Defining Minimum Treatment Parameters of Ablative Radiation Therapy in Patients With Hepatocellular Carcinoma: An Expert Consensus

PURPOSE

External beam radiation therapy (EBRT) is a highly effective treatment in select patients with hepatocellular carcinoma (HCC). However, the Barcelona Clinic Liver Cancer system does not recommend the use of EBRT in HCC due to a lack of sufficient evidence and intends to perform an individual patient level meta-analysis of ablative EBRT in this population. However, there are many types of EBRT described in the literature with no formal definition of what constitutes "ablative." Thus, we convened a group of international experts to provide consensus on the parameters that define ablative EBRT in HCC.

METHODS AND MATERIALS

Fundamental parameters related to dose, fractionation, radiobiology, target identification, and delivery technique were identified by a steering committee to generate 7 Key Criteria (KC) that would define ablative EBRT for HCC. Using a modified Delphi (mDelphi) method, experts in the use of EBRT in the treatment of HCC were surveyed. Respondents were given 30 days to respond in round 1 of the mDelphi and 14 days to respond in round 2. A threshold of ≥70% was used to define consensus for answers to each KC.

RESULTS

Of 40 invitations extended, 35 (88%) returned responses. In the first round, 3 of 7 KC reached consensus. In the second round, 100% returned responses and consensus was reached in 3 of the remaining 4 KC. The distribution of answers for one KC, which queried the a/b ratio of HCC, was such that consensus was not achieved. Based on this analysis, ablative EBRT for HCC was defined as a BED10 ≥80 Gy with daily imaging and multiphasic contrast used for target delineation. Treatment breaks (eg, for adaptive EBRT) are allowed, but the total treatment time should be ≤6 weeks. Equivalent dose when treating with protons should use a conversion factor of 1.1, but there is no single conversion factor for carbon ions.

CONCLUSIONS

Using a mDelphi method assessing expert opinion, we provide the first consensus definition of ablative EBRT for HCC. Empirical data are required to define the a/b of HCC.

Stereotactic Body Radiation Therapy (SBRT) for Hepatocellular Carcinoma (HCC) With Single Photon Emission Computed Tomography (SPECT) Functional Treatment Planning in Patients With Advanced Hepatic Cirrhosis

Purpose

We report on the feasibility and outcomes of liver stereotactic body radiation therapy (SBRT) for hepatocellular carcinoma (HCC) with single-photon emission computed tomography (SPECT) functional treatment planning in patients with Child-Pugh (CP) B/C cirrhosis.

Methods and Materials

Liver SPECT with 99mTc-sulfur colloid was coregistered to treatment planning computed tomography (CT) for the guided avoidance of functional hepatic parenchyma during SBRT. Functional liver volumes (FLVs) obtained from SPECT were compared with anatomic liver volumes defined on the planning CT. Radiation dose constraints were adapted exclusively to FLV. Local control, toxicity, and survival were reported with at least 6 months of radiographic follow-up. Pre- and posttransplant outcomes were analyzed in a subset of patients who completed SBRT as a bridge to liver transplant. Model of End-Stage Liver Disease was used to score hepatic function before and after SBRT completion.

Results

With a median follow-up of 32 months, 45 patients (58 lesions) with HCC and CP-B/C cirrhosis received SBRT to a median dose of 45 Gy (3-5 fractions). FLV loss (34%, P < .001) was observed in all patients, and the functional and anatomic liver volumes matched well in a control group of noncirrhotic/non-HCC patients. Despite marked functional parenchyma retraction, the amount of FLV on SPECT exposed to the threshold irradiation was significantly less than the CT liver volumes (P < .001) because of the optimized beam placement during dosimetry planning. Twenty-three patients (51%) successfully completed orthotopic liver transplant, with a median time to transplant of 9.2 months. With 91% in-field local control, the overall 2-year survival was 65% (90% after the orthotopic liver transplant), with no incidence of radiation-induced liver disease observed within 3 to 4 months or accelerated CP class migration from B to C within the first 6 months post-SBRT. Mean Model of End-Stage Liver Disease-Na score was not significantly elevated at 3-month intervals after SBRT completion.

Conclusions

Functional treatment planning with 99mTc sulfur colloid SPECT/CT allows identification and avoidance of functional hepatic parenchyma in patients with CP-B/C cirrhosis, leading to low toxicity and satisfactory transplant outcomes.

