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Pancreatic Neoplasms: HELP
Articles by Timothy N. Showalter
Based on 3 articles published since 2010
(Why 3 articles?)

Between 2010 and 2020, Timothy N. Showalter wrote the following 3 articles about Pancreatic Neoplasms.
+ Citations + Abstracts
1 Clinical Trial The influence of total nodes examined, number of positive nodes, and lymph node ratio on survival after surgical resection and adjuvant chemoradiation for pancreatic cancer: a secondary analysis of RTOG 9704. 2011

Showalter, Timothy N / Winter, Kathryn A / Berger, Adam C / Regine, William F / Abrams, Ross A / Safran, Howard / Hoffman, John P / Benson, Al B / MacDonald, John S / Willett, Christopher G. ·Department of Radiation Oncology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA. ·Int J Radiat Oncol Biol Phys · Pubmed #20934270.

ABSTRACT: PURPOSE: Lymph node status is an important predictor of survival in pancreatic cancer. We performed a secondary analysis of Radiation Therapy Oncology Group (RTOG) 9704, an adjuvant chemotherapy and chemoradiation trial, to determine the influence of lymph node factors--number of positive nodes (NPN), total nodes examined (TNE), and lymph node ratio (LNR ratio of NPN to TNE)--on OS and disease-free survival (DFS). PATIENT AND METHODS: Eligible patients from RTOG 9704 form the basis of this secondary analysis of lymph node parameters. Actuarial estimates for OS and DFS were calculated using Kaplan-Meier methods. Cox proportional hazards models were performed to evaluate associations of NPN, TNE, and LNR with OS and DFS. Multivariate Cox proportional hazards models were also performed. RESULTS: There were 538 patients enrolled in the RTOG 9704 trial. Of these, 445 patients were eligible with lymph nodes removed. Overall median NPN was 1 (min-max, 0-18). Increased NPN was associated with worse OS (HR=1.06, p=0.001) and DFS (HR=1.05, p=0.01). In multivariate analyses, both NPN and TNE were associated with OS and DFS. TNE>12, and >15 were associated with increased OS for all patients, but not for node-negative patients (n=142). Increased LNR was associated with worse OS (HR=1.01, p<0.0001) and DFS (HR=1.006, p=0.002). CONCLUSION: In patients who undergo surgical resection followed by adjuvant chemoradiation, TNE, NPN, and LNR are associated with OS and DFS. This secondary analysis of a prospective, cooperative group trial supports the influence of these lymph node parameters on outcomes after surgery and adjuvant therapy using contemporary techniques.

2 Article Pancreatic cancer planning: Complex conformal vs modulated therapies. 2016

Chapman, Katherine L / Witek, Matthew E / Chen, Hongyu / Showalter, Timothy N / Bar-Ad, Voichita / Harrison, Amy S. ·Department of Radiation Oncology, Thomas Jefferson University Hospital, Philadelphia, PA. · Department of Radiation Oncology, University of Wisconsin School of Medicine School of Medicine and Public Health, Madison, WI. · Department of Radiation Oncology, University of Virginia, Charlottesville, VA. · Department of Radiation Oncology, Thomas Jefferson University Hospital, Philadelphia, PA. Electronic address: amy.harrison@jefferson.edu. ·Med Dosim · Pubmed #26831922.

ABSTRACT: To compare the roles of intensity-modulated radiation therapy (IMRT) and volumetric- modulated arc therapy (VMAT) therapy as compared to simple and complex 3-dimensional chemoradiotherpy (3DCRT) planning for resectable and borderline resectable pancreatic cancer. In all, 12 patients who received postoperative radiotherapy (8) or neoadjuvant concurrent chemoradiotherapy (4) were evaluated retrospectively. Radiotherapy planning was performed for 4 treatment techniques: simple 4-field box, complex 5-field 3DCRT, 5 to 6-field IMRT, and single-arc VMAT. All volumes were approved by a single observer in accordance with Radiation Therapy Oncology Group (RTOG) Pancreas Contouring Atlas. Plans included tumor/tumor bed and regional lymph nodes to 45Gy; with tumor/tumor bed boosted to 50.4Gy, at least 95% of planning target volume (PTV) received the prescription dose. Dose-volume histograms (DVH) for multiple end points, treatment planning, and delivery time were assessed. Complex 3DCRT, IMRT, and VMAT plans significantly (p < 0.05) decreased mean kidney dose, mean liver dose, liver (V30, V35), stomach (D10%), stomach (V45), mean right kidney dose, and right kidney (V15) as compared with the simple 4-field plans that are most commonly reported in the literature. IMRT plans resulted in decreased mean liver dose, liver (V35), and left kidney (V15, V18, V20). VMAT plans decreased small bowel (D10%, D15%), small bowel (V35, V45), stomach (D10%, D15%), stomach (V35, V45), mean liver dose, liver (V35), left kidney (V15, V18, V20), and right kidney (V18, V20). VMAT plans significantly decreased small bowel (D10%, D15%), left kidney (V20), and stomach (V45) as compared with IMRT plans. Treatment planning and delivery times were most efficient for simple 4-field box and VMAT. Excluding patient setup and imaging, average treatment delivery was within 10minutes for simple and complex 3DCRT, IMRT, and VMAT treatments. This article shows significant improvements in 3D plan performance with complex planning over the more frequently compared 3- or 4-field simple 3D planning techniques. VMAT plans continue to demonstrate potential for the most organ sparing. However, further studies are required to identify if dosimetric benefits associated with inverse optimized planning can be translated into clinical benefits and if these treatment techniques are value-added therapies for this group of patients with cancer.

3 Article Conditional survival probabilities for patients with resected pancreatic adenocarcinoma. 2014

Mishra, Mark V / Champ, Colin E / Keith, Scott W / Showalter, Timothy N / Anne, Pramila R / Lawrence, Yaacov Richard / Bar-Ad, Voichita. ·*Department of Radiation Oncology, Jefferson Medical College ‚ĆDivision of Biostatistics, Thomas Jefferson University, Philadelphia, PA. ·Am J Clin Oncol · Pubmed #23111364.

ABSTRACT: BACKGROUND: The purpose of this study is to evaluate conditional survival probabilities for patients with resected pancreatic adenocarcinoma (PC). METHODS: Patients with resected PC from 1998 to 2008 were identified from the Surveillance, Epidemiology and End Results Database. Data on patient, tumor, and treatment characteristics were extracted. Overall survival (OS) rates were calculated using the Kaplan-Meier method. A multivariable analysis at different time points from survival was performed to determine independent prognostic factors associated with all-cause mortality hazard ratios using Cox proportional hazards models. RESULTS: A total of 4883 patients with resected PC were identified. The 1-, 3-, and 5-year survival estimates for patients at diagnosis were 67%, 29%, and 21%, respectively. The probability of surviving an additional 1-, 3-, or 5-year conditional upon already surviving 5 years after diagnosis were 89%, 76%, and 71%, respectively. Prognostic factors significantly correlated with improved OS at the time of diagnosis on multivariable analysis include: earlier stage, younger age, later year of diagnosis, white ethnicity, female sex, and residence in a high income district (P<0.05). Among those already surviving 3 years after diagnosis, younger age was the only prognostic factor statistically significantly correlated with improved OS (P<0.05). CONCLUSIONS: Conditional survival estimates provide additional prognostic information that may be used to counsel PC patients on how their prognosis may change over time. Further research using prospectively collected data is warranted to help determine recommended follow-up intervals and benchmarks for future clinical trials.