in dosimetry to interstitial brachytherapy. STUDY DESIGN: To determine the feasibility, toxicity, and local tissue destructive capabilities of the PRS in the liver, preliminary studies in a nontumor-bearing canine model were examined. A 6-month survival study was conducted. Each animal received three radiation treatments, in the right, central, and left hepatic regions. Three low-dose treatments were delivered to each of six animals (group A), generating a 2.0-cm-diameter radiated sphere with a dose of 20 Gy at the lesion edge. Three high-dose treatments were delivered to each of six animals (group B), generating a 3.0-cm-diameter radiated sphere with 20 Gy at the lesion edge. RESULTS: The treatment reproducibly generated sharply demarcated hepatic ablative lesions proportional to the administered dose. Mean lesion diameter at 1 month was 1.6+/-0.2 cm in group A and 3.4+/-1.0 cm in group B. Lesion size was independent of intrahepatic location, including near vascular structures. PRS therapy, when applied to portal structures, resulted in hilar damage. Hilar damage appeared to be associated with arteriolar thrombosis and bile duct injury. Treatment of regions adjacent to large hepatic veins and the IVC was not associated with vessel thrombosis or stricture. CONCLUSIONS: PRS ablation is a generally well-tolerated method that results in consistent, well-demarcated, symmetric lesions of complete necrosis with minimal adjacent parenchymal injury. Application of such an approach for the treatment of liver tumors is promising.

Complex gastrointestinal surgery: impact of provider experience on clinical and economic outcomes.

BACKGROUND: Commonly performed elective gastrointestinal surgical procedures are carried out with low morbidity and mortality in hospitals throughout the United States. Complex operative procedures on the alimentary tract are performed with a relatively low frequency and are associated with higher mortality. Volume and experience of the surgical provider team have been correlated with better clinical and economic outcomes for one complex gastrointestinal surgical procedure, pancreaticoduodenectomy. This study evaluated whether provider volume and experience were important factors influencing clinical and economic outcomes for a variety of complex gastrointestinal surgical procedures in one state. STUDY DESIGN: Complex high-risk gastrointestinal surgical procedures were defined as those with statewide in-hospital mortality of > or = 5%, frequency of greater than 200 per year in the state, and requiring special surgical skill and expertise. Six procedures met these criteria. Using publicly available discharge data, all patients discharged from Maryland hospitals from July 1989 to June 1997 with a primary procedure code for one of the six study procedures were selected. Hospitals were classified into one of six groups based on the average number of study procedures per year: 10 or less; 11 to 20; 21 to 50; 51 to 100; 101 to 200; and 201 or more procedures per year. A hospital was included if at least one procedure was performed there during the study period. No providers fell within the 51 to 100, and 101 to 200 groups, so all analyses were performed for the remaining four volume groups that were classified, respectively, as minimal (10 or fewer procedures), low (11 to 20 procedures), medium (21 to 50 procedures), and high-volume groups (201 or more procedures). Poisson regression was used to assess the relationship between in-hospital mortality and hospital volume after case-mix adjustment. Multiple linear regression models were used to assess differences in average length-of-stay and average total hospital charges among hospital volume groups. We further analyzed mortality, length-of-stay, and charges at the procedural level to understand these subgroups of complex gastrointestinal patients. We also examined the relationship between provider volume and outcomes for malignant versus benign diagnosis groups. RESULTS: Complex gastrointestinal surgical procedures were performed on 4,561 patients in Maryland from July 1989 through June 1997. The study population averaged 61.6 years of age, was 55% male, 71% Caucasian, and had predominantly Medicare as a payment source. After case-mix adjustment, patients who underwent complex gastrointestinal surgical procedures at the medium-, low-, and minimal-volume provider groups had a 2.1, 3.3, and 3.2 times greater risk of in-hospital death, respectively, than patients at the high-volume provider (p < 0.001 for all comparisons); longer lengths-of-stay, 16.1, 15.7, and 15.5 days at the low-, medium-, and minimal-volume groups, respectively, versus 14.0 days for the high-volume provider (p < 0.001 for all comparisons). Similarly, adjusted charges at the high-volume provider were, on average, 14% less than those of the low-volume group, which had the next lowest charges. Although mortality rates differed by procedure type, for each procedure, mortality increased as provider volume decreased, following the pattern found in the aggregate analysis. After case-mix adjustment, the risk of in-hospital death for patients with malignant diagnoses was significantly higher for the medium-, low-, and minimal-volume groups compared with patients at the high-volume provider, relative risk of 3.1, 4.0, and 4.2, respectively, (p < 0.001 for all comparisons). CONCLUSIONS: This study demonstrates that increased hospital experience is associated with a marked decrease in hospital mortality. The decreased mortality at the high-volume provider was also associated with shorter lengths-of-stay and lower hospital char

Acute isovolemic hemodilution during major hepatic resection--an initial report: does it safely reduce the blood transfusion requirement?

