Charles A Enke

University of Nebraska Medical Center, Omaha, Nebraska, United States

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Publications (109)367.93 Total impact

  • S Zhou · X Zhu · M Zhang · D Zheng · Q Zhang · Y Lei · S Li · J Driewer · S Wang · C Enke
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    ABSTRACT: Randomness in patient internal organ motion phase at the beginning of non-gated radiotherapy delivery may introduce uncertainty to dose received by the patient. Concerns of this dose deviation from the planned one has motivated many researchers to study this phenomenon although unified theoretical framework for computing it is still missing. This study was conducted to develop such framework for analyzing the effect. Two reasonable assumptions were made: a) patient internal organ motion is stationary and periodic; b) no special arrangement is made to start a non -gated radiotherapy delivery at any specific phase of patient internal organ motion. A statistical ensemble was formed consisting of patient's non-gated radiotherapy deliveries at all equally possible initial organ motion phases. To characterize the patient received dose, statistical ensemble average method is employed to derive formulae for two variables: expected value and variance of dose received by a patient internal point from a non-gated radiotherapy delivery. Fourier Series was utilized to facilitate our analysis. According to our formulae, the two variables can be computed from non-gated radiotherapy generated dose rate time sequences at the point's corresponding locations on fixed phase 3D CT images sampled evenly in time over one patient internal organ motion period. The expected value of point dose is simply the average of the doses to the point's corresponding locations on the fixed phase CT images. The variance can be determined by time integration in terms of Fourier Series coefficients of the dose rate time sequences on the same fixed phase 3D CT images. Given a non-gated radiotherapy delivery plan and patient's 4D CT study, our novel approach can predict the expected value and variance of patient radiation dose. We expect it to play a significant role in determining both quality and robustness of patient non-gated radiotherapy plan.
    Medical Physics 06/2015; 42(6):3343. DOI:10.1118/1.4924417 · 2.64 Impact Factor
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    ABSTRACT: Successful radiation therapy requires multi-step processes susceptible to unnecessary delays that can negatively impact clinic workflow, patient satisfaction, and safety. This project applied process improvement tools to assess workflow bottlenecks and identify solutions to barriers for effective implementation. We utilized the DMAIC (define, measure, analyze, improve, control) methodology, limiting our scope to the treatment planning process. From May through December of 2014, times and dates of each step from simulation to treatment were recorded for 507 cases. A value-stream map created from this dataset directed our selection of outcome measures (Y metrics). Critical goals (X metrics) that would accomplish the Y metrics were identified. Barriers to actions were binned into control-impact matrices, in order to stratify them into four groups: in/out of control and high/low impact. Solutions to each barrier were then categorized into benefit-effort matries to identify those of high benefit and low effort. For 507 cases, the mean time from simulation to treatment was 235 total hours. The mean process and wait time were 60 and 132 hours, respectively. The Y metric was to increase the ratio of all non-emergent plans completed the business day prior to treatment from 47% to 75%. Project X metrics included increasing the number of IMRT QAs completed at least 24 hours prior to treatment from 19% to 80% and the number of non-IMRT plans approved at least 24 hours prior to treatment from 33% to 80%. Intervals from simulation to target contour and from initial plan completion to plan approval were identified as periods that could benefit from intervention. Barriers to actions were binned into control-impact matrices and solutions by benefit-effort matrices. The DMAIC method can be successfully applied in radiation therapy clinics to identify inefficiencies and prioritize solutions for the highest impact.
