Focused radiation hepatitis after Bragg-peak proton therapy for hepatocellular carcinoma: CT findings

Gene identification and functional characterization of a Δ12 fatty acid desaturase in Tetrahymena thermophila and its influence in homeoviscous adaptation to low temperature

Homeoviscous adaptation in poikilotherms is based in the regulation of the level of desaturation of fatty acids, variation in phospholipids head groups and sterol content in the membrane lipids, in order to maintain the membrane fluidity in response to changes in environmental temperature. Increased proportion of unsaturated fatty acids is thought to be the main response to low-temperature acclimation, which is mostly achieved by fatty acid desaturases. Genome analysis of the ciliate Tetrahymena thermophila and a gene knockout approach has allowed us to identify one Δ12 FAD and to study its activity in the original host and in a yeast heterologous expression system. The "PUFA index" -relative content of polyunsaturated fatty acids compared to the sum of saturated and monounsaturated fatty acid content- was ~57% lower at 15 °C and 35 °C in the Δ12 FAD gene knockout strain (KOΔ12) compared to WT strain. We characterized the role of T. thermophila Δ12 FAD on homeoviscous adaptation and analyzed its involvement in cellular growth, cold stress response, and membrane fluidity, as well as its expression pattern during temperature shifts. Although these alterations allowed normal growth in the KOΔ12 strain at 30 °C or higher temperatures, growth was impaired at temperatures of 20 °C or lower, where homeoviscous adaptation is impaired. These results stress the importance of Δ12 FAD in the regulation of cold adaptation processes, as well as the suitability of T. thermophila as a valuable model to investigate the regulation of membrane lipids and evolutionary conservation and divergence of the underlying mechanisms.

FDG-Avid Focal Liver Reaction From Proton Therapy in a Patient With Primary Esophageal Adenocarcinoma

A 25-year-old man with IgA deficiency was treated with 2 months of chemotherapy and proton therapy for gastroesophageal junction adenocarcinoma. Restaging PET/CT 18 days posttherapy demonstrated 2 new foci of increased FDG uptake in the left hepatic lobe, which were favored to represent radiation injury as opposed to new metastases. Follow-up MRI with contrast 2 weeks later demonstrated hypoenhancement and T1/T2 hypointensity in the liver, without restricted diffusion, which correlated with the dominant FDG-avid focus. The hepatic lesions resolved on subsequent FDG PET/CT and MRI studies, confirming the diagnosis of acute radiation injury.

The Time Course of Dynamic Computed Tomographic Appearance of Radiation Injury to the Cirrhotic Liver Following Stereotactic Body Radiation Therapy for Hepatocellular Carcinoma

This study aimed to evaluate the dynamic computed tomographic (CT) appearance of focal radiation injury to cirrhotic liver tissue around the tumor following stereotactic body radiation therapy (SBRT) for hepatocellular carcinoma (HCC). Seventy-seven patients with 92 HCCs were observed for >6 months. Sixty-four and 13 patients belonged to Child-Pugh class A and B, respectively. The median SBRT dose was 48 Gy/4fr. Dynamic CT scans were performed in non-enhanced, arterial, portal, and venous phases. The median follow-up period was 18 months. Dynamic CT appearances were classified into 3 types: type 1, hyperdensity in all enhanced phases; type 2, hypodensity in arterial and portal phases; type 3, isodensity in all enhanced phases. Half of the type 2 or 3 appearances significantly changed to type 1, particularly in patients belonging to Child-Pugh class A. After 3-6 months, Child-Pugh class B was a significant factor in type 3 patients. Thus, dynamic CT appearances were classified into 3 patterns and significantly changed over time into the enhancement group (type 1) in most patients belonging to Child-Pugh class A. Child-Pugh class B was a significant factor in the non-enhancement group (type 3).

Stereotactic body radiotherapy-induced arterial hypervascularity of non-tumorous hepatic parenchyma in patients with hepatocellular carcinoma: potential pitfalls in tumor response evaluation on multiphase computed tomography

Purpose

To evaluate temporal changes in contrast enhancement patterns of non-tumorous hepatic parenchyma with a focus on arterial hypervascularity on multiphase computed tomography (CT) in patients with hepatocellular carcinoma (HCC) treated with stereotactic body radiotherapy (SBRT).