Surgical resection remains the mainstay of treatment for patients with hepatic tumors, despite the associated morbidity including the need for blood transfusion. Acute isovolemic hemodilution (AIH) has been shown to decrease the transfusion requirement for cardiac, urologic, and orthopedic procedures. However, the reported experience with AIH during hepatic resections is limited. Seven patients underwent major hepatic resection from July 1992 to June 1994 with standard AIH. Their clinical parameters were compared with those of nine matched control patients during the same time period. AIH and control patients had similar preoperative laboratory values (hematocrit, bilirubin, and coagulation studies), extent of liver resection, and pathologic diagnoses. Mean tumor diameters were larger in the AIH group (9.3 cm vs. 5.8 cm). Most important, patients managed with AIH required homologous blood transfusions significantly less often than the control group (14% vs. 67%; P=0.05). Furthermore, if they did receive transfusions, AIH patients needed fewer units of red cells (0.1+/-0.1 units vs. 1.7+/-0.6 units). There was no morbidity associated with AIH. AIH can be safely performed in patients undergoing major hepatic resection for malignancy. AIH appears to reduce the number of patients requiring homologous blood transfusion as well as the number of units transfused per patient. This technique warrants further study in a larger prospective, randomized trial.

Isolated right segmental hepatic duct injury: a diagnostic and therapeutic challenge.

Biliary leaks and injuries are not an uncommon occurrence following laparoscopic cholecystectomy. Bile leaks associated with the biliary anatomic variant of a low-inserting right segmental hepatic duct can be particularly difficult to diagnose in that results of endoscopic retrograde cholangiography (ERC) are usually interpreted as "normal" with no leaks demonstrated. The aim of this study was to describe a single institution's experience with nine patients with biliary leaks associated with this anatomic variant and to discuss their management. A retrospective analysis of the hospital records of all patients with bile duct injuries managed at a single institution between 1980 and July 1998, inclusive, was performed. Nine patients were identified as having an isolated right segmental hepatic duct injury associated with a biliary leak. Seven (78%) of the nine patients had undergone a laparoscopic cholecystectomy, whereas the remaining two patients (22%) had undergone an open cholecystectomy. All of the patients had undergone endoscopic retrograde cholangiography at outside institutions, the results of which had been interpreted as normal with no apparent leaks. The median interval from the time of cholecystectomy to referral was 1.4 months. All patients were managed with initial percutaneous access of the involved right segmental biliary system, with placement of a percutaneous transhepatic stent. After the biliary leak was controlled, all patients underwent Roux-en-Y hepaticojejunostomy to the isolated biliary segment. All patients had an uncomplicated postoperative course. There were no postoperative anastomotic leaks. Postoperative stenting was maintained for a mean of 8 months. Six (67%) of the nine patients had a long-term successful outcome with minimal or no symptoms. In three patients, recurrent symptoms with pain and/or cholangitis developed at a mean of 34 months. All three patients underwent percutaneous cholangiography, which demonstrated an anastomotic stricture, and all were managed with percutaneous balloon dilatation with a successful outcome. Currently eight (89%) of the nine patients are asymptomatic, with a mean follow-up of 70.4 months (range 12 to 226 months). One patient had intermittent right upper quadrant pain with normal liver function tests but has not required intervention. Isolated right segmental hepatic ductal injury with biliary leakage is an uncommon complication following laparoscopic cholecystectomy. A diagnostic dilemma is created by the presence of a bile leak with a normal endoscopic retrograde cholangiogram. Management begins with percutaneous access of the transected isolated ductal system followed by reconstruction as a Roux-en-Y hepaticojejunostomy.

Complete hepatic resection of metastases from leiomyosarcoma prolongs survival.

