Dose-escalated intensity modulated radiation therapy (IMRT) with use of a moderate hypofractionation regimen (72 Gy in 2.4 Gy fractions) can safely treat patients with localized prostate cancer with limited grade 2 or 3 late toxicity, according to a study published in the April 1, 2014 edition of the International Journal of Radiation Oncology • Biology • Physics (Red Journal), the official scientific journal of the American Society for Radiation Oncology (ASTRO).
Previous randomized clinical trials have shown that dose-escalated radiation therapy improves prostate cancer control compared to lower-dose conventional radiation therapy. Conventional fractionation of dose-escalated radiation therapy (1.8 or 2 Gy fractions) can take up to nine weeks to complete, while hypofractionated radiation therapy can deliver a higher biologically effective dose over a shorter period of time (six weeks) and has the potential to increase prostate cancer control without increasing toxicity.
However, there are limited data on the late toxicity of moderate hypofractionated regimens for prostate cancer. This randomized trial from the University of Texas MD Anderson Cancer Center compares the late toxicity outcomes of men with localized prostate cancer treated with either conventionally fractionated IMRT (CIMRT) or dose-escalated hypofractionated IMRT (HIMRT).
Men with organ-confined prostate cancer were enrolled in this institutional review board-approved trial from January 2001 to January 2010 and were randomized to receive either CIMRT (75.6 Gy in 1.8 Gy fractions over eight-and-a-half weeks) or HIMRT (72 Gy in 2.4 Gy fractions over six weeks). Eligible patients had biopsy-proven prostate adenocarcinoma; good performance status; stage T1b-T3b disease; a prostate-specific antigen (PSA) ≤20 ng/ml; a Gleason score <10; and no clinical, radiographic or pathologic evidence of nodal or bone metastasis.
Patients with stage cT3c or cT4 disease, a history of prior pelvic radiation therapy, or who received more than four months of hormone ablation therapy with prior or planned radical prostate surgery and with concurrent active malignancy other than nonmetastatic skin cancer or early-stage chronic lymphocytic leukemia were not eligible for the trial. The median age of the patient cohort was 68. Of the 203 patients analyzed in the study, 72 percent had stage T1 disease (146) and 89 percent had a PSA <10 ng/ml (181). Thirty-four percent (70) had Gleason 6 disease, 65 percent (131) had Gleason 7 disease and 1 percent (2) had Gleason 8 disease. Patients were classified into low-risk (28 percent = 57), intermediate risk (71 percent = 144) and high-risk (1 percent = 2) disease using current National Comprehensive Cancer Network risk-group definitions.
All patients were treated with static-field IMRT. One hundred and one (101) men received CIMRT and 102 men received HIMRT. Physician-reported toxicity was evaluated for all patients during treatment and at each follow-up visit. After completion of radiation therapy, follow-up was conducted at least every six months for the first two years post-treatment, and annually thereafter. Median follow-up was six years.
Late gastrointestinal (GI) and genitourinary (GU) toxicity were analyzed in this study, starting 90 days post-treatment, using modified Radiation Therapy Oncology Group toxicity grading. In the CIMRT arm, 17 percent (17) experienced grade 1 GI toxicity, 4 percent (4) experienced grade 2 GI toxicity and 1 percent (1) experienced grade 3 GI toxicity. In the HIMRT arm, 26 percent (27) experienced grade 1 GI toxicity, 9 percent (9) experienced grade 2 GI toxicity and 2 percent (2) experienced grade 3 GI toxicity. There was a numeric increase in the absolute frequency of late GI toxicity for men treated with HIMRT, but the difference was not statistically significant. The five-year actuarial grade 2 or 3 late GI toxicity was 5.1 percent (95 percent Confidence Interval (CI)) for patients treated with CIMRT and 10 percent for patients treated with HIMRT. The increase in late GI toxicity for men receiving HIMRT was the result of moderate and high radiation dose to a larger proportion of the rectum, which suggests that more stringent dose constraints for the rectum may result in lower late GI toxicity for those patients.
