Nina A Mayr

Publications (70)251.22 Total impact

• Article: Emerging role of stereotactic body radiotherapy in the treatment of pancreatic cancer.

  Betul Berber, Juan R Sanabria, Kelly Braun, Min Yao, Rodney J Ellis, Charles A Kunos, Jason Sohn, Mitchell Machtay, Bin S Teh, Zhibin Huang, Nina A Mayr, Simon S Lo
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  ABSTRACT: The management of pancreatic cancer continues to be challenging. Despite surgical, genetic and molecular advances, its overall prognosis remains poor. Surgical resection is the only modality that offers a chance for a cure, with an overall survival rate of 10-20% at 5 years. However, only 20% of the patients are surgical candidates because of locally advanced disease or systemic stage at presentation. Conventional radiotherapy, with or without chemotherapy, has been used to treat patients with advanced-stage pancreatic cancer, an approach with high rates of local recurrence. Stereotactic body radiation therapy, also known as stereotactic ablative radiotherapy has emerged as a treatment modality that allows the precise delivery of a large ablative radiation dose to a tumor volume while sparing surrounding organs and tissues. Phase I and II studies have shown good rates of local control of the disease but rates of distant metastasis remain significant. Strategies to combine novel systemic therapy and stereotactic body radiation therapy are to be explored.
  Expert Review of Anti-infective Therapy 04/2013; 13(4):481-7. · 2.65 Impact Factor
• Article: Stereotactic body radiation therapy for metastasis to the adrenal glands.

  Kevin Shiue, Andrew Song, Bin S Teh, Rodney J Ellis, Min Yao, Nina A Mayr, Zhibin Huang, Jason Sohn, Mitchell Machtay, Simon S Lo
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  ABSTRACT: Many primary cancers can metastasize to the adrenal glands. Adrenalectomy via an open or laparoscopic approach is the current definitive treatment, but not all patients are eligible or wish to undergo surgery. There are only limited studies on the use of conventional radiation therapy for palliation of symptoms from adrenal metastasis. However, the advent of stereotactic body radiation therapy (SBRT) - also named stereotactic ablative radiotherapy for primary lung cancer, metastases to the lung, and metastases to the liver - have prompted some investigators to consider the use of SBRT for metastases to the adrenal glands. This review focuses on the emerging data on SBRT of metastasis to the adrenal glands, while also providing a brief discussion of the overall management of adrenal metastasis.
  Expert Review of Anti-infective Therapy 12/2012; 12(12):1613-20. · 2.65 Impact Factor
• Article: Characterizing at-Risk Voxels by Using Perfusion Magnetic Resonance Imaging for Cervical Cancer during Radiotherapy.

  Zhibin Huang, Nina A Mayr, Simon S Lo, John C Grecula, Jian Z Wang, Guang Jia, William Tc Yuh
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  ABSTRACT: The number of voxels with low signal intensity (Low DCE voxels) might be potentially related to treatment failure, which might be associated with the tumor oxygenation status. Our goal was to investigate whether at-risk voxels can be used to predict treatment outcome during radiation therapy for cervical cancer. 80 patients with Stage IB2-IVB cervical cancer were included. Four sequential MRI scans were performed at pre-RT, every 2-2.5 weeks during RT, and post-radiotherapy. 3D volumetric data including tumor regression and tumor perfusion from dynamic contrast enhanced MRI (DCE-MRI) were analyzed. Based on the signal intensity (SI) curves of the DCE-MRI, the low-DCE tumor voxels was obtained for individual patients. The predictive power of low DCE voxels in predicting the treatment outcomes was evaluated by Kaplan-Meier survival analysis. Correlation of low DCE voxels with hemoglobin (Hgb) was checked by Pearson Correlation. The actuarial local control rate and survival rate in the patient group with a small number of low DCE voxels were 89.7% and 76.9%, compared with 75.6% and 51.2% in the patient group with a big number of low DCE voxels for the MRI study #1, and 94.1% and 80.4% compared with 62.1% and 34.5% for the MRI study #2, and 95.7% and 78.7% compared with 63.6% and 42.4% for the MRI study #3, respectively. Low DCE voxels were significantly correlated with Hgb. At-risk voxels can be used to predict the outcomes and help understand tumor heterogeneity of response to RT. The Hgb level and tumor perfusion during RT influence the radioresponsiveness and survival in cervical cancer patients.
  Journal of Cancer Science and Therapy 09/2012; 4(9):254-259.
• Article: Temporal Analysis of Tumor Heterogeneity and Volume for Cervical Cancer Treatment Outcome Prediction: Preliminary Evaluation

