Significant Incidental Findings Unrelated to the Primary Cancer on CT Simulation Treatment Planning Scans

Abstract

<h3>Purpose/Objective(s)</h3> Incidental tumor findings on radiographic imaging are rare and often do not manifest symptoms such as a lump or associated pain. These tumors may represent major clinically relevant findings that need additional imaging and testing. Although some studies published metastatic disease of the primary cancer, we are not aware of publications in the U.S. focusing solely on major, significant findings, and unrelated to the primary disease during radiotherapy planning. In this paper, we introduce several cases where CT planning images revealed significant clinical findings unrelated to the primary cancer that required further investigation. All patients with these major findings were followed-up for diagnostic imaging, examination, and proper referral. <h3>Materials/Methods</h3> To simulate real-life situation when CT treatment planning is performed in a radiation oncology department, the radiation oncologist reviewed a total of 115 patients with CT treatment planning that was performed during the 2-year period of 2017-2018. These CTs were performed during routine radiotherapy planning for curative purposes: brain tumors (n = 10 or 9%), head and neck cancer (n = 15 or 13%), lung cancer (n = 30 or 26%), breast cancer (n = 35 or 30%), prostate cancer (n = 25 or 22%). <h3>Results</h3> We report incidental but significant findings on radiotherapy planning CT scans unrelated to the primary cancer. A total of 4 abnormal findings (3 neoplasms and 1 benign) were discovered from a total of 115 CT scans done for radiotherapy planning. The 3 neoplasms were: hepatocellular carcinoma, thyroid cancer, and large adrenal adenoma. The one benign finding was extensive eventration of the left hemi-diaphragm. <h3>Conclusion</h3> CT planning scans are routinely performed separately in the radiation oncology department for proper treatment mapping of cancer patients. These CT images are usually stored in the RO department server and not in radiology PACS system. At the present time, it is not known how many percent of radiation oncologists routinely check CT scans for incidental findings. The 4 case reports stated in this article demonstrate that although rare, there are malignancies/abnormalities unrelated to the primary cancer that could be missed in the CT planning process. We therefore recommend that radiation oncologists take charge of this issue and implement a method of proper interpretation of CT simulation images by either the radiation oncologists responsible for the case, or designated diagnostic radiologists (if such arrangement exists), to ensure that incidental findings are not missed. In any radiation oncology (RO) department, a routine QA (quality assurance) checklist often includes: consultation note, verification of pathology, consent form, verification of dosimetry, verification of physics report etc., we believe that proper interpretation of CT simulation images for incidental findings should be part of the QA checklist in a modern RO department