    Medical Physics 06/2015; 42(6):3438. DOI:10.1118/1.4924814 · 2.64 Impact Factor
  • S Wang · J Driewer · D Zheng · Y Lei · Q Zhang · X Zhu · S Li · C Enke · B Xu · S Zhou
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    ABSTRACT: The purpose of this study is to investigate the LINAC repetition-rate (dose-rate) dependence of OCTAVIUS 1000SRS liquid ionization chamber (LIC) array for patient specific QA of SRT plans delivered with flattening-filter-free (FFF) beams. 1) The repetition-rate dependence of 1000SRS was measured in a phantom constructed with 5-cm solid water above and below the array for build-up and backscatter. A 0.3cc calibrated ion chamber was also placed along the central axis 2.3cm below the center chamber of the array for normalizing LINAC output fluctuation. The signals from the center chamber of the array under different repetition rates in the range of 400-2400 MU/min for 6xFFF and 10xFFF beams on a Varian TrueBeamSTx LINAC, normalized by the independent chamber readings, were analyzed for the array response dependence on repetition rates. 2) Twelve Step-and-shoot IMRS QA plans (6xFFF and 10xFFF) were delivered to the array under different repetition rates for analysis and comparison. 3) The absolute doses measured by the center chamber were compared to measurements using an independent ionization chamber with the identical setup, taken as the gold standard. 4) The correction factors based on the actual delivery repetition rate were applied to the measurements, and the results were compared again to the gold standard. 1) The 1000SRS array exhibited repetition-rate dependence for FFF beams, up to 5% for 6xFFF and 10% for 10xFFF; 2) The array showed clinically-acceptable repetition-rate dependence for regular flattened beams; 3) This repetition-rate dependence significantly affected the measurement accuracy, thereby affecting IMRS QA results; 4) By applying an empirical repetition-rate correction, the corrected measurements agreed better with the gold standard ion chamber measurements. OCTAVIUS 1000SRS LIC array exhibited considerable repetition-rate dependence for FFF beams, which will affect the accuracy of the absolute QA measurements, especially for IMRS plans with the step-and-shoot technique.
    Medical Physics 06/2015; 42(6):3440. DOI:10.1118/1.4924822 · 2.64 Impact Factor
  • S Zhou · X Zhu · M Zhang · D Zheng · Y Lei · Q Zhang · S Li · J Driewer · S Wang · C Enke
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    ABSTRACT: Half-beam block is a field matching technique frequently used in radiotherapy. With no setup error, a well calibrated linac, and no internal organ motion, two photon fields can be matched seamlessly dosimetry-wise with their central axes passing the match line. However, in actual clinical situations, internal organ motion is often inevitable. This study was conducted to investigate its influence on radiation dose to patient internal points directly under the matching line. A clinical setting is modeled as two half-space (x<0 and x<0) radiation fields that are turned on sequentially with a time gap of integer times of the patient internal organ motion period (T0). Our point of interest moves with patient internal organs periodically and evenly in and out of the radiation fields, resulting in an average location at x=0. When the fields are delivered without any motion management, the initial phase of the point's movement is unknown. Statistical methods are used to compute the expected value ( ) and variance (σ) of the point dose given the uncertainty. Analytical solutions are obtained for and s of dose received by a point directly under the match line. is proportional to the total beam-on time (T1), and σ demonstrates previously unknown periodic behavior. /<Dσ has local maximums (minimums) when T1 is 2n*T0 ((2n+1)*T0) (n is an integer) with an upper envelope scales as 1/T1. Worst case scenario the point dose can be zero or double of the expected value. We have analytically analyzed the internal organ motion effect on radiation dose received by a patient internal point directly under a half-beam block match line. Our results help us to better understand this phenomenon and facilitate the reduction of point dosimetric uncertainties in our clinical practice.
    Medical Physics 06/2015; 42(6):3451. DOI:10.1118/1.4924870 · 2.64 Impact Factor
  • Q Zhang · J Driewer · S Wang · S Li · D Zheng · X Zhu · W Zhen · A Wahl · C Lin · R Thompson · S Zhou · C Enke
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    ABSTRACT: The accuracy of Varian PerfectPitch six degree of freedom (DOF) robotic couch was examined using Varian Isocal phantom and cone-beam CT (CBCT) system. CBCT images of the Isocal phantom were taken at different pitch and roll angles. The pitch and roll angles were varied from 357 to 3 degrees in one degree increments by input from service console, generating a total of 49 combinations with couch angle (yaw) zero. The center positions of the 16 tungsten carbide BBs contained in the Isocal were determined with in-house image processing software. Expected BBs positions at different rotation angles were determined mathematically by applying a combined translation/rotation operator to BB positions at zero pitch and roll values. A least square method was used to minimize the difference between the expected BB positions and their measured positions. In this way rotation angles were obtained and compared with input values from the console. A total of 49 CBCT images with voxel sizes 0.51 mm × 0.51 mm × 1 mm were used in analysis. Among the 49 calculations, the maximum rotation angle differences were 0.1 degree, 0.15 degree, and 0.09 degree, for pitch, roll, and couch rotation, respectively. The mean ± standard-deviation angle differences were 0.028±0.001 degree, -0.043±0.003 degree, and -0.009±0.001 degree, for pitch, roll, and couch rotation, respectively. The maximum isocenter shifts were 0.3 mm, 0.5 mm, 0.4 mm in x, y, z direction respectively following IEC6127 convention. The mean isocenter shifts were 0.07±0.02 mm, -0.05±0.06 mm, and -0.12±0.02 mm in x, y and z directions. The accuracy of the Varian PerfectPitch six DOF couch was studied with CBCTs of the Isocal phantom. The rotational errors were less than 0.15 degree and isocenter shifts were less than 0.5 mm in any direction. This accuracy is sufficient for stereotactic radiotherapy clinical applications.
