Treatment of liver metastases with a combination of chemotherapy and hyperfractionated external radiation therapy

Radiotherapy of Liver Malignancies. From Whole Liver Irradiation to Stereotactic Hypofractionated Radiotherapy

Aims and background

Until recently radiotherapy of hepatic malignancies has played a limited role due to the well-known limited radiotolerance of the liver. The aim of this paper is to review the available data on the risk of radiation-induced liver disease (RILD) and to define the modern role of radiotherapy in the management of patients with metastatic or primary liver malignancies.

Methods

The advent of three-dimensional conformal treatment planning with dose-volume histogram analysis has made the study of partial liver irradiation possible. Limited portions of the liver may withstand high doses of radiation with minimal risk of RILD. Patients with solitary unresectable liver tumors may be treated with high-dose radiotherapy with curative intent. Recently, the feasibility of stereotactically guided treatment techniques with a single fraction or few treatment sessions has been explored in numerous institutions.

Results

The radiation tolerance of the whole liver found by several investigations is in the order of approximately 30 Gy, which seriously restricts its clinical application. The role of whole liver irradiation therefore appears of limited benefit in the palliation of patients with multiple liver metastases. The use of three-dimensional conformal techniques has made partial liver irradiation possible to doses in the 70–80 Gy range with conventional fractionation. At least two published series have reported improved local control and survival rates with dose escalation with three-dimensional conformal radiotherapy in patients with unresectable liver metastases. Similar outcomes have been recently reported with single dose (or hypofractionated) stereotactic radiotherapy both in metastatic and primary hepatic malignancies with minimal morbidity. Accurate target delineation and treatment reproducibility are the key to the success of this novel treatment approach, and specific treatment planning techniques and patient setup procedures must be developed to implement it.

Conclusions

Stereotactic high-dose radiotherapy is technically feasible for the treatment of inoperable liver malignancies, with the potential of high local control and low morbidity. Definitive evidence on the clinical advantages of this technique over other more established treatments can only be gathered from well-designed clinical studies.

External-beam radiotherapy in the management of liver metastases

This review discusses the importance of palliation of liver metastases. Although colorectal cancer comprises the majority of patients with metastatic liver disease, a number of other malignancies can be involved. Palliation of metastatic disease to liver has generally not included the use of external-beam radiotherapy because of restricted liver tolerance to radiotherapy. However, more recently, treatment policies have evolved to more generous use of palliative radiotherapy with utilization of tumor boost doses to partial liver volumes. This has resulted in improvement in palliation and a suggestion of improved survival with higher radiotherapy doses, which have been well tolerated by small volumes of liver.

Current treatment for colorectal cancer metastatic to the liver

Surgery is currently the only available treatment option which offers the potential for cure for patients with liver metastases from colorectal cancer. Of those who undergo a potentially curative operation for their primary tumour but subsequently recur, almost 80% will develop evidence of metastatic disease within the liver. Greater experience and improvements in technique in liver surgery, with an increasingly aggressive surgical approach to metastatic colorectal cancer to the liver, has resulted in prolonged disease-free survival with 5-year rates varying from 21% to 48%. In order to increase these numbers further and to treat patients not eligible for surgical therapy, new treatment modalities and strategies have been developed. This review presents an update of the current treatment for colorectal disease metastatic to the liver.

The effect of fluorodeoxyuridine on sublethal damage repair in human colon cancer cells

Although 5-fluoro-2'-deoxyuridine (FdUrd) has been combined with hyperfractionated radiation therapy in clinical trials, the optimal method of delivering radiation therapy is not yet known. To determine the importance of the time interval between fractions on the survival of tumor cells exposed to FdUrd, we studied the effect of FdUrd on sublethal damage repair in HT29 human colon cancer cells in culture. Cells were exposed to clinically achievable concentrations of FdUrd (10-100 nM) for 14 hr followed by either single dose (8-12 Gy) or split dose (4-6 Gy x 2) external cobalt irradiation. The interval between radiation fractions was varied from 0.5 to 6 hr. FdUrd impaired sublethal damage repair in a dose dependent fashion. FdUrd had no effect on the induction of DNA double strand breaks (DSB's), but significantly reduced the rate of the repair of DNA DSB's. Exposure to 100 nM FdUrd decreased intracellular TTP pools but elevated dATP pools. These findings suggest that FdUrd may decrease sublethal damage repair by perturbing nucleotide triphosphate pools, which leads to a decrease in the ability of the cell to repair DNA DSB's. Furthermore, they suggest that hyperfractionated irradiation will be superior to once daily treatment when combined with regional delivery of FdUrd.