Methods

We retrospectively identified 61 patients who had undergone multiphase contrast-enhanced CT at one, three, and six months after SBRT. Irradiated versus non-irradiated liver parenchyma was delineated by cross-correlation with the dose-volume histogram of SBRT plan. Serial changes in the contrast enhancement patterns of the irradiated versus non-irradiated liver parenchyma were evaluated by two abdominal radiologists in consensus. We compared the frequency of the contrast enhancement patterns according to the follow-up period using the Fisher-Freeman-Halton exact test.

Results

The irradiated non-tumorous hepatic parenchyma showed that the prevalence of arterial hypervascularity increased during the follow-up period (P<.01): 11.5% (7/61) in one, 45.9% (28/61) in three, and 54.1% (33/61) in six months. Contrast wash-out on the delayed phase was uncommon: 1.6% (1/61) in one, 3.3% (2/61) in three, and 0% in six months.

Conclusion

The incidence of arterial hypervascularity of the irradiated hepatic parenchyma gradually increased until six months after SBRT, which could interfere with the accurate evaluation of treatment response. The lack of wash-out on the delayed phase in the hypervascular area would distinguish SBRT-related change from residual/recurred HCC.

Microscopic and macroscopic tumor and parenchymal effects of liver stereotactic body radiotherapy

PURPOSE

To describe the histologic and volumetric changes in normal liver tissue after stereotactic body radiotherapy (SBRT) for liver metastases.

METHODS AND MATERIALS

Pre- and post-SBRT imaging studies were analyzed to evaluate the effect of SBRT on normal liver volume (NLV) in 15 patients treated in a prospective clinical trial. Two other patients underwent exploratory surgery after SBRT and histologic analyses of the irradiated liver were performed to characterize the pathologic effects of SBRT.

RESULTS

In the 15 patients studied quantitatively, the total NLV had decreased transiently at 2-3 months after SBRT and then began to regenerate at 3-8 months after SBRT. The median NLV reduction at the maximal observed effect was 315 cm(3) (range, 125-600) or 19% (range, 13-33%). Among the several dosimetric parameters evaluated, the strongest linear correlation was noted for the NLV percentage receiving 30 Gy as a predictor of maximal NLV reduction (r(2) = 0.72). The histologic changes observed 2 and 8 months after SBRT demonstrated distinct zones of tissue injury consistent with localized veno-occlusive disease.

CONCLUSION

The well-demarcated focal parenchymal changes after liver SBRT (demonstrated both radiographically and histologically) within the high-dose zone are consistent with a threshold dose-induced set of phenomena. In contrast, the more global effect of NLV reduction, which is roughly proportional to whole organ dose parameters, resembles more closely an effect determined from radiobiologically parallel architecture. These observations suggest that modeling of normal tissue effects after liver SBRT might require different governing equations for different classes of effects.

Radiation therapy for hepatocellular carcinoma: from palliation to cure

Technologic advances have provided the means to deliver tumoricidal doses of radiation therapy (RT) to patients with unresectable hepatocellular carcinoma (HCC) while avoiding critical normal tissues, providing the opportunity to use RT for curative intent treatment of HCC. For the current report, the expanded role of external beam RT in the setting of HCC from palliation to cure was reviewed. A systematic literature search was undertaken using the MEDLINE data base and secondary references to identify peer-reviewed, English-language articles that reported clinical outcomes after external beam RT alone or in combination with other treatments for HCC. Abstracts from the 2005 American Society of Clinical Oncology, American Society for Therapeutic Radiology and Oncology, American Gastrointestinal Association, and Society of Surgical Oncology Gastrointestinal Cancer Symposium also were included in the search. More than 60 articles reporting on clinical outcomes among patients who received RT for HCC have been published since 1990, including 20 articles that described unique sets of at least 15 patients. RT was used for palliation, to improve local control, and with curative intent in a wide spectrum of patients who most often were unsuitable for surgery and other treatments. Pain reduction following RT was noted in approximately 75% of patients with bone metastases from HCC who received RT. For patients with liver-confined disease treated with conformal RT, proton beam RT, and/or image guided RT with or without transarterial chemoembolization (TACE), local control response rates ranged from 40% to 90%, and the median survival ranges from 10 months to 25 months. For patients with HCC who had portal vein thrombus, the median survival after RT to treat the thrombus and/or the hepatic tumor with or without TACE ranged from 5.3 months to 9.7 months. Although outcomes after high-dose conformal RT for liver-confined HCC were excellent, the potential survival benefit of RT should be tested in randomized controlled trials that require international collaboration.

