Radiation therapy for hepatocellular carcinoma: from palliation to cure

Reappraisal of repeated transarterial chemoembolization in the treatment of hepatocellular carcinoma with portal vein invasion

BACKGROUND AND AIM

This study aimed to evaluate the therapeutic efficacy and safety of repeated transarterial chemoembolization (TACE) with additional radiation therapy (RT) in hepatocellular carcinoma (HCC) with portal vein (PV) invasion.

METHODS

We performed survival analysis of consecutive HCC patients with PV invasion according to the treatment modalities after stratification by the degree of PV invasion and liver function retrospectively.

RESULTS

During 2005, 281 patients were newly diagnosed to have HCC with PV invasion at our institution. Repeated TACE or transarterial chemoinfusion (TACI) was performed in 202 (71.9%) patients and additional RT was performed for PV invasion in 43 of them. A total of 281 patients had a median survival of 5.2 months and a 2-year survival rate (YSR) of 19.2%. Repeated TACE showed significant survival benefits compared with conservative management in patients with PV branch invasion; median survival and 2-YSR was 10.2 vs 2.3 months and 33.7% vs 0% in Child-Pugh A categorized patients and 5.5 vs 1.3 months and 10.3 vs 0% in Child-Pugh B categorized patients, respectively (P < 0.001). In patients with PV branch invasion, the survival rate was significantly longer with TACE/TACI plus RT than with TACE/TACI alone both in Child-Pugh A categorized patients (1-YSR: 63.6 vs 35.6%, P = 0.031) and Child-Pugh B categorized patients (1-YSR: 66.7 vs 7.7%, P = 0.007). Repeated TACE was well tolerated in our patients, with only one dying within one month after TACE.

CONCLUSION

Repeated TACE with additional RT can be performed safely and showed a significant survival benefit in HCC patients with PV branch invasion with conserved liver function.

Synergistic effect of radiation and interleukin-6 on hepatitis B virus reactivation in liver through STAT3 signaling pathway

PURPOSE

Hepatitis B virus (HBV) reactivation can occur after radiotherapy (RT) for hepatobiliary malignancies. Our previous in vitro culture study identified interleukin-6 (IL-6) as the main bystander mediator of RT-induced HBV replication. We attempted to examine the molecular mechanism in HBV-transgenic mice.

METHODS AND MATERIALS

HBV transgenic mice were treated with whole liver RT (4 Gy daily for 5 days) with or without administration of IL-6 (400 ng twice daily for 15 days). The serum level of HBV DNA was measured using real-time polymerase chain reaction, and the IL-6 concentration was measured using enzyme-linked immunosorbent assay. The intensity of immunostaining with antibodies to HBV core protein and phosphorylated signal transducer and activator of transcription (STAT)3 in the mouse liver was qualitatively analyzed. HepG2.2.15 cells (a human hepatoblastoma cell line that persistently produces HBV DNA) were used to investigate the molecular role of IL-6 plus RT in HBV reactivation.

RESULTS

HBV reactivation was induced in vivo with IL-6 plus RT (5.58-fold) compared with RT alone (1.31-fold, p = .005), IL-6 alone (1.31-fold, p = .005), or sham treatment (1.22-fold, p = .004). HBV core protein staining confirmed augmentation of intrahepatic HBV replication. IL-6 plus RT-induced HBV DNA replication in HepG2.2.15 cells was suppressed by the STAT3 inhibitor AG490 and by transfection with dominant-negative STAT3 plasmid. Phosphorylated STAT3 staining was strongest in liver tissue from mice treated with IL-6 plus RT. The mobility shift assay demonstrated that reactivation was mediated through the interaction of phosphorylated STAT3/hepatocyte nuclear factor-3 complex with HBV enhancer 1.

CONCLUSION

RT to the liver and longer sustained IL-6 induced HBV reactivation through the STAT3 signal transduction pathway.

