Women diagnosed with cervical cancer usually receive some form of radiation therapy to attack the tumor cells in the cervix and to prevent cancer from spreading to other organs. Ideally, a physician wants to use as much radiation as possible to kill the cancer cells, but not affect the healthy surrounding tissue or organs.
A recent report from oncology experts at the UC San Diego School of Medicine indicates that consistently hitting the targeted tumors in the cervix throughout multiple radiation therapy sessions may be more difficult than once believed. It appears that small, normal day-to-day movements of the cervix can add up to big differences in the accuracy and effectiveness of radiation treatments.
The study looked at a series of more than 500 cervical images from 10 patients with cervical cancer during 2007 to 2008. For the study, each patient had two small gold “seeds” implanted into their cervix to serve as easy-to-identify location markers during the radiation therapy and imaging.
The researchers found that the cervix could move anywhere from two to 20 millimeters, depending on the woman, between the first and last therapy sessions. The authors suggest that physicians may need to alter their radiation settings to take these movements into account in order to get the optimal radiation dose to tumors and to avoid healthy tissues.
“The study implies that you have to be very careful from the beginning to the end of treatment,” states Catheryn Yashar, M.D., assistant professor of radiation oncology who lead the study. “Future research will have to solve this problem—how to keep the cervix in our sights and still spare healthy tissue.”
Some groups are investigating the value of combining imaging techniques like PET and CT scans to improve delivery of radiation treatments to cervical cancer patients. A study from Washington University School of Medicine in St. Louis, MO found that taking the two different types of images in a single session helps give physicians a more accurate view of a patient’s cervix and the tumor(s) growing within it.
“Until recently PET/CT simulation involved obtaining a CT scan in one department and a PET in another, often on different days,” said Dr. Sasha Wahab, lead author of the study described in a Bio-Medicine report. "By using a PET and CT taken back to back with the patient in the same position, we reduce the risk of errors due to motion."
"The better we can see the tumor, the better we can treat it. This may lead to more effective treatment with lower side effects," adds Dr. Wahab.
Article Links:
UC San Diego Press Release, Feb 2009, “Cervix Moves Significantly More Than Previously Thought During Radiation for Cancer”
http://health.ucsd.edu/news/2009/2-10-cervical-movement.htm
BioNews, 2006. “Concurrent PET/CT for Radiation Therapy Planning Shows Promise Over Separate Pet and CT,”
http://news.bio-medicine.org/medicine-news-3/Concurrent-PET-CT-for-radiation-therapy-planning-shows-promise-over-separate-PET-and-CT-4990-1/
Related links:
Fayed, L., 2008. “Radiation Therapy for Cervical Cancer, About.com article:
http://cervicalcancer.about.com/od/treatment/a/radiation.htm