SURGICAL RESEARCH

Our laboratory investigations focus on clinical studies to improve the response of tumors to drug therapies, and on animal studies to investigate methods to enhance drug delivery and decrease toxicity.

Colon cancer is one of the most common malignancies in the United States. Despite attempts to improve early detection, only 50 to 60% of patients are cured. Of those who fail, almost all will have liver metastases; and, about half of those will have liver-restricted disease. Of those cases that are resectable, one third will be cured by resection of metastases alone. Of those cases that are not resectable, systemic chemotherapy offers minimally palliation, and little change of improved survival or cure. In contrast, hepatic artery (regional) chemotherapy with 5-fluoro-2'-deoxyuridine (FUdR) increases response from 25%, to 50 to 60%, in randomized studies. The treatment is well tolerated with little systemic toxicity.

Colon cancer, like many solid tumors, spreads in an orderly fashion to the lymph nodes, to the liver and, then, to the lung. However, in some instances, patients will develop lung metastases in the absence of liver metastases; the mechanism of metastasis formation is poorly understood. To examine this unusual spread of disease and to elucidate the mechanism of tumor metastases formation, we have developed a rat model of colon cancer using a variety of cell lines, some of which spread preferentially to the lung, and others that spread only to the liver. We are currently involved in studying differences in the phenotypic and genotypic characteristics of the tumor cell lines that are derived from the same parent cell line to determine how cells choose their site of metastases.

We have attempted to increase tumor response to FUdR by altering drug delivery. In a randomized trial comparing FUdR alone with FUdR and decadron, the group receiving FUdR and decadron had a tumor response of 71% and a significantly increased survival. Most recently, the results of a FUdR and leucovorin study revealed a response rate of 70 to 80% and a median survival of two years.

A pilot study was conducted to address the problem of extrahepatic disease. These patients received hepatic arterial (HA) FUdR combined with systemic 5-fluorouracil (FU) and leucovorin. We showed that these agents can be combined without loss of efficacy or increased biliary toxicity.

To evaluate combined drug therapy for use in improving local control within the liver without increasing toxicity, improving distant failure, and increasing overall survival, we developed an animal model of colorectal hepatic metastases amenable to hepatic artery chemotherapy. Using this model, we have studied combining HA FUdR with HA mitomycin C (MMC). By giving the MMC first, we demonstrated that it is possible to increase tumor response without increasing hepatic toxicity. This effect is not as significant when the MMC is given at the end of the FUdR infusion; in cell culture, the mechanism appears to be that MMC primes the cells for FUdR toxicity. Other experiments have addressed the role of decadron in HA FUdR chemotherapy. Interestingly, decadron apparently does not have a direct effect on the tumor, nor does it synergistically increase tumor FUdR cytotoxicity. We showed that the decadron works through its antiangiogenic effect.

We have previously demonstrated that the addition of bolus intra-arterial MMC to short-term FUdR reduced the risk of developing FudR-resistance during HA infusion chemotherapy (HAIC) in a rat model of hepatic metastases of colorectal cancer (Arisawa et al., J Surg Oncol 56:75, 1994). In those experiments, in vitro testing by 3-4,5-dimethylthiazol-2,5-diphenyl-tetrazolium bromide (MMT) assay demonstrated that following exposure to HAIC with FUdR and bolus intra-arterial MMC, tumors resistance to FUdR remained sensitive to MMC. We now have shown that the in vitro tests, or chemosensitivity, correlated with in vivo response and have determined that HAIC of MMC was superior to bolus injection or combined bolus and HAIC MMC.

Metachronous hepatic metastases will occur in approximately 25% of patients who have colon cancer. These metastases, like primary solid tumors, are dependent on the development of a new blood supply, or angiogenesis, for growth. Therapy targeting angiogenesis in the treatment of colorectal hepatic metastases remains to be adequately investigated. Using our BD-IX colorectal hepatic metastases rat model, we examined the role of TNP-470, an angiogenesis inhibitor, in preventing and treating isolated colorectal hepatic metastases.

We examined the effect of giving TNP470 as an adjuvant therapy beginning just prior to tumor inoculation, and compared this with delayed therapy given for a short period of time or as prolonged treatment. Animals were followed for tumor development, wound healing complications, and survival. The peri-operative administration of TNP-470 did not impact wound healing. Maximal suppression of hepatic metastases at day 28 was seen following prophylactic TNP-470 administration. All TNP-470 regimens increased survival compared to the control group, but the median survival was significantly higher when TNP-470 was administered prophylactically. Prolonged administration also resulted in significantly fewer hepatic metastases at day 28 compared to control. Early and prolonged TNP-470 improved survival. By delaying treatment until tumors were well established (grossly identifiable at day 14), all therapeutic effect was lost.

These data suggest that angiogenesis is critical to the establishment of colorectal hepatic metastases. Perioperative anti-angiogenic therapy may block successful tumor implantation. We are currently investigating anti-angiogenic therapy combined with traditional cytotoxic chemotherapy in this model in order to maximize therapeutic effect.