  Jeffrey W. Prescott, Dongqing Zhang, Jian Z. Wang, Nina A. Mayr, William T.C. Yuh, Joel Saltz, Metin Gurcan
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  ABSTRACT: In this paper, we present a method of quantifying the heterogeneity of cervical cancer tumors for use in radiation treatment outcome prediction. Features based on the distribution of masked wavelet decomposition coefficients in the tumor region of interest (ROI) of temporal dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) studies were used along with the imaged tumor volume to assess the response of the tumors to treatment. The wavelet decomposition combined with ROI masking was used to extract local intensity variations in the tumor. The developed method was tested on a data set consisting of 23 patients with advanced cervical cancer who underwent radiation therapy; 18 of these patients had local control of the tumor, and five had local recurrence. Each patient participated in two DCE-MRI studies: one prior to treatment and another early into treatment (2–4weeks). An outcome of local control or local recurrence of the tumor was assigned to each patient based on a posttherapy follow-up at least 2years after the end of treatment. Three different supervised classifiers were trained on combinational subsets of the full wavelet and volume feature set. The best-performing linear discriminant analysis (LDA) and support vector machine (SVM) classifiers each had mean prediction accuracies of 95.7%, with the LDA classifier being more sensitive (100% vs. 80%) and the SVM classifier being more specific (100% vs. 94.4%) in those cases. The K-nearest neighbor classifier performed the best out of all three classifiers, having multiple feature sets that were used to achieve 100% prediction accuracy. The use of distribution measures of the masked wavelet coefficients as features resulted in much better predictive performance than those of previous approaches based on tumor intensity values and their distributions or tumor volume alone. Key wordsCervical cancer-treatment outcome prediction-dynamic contrast-enhanced MRI-wavelet
  Journal of Digital Imaging 04/2012; 23(3):342-357. · 1.25 Impact Factor
• Article: Onset time of tumor repopulation for cervical cancer: first evidence from clinical data.

  Zhibin Huang, Nina A Mayr, Mingcheng Gao, Simon S Lo, Jian Z Wang, Guang Jia, William T C Yuh
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  ABSTRACT: Accelerated tumor repopulation has significant implications in low-dose rate (LDR) brachytherapy. Repopulation onset time remains undetermined for cervical cancer. The purpose of this study was to determine the onset time of accelerated repopulation in cervical cancer, using clinical data. The linear quadratic (LQ) model extended for tumor repopulation was used to analyze clinical data and magnetic resonance imaging-based three-dimensional tumor volumetric regression data from 80 cervical cancer patients who received external beam radiotherapy (EBRT) and LDR brachytherapy. The LDR dose was converted to EBRT dose in 1.8-Gy fractions by using the LQ formula, and the total dose ranged from 61.4 to 99.7 Gy. Patients were divided into 11 groups according to total dose and treatment time. The tumor control probability (TCP) was calculated for each group. The least χ(2) method was used to fit the TCP data with two free parameters: onset time (T(k)) of accelerated repopulation and number of clonogens (K), while other LQ model parameters were adopted from the literature, due to the limited patient data. Among the 11 patient groups, TCP varied from 33% to 100% as a function of radiation dose and overall treatment time. Higher dose and shorter treatment duration were associated with higher TCP. Using the LQ model, we achieved the best fit with onset time T(k) of 19 days and K of 139, with uncertainty ranges of (11, 22) days for T(k) and (48, 1822) for K, respectively. This is the first report of accelerated repopulation onset time in cervical cancer, derived directly from clinical data by using the LQ model. Our study verifies the fact that accelerated repopulation does exist in cervical cancer and has a relatively short onset time. Dose escalation may be required to compensate for the effects of tumor repopulation if the radiation therapy course is protracted.
  International journal of radiation oncology, biology, physics 03/2012; 84(2):478-84. · 4.59 Impact Factor
• Article: Direct sagittal image registration and tumor delineation on sagittal magnetic resonance imaging sequences for image-guided brachytherapy of cervical cancer.

