3-D conformal radiation therapy in upper gastrointestinal cancer. The University of Michigan experience

Radiation oncology approaches in liver malignancies

Radiation therapy plays an increasingly important role in the treatment of hepatic malignancies. There is convincing evidence of safety and efficacy employing brachytherapy (yttrium-90), three-dimensional conformal radiotherapy, intensity-modulated radiotherapy, stereotactic body radiotherapy (SBRT), and proton beam therapy (PBT) in all stages of primary and metastatic involvement in the liver. Technologic advances in tumor imaging, real-time tracking of moving targets during radiotherapy delivery, and superb radiation dose deposition control have enabled treatment of previously unapproachable lesions. Recently completed and ongoing clinical trials are refining optimal dose fractionation schedules for SBRT as monotherapy. Radioembolization as part of first-line therapy in metastatic colorectal tumors is being tested in large international trials combined with FOLFOX6 and bevacizumab, as well as in hepatocellular carcinoma with sorafenib. PBT is becoming more available as new facilities open in many countries providing particle beam therapy, which delivers unparalleled control of radiation dose close to critical structures. A major point of research is understanding how best to safely destroy tumors in the background of often fragile hepatic function from cirrhosis or heavily pretreated chemotherapy liver parenchyma. Fortunately, serious complications from radiotherapy are rare, acute toxicities are typically Common Terminology Criteria for Adverse Events v4.0 grade 1-2, with consistent response rates of 50% to 97% in the modern era.

Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC): an introduction to the scientific issues

Advances in dose-volume/outcome (or normal tissue complication probability, NTCP) modeling since the seminal Emami paper from 1991 are reviewed. There has been some progress with an increasing number of studies on large patient samples with three-dimensional dosimetry. Nevertheless, NTCP models are not ideal. Issues related to the grading of side effects, selection of appropriate statistical methods, testing of internal and external model validity, and quantification of predictive power and statistical uncertainty, all limit the usefulness of much of the published literature. Synthesis (meta-analysis) of data from multiple studies is often impossible because of suboptimal primary analysis, insufficient reporting and variations in the models and predictors analyzed. Clinical limitations to the current knowledge base include the need for more data on the effect of patient-related cofactors, interactions between dose distribution and cytotoxic or molecular targeted agents, and the effect of dose fractions and overall treatment time in relation to nonuniform dose distributions. Research priorities for the next 5-10 years are proposed.

Image-guided intensity-modulated radiation therapy for gallbladder carcinoma

PURPOSE

Clinical and technical parameter analysis of patients treated with ultrasound-based image-guided tomotherapeutic IMRT for gallbladder cancer.

METHODS AND MATERIALS

Between 8/2001 and 5/2005, 10 patients with primary tumors of the gallbladder were treated by image-guided IMRT to median doses of 59 Gy. To analyze normal tissue radiation exposure reduction using this novel approach, a virtual plan comparison between actually delivered IMRT plans and re-computed plans with identical inverse planning parameters but more conventional PTV safety margins was conducted.

RESULTS

Average CTV was 379 cm(3), with a mean initial PTV of 834 cm(3). In 9/10 patients, a boost was delivered to a mean CTV(boost) of 171 cm(3) and average PTV(boost) of 241 cm(3). One patient reported RTOG grade 3 acute toxicity. All other patients exhibited Grade 2 or lower acute toxicity. Preliminary median overall survival was 16.7 months (range 3.2-34.9 months), with 5/10 patients alive at analysis. Virtual plan comparison revealed significant organ-at-risk sparing by the enabled PTV margin reduction.

CONCLUSION

Ultrasound-based image-guided IMRT is a feasible mechanism of delivering conformal radiation doses to tumors of the gallbladder with acceptable toxicity. Early outcome data with this novel radiation planning and delivery technique are encouraging and comparable to previously reported literature.

Resin 90Y-microsphere brachytherapy for unresectable colorectal liver metastases: modern USA experience

PURPOSE

Salvage therapy for patients with unresectable colorectal liver metastases that were refractory to oxaliplatin and irinotecan was performed via radioactive microspheres. High doses of radiation were delivered to tumors from permanently implanted 90Y microspheres, delivered through the hepatic arterial vessels.

METHODS AND MATERIALS

Patients from 7 institutions were selected for treatment after screening-defined vascular access to all the tumors, and imaging-confirmed microspheres would be implanted only in the liver tumors. All patients were followed with laboratory and imaging studies at regular intervals until death. Toxicities, both acute and late, were recorded, and actuarial survival determined.