The triple-phase CT image appearance of post-irradiated livers

OBJECTIVE

To evaluate the sequential CT appearance of the liver after hepatic irradiation and to investigate the correlation between CT findings and radiation-induced hepatic injury.

MATERIAL AND METHODS

The triple-phase CT images of 18 patients with hepatocellular carcinomas (HCC) after hepatic irradiation were retrospectively reviewed (in total 41 CT studies). The high-dose region within the liver was defined as the area receiving more than 90% of the prescribed irradiation dose. The mean radiation dose was 55.5 Gy. Density changes and patterns of enhancement in the high-dose region were classified as three types: type I, constant low-density change in all phases; type II, low-density change in both pre-contrast and arterial phases, and iso-density change in the portal phase; type III, low- or iso-density change in the pre-contrast phase, low- or high-density change in the arterial phase, and persistent high-density change in the portal phase. The interval between completion of radiotherapy and the CT examinations ranged from 9 to 469 days, with a mean of 147 days.

RESULTS

Nine of the 41 CT studies presented with type I, 9 with type II, and 16 with type III CT findings. The mean interval between completion of radiotherapy and the appearance of types I, II, and III CT findings were 74, 183, and 220 days, respectively. The interval was significantly shorter for type I findings than for type II and type III. The difference in interval was not significant between type II and type III. A type I finding with constant low-density change in the high-dose region of the liver was the most common pattern of CT findings within the first 3 months after hepatic irradiation. Either types II or III findings were frequently seen after 3 months.

CONCLUSION

The sequential CT appearance and the density changes may indicate correlation with the pathogenesis of veno-occlusive disease.

Superparamagnetic iron oxide-enhanced MR imaging for early and late radiation-induced hepatic injuries

Superparamagnetic iron oxide (SPIO)-enhanced MRI was performed in twenty-one patients undergoing proton-beam radiotherapy for hepatocellular carcinomas. Patients were divided into two groups: early and late phase hepatic injuries. Each group was investigated 3 to 9 weeks and 4 to 65 months after the start of irradiation, respectively. T(1)-weighted, T(2)-weighted, and T(2)*-weighted images were obtained before and after SPIO administration. In all postcontrast sequences in the early phase, irradiated livers demonstrated relatively higher intensity than nonirradiated livers and the radiation-to-liver contrast-to-noise ratio (C/N) was improved. Postcontrast T(2)*-weighted images showed the highest C/N. In the late phase, the irradiated areas showed high intensity on T(2)-weighted images and low intensity on T(1)-weighted images without SPIO, while high intensity on T(1)-weighted images with SPIO. The C/N increased with SPIO in all sequences and postcontrast T(2)-weighted images showed the highest C/N in the late phase. SPIO-enhanced MRI is useful to evaluate this entity both in the early and late phase of clinical studies.

Changes in the liver parenchyma after proton beam radiotherapy: evaluation with MR imaging

The objective of this study was to describe magnetic resonance (MR) findings with a 1.5T imager for hepatic parenchymal changes after proton beam radiotherapy. Thirty-two patients who received proton radiotherapy with doses of 50-87 Gy underwent MR imaging 1-75 months (mean 22 months) after the start of irradiation. Axial T(2), T(1)-weighted imaging, and a dynamic study after a gadolinium injection were performed. The irradiated areas showed hypointense in T(1)-weighted images, hyperintense in T(2)-weighted images, and intense and prolonged enhancement on the dynamic study (maximum relative enhancement 441.8%+/-263.3 vs. surrounding liver 145.6%+/-67.7, p<0.0001). T(2) values of the irradiated areas were 50.6 to 65.8 msec greater than in the surrounding liver (p<0.005). The values increased with time, being significantly greater 13 months or longer after the beginning of the therapy than after a period of less than 3 months (p<0.05). Pathologic examinations (n = 3) indicated that the irradiated areas were composed of collapsed lobules with hepatic small vein occlusions, and rich extracellular matrices which retained extracellular fluid. MR imaging can demonstrate hepatic parenchymal changes after proton beam radiotherapy, and show the changes are irreversible.