Online Adaptive MRI-Guided Stereotactic Body Radiotherapy for Pancreatic and Other Intra-Abdominal Cancers

A 1.5T MRI combined with a linear accelerator (Unity®, Elekta; Stockholm, Sweden) is a device that shows promise in MRI-guided stereotactic body radiation treatment (SBRT). Previous studies utilized the manufacturer's pre-set MRI sequences (i.e., T2 Weighted (T2W)), which limited the visualization of pancreatic and intra-abdominal tumors and organs at risk (OAR). Here, a T1 Weighted (T1W) sequence was utilized to improve the visualization of tumors and OAR for online adapted-to-position (ATP) and adapted-to-shape (ATS) during MRI-guided SBRT. Twenty-six patients, 19 with pancreatic and 7 with intra-abdominal cancers, underwent CT and MRI simulations for SBRT planning before being treated with multi-fractionated MRI-guided SBRT. The boundary of tumors and OAR was more clearly seen on T1W image sets, resulting in fast and accurate contouring during online ATP/ATS planning. Plan quality in 26 patients was dependent on OAR proximity to the target tumor and achieved 96 ± 5% and 92 ± 9% in gross tumor volume D90% and planning target volume D90%. We utilized T1W imaging (about 120 s) to shorten imaging time by 67% compared to T2W imaging (about 360 s) and improve tumor visualization, minimizing target/OAR delineation uncertainty and the treatment margin for sparing OAR. The average time-consumption of MRI-guided SBRT for the first 21 patients was 55 ± 15 min for ATP and 79 ± 20 min for ATS.

Quantifying Liver Heterogeneity via R2*-MRI with Super-Paramagnetic Iron Oxide Nanoparticles (SPION) to Characterize Liver Function and Tumor

Simple Summary

Super-paramagnetic iron oxide nanoparticles (SPIONs) are phagocytized by the hepatic Kupffer cells (KC) in the liver and shorten MRI signals within the volume of functional liver parenchyma (FLP) where KCs are found. However, malignant tumors lacking KCs exhibit minimal signal change, resulting in increasing liver heterogeneity. This study investigates whether SPIONs improve liver heterogeneity on R2*-MRI to characterize FLP and non-FLP (i.e., tumor, hepatic vessels, liver fibrosis and scarring associated with hepatic cirrhosis, prior liver-directed therapies or hepatic resection). By using SPIONs, liver heterogeneity was improved across two MRI sessions with and without an intravenous SPION injection, and the volume of FLP was identified in our auto-contouring tool. This is a desirable technique for achieving more accurate characterizations of liver function and tumors during radiation treatment planning.

Abstract

The use of super-paramagnetic iron oxide nanoparticles (SPIONs) as an MRI contrast agent (SPION-CA) can safely label hepatic macrophages and be localized within hepatic parenchyma for T2*- and R2*-MRI of the liver. To date, no study has utilized the R2*-MRI with SPIONs for quantifying liver heterogeneity to characterize functional liver parenchyma (FLP) and hepatic tumors. This study investigates whether SPIONs enhance liver heterogeneity for an auto-contouring tool to identify the voxel-wise functional liver parenchyma volume (FLPV). This was the first study to directly evaluate the impact of SPIONs on the FLPV in R2*-MRI for 12 liver cancer patients. By using SPIONs, liver heterogeneity was improved across pre- and post-SPION MRI sessions. On average, 60% of the liver [range 40–78%] was identified as the FLPV in our auto-contouring tool with a pre-determined threshold of the mean R2* of the tumor and liver. This method performed well in 10 out of 12 liver cancer patients; the remaining 2 needed a longer echo time. These results demonstrate that our contouring tool with SPIONs can facilitate the heterogeneous R2* of the liver to automatically characterize FLP. This is a desirable technique for achieving more accurate FLPV contouring during liver radiation treatment planning.

Liver transplant mortality and morbidity following preoperative radiotherapy for hepatocellular carcinoma

BACKGROUND

Radiotherapy (RT) can be used for tumor downstaging and as a bridge to transplantation in hepatocellular carcinoma (HCC), but its effect on surgical complications is unknown. Therefore, we investigated post-transplant mortality and acute readmission rates in HCC with and without preoperative RT using the National Cancer Database (NCDB).