    Medical Physics 06/2015; 42(6):3274. DOI:10.1118/1.4924133 · 2.64 Impact Factor
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    ABSTRACT: BACKGROUND The androgen receptor (AR) plays a dominant role in the pathogenesis of prostate cancer. 5-Radioiodo-3′-O-(17β-succinyl-5α-androstan-3-one)-2′-deoxyuridin-5′-yl phosphate (RISAD-P) is an AR-targeting reagent developed for noninvasive assessment of AR and proliferative status of the AR-expressing tumors, and for molecular radiotherapy with Auger electron-emitting radionuclides. In this study, the preclinical toxicity and targeting potential of RISAD-P was evaluated.METHODS Effects of nonradioactive ISAD-P and RISAD-P labeled with 123I, 124I, and 125I were evaluated in male mice. Expanded-acute single dose toxicity studies, hematologic toxicity, liver and kidney function, pharmacokinetics, biodistribution, and imaging studies were conducted. Imaging and pilot therapy studies were conducted in transgenic mice.RESULTSRISAD-P is not toxic at doses projected for clinical use. Its tissue distribution compares favorably with the distribution reported for 18F-dihydrotestosterone derivatives. RISAD-P has excellent prostate cancer targeting properties. One hour after 125IRISAD-P administration, nearly 10% of the injected dose is associated with prostate tumor. The tumor clearance is biphasic and plateaus between 24 and 48 hr post-injection. The estimated radiation doses calculated for 1 g tumor using the MIRD convention are well within the therapeutic range with values of 170, 250, 1,240 Gy × MBq−1 × g−1 for 125I-, 123I-, and 124I-labeled RISAD-P, respectively. The transient uptake of radioactivity is observed in the genitourinary tract and stomach. Without the potassium iodide blockade, thyroid uptake is also observed.CONCLUSIONS Biodistribution, toxicity, and radiation dosimetry studies suggest that RISAD-P holds characteristics of a promising candidate for imaging of AR expression and tumor proliferation, as well as molecular radiotherapy for metastatic or locally, regionally advanced prostate cancer. Prostate © 2014 Wiley Periodicals, Inc.
    The Prostate 01/2015; 75(1). DOI:10.1002/pros.22885 · 3.57 Impact Factor
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    ABSTRACT: Radiation therapy is a staple treatment for pancreatic cancer. However, owing to the intrinsic radioresistance of pancreatic cancer cells, radiation therapy often fails to increase survival of pancreatic cancer patients. Radiation impedes cancer cells by inducing DNA damage, which can activate cell cycle checkpoints. Normal cells possess both a G1 and G2 checkpoint. However, cancer cells are often defective in G1 checkpoint due to mutations/alterations in key regulators of this checkpoint. Accordingly, our results show that normal pancreatic ductal cells respond to ionizing radiation (IR) with activation of both checkpoints whereas pancreatic cancer cells respond to IR with G2/M arrest only. Overexpression/hyperactivation of Rac1 GTPase is detected in the majority of pancreatic cancers. Rac1 plays important roles in survival and Ras-mediated transformation. Here, we show that Rac1 also plays a critical role in the response of pancreatic cancer cells to IR. Inhibition of Rac1 using specific inhibitor and dominant negative Rac1 mutant not only abrogates IR-induced G2 checkpoint activation, but also increases radiosensitivity of pancreatic cancer cells through induction of apoptosis. These results implicate Rac1 signaling in the survival of pancreatic cancer cells following IR, raising the possibility that this pathway contributes to the intrinsic radioresistance of pancreatic cancer.