Additionally, there was not a statistically significant difference in the absolute frequency of late GU toxicity in men treated with CIMRT or HIMRT. In the CIMRT arm, 15 percent (15) experienced grade 1 GU toxicity, 14 percent (14) experienced grade 2 GU toxicity and 1 percent (1) experienced grade 3 GU toxicity. In the HIMRT arm, 10 percent (10) experienced grade 1 GU toxicity and 15 percent (15) experienced grade 2 GU toxicity; no patients reported grade 3 GU toxicity. The five-year actuarial grade 2 or 3 late GU toxicity was 16.5 percent (95 percent CI) for patients treated with CIMRT and 15.8 percent for patients treated with HIMRT.
“These results demonstrate that the length of radiation treatment for prostate cancer can be safely decreased to six weeks (from eight-and-a-half weeks) by delivering larger daily doses of radiation without increasing the urinary and bowel effects,” said Karen E. Hoffman, MD, a co-author of the study and assistant professor in the Division of Radiation Oncology at the University of Texas MD Anderson Cancer Center in Houston. “Decreasing the length of treatment decreases the cost and is more convenient for patients.”
Brittany Ashcroft | EurekAlert!
LIGO confirms RIT's breakthrough prediction of gravitational waves
12.02.2016 | Rochester Institute of Technology
Milestone in physics: gravitational waves detected with the laser system from LZH
12.02.2016 | Laser Zentrum Hannover e.V.
Today, plants and microorganisms are heavily used for the production of medicinal products. The production of biopharmaceuticals in plants, also referred to as “Molecular Pharming”, represents a continuously growing field of plant biotechnology. Preferred host organisms include yeast and crop plants, such as maize and potato – plants with high demands. With the help of a special algal strain, the research team of Prof. Ralph Bock at the Max Planck Institute of Molecular Plant Physiology in Potsdam strives to develop a more efficient and resource-saving system for the production of medicines and vaccines. They tested its practicality by synthesizing a component of a potential AIDS vaccine.
The use of plants and microorganisms to produce pharmaceuticals is nothing new. In 1982, bacteria were genetically modified to produce human insulin, a drug...
Atomic clock experts from the Physikalisch-Technische Bundesanstalt (PTB) are the first research group in the world to have built an optical single-ion clock which attains an accuracy which had only been predicted theoretically so far. Their optical ytterbium clock achieved a relative systematic measurement uncertainty of 3 E-18. The results have been published in the current issue of the scientific journal "Physical Review Letters".
Atomic clock experts from the Physikalisch-Technische Bundesanstalt (PTB) are the first research group in the world to have built an optical single-ion clock...
The University of Würzburg has two new space projects in the pipeline which are concerned with the observation of planets and autonomous fault correction aboard satellites. The German Federal Ministry of Economic Affairs and Energy funds the projects with around 1.6 million euros.
Detecting tornadoes that sweep across Mars. Discovering meteors that fall to Earth. Investigating strange lightning that flashes from Earth's atmosphere into...
Physicists from Saarland University and the ESPCI in Paris have shown how liquids on solid surfaces can be made to slide over the surface a bit like a bobsleigh on ice. The key is to apply a coating at the boundary between the liquid and the surface that induces the liquid to slip. This results in an increase in the average flow velocity of the liquid and its throughput. This was demonstrated by studying the behaviour of droplets on surfaces with different coatings as they evolved into the equilibrium state. The results could prove useful in optimizing industrial processes, such as the extrusion of plastics.
The study has been published in the respected academic journal PNAS (Proceedings of the National Academy of Sciences of the United States of America).
Exceeding critical temperature limits in the Southern Ocean may cause the collapse of ice sheets and a sharp rise in sea levels
A future warming of the Southern Ocean caused by rising greenhouse gas concentrations in the atmosphere may severely disrupt the stability of the West...
12.02.2016 | Event News
09.02.2016 | Event News
02.02.2016 | Event News
12.02.2016 | Physics and Astronomy
12.02.2016 | Life Sciences
12.02.2016 | Medical Engineering