METHODS

After exclusion, 11,091 transplant patients were analyzed, 165 of whom received RT prior to transplant. Multivariable binomial logistic regression analysis identified characteristics associated with use of RT, and factors associated with increased 30/90-day mortality and 30-day readmission, following propensity matching.

RESULTS

Although RT (median 40 Gy in 5 fractions) was more often delivered to larger tumors and advanced stages, it resulted in 59% downstaging rate, 39% pathologic complete response rate, and a median of 4 additional months to transplantation. Crude 30/90-day mortality rates were both 1.2% with preoperative RT, compared to 2.7% and 4.4% without. The 30-day readmission rate was 5.5% with RT and 10.7% without it. Propensity matched analysis demonstrated no statistical differences in 30/90-day mortality and a lower 30-day readmission rate with preoperative RT. Age >58, stage III disease, lack of transarterial chemoembolization, and shorter time to transplant independently predicted higher 90-day mortality.

CONCLUSION

Preoperative RT for HCC did not increase postoperative mortality or length of stay following liver transplant.

Proton beam therapy versus stereotactic body radiotherapy for hepatocellular carcinoma: practice patterns, outcomes, and the effect of biologically effective dose escalation

BACKGROUND

Stereotactic body radiation therapy (SBRT) and proton beam therapy (PBT) generally are safe and effective for non-operative hepatocellular carcinoma (HCC). To date, data comparing the two modalities are limited. We aimed to identify the practice patterns and outcomes of nonsurgical HCC cases treated definitively with either SBRT or PBT.

METHODS

We queried the National Cancer Database for T1-2N0 HCC patients receiving PBT or SBRT from 2004 to 2015. Patients were excluded for any treatment other than non-palliative external beam radiotherapy. A multivariable binomial regression model identified patterns of SBRT/PBT use, and propensity-matched multivariable Cox regression assessed correlates of survival.

RESULTS

A total of 71 patients received PBT and 918 patients received SBRT (median follow-up 45 months). SBRT was used in 1.8% of nonoperative early stage HCC cases in 2004 and 4.2% of cases in 2015, whereas PBT was used in 0.1-0.2% of cases every year. The median biologically effective dose (BED) for SBRT and PBT was 100 Gy10 and 98 Gy10, respectively (OR =0.70, P=0.17). Factors predictive of receiving PBT included: white race, higher comorbidity score, higher education, metropolitan residence, tumors >5 cm and recent treatment (all P<0.05). Both PBT (HR =0.48, 95% CI: 0.29-0.78) and BED ≥100 Gy10 (HR =0.61, 95% CI: 0.38-0.98) were independent predictors for longer survival.

CONCLUSIONS

Although not implying causation and requiring prospective corroboration, PBT was independently associated with longer survival than SBRT, despite being delivered to HCC patients with multiple poor prognostic factors. PBT may also allow for safer BED escalation, which also independently associated with outcomes.

Stereotactic Body Radiation Therapy: A New Strategy for Loco-Regional Treatment for Hepatocellular Carcinoma While Awaiting Liver Transplantation

BACKGROUND

Trans-arterial chemoembolization and radiofrequency ablation are commonly used for control of hepatocellular carcinoma (HCC) on liver transplant (LTx) waiting list. Stereotactic body radiation therapy (SBRT) was introduced to our institution for HCC as a bridging or downsizing therapy to LTx.

PATIENTS AND METHODS

Twenty-five HCC lesions in 22 patients were treated with SBRT while waiting for LTx from January 2010 to December 2015. Nineteen of these patients received deceased donor LTx. SBRT was defined as 40-50 Gy delivered in 4-6 fractions. Pre- and post-liver transplant outcome were analyzed in addition to the dropout rate and tumor response to SBRT.

RESULTS

Median size of original tumors was 3.2 cm (2.0-8.9), and median size of tumor after SBRT was significantly smaller at 0.9 cm (0-3.2) in the explanted livers (p < 0.01). The dropout rate was 9%, and they were only downsized patients outside of Milan criteria. Liver disease did not progress between pre- and post-SBRT except one patient. Twenty-eight percent of treated HCCs showed complete pathologic response, and 22% had extensive partial response with some residual tumor. No HCC recurrence was experienced after LTx.