    Oncotarget 10/2014; 1(21). DOI:10.18632/oncotarget.2500 · 6.36 Impact Factor
  • International journal of radiation oncology, biology, physics 09/2014; 90(1):S390-S391. DOI:10.1016/j.ijrobp.2014.05.1251 · 4.26 Impact Factor
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    ABSTRACT: Purpose/Objective(s) Different prescription (Rx) isodose lines are used in stereotactic radiosurgery (SRS) and stereotactic radiation therapy (SRT). This study aimed at investigating the dosimetric effect of Rx lines selection on normal tissues for Linac-based SRS and SRT. Materials/Methods Eight SRS or SRT patients (11 tumors) previously treated in our institution with dynamic conformal arcs and a Rx line at 90% were randomly selected. For each patient, alternative plans with 80%, 70%, 60%, and 50% Rx lines were retrospectively generated, yielding a total of 40 plans for the 8 patients. For each plan, PTV coverage was assessed and deemed acceptable based on our clinical standard. Two absolute doses corresponding to the 50% and 30% dose for the original 90% Rx line plan were calculated and denoted as D50 and D30. The volumes of D50 and D30 were calculated for all plans. R50 and R30 were computed as the volume ratios of D50s and D30s of alternative plans (50-80% Rx line) to D50 and D30 of clinical plans (90%), and used to quantify normal tissue sparing. Results The average PTV volume for those 11 tumors is 7cc (range from 0.4cc to 37.3 cc). The conformity indexes of those 40 plans range from 1.1 to 1.6. R50 (mean ± standard deviation) are 0.685±0.200, 0.621±0.148, 0.641±0.125,0.790±0.126,1±0 for Rx line plans of 50, 60, 70, 80 and 90%, respectively. R30 are 0.770±0.205, 0.702±0.163, 0.711±0.135, 0.816±0.109, 1±0 for the same cases. The lowest R50 and R30 are achieved when the Rx isodose lines are 70% or 60%, indicating sharper dose falloff and better normal tissue sparing with such Rx line selections. At the same time, decreasing Rx lines inherently result in increasing hot spot within the target (RTOG dose homogeneity index increases from 1.11±0.02 for the 90% Rx case to 1.99±0.07 for the 50% Rx case). Thus, part of PTV is covered by higher dose when the Rx lines decreases, resulting in higher tumor control probability (TCP) when the PTV dose coverage is similar. In other words, compared with plans with 90% Rx line, Rx isodose lines of 60 or 70% yield plans with potentially higher TCP and lower normal tissue complication probabilities (NTCP). ANOVA (Analysis of variance) analysis finds the R50 and R30 differences between the alternative plans (50-80% Rx lines) and clinical plan (90% Rx line) are significant (p<0.001). Conclusions By decreasing the Rx isodose line, OARs and normal tissues receive less radiation dose. While an 80% Rx line also results in normal tissue sparing compared with 90% Rx line, greater sparing will be achieved with 60 or 70% Rx line, in which case dose heterogeneity will increase, but this could potentially yield an increased TCP while at the same time lowering NTCP. On the other hand, the gain of increased TCP and decreased NTCP needs to be weighted over possible tumor necrosis due the larger maximum dose within the target.
