PET CT Thresholds for Radiotherapy Target Definition in Non–Small-Cell Lung Cancer: How Close are we to the Pathologic Findings?Page 699
K. Wu, Y. C. Ung, J. Hornby, M. Freeman, D. Hwang, M. S. Tsao, M. Dahele, G. Darling, D. E. Maziak, R. Tirona, K. MAH and C. S. Wong
This article on PET-CT thresholds for radiation target definition in non-small cell lung cancer (NSCLC) examines the difficulty of determining the best threshold settings to use when radiation oncologists outline the tumor for treatment. Changing threshold settings can give vastly different contoured tumor volumes. This study compared different CT (i.e. lung and mediastinal settings) and PET (i.e. percent of maximal intensity) thresholds with the gross pathological dimension in early stage resected NSCLC to find the best correlation. A CT threshold of 1600HU window and -300HU level and a 50% PET intensity level gave the best correlation with the pathological dimension.
Late Gastrointestinal Toxicity after Dose-Escalated Conformal Radiotherapy for Early Prostate Cancer: Results from the UK Medical Research Council RT01 Trial (ISRCTN47772397)Page 773
I. Syndikus, R. C. Morgan, M. R. Sydes, J. D. Graham, and D. P. Dearnaley on behalf of the MRC RT01 collaborators
“This article summarises the late gastrointestinal toxicity seen in the RT01 trial, which compared standard (64Gy) and dose-escalated (74Gy) conformal radiotherapy (CFRT) for men with localised prostate cancer also receiving hormone therapy. Both arms showed increased gastrointestinal problems, peaking 18-36 months after CFRT. Patients on the dose-escalated arm were found to be at significantly higher risk of rectal bleeding, diarrhoea and proctitis; however these remained within clinically acceptable levels and seemed not to trouble patients too much. The prevalence of most toxicities returned to pre-treatment levels by 5 years. Further improvements in radiotherapy technique might maintain the benefits of dose-escalation while improving patient acceptability.”
Response to Multiple Radiation Doses of Human Colorectal Carcinoma Cells Infected With Recombinant Adenovirus Containing Dominant-Negative KU70 FragmentPage 877
M. Urano, F. He, A. Miinami, C. C. Ling, and G. C. Li
Drs. Urano, Li and colleagues successfully demonstrated in vitro that molecular inhibition of DNA double strand breaks (DNA-DSB) repair enhanced radiation response of human colorectal carcinoma cells. Ku70 is a key protein in the DNA-DSB repair pathway and a dominant negative Ku70 fragment (DNKu70) suppresses Ku70 activity. They generated replication-defective adenovirus, with DNKu70 controlled by the CMV promoter, infected tumor cells with the virus. It has been shown that infected cells express high level of DNKu70, are deficient in DNA damage repair. They showed significantly enhanced radiation response of these cells. Clinical significance is that for infected tumor cells, multiple small doses lead to greater enhancement than a large single dose. If compared with their previous paper (IJROBP, vol. 71, p.533, 2008), DNKu70-transduced Rat-1 fibroblasts showed greater enhancement than the DNKu70-virus infected tumor cells. Their literature survey suggests improvement of virus infection method could further enhance radiation response.
Interfraction and Intrafraction Changes in Amplitude of Breathing Motion in Stereotactic Liver RadiotherapyPage 918
R. B. Case, D. J. Moseley, J. J. Sonke, C. L. Eccles, R. E. Dinniwell, J. KIM, A. Bezjak, M. Milosevic, K. K. Brock, and L. A. Dawson
“Changes in liver breathing motion amplitude in 29 patients treated with stereotactic body radiation therapy were measured on 314 respiratory sorted cone beam CT scans obtained before and after each radiation fraction. Compared to the mean (maximum) craniocaudal (CC) and anteroposterior (AP) liver motion amplitude of 8.0 (18.8) and 4.3 (12.1) mm, the change in amplitude was minimal. 50% of CC and AP amplitude changes were less than 1.7 and 1.6 mm, significantly smaller than baseline changes in liver position relative to the vertebral bodies. Amplitude change was not correlated with magnitude of liver motion or intrafraction time.”
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