Although liver resection has been shown to prolong survival in selected patients with metastases from colorectal cancer, the benefit for other metastatic tumors is unproved. To determine whether hepatic resection has a role in the management of metastatic leiomyosarcoma, medical records from 11 consecutive patients who underwent resection of isolated metastases from leiomyosarcoma between 1984 and 1995 were reviewed. All liver resections were for leiomyosarcomas originating in the viscera (n = 6) or retroperitoneum (n = 5). The average disease-free interval was 16 months. Five of 11 primary tumors were classified as low grade, whereas six were high grade. Hepatic resections included lobectomy or extended lobectomy (n = 4), segmentectomy and/or wedge resection (n = 5), and complex resection (n = 2). There were no operative deaths. Median survival of all patients after liver resection was 39 months. Patients who underwent complete resection of hepatic metastases (n = 6) had a significantly longer survival than those who had incomplete resections (n = 5) (P = 0.03, log-rank test). Furthermore, five of six patients who underwent complete resection are alive after hepatectomy with a median follow-up of 53 months. Therefore, in selected patients with isolated liver metastases from visceral and retroperitoneal leiomyosarcomas, complete resection of hepatic metastases results in prolonged survival.

Results of salvage abdominoperineal resection for recurrent anal carcinoma following combined chemoradiation therapy.

Combined chemotherapy and radiation therapy is the standard treatment for epidermoid carcinoma of the anal canal. Failures are often not associated with distant recurrence and are therefore potentially amenable to salvage abdominoperineal resection. The aim of this study was to review our experience with abdominoperineal resection following failure of chemoradiation therapy for epidermoid carcinoma of the anus. Between 1980 and 1998, 17 patients underwent salvage abdominoperineal resection following failure of chemoradiation therapy. Four patients were excluded from survival analysis because resection was performed with palliative intent. Survival curves were based on the method of Kaplan and Meier, and univariate analysis of predictive variables was performed using the log-rank test. Twelve patients underwent abdominoperineal resection for persistent disease and five patients for recurrent disease. No operative deaths occurred, but local complications including perineal wound infection and wound breakdown was seen in 8 of 17 patients and 6 of 17 patients, respectively. Patients undergoing omental flap reconstruction (n = 3) or no pelvic reconstruction (n = 5) had a higher incidence of perineal breakdown compared to those undergoing muscle flap reconstruction (n = 9) (P <0.05). The median follow-up time for the patients operated on with curative intent was 53 months. The 5-year actuarial survival was 47%. Potential prognostic factors that were not found to have an impact on survival included margin status of resection, sphincter invasion, and degree of differentiation. Only pathologic tumor size greater than 5.0 cm (P <0.001) and age over 55 years (P <0.05) adversely affected survival. Selected patients with recurrent or persistent anal carcinoma following chemoradiation therapy can be offered salvage abdominoperineal resection. This operation is associated with a high incidence of local wound complications, and muscle flap reconstruction should be considered when possible. Prolonged survival can be achieved in some patients following salvage resection for epidermoid carcinoma of the anal canal.

Should hepatic resections be performed at high-volume referral centers?

Recent studies have demonstrated the relationship between clinical outcomes of complex surgical procedures and provider volume. Hepatic resection is one such high-risk surgical procedure. The aim of this analysis was to determine whether mortality and cost of performing hepatic resection are related to surgical volume while also examining outcomes by extent of resection and diagnosis, variables seen with this procedure. Maryland discharge data were used to study surgical volume, length of stay, charges, and mortality for 606 liver resections performed at all acute-care hospitals between January 1990 and June 1996. One high-volume provider accounted for 43.6% of discharges, averaging 40.6 cases per year. In comparison, the remainder of resections were performed at 35 other hospitals, averaging 1.5 cases per year. Data were stratified into these high- and low-volume groups, and adjusted outcomes were compared. The mortality rate for all procedures in the low-volume group was 7.9% compared to 1.5% for the high-volume provider (P <0.01, relative risk = 5.2). No overall differences were observed between low- and high-volume providers in total hospital charges. When analyzing by procedure type and diagnosis, lower mortality was seen in the high-volume center for both minor and major resections, as well as resections for metastatic disease. It was concluded that hepatic resection can be performed more safely and at comparable cost at high-volume referral centers.

Management of hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is responsible for a significant amount of morbidity and mortality throughout the world. In many countries, including the United States, a definite increase in the incidence of HCC has been reported recently, largely attributable to the increasing incidence of hepatitis C infection. Unfortunately, the current management of HCC is confusing due to the large number of treatment options available. The difficulty of managing a patient with HCC is compounded by the lack of well-designed, randomized clinical trials comparing the various treatment modalities. Nevertheless, many exciting management options are currently available that may prove valuable in the treatment of this disease. Partial hepatic resection or, in some instances, liver transplantation offers the best chance for cure. However, various ablative therapies, including percutaneous ethanol injection, radiofrequency ablation, and cryosurgery, may produce a survival benefit. In the future, systemic chemotherapy and transarterial chemoembolization, employed either alone or as adjuncts to ablation or resection, may play an increasing role in palliating or down-staging a patient with advanced HCC. This overview of the state-of-the-art management of HCC attempts to guide the practicing physician in selecting the best treatment plan for an individual with HCC.

