Assessment of contrast enhanced respiration managed cone-beam CT for image guided radiotherapy of intrahepatic tumors

PURPOSE

Contrast enhancement and respiration management are widely used during image acquisition for radiotherapy treatment planning of liver tumors along with respiration management at the treatment unit. However, neither respiration management nor intravenous contrast is commonly used during cone-beam CT (CBCT) image acquisition for alignment prior to radiotherapy. In this study, the authors investigate the potential gains of injecting an iodinated contrast agent in combination with respiration management during CBCT acquisition for liver tumor radiotherapy.

METHODS

Five rabbits with implanted liver tumors were subjected to CBCT with and without motion management and contrast injection. The acquired CBCT images were registered to the planning CT to determine alignment accuracy and dosimetric impact. The authors developed a simulation tool for simulating contrast-enhanced CBCT images from dynamic contrast enhanced CT imaging (DCE-CT) to determine optimal contrast injection protocols. The tool was validated against contrast-enhanced CBCT of the rabbit subjects and was used for five human patients diagnosed with hepatocellular carcinoma.

RESULTS

In the rabbit experiment, when neither motion management nor contrast was used, tumor centroid misalignment between planning image and CBCT was 9.2 mm. This was reduced to 2.8 mm when both techniques were employed. Tumors were not visualized in clinical CBCT images of human subjects. Simulated contrast-enhanced CBCT was found to improve tumor contrast in all subjects. Different patients were found to require different contrast injections to maximize tumor contrast.

CONCLUSIONS

Based on the authors' animal study, respiration managed contrast enhanced CBCT improves IGRT significantly. Contrast enhanced CBCT benefits from patient specific tracer kinetics determined from DCE-CT.

Outcomes following definitive stereotactic body radiotherapy for patients with Child-Pugh B or C hepatocellular carcinoma

PURPOSE

To report outcomes in patients with Child-Pugh B or C (CP B/C) hepatocellular carcinoma (HCC) treated with stereotactic body radiotherapy (SBRT).

METHODS AND MATERIALS

A prospective study of SBRT was developed for patients with CP B7 or B8 unresectable HCC, <10 cm. Selected ineligible patients (e.g. CP>B8, >10 cm) treated off-study from 2004 to July 2012 were also reviewed. Patients were excluded if they were treated as a bridge-to-liver-transplant.

RESULTS

29 patients with CP B/C HCC were treated with SBRT (median dose 30 Gy in 6 fractions) from 2004 to December 2012. The majority had CP B7 liver function (69%) and portal vein tumor thrombosis (76%). The median survival was 7.9 months (95% CI: 2.8-15.1). Survival was significantly better in patients with CP=B7 and AFP≤4491 ng/mL. Of 16 evaluable patients, 63% had a decline in CP score by ≥2 points at 3 months.

CONCLUSION

SBRT is a treatment option for selected HCC patients with small HCCs and modestly impaired (CP B7) liver function.

Hepatocellular carcinoma radiation therapy: review of evidence and future opportunities

Hepatocellular carcinoma (HCC) is a leading cause of global cancer death. Curative therapy is not an option for most patients, often because of underlying liver disease. Experience in radiation therapy (RT) for HCC is rapidly increasing. Conformal RT can deliver tumoricidal doses to focal HCC with low rates of toxicity and sustained local control in HCC unsuitable for other locoregional treatments. Stereotactic body RT and particle therapy have been used with long-term control in early HCC or as a bridge to liver transplant. RT has also been effective in treating HCC with portal venous thrombosis. Patients with impaired liver function and extensive disease are at increased risk of toxicity and recurrence. More research on how to combine RT with other standard and novel therapies is warranted. Randomized trials are also needed before RT will be generally accepted as a treatment option for HCC. This review discusses the current state of the literature and opportunities for future research.