Visualizing Bioabsorbable Spacer Effectiveness by Confirming the Distal-Tail of Carbon-Ion Beams: First-In-Human Report

Abstract

In particle therapy, bioabsorbable polyglycolic acid (PGA) spacer was developed to reduce the healthy organ irradiation dose, especially in the gastrointestinal tract. The PGA spacer is safe and effective; however, there are no reports that have confirmed whether the PGA spacer which inserted in the body actually stops the carbon-ion (C-ion) beams. Here, we visualized and confirmed that the PGA spacer stops the C-ion beams in the body based on the dose distribution using auto-activation positron emission tomography (AAPET). A 59-year-old dedifferentiated retroperitoneal liposarcoma patient underwent C-ion radiotherapy (C-ion RT) on referral. A month before C-ion RT initiation, the patient underwent PGA spacer placement. Postoperatively, the patient received 4.4 Gy (RBE) per fraction of C-ion RT, followed by AAPET. AAPET revealed lower positron emitter concentrations at the distal tissue ventral to the PGA spacer than in the planning target volume. In observing the efficacy of the PGA spacer, the AAPET images and the average count per second of the positron emitter suggested that the PGA spacer stopped the C-ion beams in the body in accordance with the dose distribution. Therefore, AAPET was useful in confirming the PGA spacer’s effectiveness in this study, and the PGA spacer stopped the C-ion beams.

Multidisciplinary management of locally recurrent rectal cancer with carbon ion radiotherapy followed by prophylactic removal of the irradiated bowel: a case report

“…In cases where the tumor is in close proximity with the intestinal tract but does not directly invade the tumor, recent efforts have expanded the indication of CIRT by physically separating the tumor from the surrounding organs with high risk of irradiation adverse effects using spacer insertion before CIRT [ 22 , 23 ]. However, this spacer cannot be used when the recurrent lesion has directly invaded the organs at risk of irradiation adverse effects, as in this case owing to the increased risk of recurrent cancer seeding and infectious complications associated with intestinal tract injury during spacer placement surgery.…”

“…However, this spacer cannot be used when the recurrent lesion has directly invaded the organs at risk of irradiation adverse effects, as in this case owing to the increased risk of recurrent cancer seeding and infectious complications associated with intestinal tract injury during spacer placement surgery. Therefore, there have been few cases of its use in patients undergoing surgical intervention prior to CIRT [ 21 , 22 ]. In cases where spacer insertion surgery is not possible, it may be feasible to use a multidisciplinary approach involving CIRT followed by prophylactic-irradiated intestine removal, which was used in this case.…”