CONCLUSION

SBRT is indicated to be safe, effective treatment for HCC on LTx waiting list, and it leads to satisfactory post-liver transplant outcomes.

Predictors of post-operative mortality following pancreatectomy: A contemporary nationwide analysis

e15706

Background: To date, the only curative option for pancreatic cancer is surgical resection, which only 15-20% of patients are eligible for at diagnosis. The conventional operation is a pancreaticoduodenectomy which carries a mortality risk of 3-7%. We used the National Cancer Database (NCDB) to examine surgical outcomes following pancreatectomy. Methods: We queried the NCDB from 2004-2015 for patients with stage I-III adenocarcinoma of the pancreas treated surgically. Outcomes reported were 30 and 90 day mortality, readmission within 30 days, and prolonged hospital stay. Prolonged hospital stay was defined as 17 days and 8 cases per year was used to define high volume centers. Multivariable logistic regression was used to identify predictors of all outcomes. Propensity matching was conducted to account for indication bias. Results: We identified 24,798 patients meeting eligibility criteria. The median patient age was 66 (40-90). The majority of patients were stage T3 (47%) N0 (65%) with pancreatic head lesions (83%). Fifty-seven percent of patients were treated with a Whipple procedure. Most patients (83%) were treated with surgery up front. Overall unadjusted risk of 30 day and 90 mortality ranged from 1.32-2.54% and 4.1-7.12%, respectively, depending on extent of surgery. On multivariable analysis predictors of 30 day mortality included preoperative therapy, increased age, higher comorbidity score, lower income, type of surgery, and treatment at a low volume center. Ninety day mortality was associated with preoperative therapy, increased age, increased comorbidity score, higher T stage, more extensive surgery, and treatment at a low volume center. Multivariable analysis revealed increased comorbidity score, treatment at an academic facility, and non-partial pancreatectomy as predictive of readmission. Prolonged hospital stay was associated with increasing age, decreased education, lower income, non-Caucasian race, more extensive surgery, and more remote year of treatment. Propensity matched Kaplan-Meier analysis showed improved survival with treatment at high volume centers, median survival of 23 months compared to 21 months (p = 0.0026). Conclusions: In the largest population based series to date, the 30 day mortality rates remain acceptably low with an increase seen at 90 days. The predictors of post-operative mortality seen here (age, comorbidity score, extent of surgery, and center volume) highlight the need for appropriate patient selection and physician experience to help achieve the best possible perioperative outcomes.

Survival Outcomes After Surgical Management of the Primary Tumor With and Without Radiotherapy for Metastatic Rectal Adenocarcinoma: A National Cancer Database (NCDB) Analysis

BACKGROUND

With advances in systemic therapies, the role of primary tumor resection may be of increased importance in patients with metastatic rectal cancer. The role of combining pelvic radiotherapy with surgical resection in the metastatic setting is unknown. We utilized the National Cancer Database to examine outcomes in patients with metastatic rectal adenocarcinoma with primary tumor resection with and without pelvic radiotherapy.

MATERIALS AND METHODS

We queried the National Cancer Database from 2004 to 2014 for patients with stage IV rectal adenocarcinoma receiving chemotherapy. We identified 4051 patients in that group that had primary tumor resection. Patients were then stratified by receipt of pelvic radiotherapy (yes = 1882; no = 2169) Univariable and multivariable analyses identified characteristics predictive of overall survival. Propensity-adjusted Cox proportional hazard ratios for survival were used to account for indication bias.

RESULTS

The median patient age was 63 years (range, 18-90 years) with a median follow-up of 32.3 months (range, 3.02-151.29 months). There were proportionately more patients with T3/T4 disease or N1 disease in the surgery plus radiotherapy arm. The median survival was 46.3 months versus 35.3 months in favor of addition of radiotherapy (P < .001). The 2- and 5-year overall survival was 68.4% and 24.8% for surgical resection alone compared with 77.2% and 39.6% for surgery + radiotherapy. On propensity-adjusted multivariable analysis, radiotherapy was associated with a statistically significant reduction in risk of death (hazard ratio, 0.722; 95% confidence interval, 0.0665-0.784).

CONCLUSION

This analysis indicates that in patients with metastatic rectal adenocarcinoma receiving chemotherapy, pelvic radiotherapy in addition to primary tumor resection may be of significant benefit.