Treatment of cancers involving the liver and porta hepatis with external beam irradiation and intraarterial hepatic fluorodeoxyuridine

A Phase I/II clinical trial was designed for patients with malignancies of the liver and porta hepatis. This protocol employed three concepts: a) boost treatment to gross tumor within the liver for selected patients, determined by the dose-volume histogram (DVH) of the normal liver that would be irradiated by boost treatment; b) concurrent use of intraarterial hepatic 5-fluorodeoxyuridine (FdUrd) as a radiosensitizer; and c) hyperfractionation (1.5 Gy fractions given bid greater than 4 hr apart). This report describes the results of treatment of the first 33 patients entered onto this study, with a minimum follow-up of 1 year. Twenty patients received only whole liver irradiation (33 Gy). Thirteen patients were treated with whole liver irradiation (30 Gy) plus a 15 Gy (6 patients) or 30 Gy (7 patients) boost (total 45 Gy and 60 Gy to the tumor, respectively). Forty-eight percent of the evaluable patients (14/29) had an objective response, based on CT scan. The median duration of response was 8 months. The chief toxicities were fatigue, nausea, gastritis, and diarrhea, which were less than or equal to grade 2 in severity. Two patients developed mild radiation hepatitis which was treated successfully with diuretics. These data suggest that the treatment of intrahepatic malignancies can be guided by the concept of DVH analysis of the normal liver to allow the safe administration of doses of radiation that are potentially tumoricidal and are well above those that would be predicted to be tolerable for the whole liver.

The treatment of hepatic metastases from colorectal cancer with radiation therapy alone or combined with chemotherapy or misonidazole

In summary, whole liver RT alone is generally well tolerated and, in most cases, offers some palliative benefit. It is difficult to determine its ultimate impact on survival since many patients treated with this single modality have extra-hepatic disease. In addition, the dose of radiation which the liver can tolerate is not adequate to control gross disease. The addition of chemotherapy (systemic and/or intra-hepatic) appears promising. However, further follow-up and randomized trials need to be performed before this is known with certainty. The use of misonidazole in the dosages and techniques employed by the RTOG did not appear to enhance overall survival. More innovative techniques of delivering RT, including intraoperative brachytherapy, radiolabeled antibodies, and hyperfractionated external beam RT require further investigation in order to determine their efficacy.

Regional treatment of hepatic metastases and hepatocellular carcinoma

Hepatic metastases represent a common site of dissemination for a number of primary malignancies related in part to the dual blood supply, large blood flow, and receptive environment of the hepatic parenchyma. Although this review focuses on regional therapy, we have included sections on systemic therapy to better interpret the results with intrahepatic therapy. We will also discuss the efficiency of hepatic arterial ligation, embolization, and radiotherapy of hepatic metastases. Primary gastrointestinal neoplasms are particularly prone to produce hepatic metastases. Because colorectal carcinoma metastasizes to the liver in up to 70% of patients with advanced disease, the treatment of hepatic metastases is a relevant topic. We will discuss the systemic and regional therapy of colorectal, gastric, and gallbladder cancers. Breast carcinoma and malignant melanoma frequently metastasize to the liver, and we have described systemic and regional treatments of these diseases. Because sarcomas are often treated by regional therapy, we have included a section on the treatment of hepatic sarcomas. Neuroendocrine tumors (carcinoid and islet cell), although often slow growing, frequently metastasize to the liver and then cause symptomatic problems. Much of the work done with embolization and hepatic ligation in the treatment of hepatic metastases has been performed in neuroendocrine tumors, and these studies, as well as the systemic and regional chemotherapy of hepatic metastases, will be described. The last section concerns the treatment of hepatocellular carcinoma. We have outlined the staging systems used. We then detail the results of systemic and intrahepatic therapy, embolization, and hepatic ligation in the treatment of hepatocellular carcinoma. Because hepatic metastases are a frequent problem, many patients are available for clinical investigation. It is hoped that newer strategies for the treatment of liver metastases will lead to higher response rates and perhaps control of local disease. These therapeutic approaches may also give us leads to the treatment of systemic disease.

Hepatic arterial chemotherapy for primary and metastatic liver cancers

Hepatic arterial chemotherapy represents a means of selectively exposing hepatic tumor to cytotoxic agents. Although 5-fluoro-2'-deoxyuridine has been shown to generate a higher response rate in the treatment of colorectal liver metastases than that achieved by intravenous infusion, responses are largely incomplete and rarely of long duration. This review describes the rationale for the use of the thymidine analogs 5-bromo-2'-deoxyuridine and 5-iodo-2'-deoxyuridine in hepatic arterial infusions and indicates how combination therapy adding radiotherapy, specifically with hepatic arterially administered yttrium-90 microspheres, might generate a new, more efficient and effective therapeutic approach.