RESULTS

A total of 208 patients were treated from April 2002 to April 2005. Median follow-up of the 129 men and 79 women is 13 months (range, 1-42 months). Median survival is 10.5 months for responders but only 4.5 months in nonresponders. No treatment-related procedure deaths or radiation-related venoocclusive liver failures were found. Computed tomography partial response was 35%; positron emission tomography response of 91% and reduction in carcinoembryonic antigen of 70% were achieved.

CONCLUSIONS

In this group of heavily pretreated patients, radioactive microspheres produced an encouraging median survival, with acceptable toxicity, and a significant objective response rate, which suggests that further investigation of this approach is warranted.

Pathologic response and microdosimetry of (90)Y microspheres in man: review of four explanted whole livers

INTRODUCTION

Radioactive microsphere (90)Y therapy is increasingly used for primary and metastatic solid tumors in the liver. We present an analysis of 4 explanted livers previously treated with (90)Y microsphere agents (glass or resin). One tumor nodule was analyzed with submillimeter three-dimensional microdosimetry.

METHODS AND MATERIALS

Four patients received hepatic artery delivery of (90)Y microspheres for unresectable hepatocellular and colon cancers. Whole livers were explanted as part of lifesaving cadaveric transplant in 2 patients with hepatoma. These patients had received glass microspheres as a procedural bridge to transplant. Autopsy was performed on 2 patients with colon cancer who died of progressive metastatic disease and who had been treated with resin microspheres. Complete pathologic review was performed on each whole liver, including estimation of the response of the tumor to therapy, distribution of microspheres in the tumor and normal liver tissues, and normal-tissue radiation response. A biopsy taken from the edge of a tumor nodule was sectioned serially for three-dimensional radiation dosimetry analyses. Three-dimensional microsphere coordinates within the biopsy specimen were used to calculate dosage using a three-dimensional dose kernel. Isodose coverage of tumor and normal liver areas and total dose delivered were determined.

RESULTS

Preferential and heterogeneous deposition of microspheres was noted at the edge of tumor nodules compared with the center portion of the tumor or normal liver parenchyma. Both glass and resin microspheres delivered high cumulative doses to the tumor, which varied from 100 Gy to more than 3000 Gy. No veno-occlusive disease or widespread radiation hepatitis was seen.

CONCLUSION

Microsphere ((90)Y) therapy delivers high numbers of spheres with resulting high total doses of radiation, preferentially in the periphery of tumors. Normal liver parenchyma showed little radiation effect away from the tumors. Heterogeneous high-dose regions in the tumor were produced by both glass and resin microspheres.

Adjuvant therapy for pancreatic cancer: current treatment approaches and future challenges

The past several decades have witnessed advances in the management of pancreatic cancer; however, much remains to be accomplished. Emerging techniques in the fields of surgery, RT, chemotherapy, and immunotherapy offer hope for greater locoregional control, survival, and quality of life for these patients.

Intensity modulated radiation therapy: a clinical review

Intensity modulated radiotherapy represents a significant advance in conformal radiotherapy. In particular, it allows the delivery of dose distributions with concave isodose profiles such that radiosensitive normal tissue close to, or even within a concavity of, a tumour may be spared from radiation injury. This article reviews the clinical application of this technique to date, and discusses the practical issues of treatment planning and delivery from the clinician's perspective.

Optimization of beam orientations and weights for coplanar conformal beams in treating pancreatic cancer

In treating pancreatic cancer with external-beam radiotherapy, radiation dose given to the tumor volume is largely limited by the tolerance of the normal structures near the disease site, including the kidneys, liver, stomach, small bowel, and spinal cord. The purpose of this work was to investigate whether a coplanar conformal therapy technique with beam optimization could reduce dose to the normal tissues compared to the conventional 4-field technique; and if this was true, whether other beam arrangements were more effective than the 4-field technique in treating pancreatic cancer. In this study, 9 patients who were treated previously for T3N0 or T3N1 pancreatic cancer with external-beam therapy of 30 Gy in 10 fractions were selected. Beam orientations and weights were optimized for 4 to 6 coplanar conformal beams using a simulated annealing algorithm to minimize the kidney volume receiving more than 20 Gy. Optimized plans were compared with standard plans using a 4-field technique with respect to the isodose distributions and dose volume histograms. For the standard 4-field plans giving 30 Gy to the tumor volume, the total kidney volume above 20 Gy ranged from 10% to 35%, with a mean of 22% and a standard deviation of 7%. Optimization of the beam orientations and weights reduced this volume by approximately 2 times without a significant increase of dose to the liver, stomach, and small bowel. This indicated that the radiation toxicity to the kidneys could be reduced substantially by a careful selection of oblique beam angles and weights. Analysis of the optimized plans showed that beam arrangements which involved left and right anterior oblique beams were superior to the conventional 4-field technique for reducing the kidney dose in treating pancreatic cancer.