  Jeffrey D Radawski, Zhibin Huang, Jian Z Wang, William T C Yuh, Nina A Mayr
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  ABSTRACT: To test and evaluate direct sagittal-plane tumor delineation for MRI-based image-guided brachytherapy (IGBT) planning for patients with cervical cancer. An image registration method based on the sagittal source MR images was developed and employed in ten patients with an indwelling ring/tandem applicator. The gross tumor volume (GTV) was delineated separately on the sagittal (GTV-S) and axial images (GTV-A). GTV conformity indices and dose-volume histogram analyses were compared among GTV-S and GTV-A (paired t-test). Image quality and delineation in the sagittal images was graded superior to the axial images. The ratio of common volume of the axial and sagittal volumes to that of the axial volume was 0.77 +/- (standard deviation) 0.2. The GTV-S mean volume (19.6 +/- 13.8 mL) was significantly larger than the GTV-A mean volume (10.3 +/- 7.3 mL, p=0.003). The GTV-S mean D99 (5.2 +/- 2.5 Gy) was significantly lower than the GTV-A mean D99 (6.9 +/- 2.7 Gy, p=0.013). The GTV-S mean D90 (6.8 +/- 2.8 Gy) was significantly lower than the GTV-A mean D90 (8.5 +/- 3.1 Gy, p=0.016). Registration of the sagittal source MRI and contouring the GTV directly on the sagittal images is feasible and practical for IGBT. Consistently larger sagittal GTVs may be explained by the better visualization and more continuous tumor topology in the sagittal plane, compared to the discrete oblique sectioning of the uterus/tumor and partial volume loss in the axial plane.
  Discovery medicine 01/2012; 13(68):47-56.
• Article: A generalized linear-quadratic model incorporating reciprocal time pattern of radiation damage repair.

  Zhibin Huang, Nina A Mayr, Simon S Lo, Jian Z Wang, Guang Jia, William T C Yuh, Roberta Johnke
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  ABSTRACT: It has been conventionally assumed that the repair rate for sublethal damage (SLD) remains constant during the entire radiation course. However, increasing evidence from animal studies suggest that this may not the case. Rather, it appears that the repair rate for radiation-induced SLD slows down with increasing time. Such a slowdown in repair would suggest that the exponential repair pattern would not necessarily accurately predict repair process. As a result, the purpose of this study was to investigate a new generalized linear-quadratic (LQ) model incorporating a repair pattern with reciprocal time. The new formulas were tested with published experimental data. The LQ model has been widely used in radiation therapy, and the parameter G in the surviving fraction represents the repair process of sublethal damage with T(r) as the repair half-time. When a reciprocal pattern of repair process was adopted, a closed form of G was derived analytically for arbitrary radiation schemes. The published animal data adopted to test the reciprocal formulas. A generalized LQ model to describe the repair process in a reciprocal pattern was obtained. Subsequently, formulas for special cases were derived from this general form. The reciprocal model showed a better fit to the animal data than the exponential model, particularly for the ED50 data (reduced χ(2) (min) of 2.0 vs 4.3, p = 0.11 vs 0.006), with the following gLQ parameters: α/β = 2.6-4.8 Gy, T(r) = 3.2-3.9 h for rat feet skin, and α/β = 0.9 Gy, T(r) = 1.1 h for rat spinal cord. These results of repair process following a reciprocal time suggest that the generalized LQ model incorporating the reciprocal time of sublethal damage repair shows a better fit than the exponential repair model. These formulas can be used to analyze the experimental and clinical data, where a slowing-down repair process appears during the course of radiation therapy.
  Medical Physics 01/2012; 39(1):224-30. · 2.83 Impact Factor
• Article: Characterizing tumor heterogeneity with functional imaging and quantifying high-risk tumor volume for early prediction of treatment outcome: cervical cancer as a model.