    International journal of radiation oncology, biology, physics 09/2014; 90(1):S907. DOI:10.1016/j.ijrobp.2014.05.2578 · 4.26 Impact Factor
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    International journal of radiation oncology, biology, physics 09/2014; 90(1):S87-S88. DOI:10.1016/j.ijrobp.2014.05.479 · 4.26 Impact Factor
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    ABSTRACT: Objectives: A new dosimetric variable, dose dropping speed (DDS), was proposed and used to evaluate normal tissue sparing among stereotactic radiosurgery (SRS) plans with different prescription isodose lines. Methods: Forty plans were generated for 8 intracranial SRS cases, prescribing to isodose levels (IDLs) ranging from 50% to 90% in 10% increments. Whilst maintaining similar coverage and conformity, plans at different IDLs were evaluated in terms of normal tissue sparing using the proposed DDS. The DDS was defined as the greater decay coefficient in a double exponential decay fit of the dose drop-off outside the PTV, which models the steep portion of the drop-off. Provided that the prescription dose covers the whole PTV, a greater DDS indicates better normal tissue sparing. Results: Among all plans, the DDS was found the lowest for the prescription at 90% IDL and the highest for the prescription at 60% or 70%. Beam profile slope change in penumbra and its field size dependence were explored and given as the physical basis of the findings. Conclusions: A variable was proposed for SRS plan quality evaluation. Using this measure, prescriptions at 60% and 70% IDLs were found to provide best normal tissue sparing. Advances in knowledge: A new variable was proposed based on which normal tissue sparing was quantitatively evaluated, comparing different prescription IDLs in SRS.
    British Journal of Radiology 08/2014; DOI:10.1259/bjr.20140362 · 2.03 Impact Factor
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    ABSTRACT: Purpose: The dose dropping speed (DDS) in normal tissue was proposed to assess plan quality. It was tested in stereotactic radiosurgery (SRS) cases. Methods: The DDS was tested with a total 40 plans for 8 SRS cases. Dynamic conformal arc plans were generated for each case, with prescription dose to isodose levels (IDL) ranging from 50% to 90% with 10% increment to cover the PTV. Forty non-overlapping rind structures of 1mm thickness were created layer by layer from each PTV surface. The average dose in each rind was calculated and fitted with a double exponential function (DEF) of the distance from the PTV surface, which models the steep and moderate portions of the average dose curve in normal tissue. The parameter charactering the steep portion of the average dose curve in the DEF quantifies the DDS in the normal tissue receiving high dose. Provided that the prescription dose covers the whole PTV, a greater DDS indicates better normal tissue sparing. Results: Among all plans, the DDS was found to be the smallest for prescription of 90% IDL and reached a higher plateau region for prescription to 60% or 70%. The ratio of the highest slope to that of 90% prescription was 1.68±0.35. Analyzed with ANOVA, the DDS difference between the plans with prescription to 60% or 70% IDLS and those with prescription to 90% IDL were found significant (p<0.01). This can be attributed to the field size and penumbra slope change with different prescription levels. The trend became less pronounced with increasing PTV size due to less change of field profile for larger field size. Conclusion: A method was proposed to estimate dose dropping speed as a measure of plan quality. Based on this measure, prescriptions to 60% and 70% IDLs were found to provide best normal tissue sparing.
    Medical Physics 07/2014; 41(7):157. DOI:10.1118/1.4888064 · 2.64 Impact Factor
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    ABSTRACT: Human liver has an unusual sensitivity to radiation that limits its use in cancer therapy or in preconditioning for hepatocyte transplantation. Because the characteristic veno-occlusive lesions of radiation-induced liver disease do not occur in rodents, there has been no experimental model to investigate the limits of safe radiation therapy or explore the pathogenesis of hepatic veno-occlusive disease. We performed a dose-escalation study in a primate, the cynomolgus monkey, using hypofractionated stereotactic body radiotherapy in 13 animals. At doses ≥40 Gy, animals developed a systemic syndrome resembling human radiation-induced liver disease, consisting of decreased albumin, elevated alkaline phosphatase, loss of appetite, ascites, and normal bilirubin. Higher radiation doses were lethal, causing severe disease that required euthanasia approximately 10 weeks after radiation. Even at lower doses in which radiation-induced liver disease was mild or nonexistent, latent and significant injury to hepatocytes was demonstrated by asialoglycoprotein-mediated functional imaging. These monkeys developed hepatic failure with encephalopathy when they received parenteral nutrition containing high concentrations of glucose. Histologically, livers showed central obstruction via an unusual intimal swelling that progressed to central fibrosis. The cynomolgus monkey, as the first animal model of human veno-occlusive radiation-induced liver disease, provides a resource for characterizing the early changes and pathogenesis of ven occlusion, for establishing nonlethal therapeutic dosages, and for examining experimental therapies to minimize radiation injury.