Outcomes of Stereotactic Body Radiotherapy for Hepatocellular Carcinoma with Severe Cirrhosis and Ineligibility for Transplant

BACKGROUND/AIM

Our study reviewed the results of patients with hepatocellular carcinoma and Child-Pugh score 8-11 cirrhosis treated with stereotactic body radiotherapy when liver transplant was not an option.

PATIENTS AND METHODS

A retrospective review was performed on 15 patients with Child-Pugh class B and C cirrhosis treated with stereotactic body radiotherapy. The median total dose was 35 Gy in 4-5 fractions. None were listed for a liver transplant due to either being outside of the Milan criteria or to medical contraindications.

RESULTS

The overall survival was 26.7% at 6 months, with a mean survival of 152 days. The mean survival with and without ascites was 3.3 months and 8.3 months, respectively.

CONCLUSION

For hepatocellular carcinoma with cirrhosis of Child-Pugh score 8 or more, prognosis after liver stereotactic body radiotherapy was suboptimal. While irradiation achieved local tumor control, progressive cirrhosis was a common cause of death. Patients without ascites at the time of radiotherapy had the best prognosis.

Stereotactic body radiotherapy used as a bridge to liver transplant in patients with hepatocellular carcinoma and Child-Pugh score ≥8 cirrhosis

INTRODUCTION

To report on SBRT as a bridge to OLT for patients with HCC and Child-Pugh ≥8 cirrhosis.

METHODS

Retrospective review of 15 patients, treated from 2010-2017. Three patients excluded secondary to delisting from prohibitive substance. Twelve patients (17 lesions) included for final analysis. Hepatic SPECT functional treatment planning utilized.

RESULTS

The median age of 60 years with a median CP 9 and MELD 14. The median SBRT dose was 40 Gy in 5 fractions, and median tumor size was 2.3cm (1.2-5.3cm). Median follow-up and survival was 40-months and 46-months, respectively. One patient succumbed to renal/hepatic failure before OLT. Radiographic response was 80%. pCR at explant was 46%. No grade ≥ 3 acute toxicities. Median time to progression of CP ≥ 2 was 9.7-months and MELD progression was not met before OLT.

CONCLUSION

SBRT with functional treatment planning can be used safely as a bridge to OLT in select patients with CP ≥8 cirrhosis.

Stereotactic body radiotherapy (SBRT) with or without surgery for primary and metastatic liver tumors

OBJECTIVES

We report single center experience on the outcome and toxicity of SBRT alone or in combination with surgery for inoperable primary and metastatic liver tumors between 2007 and 2014.

PATIENTS AND METHODS

Patients with 1-4 hepatic lesions and tumor diameter ≤9 cm received SBRT at 46.8Gy ± 3.7 in 4-6 fractions. The primary end point was local control with at least 6 months of radiographic followup, and secondary end points were toxicity and survival.

RESULTS

Eighty-seven assessable patients (114 lesions) completed liver SBRT for hepatoma (39) or isolated metastases (48) with a median followup of 20.3 months (range 1.9-64.1). Fourteen patients underwent liver transplant with SBRT as a bridging treatment or for tumor downsizing. Eight patients completed hepatic resections in combination with planned SBRT for unresectable tumors. Two-year local control was 96% for hepatoma and 93.8% for metastases; it was 100% for lesions ≤4 cm. Two-year overall survival was 82.3% (hepatoma) and 64.3% (metastases). No incidence of grade >2 treatment toxicity was observed.

CONCLUSION

In this retrospective analysis we demonstrate that liver SBRT alone or in combination with surgery is safe and effective for the treatment of isolated inoperable hepatic malignancies and provides excellent local control rates.

A method for registration of single photon emission computed tomography (SPECT) and computed tomography (CT) images for liver stereotactic radiotherapy (SRT)

PURPOSE

To describe a simple method of coregistration of nonanatomic liver SPECT and CT images acquired in separate sessions for three-dimensional (3D)-CRT planning utilizing dual radiolabeled and radiopaque body surface markers, and evaluate the accuracy of the registration on the patient surface.