  Nina A Mayr, Zhibin Huang, Jian Z Wang, Simon S Lo, Joline M Fan, John C Grecula, Steffen Sammet, Christina L Sammet, Guang Jia, Jun Zhang, Michael V Knopp, William T C Yuh
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  ABSTRACT: Treatment response in cancer has been monitored by measuring anatomic tumor volume (ATV) at various times without considering the inherent functional tumor heterogeneity known to critically influence ultimate treatment outcome: primary tumor control and survival. This study applied dynamic contrast-enhanced (DCE) functional MRI to characterize tumors' heterogeneous subregions with low DCE values, at risk for treatment failure, and to quantify the functional risk volume (FRV) for personalized early prediction of treatment outcome. DCE-MRI was performed in 102 stage IB(2)-IVA cervical cancer patients to assess tumor perfusion heterogeneity before and during radiation/chemotherapy. FRV represents the total volume of tumor voxels with critically low DCE signal intensity (<2.1 compared with precontrast image, determined by previous receiver operator characteristic analysis). FRVs were correlated with treatment outcome (follow-up: 0.2-9.4, mean 6.8 years) and compared with ATVs (Mann-Whitney, Kaplan-Meier, and multivariate analyses). Before and during therapy at 2-2.5 and 4-5 weeks of RT, FRVs >20, >13, and >5 cm(3), respectively, significantly predicted unfavorable 6-year primary tumor control (p = 0.003, 7.3 × 10(-8), 2.0 × 10(-8)) and disease-specific survival (p = 1.9 × 10(-4), 2.1 × 10(-6), 2.5 × 10(-7), respectively). The FRVs were superior to the ATVs as early predictors of outcome, and the differentiating power of FRVs increased during treatment. Our preliminary results suggest that functional tumor heterogeneity can be characterized by DCE-MRI to quantify FRV for predicting ultimate long-term treatment outcome. FRV is a novel functional imaging heterogeneity parameter, superior to ATV, and can be clinically translated for personalized early outcome prediction before or as early as 2-5 weeks into treatment.
  International journal of radiation oncology, biology, physics 12/2011; 83(3):972-9. · 4.59 Impact Factor
• Source

  Available from: Simon S Lo

  Article: Stereotactic radiosurgery alone for patients with 1-4 radioresistant brain metastases.

  Simon S Lo, James W Clarke, John C Grecula, John M McGregor, Nina A Mayr, Robert Cavaliere, Kari L Kendra, Nilendu Gupta, Jian Z Wang, Atom Sarkar, Thomas E Olencki
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  ABSTRACT: Brain metastases from radioresistant histologies are perceived to be less responsive to WBRT compared to other histologies, and stereotactic radiosurgery (SRS) may provide better local control. The aim of this study was to examine the outcomes of patients with 1-4 brain metastasis from radioresistant histologies (renal cell carcinoma and melanoma) treated with SRS alone. Thirty-eight patients with 1-4 radioresistant brain metastases (66 lesions) were treated with SRS alone. The median age was 55 years. Fourteen and 24 patients had renal cell carcinoma (RCC) and melanoma brain metastases, respectively. Distribution of number of lesions was as follows: one lesion, 22 patients; 2 lesions, 8 patients; 3 lesions, 5 patients; and 4 lesions, 3 patients. Distribution of RTOG recursive partitioning analysis (RPA) classes was as follows: II, 37 patients and III, 1 patient. The median marginal dose was 20 Gy. The median follow-up was 6.1 months. The 3-, 6-, 9-, 12-, and 18-month local control (LC) rates were 87.9, 81.4, 67.9, 67.9, and 60.3%, respectively. The corresponding free-from-distant-brain failure (FFDBF) rates were 71.3, 58.1, 49.8, 40.2, and 27.6%. The corresponding progression-free survival (PFS) rates were 55.3, 41.9, 33, 23.3, and 13.3%. RCC histology was associated with better LC (P = 0.0055). Although SRS alone could yield reasonable LC in patients with 1-4 radioresistant brain metastases, the risk of distant brain failure was substantial. The approach of routine omission of WBRT outside of a trial setting should be used judiciously.
  Medical Oncology 12/2011; 28 Suppl 1:S439-44. · 2.14 Impact Factor
• Article: Emerging applications of stereotactic body radiation therapy for head and neck cancer.

  Farzan Siddiqui, David Raben, Jiade J Lu, John C Grecula, Simon S Lo, Zhibin Huang, Nina A Mayr, Bin S Teh, Min Yao
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  ABSTRACT: Head and neck cancer is typically managed with surgery, radiation therapy, chemotherapy or various combinations of the above. In patients who develop recurrence after radiation therapy, treatment options are limited. Reirradiation can be offered but the amount of additional radiation that can be given is limited and there is an increased risk of serious complications. Stereotactic radiation therapy has been used as a boost or salvage therapy at recurrence for nasopharyngeal carcinoma. The use of stereotactic body radiation therapy for head and neck cancer has expanded to include sites outside of the base of skull region, especially in the recurrent setting, and clinical data are emerging. This article will highlight some of the technical and clinical advances in this area.
  Expert Review of Anti-infective Therapy 09/2011; 11(9):1429-36. · 2.65 Impact Factor
• Article: Stereotactic body radiation therapy for prostate cancer.