NCCN Practice Guidelines for Colorectal Cancer.

The NCCN Colorectal Cancer Guidelines panel believes that a multidisciplinary approach is necessary for the management of the patient with colorectal cancer. The panel endorses the concept that treatment of patients in a clinical trial has priority over standard or accepted therapy. The recommended surgical procedure for resectable colon cancer is an en bloc resection; laparoscopic surgery should be done only in the context of a clinical trial. For patients with stage III disease, 5-FU-based adjuvant therapy is recommended. A patient who has metastatic disease in the liver or lung should be considered for surgical resection if he or she is a candidate for surgery and if surgery can extend survival. Surgery should be followed by adjuvant chemotherapy. The panel advocates a conservative post-treatment surveillance program for colon and rectal carcinoma patients. Serial CEA determinations are appropriate if the patient is a candidate for aggressive surgical resection, should recurrence be detected. Abdominal and pelvic CT scans should be utilized only when there are clinical indications of possible recurrence. Patients whose disease progresses during 5-FU-based therapy should be treated with irinotecan or encouraged to participate in a phase I or phase II clinical trial.

Gamma probe-directed biopsy of the sentinel node in oral squamous cell carcinoma.

OBJECTIVE: Management of the N0 neck in head and neck squamous cell carcinoma is an important issue for the head and neck surgeon. Experience with radionuclide-labeled colloid injection to identify a sentinel node in malignant melanoma suggests a high level of accuracy for this approach to identify microscopic metastasis when present. We set out to explore the feasibility of using the handheld gamma probe to identify radiolabeled sentinel nodes in oral squamous cell carcinoma. PATIENT POPULATION: Five individuals with N0 necks and accessible oral or oropharyngeal primary sites from a major tertiary referral center. METHODS: Radiolabel with unfiltered technetium Tc 99m sulfur colloid was injected in quadrants around the primary site followed by immediate dynamic lymphoscintigraphy. Open biopsy of the sentinel node was accomplished within 2 hours of injection after extirpation of the primary site. Regional or complete neck dissection was performed after sentinel node biopsy. RESULTS: Sentinel node biopsy accurately identified one or several nodes in 2 cases, including nodes containing metastatic cancer in 1. In the other 3 cases, the radiolabel failed to identify the sentinel node despite the presence of metastatic disease in the nodes at final pathologic study in 2. CONCLUSIONS: Detection and biopsy of the sentinel node are feasible for selected patients with oral head and neck squamous cell carcinoma with N0 necks. There is a potential savings of time, cost, and morbidity with this approach. However, several substantial problems were encountered with the technique in this limited series of patients. Establishing the reliability of lymphoscintigraphy in this setting would require testing in a much larger patient cohort. Our experience suggests that such an investment may not be warranted.

Feasibility of ablating normal renal parenchyma by interstitial photon radiation energy: study in a canine model.

BACKGROUND AND PURPOSE: A miniature photon radiosurgery system (PRS) has been described as an alternative to surgical resection and external-beam radiation for tumors and may now offer an alternative for ablation of renal lesions. We evaluated the feasibility of ablation by PRS in a normal parenchyma canine model. MATERIALS AND METHODS: Twelve mongrel dogs were used in this survival study. In the left and right kidneys of each animal, a peripheral lesion and central-hilar lesion, respectively, were induced with PRS. The probes were placed in the renal parenchyma, and local radiation of 15 Gy at a radius of 1.3 cm was delivered over 10 minutes. Serum electrolytes were measured serially. Computed tomography scans were obtained, and the animals were sacrificed for pathologic correlation. In a separate study, the liver received three additional treatments of 10 to 20 minutes of radiation. RESULTS: Eleven dogs survived this 6-month study and were sacrificed as scheduled. One animal expired after 2 weeks from radiation-induced fulminant hepatic failure with normal renal function. No other complications were observed. The average lesion size was 2.5 cm in diameter. Histologic analysis confirmed coagulative necrosis with sharp demarcation from the surrounding parenchyma. CONCLUSION: Preliminary studies demonstrate the feasibility of PRS ablation of the renal parenchyma. Further tumor model testing will be important to determine the ultimate efficacy of local photon radiation energy.