METHODS

Ten patients treated for liver metastases or hepatocellular carcinoma with stereotactic body radiation therapy or 3D-CRT were selected for this study to evaluate the SPECT∕CT registration process. All patients were positioned in a custom-molded vacuum bag on the flat table top. Nine radiopaque markers were taped to the abdominal surface in three axial planes at the level of the liver. Following CT imaging, the nine radiopaque markers were then labeled with radioactive tags, each containing 10 μCi of (99m)Tc, and SPECT images were acquired. The metric used to evaluate the registration was the fiducial registration error (FRE), defined as the root mean square of the distance between pairs of homologous markers on the CT and SPECT images. The evaluation of the registration accuracy was performed in two steps: first the minimum number of markers necessary to obtain a robust registration was optimized; second the FRE was calculated on the remaining set of unused markers. Additionally, the deformation of the patient's abdominal surface between CT and SPECT acquisition sessions was evaluated using the distances between all possible unused marker pairs on the CT and SPECT images separately. The root mean square of the CT-to-SPECT difference between those distances was used to define the deformation index (DI). The registration method was evaluated on all ten patients in addition to an anthropomorphic phantom study.

RESULTS

The minimum number of markers above which the registration was not improved by more than 1 mm was 4. The FRE, calculated over the 5 remaining markers, was 6.1 mm for the patient population and 1.8 mm for the phantom study. The DI was 5.0 mm on average over all 10 patients and correlated well with the FRE. The DI was 1.6 mm for the phantom study, which represented the imaging systems' resolution and the ability to place the CT and SPECT markers at the exact same location.

CONCLUSIONS

It is feasible to use radiolabeled and radiopaque dual body surface markers for registration of SPECT and CT images acquired in separate sessions allowing conformal avoidance of SPECT-defined functional normal liver. Point-based rigid registration accuracy on the patient surface of 6.1 mm can be achieved using 4 dual body surface markers. The main contribution to the registration error is the deformation of the abdominal surface, arising from the inability to setup the patient in the exact same position at different times on two different imaging systems, and to properly account for breathing artifacts on the CT and SPECT images.

Combination of IG-IMRT and permanent source prostate brachytherapy in patients with organ-confined prostate cancer: GU and GI toxicity and effect on erectile function

PURPOSE

To assess toxicity outcomes of image-guided intensity-modulated radiation therapy (IG-IMRT) combined with permanent prostate seed implant in a cohort of patients with localized prostate cancer.

METHODS AND MATERIALS

A retrospective analysis was performed on 67 patients with the median pretreatment prostate-specific antigen level of 5.4. The Gleason score was less than 7 in 7 patients, 7 in 52 patients, and greater than 7 in 8 patients. The median followup was 28.2 months (range, 12-89.5 months). Treatment consisted of 45 (n=65) or 50.4 Gy (n=2) at 1.8 Gy/fraction of IG-IMRT to the prostate and seminal vesicles. Eight patients had simultaneous irradiation of pelvic lymph nodes to 45 (n=65) or 50.4 Gy (n=2). After IG-IMRT, patients received transperineal prostate implant boost with either (103)Pd (n=65, the prescribed D(90) of 100 Gy) or (125)I (n=2, D(90) of 110 Gy). Eleven patients received androgen deprivation therapy with radiotherapy.

RESULTS

Toxicity higher than Grade 3 was not observed. The combined incidence of acute and late Grade 3 genitourinary toxicity was 6%. The combined incidence of acute and late Grade 3 gastrointestinal toxicity was 3%. At least one episode of gastrointestinal bleeding on followup, which could be attributed to radiation, was recorded in 14.9% of patients. For patients achieving erections before radiation, the 3-year Kaplan-Meier potency preservation rate was 66.5%.

CONCLUSIONS

The early toxicity of the combination of IG-IMRT and low-dose rate brachytherapy boost in this study was favorable.