Effective Dose from Stray Radiation for a Patient Receiving Proton Therapy for Liver Cancer

Because of its advantageous depth-dose relationship, proton radiotherapy is an emerging treatment modality for patients with liver cancer. Although the proton dose distribution conforms to the target, healthy tissues throughout the body receive low doses of stray radiation, particularly neutrons that originate in the treatment unit or in the patient. The aim of this study was to calculate the effective dose from stray radiation and estimate the corresponding risk of second cancer fatality for a patient receiving proton beam therapy for liver cancer. Effective dose from stray radiation was calculated using detailed Monte Carlo simulations of a double-scattering proton therapy treatment unit and a voxelized human phantom. The treatment plan and phantom were based on CT images of an actual adult patient diagnosed with primary hepatocellular carcinoma. For a prescribed dose of 60 Gy to the clinical target volume, the effective dose from stray radiation was 370 mSv; 61% of this dose was from neutrons originating outside of the patient while the remaining 39% was from neutrons originating within the patient. The excess lifetime risk of fatal second cancer corresponding to the total effective dose from stray radiation was 1.2%. The results of this study establish a baseline estimate of the stray radiation dose and corresponding risk for an adult patient undergoing proton radiotherapy for liver cancer and provide new evidence to corroborate the suitability of proton beam therapy for the treatment of liver tumors.

Innovative therapy for hepatocellular carcinoma: three-dimensional high-dose photon radiotherapy

The development of three-dimensional conformal radiotherapy (3DCRT) has enabled high dose radiation to be directed to tumour with a frank sparing of the non-tumour surrounding liver parenchyma without restriction due to tumour topography and size, presence of peritumourous satellite nodules or associated segmental portal vein thrombosis. 3DCRT can be safely delivered alone or concomitantly with transarterial chemoembolization (TACE), giving very encouraging results. Efficacy is strongly related to a smaller tumor size and higher dose of radiation while toxicity closely correlates to the pre-radiotherapy liver functions and the dose delivered to the uninvolved liver. These data has led to integrate 3DCRT in the multimodal treatment of HCC as a possible curative-intent option as well as surgical resection or percutaneous procedures although phase-III controlled studies are warranted to clarify this point. This may represent a promising approach in patients who are inoperable or for whom other ablation therapies are not feasible. The next steps will be the optimization of delivery modes of this type of photon therapy, taking account that other radiation modalities such as proton beam therapy for instance might be shown as of great interest within the next few years.

Transcatheter arterial chemoembolization in combination with radiotherapy for unresectable hepatocellular carcinoma: a systematic review and meta-analysis

BACKGROUND AND PURPOSE

To evaluate the efficacy and safety of transcatheter arterial chemoembolization (TACE) plus radiotherapy (RT) for unresectable hepatocellular carcinoma (UHCC) using meta-analysis of data from the literature involving available randomized controlled trials of TACE in combination with RT compared with that of TACE alone (Therapy I versus II) in treating UHCC.

MATERIAL AND METHODS

We searched the Cochrane Library, MEDLINE, CENTRAL, EMBASE, CBMdisc, and CNKI as well as employing manual searches. Meta-analysis was performed on the results of homogeneous studies. Analyses subdivided by study design were also performed.

RESULTS

We found 17 trials involving 1476 patients. 5 of total were Randomized Controlled Trials (RCTs) and 12 were Non-randomized Controlled Clinical Trials (CCTs). In terms of quality, 5 RCTs were graded B, and 12 CCTs were graded C. Our results showed that Therapy I, compared with Therapy II, significantly improved the survival and the tumor response of patients, and was thus more therapeutically beneficial. Serious adverse events were not increased exception for total bilirubin (TB) level.

CONCLUSIONS

Therapy I was more therapeutically beneficial. However, considering the strength of the evidence, additional randomized controlled trials are needed before Therapy I can be recommended routinely.