Acute radiation-induced hepatic injury: evaluation by triphasic contrast enhanced helical CT

We report a case of radiation-induced hepatic injury as a complication of localized abdominal radiotherapy for epidural spread of non-Hodgkin's lymphoma. The liver was evaluated by triphasic contrast enhanced helical CT scan. Hepatic biopsy demonstrated changes typical of veno-occlusive disease. The pattern of hepatic enhancement resulting from the radiation-induced veno-occlusive process is discussed.

CT evaluation of hepatic injury following proton beam irradiation: appearance, enhancement, and 3D size reduction pattern

PURPOSE

The purpose of this study was to investigate the long-term imaging appearances of hepatic injury following proton beam irradiation. The time-attenuation curves, time of appearance and recovery, and 3D size reduction pattern are described in patients of different ages and genders with different irradiation doses, irradiated portals, and Child groups.

METHOD

Forty-six patients with hepatocellular carcinoma underwent 50 to 84 Gy proton beam irradiation in periods of 14-52 days. CT including noncontrast and dynamic study was performed every 3 months starting 3 weeks after the end of irradiation. The 3D volume measurement of areas of radiation-induced hepatic injury was performed through incremental dynamic CT images in every follow-up study. CT follow-up study of the patients was done for 12-76 months.

RESULTS

Radiation-induced hepatic injury was observed as low attenuation areas on noncontrast CT and enhanced areas on dynamic study in the regions corresponding to the irradiation portals. Of our cases, 67.5% showed the appearance of radiation hepatitis in 3-4 weeks and 95.3% in 3-4 months after the end of irradiation. In both periods, there was a significant delay in the female patients. The time-attenuation curve showed an early and prolonged enhancement of the irradiated regions. The volume reduction pattern of the injured areas was found to be longstanding, exponential, and directed from periphery to the center.

CONCLUSION

Early appearance of radiation-induced hepatic injury was found only to be gender dependent, with a tendency to occur with higher irradiated doses; no other parameters affected this phenomenon in our cases. Disappearance of the injured areas, if present, takes a long time (at least 42 months).

Radiation tolerance of cirrhotic livers in relation to the preserved functional capacity: analysis of patients with hepatocellular carcinoma treated by focused proton beam radiotherapy

PURPOSE

To determine the preserved functional capacity of the liver as a probable determinant of radiation tolerance in patients with cirrhosis and hepatocellular carcinoma, who underwent proton beam radiotherapy.

MATERIALS AND METHODS

We reviewed computed tomographic (CT) scans of 26 patients with cirrhosis and hepatocellular carcinoma during a period of 12-27 months after proton beam radiotherapy. Tumors were treated with focused proton beams with target doses of 140-186 TDF (time, dose, and fractionation). We measured the degree of hypertrophy of the untreated liver volume by measuring the total liver volume and the treated liver volume which was radiologically identified on contrast-enhanced CT scans. The risk of radiation-induced liver failure was estimated using the prediction score (PS) originally used for estimating posthepatectomy liver failure, substituting the planned treated liver volume for the resection liver volume.

RESULTS

The degree of hypertrophy ranged from -19% to 51%, and was significantly positively correlated with the ratio of the planned treated liver volume to the functional liver volume. The PS agreed well with observed radiation tolerance in 21 patients, but underestimated the tolerance in 5. This underestimation was diminished when the PS was recalculated using the identified untreated liver volume in lieu of the planned untreated liver volume.

CONCLUSION

As in surgical treatment, radiation tolerance of the cirrhotic liver after focused treatment is closely related to the preserved functional capacity of the identified untreated liver volume, which shows compensatory hypertrophy following radiotherapy.

Clearance of parenchymal tumors following radiotherapy: analysis of hepatocellular carcinomas treated by proton beams

Clearance of a parenchymal tumor following radiotherapy was determined by using follow-up CT scans of 18 hepatocellular carcinoma tumors treated with focused proton beams. Regression analysis of the daily decrement (DD) and the diameter (D) of a tumor mass in each CT observation interval, DD = a*Db, showed that the exponent b was 3.0 or larger in early periods and 2.0 or smaller in late periods. This suggests that the clearance depends initially on the tumor volume, subsequently on the tumor surface area, and then it becomes much more moderate, possibly due to radiation damage to the parenchymal tissues.