A region growing method for tumor volume segmentation on PET images for rectal and anal cancer patients

The application of automated segmentation methods for tumor delineation on 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) images presents an opportunity to reduce the interobserver variability in radiotherapy (RT) treatment planning. In this work, three segmentation methods were evaluated and compared for rectal and anal cancer patients: (i) Percentage of the maximum standardized uptake value (SUV% max), (ii) fixed SUV cutoff of 2.5 (SUV2.5), and (iii) mathematical technique based on a confidence connected region growing (CCRG) method. A phantom study was performed to determine the SUV% max threshold value and found to be 43%, SUV43% max. The CCRG method is an iterative scheme that relies on the use of statistics from a specified region in the tumor. The scheme is initialized by a subregion of pixels surrounding the maximum intensity pixel. The mean and standard deviation of this region are measured and the pixels connected to the region are included or not based on the criterion that they are greater than a value derived from the mean and standard deviation. The mean and standard deviation of this new region are then measured and the process repeats. FDG-PET-CT imaging studies for 18 patients who received RT were used to evaluate the segmentation methods. A PET avid (PETavid) region was manually segmented for each patient and the volume was then used to compare the calculated volumes along with the absolute mean difference and range for all methods. For the SUV43% max method, the volumes were always smaller than the PETavid volume by a mean of 56% and a range of 21%-79%. The volumes from the SUV2.5 method were either smaller or larger than the PETavid volume by a mean of 37% and a range of 2%-130%. The CCRG approach provided the best results with a mean difference of 9% and a range of 1%-27%. Results show that the CCRG technique can be used in the segmentation of tumor volumes on FDG-PET images, thus providing treatment planners with a clinically viable starting point for tumor delineation and minimizing the interobserver variability in radiotherapy planning.

Chronomodulated chemotherapy and irradiation: an idea whose time has come?

The chronomodulated delivery of systemic chemotherapy given with irradiation (chemoradiation) is driven by an understanding of: the chronobiology of normal tissue response to cytotoxic insult, chronopharmacology, and by technologic advances in vascular access and in the availability of portable programmable pumps. Since circadian variation exists in the proliferative activity of acute-reacting normal tissues like the gut and bone marrow, a potential therapeutic gain can be realized by the chronomodulated administration of S-phase chemotherapeutic agents at biological times when these normal tissues are in a different cell phase and thus relatively spared (chronotolerance). The reasons for this are complex and possibly include newly described time-keeping genes that may influence the cell cycle. Another important aspect of chronotolerance is based on chronopharmacologic behavior of S-phase chemotherapeutic radiation sensitizing agents, especially 5-fluorouracil (5-FU). In this review laboratory and clinical evidence is presented for using chronomodulated 5-FU or the topoisomerase-I inhibitor, camptothecin, when best tolerated biologically. Although the main body of this work has been accomplished with pure chemotherapy schedules, there is emerging clinical evidence this approach to treatment also applies to the application of chemoradiation. This knowledge has been exploited only recently in the clinic. These data should be viewed as a call for additional studies to investigate the precise timing of systemic chemotherapeutic radio sensitizers to ameliorate toxicity and maximize treatment effect, especially with newer and potentially more toxic chemoradiation programs.

Mutations in the Ca2+ binding site of the Paracoccus denitrificans cytochrome c oxidase

Recent structure determinations suggested a new binding site for a non-redox active metal ion in subunit I of cytochrome c oxidase both of mitochondrial and of bacterial origin. We analyzed the relevant metal composition of the bovine and the Paracoccus denitrificans enzyme and of bacterial site-directed mutants in several residues presumably liganding this ion. Unlike the mitochondrial enzyme where a low, substoichiometric content of Ca2+ was found, the bacterial wild-type (WT) oxidase showed a stoichiometry of one Ca per enzyme monomer. Mutants in Asp-477 (in immediate vicinity of this site) were clearly diminished in their Ca content and the isolated mutant enzyme revealed a spectral shift in the heme a visible absorption upon Ca addition, which was reversed by Na ions. This spectral behavior, largely comparable to that of the mitochondrial enzyme, was not observed for the bacterial WT oxidase. Further structure refinement revealed a tightly bound water molecule as an additional Ca2+ ligand.