Stereotactic body radiation therapy with or without transarterial chemoembolization for patients with primary hepatocellular carcinoma: preliminary analysis

Background

The objectives of this retrospective study was to evaluate the efficacy of stereotactic body radiation therapy (SBRT) for small non-resectable hepatocellular carcinoma (HCC) and SBRT combined with transarterial chemoembolization (TACE) for advanced HCC with portal vein tumor thrombosis (PVTT).

Methods

Thirty one patients with HCC who were treated with SBRT were used for the study. We studied 32 HCC lesions, where 23 lesions (22 patients) were treated targeting small non-resectable primary HCC, and 9 lesions (9 patients) targeting PVTT using the Cyberknife. All the 9 patients targeting PVTT received TACE for the advanced HCC. Tumor volume was 3.6–57.3 cc (median, 25.2 cc) and SBRT dose was 30–39 Gy (median, 36 Gy) in 3 fractions for consecutive days for 70–85% of the planned target volume.

Results

The median follow up was 10.5 months. The overall response rate was 71.9% [small HCC: 82.6% (19/23), advanced HCC with PVTT: 44.4% (4/9)], with the complete and partial response rates of 31.3% [small HCC: 26.1% (6/23), advanced HCC with PVTT: 11.1% (1/9)], and 50.0% [small HCC: 56.5% (13/23), advanced HCC with PVTT: 33.3% (3/9)], respectively. The median survival period of small HCC and advanced HCC with PVTT patients was 12 months and 8 months, respectively. No patient experienced Grade 4 toxicity.

Conclusion

SBRT for small HCC and SBRT combined with TACE for advanced HCC with PVTT showed feasible treatment modalities with minimal side effects in selected patients with primary HCC.

Stage IV ovarian cancer: disease site-specific rationale for postoperative treatment

OBJECTIVES

We aimed to define the site-specific patterns of treatment failure in stage IV ovarian cancer.

METHODS

Data from all consecutive Mayo Clinic patients with stage IV epithelial ovarian cancer, from 1994 through 2003, were collected and analyzed. Statistical analyses included the chi(2) test and Kaplan-Meier curves with log-rank tests.

RESULTS

Review of our patient database identified 109 patients with stage IV ovarian cancer: mean age, 62 years (range, 36-83 years); 5-year overall survival, 15%. Most patients (74%) had intraperitoneal disease at the time of relapse, 36% had pleural effusion, and 49% had extraperitoneal metastases. At the time of death 75% had intraperitoneal localizations, 51% had pleural effusion, and 46% had extraperitoneal metastases. Patients with pleural effusion were more likely to have pleural disease at relapse and at last follow-up. Extrapleural disease at the time of diagnosis predicted extrapleural disease at relapse and at last follow-up. Most patients classified as having stage IV disease by pleural cytology only, as opposed to all other patients, had intraperitoneal disease at relapse (88% vs 58.7%, P=.001) and last follow-up (88.5% vs 59.6%, P=.001). Patients having stage IV disease by pleural cytology only had survival benefit when disease was optimally debulked in the abdomen and pelvis (median survival, 3.1 years vs 1.3 years; P=.001). Patients with multiple unresectable liver metastases had poor prognosis (median survival, 1.2 years) owing to progression of liver disease.

CONCLUSIONS

Clinical trials for stage IV ovarian cancer should reflect the site-specific risks for recurrence according to disease location at diagnosis.

Treatment planning study to determine potential benefit of intensity-modulated radiotherapy versus conformal radiotherapy for unresectable hepatic malignancies

PURPOSE

To compare intensity-modulated radiotherapy (IMRT) with conformal RT (CRT) for hypofractionated isotoxicity liver RT and explore dose escalation using IMRT for the same/improved nominal risk of liver toxicity in a treatment planning study.