  Hiromichi Ishiyama, Bin S Teh, Simon S Lo, Thomas Mathews, Angel Blanco, Robert Amato, Rodney J Ellis, Nina A Mayr, Arnold C Paulino, Bo Xu, Brian E Butler
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  ABSTRACT: Stereotactic body radiation therapy (SBRT) is a promising treatment option for prostate cancer. Hypofractionation regimens, such as SBRT, may be more advantageous compared with conventional regimens because low α:β ratio of prostate cancer has high sensitivity to dose per fraction. In addition, a smaller and tighter margin with SBRT is expected to provide a low toxicity rate without reducing tumor control. The purpose of this article is to examine radiobiological, technical and clinical aspects of SBRT for prostate cancer.
  Future Oncology 09/2011; 7(9):1077-86. · 3.16 Impact Factor
• Article: Emerging application of stereotactic body radiation therapy for gynecologic malignancies.

  Nina A Mayr, Zhibin Huang, Jason W Sohn, Simon S Lo, Bin S Teh, Jiade J Lu, John C Grecula, Charles Kunos
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  ABSTRACT: Stereotactic body radiation therapy (SBRT) involves delivery of image-guided, ablative radiation doses to planning treatment volume(s) using sophisticated dosimetric planning and target localization. Early on, clinical investigators pursued SBRT for the treatment of early stage non-small-cell lung cancer, lung and liver oligometastases and spinal metastases. As a result of its clinical efficacy in these disease sites, SBRT has been explored in the management of persistent or recurrent gynecological cancers. This article will consider indications for SBRT application in gynecological cancer management, will reflect on outcomes from key SBRT clinical trials and will discuss new therapeutic roles of SBRT for gynecological cancers.
  Expert Review of Anti-infective Therapy 07/2011; 11(7):1069-75. · 2.65 Impact Factor
• Article: The role of local therapy in the management of lung and liver oligometastases.

  Simon S Lo, Susan D Moffatt-Bruce, Laura A Dawson, Roderich E Schwarz, Bin S Teh, Nina A Mayr, Jiade J Lu, John C Grecula, Thomas E Olencki, Robert D Timmerman
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  ABSTRACT: Despite recent advances in oncologic therapy, an important proportion of patients with primary cancer will develop distant metastasis. The standard therapy for metastatic cancer is systemic therapy, which typically does not yield excellent response rates for most solid tumors. Data in the literature support the existence of a state of limited metastasis or oligometastasis. Favorable outcomes have been observed in selected patients with oligometastases that are treated with local ablative therapies, which include surgical extirpation, stereotactic body radiation therapy, and radiofrequency ablation. Lung and liver are the two most common sites of oligometastases considered for local ablative therapy and this Review will focus on the role of local therapy in oligometastases that arise in these organs.
  Nature Reviews Clinical Oncology 05/2011; 8(7):405-16. · 11.96 Impact Factor
• Article: Imaging changes after stereotactic body radiation therapy for lung and liver tumors.

  Simon S Lo, Bin S Teh, Jian Z Wang, Zhibin Huang, Jennifer Zook, Tracy Price, Nina A Mayr, John C Grecula, Robert D Timmerman, Higinia R Cardenes
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  ABSTRACT: Stereotactic body radiation therapy (SBRT) is gaining wide acceptance as a treatment modality for lung and liver tumors, and it is crucial to make an accurate evaluation of the local effects of ablative doses of radiation in terms of local tumor control and normal tissue reaction or damage. The very complex radiation dose distribution of SBRT, the use of a large number of non-opposing and noncoplanar beams, and the delivery of individual ablative doses of radiation may cause substantially different radiographic appearance on diagnostic imaging compared with conventional radiation therapy. Different patterns of radiographic changes have been observed in the lung and liver after SBRT. This article reviews the post-SBRT imaging changes in the lung and liver. Since computed tomography and PET are the most commonly used diagnostic imaging tools for monitoring lung tumor and computed tomography for liver tumors, this article will focus on the changes observed on those imaging modalities.
  Expert Review of Anti-infective Therapy 04/2011; 11(4):613-20. · 2.65 Impact Factor
• Article: Sequential magnetic resonance imaging of cervical cancer: the predictive value of absolute tumor volume and regression ratio measured before, during, and after radiation therapy.