The clinical assessment of tumor-associated neovascularization, as measured by microvessel density (MVD) in histologic sections, has been linked to the risk of metastasis and overall survival in many tumors including adenocarcinomas of the colon. However, little work has focused on angiogenesis associated with premalignant lesions. The adenoma has been established as the precursor of colorectal carcinoma. As such, we hypothesized that this premalignant stage would be associated with an increase in MVD.

Histologic sections were cut from archival specimens obtained from previously untreated patients who had undergone surgical resection for ascending colon adenocarcinoma, and were found to have synchronous adenomas with low grade dysplasia. MVD was quantitated in the area of the polyp and the most superficial peritumoral stroma of the invasive cancer. We found that MVD was significantly increased in both adenomas and adenocarcinomas when compared to normal mucosa. While the difference in MVD between adenomas and invasive cancers was significant, the increase in MVD from normal mucosa to adenoma was greater in magnitude than the increase in MVD between adenomas and carcinomas.

These data support our previous work involving head and neck squamous cell cancer in which a similar spectrum of histologies was evaluated in oral tongue lesions, and suggest that angiogenesis represents an early event during the development of cancer. We are currently investigating the general mechanisms involved with angio-genesis that may govern carcinogenesis.

The hypothesis that surgical outcomes are superior in hospitals that perform a greater versus lesser volume of a particular surgical procedure (positive volume-outcome relationships) and in teaching versus non-teaching centers is drawing increasing attention. The finding of such relationships has led to the suggestion that surgical procedures for cancer should be regionalized to high-volume or teaching hospitals. For a large population (Ontario, Canada) and for colorectal cancer surgery, we did not find improved outcomes in higher-volume or teaching hospitals, though there were quality concerns in all groups. We have obtained linked Surveillance, Epidemiology, and End Results (SEER)-Medicare data to analyze such relationships at the national level for colorectal and breast cancer.

We are unaware of any validated health measurement instruments to assess the quality of surgical procedures. Utilizing a modified Delphi technique, we have designed a 28-item instrument to measure quality of rectal cancer surgery. Items can be found at four points in the chart of a patient undergoing surgery for rectal cancer: the admission note, the operative report, the pathology report, and the discharge note. We have reviewed charts from patients treated in a number of Fox Chase Network hospitals. Instrument scores will be correlated with outcomes, such as operative mortality, local recurrence, and long-term survival. The ability to objectively measure quality of rectal cancer surgery would add considerably to quality assessment and improvement efforts.

Most solid tumors exhibit a steep dose-response curve such that minimal increments in drug delivery result in a significant increase in tumor response. However, drug delivery is generally limited by local or systemic toxicity. Regional chemotherapy progressed by increasing tumor response and survival in patients by delivering the same drug at higher doses locally into the liver. This treatment relies on choosing drugs that are cleared in one pass through the liver, and that are rapidly excreted systemically. However, the liver does not clear some drugs adequately, and as a result, higher doses cannot be delivered regionally. For these chemotherapeutic agents, we have studied the role of isolated liver perfusion with hemofiltration to clear the drug. Studies in large animals have shown that cisplatinum, an agent useful in a variety of tumors such as colorectal cancer, sarcoma and melanoma, can be delivered in doses three times the lethal dose, by filtering the drug from the hepatic venous outflow. The treatment can be delivered without a laparotomy and, hence, done repeatedly.

Having perfected this technique, we are now expanding its use to other drugs such as tumor necrosis factor (TNF), which has been used in isolated limb perfusion with remarkable responses for both melanoma and sarcoma. Preliminary experiments show that we can administer ten times the maximum tolerated systemic dose. Systemic administration of the drug yields only minimal responses, with systemic toxicity limiting drug delivery. To date, very large doses of TNF into the liver has not been hepatotoxic, suggesting that tumoricidal doses can be delivered into the liver without significant morbidity.

Because of the well-characterized progression of lesions from leukoplakia to invasive cancer, as well as the known "field cancerization" effect, the head and neck is an excellent model to study molecular carcinogenesis. No common tumor other than lung cancer shows a stronger association with a known carcinogen, and this influence on genetic mutations is being analyzed. The synthesis of DNA damaged by ionizing radiation is inhibited by wild type p53. This control is lost with mutant p53. Moreover, mutated p53 stimulated the multiple drug resistance gene 1 (MDR1) gene, while wild type p53 represses the gene. p53 is known to be frequently mutated in head and neck tumors. In collaboration with Dr. Klein-Szanto, we are studying the type and frequency of p53 mutations in head and neck tumors, a subset of which have been treated on the in-house phase II study of N-(phosphonacetyl)-L-aspartate (PALA), 5-FU and recombinant interferon (IFN)-alpha. We are correlating these mutations with epidemiologic and treatment information. It is our hope that these mutations may serve as prognosticators for radiation and chemosensitivity.

We are developing a prospective database to evaluate functional rehabilitation and results after neck dissections and/or radiation therapy. We hope to define the disability and the role of early intervention in the head and neck patient.

See SURGICAL ONCOLOGY report

^§   Fox Chase researcher

^a   R. Dalton: Department of Surgery, Gundersen Clinic, Ltd., LaCrosse, WI 54601

Illustrations or unpublished data in these reports should not be used without permission of the author.

Fox Chase Cancer Center

Scientific Report 1998