Research on dynamic analysis for non-invasive high-precision radiotherapy for pancreatic cancer

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K16757
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 52040:Radiological sciences-related
• Research Institution: Kyoto University
• Principal Investigator: SASAKI Makoto 京都大学, 医学研究科, 技術職員 (60725604)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 膵臓癌 / 強度変調回転放射線治療 / 呼気息止め法 / 体内マーカ / 体外マーカ / 至適マージン / 観察者変動

Outline of Final Research Achievements

When performing volumetric modulated arc therapy (VMAT) for patients with pancreatic cancer, in about 80% of total breath-holds (BH), the localization of pancreatic cancer could be represented by that of the external markers placed on the patient's abdominal wall. Moreover, a strong correlation was observed between the movement of pancreatic cancer and the external marker in 60% of BH sessions in which the movement of pancreatic cancer exceeded 2 mm. For the 20% that cannot be substituted with the external marker, it found that a region that compensates for the movement of pancreatic cancer (margin) was necessary.
Positioning errors were assessed by comparing treatment planning CT images with a total of 810 cone-beam CT images acquired before VMAT (image matching).Consequently, the optimal margins were calculated. However, image matching included observer variations. Therefore, an automatic image matching system that does not depend on the image matching experience should be developed.

Free Research Field

放射線科学

Academic Significance and Societal Importance of the Research Achievements

膵臓癌のように呼吸性に動く腫瘍に対して放射線治療を行う場合、日本国内では呼吸性移動対策として息止め法が最も使用される。息止め法における課題は、体内の膵臓癌の位置再現性と治療中の位置変動の評価である。これらは、腹部内に体内マーカを刺入し、X線透視を用いて評価することが多いが、侵襲性を伴う。したがって、体内マーカの代わりに体外マーカを用いて、非侵襲的に膵臓癌の位置再現性や位置変動を評価できれば、患者の身体的かつ、金銭的なメリットは大きい。
本研究では、膵臓癌の位置再現性は約8割の息止めで、また治療中の変動は約9割で体外マーカによる代用が可能であることを示した。