  Jian Z Wang, Nina A Mayr, Dongqing Zhang, Kaile Li, John C Grecula, Joseph F Montebello, Simon S Lo, William T C Yuh
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  ABSTRACT: The objectives of this study were to investigate outcome prediction by measuring absolute tumor volume and regression ratios using serial magnetic resonance imaging (MRI) during radiation therapy (RT) for cervical cancer and to develop algorithms capable of identifying patients at risk of a poor therapeutic outcome. Eighty patients with stage IB2 through IVA cervical cancer underwent 4 MRI scans: before RT (MRI1), during RT at 2 to 2.5 weeks (MRI2) at 4 to 5 weeks (MRI3), and 1 to 2 months after RT (MRI4). The median follow-up was 6.2 years (range, 0.2-9.4 years). Tumor volumes at MRI1, MRI2, MRI3, and MRI4 (V1, V2, V3, and V4, respectively) and tumor regression ratios (V2/V1, V3/V1, and V4/V1) were measured by 3-dimensional volumetry. Predictive metrics based on tumor volume/regression parameters were correlated with ultimate clinical outcomes, including tumor local recurrence (LR) and dying of disease (DOD). Predictive power was evaluated using the Mann-Whitney test, sensitivity/specificity analyses, and Kaplan-Meier analyses. Both tumor volume and regression ratio were strongly correlated with LR (P=.06, P = 5×10(-4), P=1×10(-6), and P=2×10(-8) for V1, V2, V3, and V4, respectively; and P=7×10(-5), P=1×10(-6), and P=1×10(-8) for V2/V1, V3/V1, and V4/V1, respectively) and DOD (P=.015, P=.004, P=.001, and P=3×10(-4) for V1, V2, V3, and V4, respectively; and P=.03, P=.009, and P=3×10(-4) for V2/V1, V3/V1, and V4/V1, respectively). Algorithms that combined tumor volumes and regression ratios improved predictive power (sensitivity, 61%-89%; specificity, 79%-100%). The strongest predictor, pre-RT volume and regression ratio at MRI3 (V1>40 cm3 and V3/V1>20%, respectively), achieved 89% sensitivity, 87% specificity, and 88% accuracy for LR and achieved 54% sensitivity, 83% specificity, and 73% accuracy for DOD. The current results suggested that tumor volume/regression parameters obtained during primary therapy are useful in predicting LR and DOD. Both tumor volume and regression ratio provided important information as early outcome predictors that may guide early intervention for patients with cervical cancer who are at high risk of treatment failure.
  Cancer 11/2010; 116(21):5093-101. · 4.77 Impact Factor
• Article: When tumor repopulation starts? The onset time of prostate cancer during radiation therapy.

  Mingcheng Gao, Nina A Mayr, Zhibin Huang, Hualin Zhang, Jian Z Wang
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  ABSTRACT: To analyze published clinical data and provide a preliminary estimate of tumor repopulation rate and its onset time during radiation therapy for prostate cancer. Data on prostate cancer treated with external beam radiotherapy (EBRT) by Perez et al. (2004), Amdur et al. (1990) and Lai et al. (1991) were analyzed in this study. The stage-combined pelvic control rate from Perez et al. was calculated to be 0.95±0.01, 0.87±0.02, and 0.72±0.04 for patients treated ≤7 weeks, 7.1-9 weeks, and >9 weeks respectively. Based on the Linear-Quadratic model, extended to account for tumor repopulation, the least χ² method was used to fit the clinical data and derive the onset time (T(k)) and effective doubling time (T(d)) for prostate cancer. Similar analysis was performed for the other two datasets. Best fit was achieved with onset time T(k)=34±7 days and doubling time T(d)=12±2 days. These parameters were independent of the choice of the α/β values currently published in the literature. Analyses of the other two datasets showed T(k)=42±7 days with T(d)=9 ± 3 days, and T(k)=34±6 days with T(d)=34±5 days, respectively. T(k) was found to be dependent on tumor stage. Consistent values for onset time T(k) were obtained from different datasets, while the range of doubling time T(d) was large. Tumor repopulation starts no later than 58 days (at 90% confidence level) in the course of EBRT for prostate cancer.
  Acta oncologica (Stockholm, Sweden) 11/2010; 49(8):1269-75. · 2.27 Impact Factor
• Article: Reporting of true spinal cord dose is encouraged for stereotactic body radiation therapy for spinal tumors. In regard to Sahgal et al. (Int J Radiat Oncol Biol Phys 2010;77:548-553).