METHODS AND MATERIALS

A total of 26 CRT plans were evaluated. Prescription doses (24-54 Gy within six fractions) were individualized on the basis of the effective liver volume irradiated maintaining < or =5% risk of radiation-induced liver disease. The dose constraints included bowel (0.5 cm(3)) and stomach (0.5 cm(3)) to < or =30 Gy, spinal cord to < or =25 Gy, and planning target volume (PTV) to < or =140% of the prescribed dose. Two groups were evaluated: (1) PTV overlapping or directly adjacent to serial functioning normal tissues (n = 14), and (2) the liver as the dose-limiting normal tissue (n = 12). IMRT plans using direct machine parameter optimization maintained the CRT plan beam arrangements, an estimated radiation-induced liver disease risk of 5%, and underwent dose escalation, if all normal tissue constraints were maintained.

RESULTS

IMRT improved PTV coverage in 19 of 26 plans (73%). Dose escalation was feasible in 9 cases by an average of 3.8 Gy (range, 0.6-13.2) in six fractions. Three of seven plans without improved PTV coverage had small gross tumor volumes (< or =105 cm(3)) already receiving 54 Gy, the maximal prescription dose allowed. In the remaining cases, the PTV range was 9.6-689 cm(3); two had overlapped organs at risk; and one had four targets. IMRT did not improve these plans owing to poor target coverage (n = 2) and nonliver (n = 2) dose limits.

CONCLUSION

Direct machine parameter optimization IMRT improved PTV coverage while maintaining normal tissue tolerances in most CRT liver plans. Dose escalation was possible in a minority of patients.

Change in contrast enhancement of HCC on 1-month follow-up CT after local radiotherapy: an early predictor of final treatment response

BACKGROUND

The purpose of this study was to evaluate the change in contrast enhancement of HCC on 1-month follow-up CT after local radiotherapy (RT) as an early predictor of final treatment response.

MATERIALS

Fifty patients who underwent local RT for HCCs had both pre-RT and post-RT CT scans including 1-month follow-up CT. We assessed the final treatment response by using the change in maximal tumor size on 6-12-month follow-up CT scan after RT. We also evaluated the change in tumor enhancement between pre-RT and 1-month follow-up CT scans.

RESULTS

A final treatment response was achieved in 27 (54%) of 50 patients, who showed either a complete response (n=11) or a partial response (n=16). Compared with non-responsive patients (n=23), responsive patients showed a significant decrease in tumor enhancement on 1-month follow-up CT after RT in both objective and subjective analyses (each P<0.001).

CONCLUSION

The change in contrast enhancement of HCC seen on the 1-month follow-up CT in patients after local RT may be used as an early predictor of final treatment response.

Pilot clinical trial of localized concurrent chemoradiation therapy for locally advanced hepatocellular carcinoma with portal vein thrombosis

BACKGROUND

Patients with advanced hepatocellular carcinoma (HCC) with portal vein thrombosis (PVT) have a particularly grave prognosis. In the current study, an attempt was made to localize chemoradiation therapy (CCRT) followed by hepatic arterial infusion chemotherapy (HAIC) in patients with locally advanced HCC with PVT and good reserve liver function. The objective of the current study was to evaluate the therapeutic effect of localized CCRT followed by HAIC as a new treatment modality for these patients.

METHODS

Between January 1998 and December 2003, 40 patients were recruited. Concurrent regional chemotherapy using an intra-arterial implanted port plus localized external beam radiotherapy was performed with a total of 45 gray (Gy) over 5 weeks with conventional fractionation and hepatic arterial infusion of 5-fluorouracil (5-FU), which was administered during the first and fifth weeks of radiotherapy. One month after localized CCRT, HAIC with 5-FU and cisplatin was administered every 4 weeks.

RESULTS

One month after localized CCRT, an objective response was observed on the intention-to-treat analysis in 18 of 40 patients (45%). The actuarial 3-year overall survival rate was 24.1% and the median survival time was 13.1 months from the start of radiation treatment. Responders after localized CCRT demonstrated significantly better survival (P = .033) than nonresponders.

CONCLUSIONS

The substantial response rate as well as median survival time noted in the current study encourages the use of this new approach in patients with locally advanced HCC with PVT.