    International journal of radiation oncology, biology, physics 12/2013; 88(2). DOI:10.1016/j.ijrobp.2013.10.037 · 4.26 Impact Factor
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    ABSTRACT: The NCCN Guidelines for Prostate Cancer provide multidisciplinary recommendations on the clinical management of patients with prostate cancer. This report highlights notable recent updates. Radium-223 dichloride is a first-in-class radiopharmaceutical that recently received approval for the treatment of patients with symptomatic bone metastases and no known visceral disease. It received a category 1 recommendation as both a first-line and second-line option. The NCCN Prostate Cancer Panel also revised recommendations on the choice of intermittent or continuous androgen deprivation therapy based on recent phase III clinical data comparing the 2 strategies in the nonmetastatic and metastatic settings.
    Journal of the National Comprehensive Cancer Network: JNCCN 12/2013; 11(12):1471-1479. · 4.18 Impact Factor
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    ABSTRACT: The immunogenicity of a cellular immunotherapy using genetically modified vaccines to express α(1,3)galactosyl epitopes (αGal) was evaluated in advanced prostate cancer (PC) patients. In this dose escalation phase I study, we report safety, feasibility, and immunologic data of an immunotherapy composed of 2 human PC cell lines engineered to express αGal epitopes (HyperAcute-Prostate, HAP, NewLink Genetics). Eight patients received up to 12 biweekly vaccinations with HAP. Enrolled patients (aged range, 53-85 y) had American Joint Committee on Cancer stage IV, any T, any N, M1, Eastern Cooperative Oncology Group PS≤2, at least 1 prior hormonal treatment and <3 prior chemotherapies, adequate bone marrow and organ function, and albumin ≥3.0 g/dL. Serum IgG antibodies to synthetic peptides overexpressed in PC were determined by enzyme-linked immunosorbent assay. Results indicate that HAP immunotherapy induced humoral immune responses to autoantigens in 2 of 8 patients. These patients developed IgG antibody to multiple epitopes overexpressed in PC after immunization. These responding patients received higher doses of the immunotherapy suggesting a dose response. Two immunogenic proteins (prostate-specific membrane antigen, hepsin) belong to the extracellular molecules family participating in malignant cell invasion. Median overall survival for patients was 25.1 months with 1 patient surviving over 70 months with stable PSA and bone metastasis before expiring of other causes. Three of 8 patients showed PSA stabilization (>100 d). In conclusion, HAP immunotherapy induces IgG responses to epitopes from autoantigens overexpressed in PC suggesting dose-dependent effect. HAP represents a viable immunotherapy approach to induce immune responses against tumor cells and may provide clinical benefit with minimal toxicity.
    Journal of immunotherapy (Hagerstown, Md.: 1997) 11/2012; 36(1). DOI:10.1097/CJI.0b013e3182780abc · 4.01 Impact Factor
  • C Lin · M E Charlton · C K Brown · C A Enke · F R Loberiza
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    ABSTRACT: grade 3 and 6% had grade 4 toxicity. Grade 3 and higher toxicities are summarized in the table. All patients completed chemotherapy except 8% missed and 12% needed dose reduction for the last cycle. A total of 14% patients needed hospitalization and 12% needed transfusion. Overall, severe myelotoxicity decreased from 60% to 33% for cervical cancer. Grade 2 or higher myelotoxicity decreased from 45% to 36% for rectal cancer. The toxicity rates for anal cancer are comparable at 55% to the previously reported rate of 51%. Conclusions: The rates of myelotoxicity have decreased with the utiliza-tion of the current dose constraints in IMRT planning for cervical and rectal cancer however neutropenia rates continue to be high for anal cancer, which may be attributed to the toxic effects of chemotherapy with mitomycin and 5-FU used concurrently. Further research is needed to validate the findings of this study in larger population in multi institutional setting. Purpose/Objective(s): Gastrointestinal (GI) melanoma is a rare disease. Whether it is different from skin melanoma remains unclear. The objective of this study is to compare the overall survival (OS), cancer specific survival (CSS) and prognostic factors of GI melanoma to those of skin melanoma using the Surveillance, Epidemiology, and End Results (SEER) registry. Materials/Methods: Patients diagnosed with invasive GI and Skin mela-noma between 1973 and 2008 were identified from the SEER database. Prognostic factors analyzed included age (18-60/61-100), gender, race (White/nonwhite), marital status, stage (localized/regional/distant), year of diagnosis (1973-1987/1988-1997/1998-2008), and type of treatment (radiation therapy (RT)/surgery). OS and CSS were evaluated using the Kaplan-Meier method. Cox proportional hazards regression analysis examined what variables are prognostic of survival. Results: A total of 406 patients with GI melanoma and 173622 patients with skin melanoma were identified. The median age was 69 and 57 for the GI and skin groups, respectively. The GI group tends to be older and with more advanced stage than the skin group. Among the GI group, 85% underwent surgery and 18% received RT while 95% of skin melanoma patients underwent surgery and 2% received RT. The GI group had a median OS and CSS of 15 and 16 months, respectively while the skin group had a median OS of 283 months and did not reach a median CSS. Cox analysis showed that the skin melanoma had significantly lower risk of total mortality and cancer mortality compared to GI melanoma (Hazard Ratio (HR) 0.40, p < 0.0001) and (HR 0.34, p < 0.0001). Factors significantly associated with improved OS and CSS in the skin group included: age 60, female gender, non-white race, early stage, being married, more current diagnosis, undergoing surgery and not receiving RT. In contrast, factors associated with improved OS and CSS in the GI group included: age 60, early stage, non-white race and undergoing surgery. Subgroup analysis on patients who underwent surgery showed that lymph node status is the only prognostic factor for GI melanoma, while all of the previously identified prognostic factors except for race are associated with OS and CSS in the skin group. Conclusions: Outcomes of patients with GI melanoma are significantly inferior to patients with skin melanoma. The melanomas in these two sites also have different prognostic factors. Based on these findings, future studies should explore the reasons behind these differences, which may enable one to identify patients who may have optimal outcomes.
    International Journal of Radiation OncologyBiologyPhysics 11/2012; 84(3). DOI:10.1016/j.ijrobp.2012.07.939 · 4.26 Impact Factor
  • S. Zhou · E. Hu · S. Chen · D. Zheng · J. Driewer · C. Lin · A. Wahl · W. Zhen · C. Enke
    International Journal of Radiation OncologyBiologyPhysics 11/2012; 84(3):S83. DOI:10.1016/j.ijrobp.2012.07.220 · 4.26 Impact Factor
  • K. Denniston · C. Lin · C.K. Brown · W. Zhen · C. Enke
    International Journal of Radiation OncologyBiologyPhysics 11/2012; 84(3):S637-S638. DOI:10.1016/j.ijrobp.2012.07.1702 · 4.26 Impact Factor
  • S. Chen · C. Lin · C. Enke · S. Zhou
    International Journal of Radiation OncologyBiologyPhysics 11/2012; 84(3):S720. DOI:10.1016/j.ijrobp.2012.07.1927 · 4.26 Impact Factor
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    ABSTRACT: The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Prostate Cancer provide multidisciplinary recommendations for the clinical management of patients with prostate cancer. These NCCN Guidelines Insights highlight notable recent updates. Abiraterone acetate is a first-in-class hormonal agent that represents a new standard of care for patients with metastatic castration-recurrent prostate cancer who have previously received docetaxel (category 1 recommendation). Abiraterone acetate also received category 2B recommendations in the prechemotherapy setting for asymptomatic patients or symptomatic patients who are not candidates for docetaxel. The NCCN Prostate Cancer Panel also added new indications for existing agents, including the option of sipuleucel-T as second-line therapy. In addition, brachytherapy in combination with external beam radiation therapy with or without androgen deprivation therapy is now an alternative for patients with high-risk localized tumors or locally advanced disease.
    Journal of the National Comprehensive Cancer Network: JNCCN 09/2012; 10(9):1081-1087. · 4.18 Impact Factor

Publication Stats

1k Citations
367.93 Total Impact Points


  • 2001–2015
    • University of Nebraska Medical Center
      • Department of Radiation Oncology
      Omaha, Nebraska, United States
  • 2006–2012
    • The Nebraska Medical Center
      Omaha, Nebraska, United States
    • University of Texas MD Anderson Cancer Center
      Houston, Texas, United States