  Simon S Lo, Jian Z Wang, Jeffrey D Radawski, Nina A Mayr
  International journal of radiation oncology, biology, physics 09/2010; 78(1):314; author reply 314. · 4.59 Impact Factor
• Article: Stereotactic body radiation therapy for oligometastases.

  Simon S Lo, Bin S Teh, Nina A Mayr, Thomas E Olencki, Jian Z Wang, John C Grecula, Jiade J Lu, Robert D Timmerman
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  ABSTRACT: There are data in the literature to suggest the presence of an oligometastatic state, and local aggressive therapy of the oligometastases may improve outcomes including survival. Stereotactic body radiation therapy has emerged as one of the local therapy options for oligometastases in various body sites, most commonly in the lung and the liver. Retrospective studies and clinical trials have demonstrated promising results with the use of stereotactic body radiation therapy for oligometastases. However, most of the studies have relatively short follow-up intervals. Longer follow-up is necessary to better define the role of stereotactic body radiation therapy in the management of patients with oligometastases. Given the high propensity for distant progression, the combination of novel systemic therapy and stereotactic body radiation therapy is to be explored.
  Discovery medicine 09/2010; 10(52):247-54.
• Article: Stereotactic body radiation therapy (SBRT) for genitourinary malignancies.

  Bin S Teh, Hiromichi Ishiyama, Thomas Mathews, Bo Xu, E Brian Butler, Nina A Mayr, Simon S Lo, Jiade J Lu, Angel I Blanco, Arnold C Paulino, Robert D Timmerman
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  ABSTRACT: Stereotactic body radiation therapy (SBRT) is a novel treatment modality in radiation oncology that delivers a very high dose of radiation to the tumor target with high precision using single or a small number of fractions. SBRT is the result of technological advances in patient/tumor immobilization, image guidance, and treatment planning and delivery. This modality is safe and effective in both early stage primary cancer and oligometastases. Compared to the use of stereotactic radiosurgery for other tumor sites, SBRT is slow to be adopted in the management of genitourinary malignancies. There are now emerging data that show the safety and efficacy of this treatment modality in genitourinary (GU) malignancies especially in prostate cancer and renal cell carcinoma. Preclinical data, clinical experience, and challenges are reviewed and discussed.
  Discovery medicine 09/2010; 10(52):255-62.
• Article: A generalized linear-quadratic model for radiosurgery, stereotactic body radiation therapy, and high-dose rate brachytherapy.

  Jian Z Wang, Zhibin Huang, Simon S Lo, William T C Yuh, Nina A Mayr
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  ABSTRACT: Conventional radiation therapy for cancer usually consists of multiple treatments (called fractions) with low doses of radiation. These dose schemes are planned with the guidance of the linear-quadratic (LQ) model, which has been the most prevalent model for designing dose schemes in radiation therapy. The high-dose fractions used in newer advanced radiosurgery, stereotactic radiation therapy, and high-dose rate brachytherapy techniques, however, cannot be accurately calculated with the traditional LQ model. To address this problem, we developed a generalized LQ (gLQ) model that encompasses the entire range of possible dose delivery patterns and derived formulas for special radiotherapy schemes. We show that the gLQ model can naturally derive the traditional LQ model for low-dose and low-dose rate irradiation and the target model for high-dose irradiation as two special cases of gLQ. LQ and gLQ models were compared with published data obtained in vitro from Chinese hamster ovary cells across a wide dose range [0 to approximately 11.5 gray (Gy)] and from animals with dose fractions up to 13.5 Gy. The gLQ model provided consistent interpretation across the full dose range, whereas the LQ model generated parameters that depended on dose range, fitted only data with doses of 3.25 Gy or less, and failed to predict high-dose responses. Therefore, the gLQ model is useful for analyzing experimental radiation response data across wide dose ranges and translating common low-dose clinical experience into high-dose radiotherapy schemes for advanced radiation treatments.
  Science translational medicine 07/2010; 2(39):39ra48. · 7.80 Impact Factor