Advances in experimental and translational research in the treatment of hepatocellular carcinoma

Hepatocellular cancer (HCC) is the fifth-leading cause of cancer and the third-leading cause of cancer related deaths world-wide. Current treatment options are limited, as HCC has been shown to be a highly resistant type of cancer to most current treatment modalities. Novel approaches are being explored in the fields of gene therapy, viral oncolytics, radioembolization, and several new biologic therapies. This article summarizes these recent clinical findings and discusses what role they will have in the future treatment of HCC.

Combination of PTEN and gamma-ionizing radiation enhances cell death and G(2)/M arrest through regulation of AKT activity and p21 induction in non-small-cell lung cancer cells

PURPOSE

To identify the role of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) during gamma-ionizing radiation (gamma-IR) treatment for non-small-cell lung cancer cells.

METHODS AND MATERIALS

Wild-type PTEN or mutant forms of PTEN plasmids were transfected to construct stable transfectants of the NCI-H1299 non-small-cell lung cancer cell line. Combined effects of PTEN expression and IR treatment were tested using immunoblot, clonogenic, and cell-counting assays. Related signaling pathways were studied with immunoblot and kinase assays.

RESULTS

At steady state, stable transfectants showed almost the same proliferation rate but had different AKT phosphorylation patterns. When treated with gamma-IR, wild-type PTEN transfectants showed higher levels of cell death compared with mock vector or mutant transfectants, and showed increased G(2)/M cell-cycle arrest accompanied by p21 induction and CDK1 inactivation. NCI-H1299 cells were treated with phosphosinositide-3 kinase (PI3K)/AKT pathway inhibitor (LY29002), resulting in reduced AKT phosphorylation levels. Treatment of NCI-H1299 cells with LY29002 and gamma-IR resulted in increased cell-cycle arrest and p21 induction. Endogenous wild-type PTEN-containing NCI-H460 cells were treated with PTEN-specific siRNA and then irradiated with gamma-IR: however reduced PTEN levels did not induce cell-cycle arrest or p21 expression.

CONCLUSIONS

Taken together, these findings indicate that PTEN may modulate cell death or the cell cycle via AKT inactivation by PTEN and gamma-IR treatment. We also propose that a PTEN-PI3K/AKT-p21-CDK1 pathway could regulate cell death and the cell cycle by gamma-IR treatment.

Estimate of radiobiologic parameters from clinical data for biologically based treatment planning for liver irradiation

PURPOSE

The Radiation Therapy Oncology Group (RTOG) is initiating a few new hypofractionation regimens (RTOG 0438) to treat liver cancer patients. To evaluate the radiobiologic equivalence between different regimens requires reliable radiobiologic parameters. The purpose of this work is to estimate a plausible set of such parameters for liver tumors and to design new optimized dose fractionation schemes to increase patient survival.

METHODS AND MATERIALS

A model was developed to fit clinical survival data from irradiation of a series of primary liver patients. The model consists of six parameters including radiosensitivity parameters alpha and alpha/beta, potential doubling time T(d). Using this model together with the Lyman model for calculations of the normal tissue complication probability, we designed a series of hypofractionated treatment strategies for liver irradiation.

RESULTS

The radiobiologic parameters for liver tumors were estimated to be: alpha/beta = 15.0 +/- 2.0 Gy, alpha = 0.010 +/- 0.001 Gy (-1), T(d) = 128 +/- 12 day. By calculating the biologically effective dose using the obtained parameters, it is found that for liver patients with an effective liver volume of approximately 45% the dose fractionation regimens suggested in RTOG 0438 can be escalated to higher dose for improved patient survival ( approximately 80% at 1 year) while keeping the normal tissue complication probability to less than 10%.

CONCLUSIONS

A plausible set of radiobiologic parameters has been obtained based on clinical data. These parameters may be used for radiation treatment planning of liver tumors, in particular, for the design of new treatment regimens aimed at dose escalation.

Potential prognostic benefits of radiotherapy as an initial treatment for patients with unresectable advanced hepatocellular carcinoma with invasion to intrahepatic large vessels

OBJECTIVES

To examine the efficacy and prognostic benefits of radiotherapy (RT) in patients who have unresectable advanced hepatocellular carcinoma (HCC) with invasion to intrahepatic large vessels (IHLVs).

