(P066) The Role of PET/CT in Radiation Treatment Planning for Non–Small-Cell Lung Cancer: Results of a National Survey

Dhwani Parikh, MD, Hani Ashamalla, MD; Rutgers Cancer Institute of New Jersey; New York Methodist Hospital

Purpose and Objectives: Positron emission tomography (PET)/CT imaging is rapidly being embraced by the radiation oncology community as a tool to improve the accuracy of target volume delineation for treatment optimization in various malignancies, particularly for non–small-cell lung cancer (NSCLC). The purpose of this study was to determine the standard practice patterns of the use of PET/CT imaging in treatment planning by radiation oncologists nationwide.

Materials and Methods: An array of questions regarding the use of PET/CT in treatment planning was developed using a web-based platform (SurveyMonkey.com). The initial questions focus on the general use of PET/CT in treatment planning, while the latter set of questions addresses the use and implications of PET/CT in treatment planning for NSCLC patients. A list of recipients was obtained from the American Society for Radiation Oncology (ASTRO) Membership Directory. An email with the link for the survey was sent to approximately 1,500 practitioners. The responses were then collected and analyzed.

Results: A total of 212 practitioners (14%) responded to the survey. Approximately 78% of the responders use PET/CT for tumor staging, while 70% routinely uses PET/CT for treatment planning purposes. The most common sites for which PET/CT is used in treatment planning are NSCLC, head and neck cancer, esophageal cancer, and lymphoma. The majority of radiation oncologists (87%) use PET/CT to delineate volumes by fusing the PET/CT to the CT simulation scan. The most commonly used technique to delineate a gross target volume on PET/CT is by the visual method (64%). In the treatment planning of NSCLC, approximately 55% of radiation oncologists indicate that the use of PET/CT results in an increase in the treatment volume by 10% to 30%, with the majority of the expanded treatment volumes resulting from fluorodeoxyglucose (FDG)-avid lymph node (LN) stations that were not readily identifiable by CT scan alone. If an LN is < 1 cm in size but is FDG-avid, 72% of responders indicate that it would be included in the target volume. About 50% of the respondents indicated that the use of PET/CT results in a decrease in treatment volume by 10% to 30%, due mostly to atelectatic lung. In monitoring response following radiation therapy, 80% of the responders obtain a PET/CT 8 weeks after completion of treatment. A standardized uptake value (SUV) cutoff of 3.1–4 is used to identify persistent or recurrent disease by 47% of responders. Of note, approximately 69% of the responders work in a private practice setting, and 31% practices in an academic center; the majority of the responders (60%) treat 10–50 cases of NSCLC annually.

Conclusions: To our knowledge, this represents the largest national survey amongst radiation oncologists on the patterns of use of PET/CT in modern treatment planning. Our findings illustrate the need for continuous training and ongoing standardization in an effort to optimize the use of PET/CT in radiation treatment planning.