Specific cation binding site in mammalian cytochrome oxidase

Calcium ion binds reversibly with cytochrome c oxidase from beef heart mitochondria (Kd approximately 2 microM) shifting alpha- and gamma-absorption bands of heme a to the red. Two sodium ions compete with one Ca2+ for the binding site with an average dissociation constant square root[K1(Na) x K2(Na)] approximately 3.6 mM. The Ca2+-induced spectral shift of heme a is specific for mammalian cytochrome c oxidase and is not observed in bacterial or yeast aa3 oxidases although the Ca2+-binding site has been revealed in the bacterial enzyme [Ostermeier, C., Harrenga, A., Ermler, U. and Michel, H. (1997) Proc. Natl. Acad. Sci. USA 94, 10547-10553]. As His-59 and Gln-63 involved in Ca2+ binding with Subunit I of P. denitrificans oxidase are not conserved in bovine oxidase, these residues have to be substituted by alternative ligands in mammalian enzyme, which is indeed the case as shown by refined structure of bovine heart cytochrome oxidase (S. Yoshikawa, personal communication). We propose that it is interaction of Ca2+ with the species-specific ligand(s) in bovine oxidase that accounts for perturbation of heme a. The Ca2+/Na2+-binding site may be functionally associated with the exit part of 'pore B' proton channel in subunit I of mammalian cytochrome c oxidase.

4-hydroxy-2-nonenal-protein adducts and apoptosis in murine lung cells after acute ozone exposure

Ozone is a photochemically generated pollutant that can cause acute pulmonary inflammation and induce cellular injury and may contribute to the development or exacerbation of chronic lung diseases. Despite extensive investigation, the mechanisms of ozone and oxidant-induced cellular injury are still uncertain. Ozone has been reported to cause the formation of aldehydes in biological fluids that could explain many of the cellular effects caused by ozone. One of the most toxic aldehydes formed during oxidant-induced lipid peroxidation is 4-hydroxy-2-nonenal (HNE). HNE reacts primarily with Cys and secondarily with Lys and His amino acids, altering protein function and forming protein adducts that can be detected using specific adducts. In this study, we investigated whether ozone could cause the formation of HNE by assaying for HNE-protein adducts in cells isolated by lung lavage from C3H/HeJ mice exposed to 2.0 and 0.25 ppm ozone for 3 hr. Since oxidative stress and HNE have been shown to cause apoptosis we also examined the lung lavage cells for evidence of apoptosis following ozone exposure. Using a specific polyclonal antibody against HNE-amino acid adducts, two principle HNE-protein adducts were detected by Western analysis in cells obtained after ozone exposure at approximately 86-90 and 32 kDa. In addition to cell necrosis, apoptosis of lung cells was significant 3 hr after ozone exposure as detected using a Cell Death ELISA procedure and confirmed with DNA ladder and morphological analysis. The apoptotic cell injury peaked at 6 hr postexposure and decreased by 24 hr. Taken together, these results demonstrate that HNE is formed in vivo following ozone exposure and HNE appears to form specific protein adducts in lung cells. Furthermore, ozone can cause lung cell injury by an apoptotic mechanism in addition to a necrotic mechanism. Since HNE is toxic to cells and is formed as a result of ozone exposure, it may contribute to the lung cell injury following ozone exposure.

4-Hydroxynonenal-induced cell death in murine alveolar macrophages

Oxidative stress is known to cause apoptosis in many cell types, yet the mechanism of oxidative stress-induced apoptosis is not clear. Oxidative stress has been described to cause peroxidation of polyunsaturated fatty acids. 4-Hydroxynonenal (HNE) is a diffusible product of lipid peroxidation and has been shown to be toxic to cells. In this study, the effects of HNE on isolated alveolar macrophages (AM) from two murine strains (C3H/HeJ and C57BL/6J) were examined. HNE induced the formation of protein adducts in AMs from both strains of mice in a dose-dependent manner, and the amounts of HNE-protein adducts formed in cells from both strains were very similar. In the HNE dose range from 1 to 100 microM, AMs from both strains had very little necrosis as shown by trypan blue staining. However, AMs from both C3H/HeJ and C57BL/6J mice had extensive apoptosis at 100 microM HNE, but little or no apoptosis at 25 microM HNE. Furthermore, AMs from C57BL/6J mice had significant apoptosis at 50 microM HNE while AMs from C3H/HeJ mice had no significant apoptosis at this dose. At low doses of HNE (10 to 25 microM), there was induction of heme oxygenase 1. The data indicated that HNE induces apoptosis in murine macrophages, and cells from different strains of mice have different sensitivities to the HNE-induced apoptosis. The cause of the difference in susceptibility is not known, but it is possible that different stress response and/or apoptosis-regulating proteins may be in part responsible. Our observation that a product of lipid peroxidation causes apoptosis suggested that it might be a mediator for oxidative stress-induced apoptosis.