METHODS

Sixty-eight patients who had advanced HCC with invasion to IHLVs were studied. Thirty-two consecutive patients initially received 3-dimensional conformal RT for HCC invasion to IHLVs. Tumor response, prognostic factors, and survival were studied in the patients given RT. Prognostic factors and survival were assessed in the study group as a whole. Data were analyzed using the Kaplan-Meier method, univariate analysis, and a Cox model.

RESULTS

The rate of objective response to RT was 48%. Predictors of survival in the patients who received RT were a hepatic function of Child-Pugh class A (p = 0.0263) and a response to RT (p = 0.0121). In the study group as a whole, independent predictors of survival in a Cox model were multinodular HCC (p = 0.007), inferior vena caval invasion (p = 0.001), a serum alpha-fetoprotein level of >1,000 ng/ml (p = 0.032), and the performance of RT (p < 0.001). Notably, the median survival of the nonresponders to RT (n = 15) was significantly longer than that of the patients who received no treatment for HCC (n = 21; 7.0 vs. 3.4 months, p = 0.0014).

CONCLUSION

RT is considered an effective initial treatment for HCC invasion to IHLVs, and may offer survival benefits, even in nonresponders, because of the induction of stable disease.

Early detection of liver cancer: diagnosis and management

Hepatocellular carcinoma (HCC) is the fifth most common cause of cancer deaths worldwide, and the incidence is rising. Despite a wide array of treatment options, fewer than half of candidates for potentially curative treatments receive them. The diagnosis and management of HCC require a multidisciplinary approach involving various clinical specialties. The foundation of diagnosis is high-quality imaging, with MRI being the test of choice. Some patients also require guided biopsy when MRI is equivocal. Treatment options depend upon the tumor stage and the degree of underlying synthetic dysfunction. Potentially curative treatments include surgical resection and transplantation. Other treatments that prolong survival include percutaneous ablation and transarterial chemoembolization. A new oral agent, sorafenib, was recently shown to prolong survival in patients with advanced HCC. By increasing surveillance and treatment of HCC, outcomes for these patients may be improved.

Changes in quality of life and its related factors in liver cancer patients receiving stereotactic radiation therapy

PURPOSE

Due to the increasing use of stereotactic radiotherapy (SRT) in treating advanced liver cancer patients, the purpose of this longitudinal study was to explore the changes and factors related to quality of life (QOL) in patients receiving SRT treatment.

MATERIALS AND METHODS

Liver cancer patients receiving SRT in northern Taiwan were recruited. The patients were followed up during the baseline pre-SRT and the first 6 weeks of SRT (T0 to T6) in assessing functional status and symptom severity, while depression, selected laboratory data, and QOL were assessed every 3 weeks (T0, T3, and T6). Generalized estimating equations (GEE) analysis was used to explore the significant factors related to the change in QOL.

RESULTS

Ninety-nine patients with advanced liver cancer completed seven interviews. The results showed that QOL during SRT was moderate and relatively stable. Performance functional status, depression, the level of albumin, and overall symptom severity were significantly associated with changes in QOL. A further analysis of the relationships between individual symptom severity and QOL revealed that fatigue, lack of appetite, pain, and nausea were the symptoms most affecting QOL across the 6 weeks of SRT.

CONCLUSION

Liver cancer patients had stable and moderate levels of QOL during SRT. Factors related to QOL across the 6 weeks were multi-dimensional. Both overall symptom severity and selected individual symptoms were important to patients' QOL. These factors should all be carefully assessed and clinically treated to enhance liver cancer patients' QOL during SRT.

Intercepting Radiotherapy Using a Real-Time Tumor-Tracking Radiotherapy System for Highly Selected Patients With Hepatocellular Carcinoma Unresectable With other Modalities

PURPOSE

To assess the clinical outcome of intercepting radiotherapy, in which radiotherapy is delivered only when a tumor in motion enters a target area, using a real-time tumor-tracking radiotherapy (RTRT) system for patients with hepatocellular carcinoma who were untreatable with other modalities because the tumors were adjacent to crucial organs or located too deep beneath the skin surface.

METHODS AND MATERIALS

Eighteen tumors, with a mean diameter of 36 mm, were studied in 15 patients. All tumors were treated on a hypofractionated schedule with a tight margin for setup and organ motion using a 2.0-mm fiducial marker in the liver and the RTRT system. The most commonly used dose of radiotherapy was 48 Gy in 8 fractions. Sixteen lesions were treated with a BED(10) of 60 Gy or more (median, 76.8 Gy).

RESULTS

With a mean follow-up period of 20 months (range, 3-57 months), the overall survival rate was 39% at 2 years after RTRT. The 2-year local control rate was 83% for initial RTRT but was 92% after allowance for reirradiation using RTRT, with a Grade 3 transient gastric ulcer in 1 patient and Grade 3 transient increases of aspartate amino transaminase in 2 patients.

CONCLUSIONS

Intercepting radiotherapy using RTRT provided effective focal high doses to liver tumors. Because the fiducial markers for RTRT need not be implanted into the tumor itself, RTRT can be applied to hepatocellular carcinoma in patients who are not candidates for other surgical or nonsurgical treatments.

Individualized image guided iso-NTCP based liver cancer SBRT

A highly individualized stereotactic body radiotherapy (SBRT) strategy was developed to allow a wide spectrum of patients with liver cancer to be treated. This phase I/II study encompasses individualization of immobilization, radiation planning, PTV margin determination, image guidance strategy and prescription dose. Active breathing control breath hold is used to immobilize the liver when feasible. Image guidance strategies include orthogonal MV images and orthogonal kV fluoroscopy using the diaphragm for a surrogate for the liver, and kV cone beam CT using the liver or tumour for guidance. The prescription dose is individualized to maintain the same estimated risk of radiation-induced liver disease (RILD), based on a normal tissue complication probability (NTCP) model, with a maximum permitted dose of 60 Gy in 6 fractions. Since August 2003, 79 patients with hepatocellular carcinoma (33), intrahepatic cholangiocarcinoma (12) and liver metastases (34) were treated. The median tumour volume was 293 cm3 (2.9-3 088 cm3). The median prescribed dose was 36.6 Gy (24.0 Gy-57.0 Gy) in 6 fractions. The median effective liver volume irradiated was 45% (9-80%). Sixty percent of patients were treated with breath hold to immobilize their liver. Intra-fraction reproducibility (sigma) of the liver with repeat breath holds was excellent (1.5 mm); however inter-fraction reproducibility (sigma) was worse (3.4 mm). Image guidance reduced the residual systematic and random setup errors significantly.

Image-guided radiotherapy: rationale, benefits, and limitations

Technological advances have greatly enhanced the specialty of radiation oncology by allowing more healthy tissue to be spared for the same or better tumour coverage. Developments in medical imaging are integral to radiation oncology, both for design of treatment plans and to localise the target for precise administration of radiation. At planning, definition of the tumour and healthy tissue is based on CT, augmented frequently with MRI and PET. At treatment, three-dimensional soft-tissue imaging can also be used to localise the target and tumour motion can be tracked with fluoroscopic imaging of radio-opaque markers implanted in or near the tumour. These developments allow changes in tumour position, size, and shape that take place during radiotherapy to be measured and accounted for to boost geometric accuracy and precision of radiation delivery. Image-guided treatment also enhances uniformity in doses administered in a population of patients, thus improving our ability to measure the effect of dosimetric and non-dosimetric factors on tumour and healthy tissue outcomes in clinical trials. Increased precision and accuracy of radiotherapy are expected to augment tumour control, reduce incidence and severity of toxic effects after radiotherapy, and facilitate development of more efficient shorter schedules than currently available.