PMC9685382_01
T2-weighted magnetic resonance images before the salvage treatment. The recurrence tumor (arrows) was adjacent to a sigmoid colon. The possibility of adhesions between the tumor and the sigmoid colon was suspected.
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However, there was a possibility of adhesion between the tumor and the sigmoid colon, which meant a risk that the radiation dose to the sigmoid colon would exceed its tolerable dose when a tumoricidal dose was delivered to the recurrent tumor (Fig. 1).
The procedure of inserting a spacer into the pelvic floor. (A) A polypropylene mesh implant 150 x 150 mm in size for the treatment of intestinal hernia was used. (B) After inverting the intestine, the lower portion of the abdominal cavity was examined; the sigmoid colon was mildly adherent to the retroperitoneum, but there was no direct adhesion to the tumor (red circle). (C) The mesh implant, folded 6 times and stitched together with sutures, was inserted into the pelvic floor as a spacer. (D) The inverted intestine was placed back on the spacer, and the operation was completed.
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After confirming that the sigmoid colon had separated from the pelvic wall, the spacer was fixed with sutures (Prolene 3-0 stitches; Ethicon, Inc; Vicryl 3-0; Ethicon, Inc) and the surgery was completed (Fig. 2).
Comparison of computed tomography images between (A) before treatment and (B) after spacer insertion. The tumor (thick arrows) was separated from the sigmoid colon (arrow heads) due to a spacer (thin arrows).
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The subsequent computed tomography (CT) images revealed an approximately 10-mm-thick spacer between the tumor and the adjacent sigmoid colon (Fig. 3).
A dose distribution of external beam radiation therapy with the 4-field box irradiation technique of 0 , 90 , 180 , and 270  portals. This patient was prescribed a dose of 50 Gy in 25 fractions.
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EBRT and high-dose-rate ISBT (HDR-ISBT). EBRT was performed at 50 Gy in 25 fractions with the 4-fields box irradiation technique of 0 , 90 , 180 , and 270  portals, using high-energy, 15-MV x-ray photons from a linear accelerator (Fig. 4).
Brachytherapy treatment planning calculated by PLATO and shown in Oncentra (Nucletron, Veenendaal, The Netherlands). (A) The upper panel shows the dose distribution of brachytherapy. (B) The lower panel shows a 3-dimensional reconstruction of the tumor (red), the needle applicators, the sigmoid colon (blue), and the spacer (cyan).
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Dose calculation was performed by a manual graphical modification to completely cover the CTV with the 100% prescribed isodose line of 6 Gy while minimizing dose to OARs (Fig. 5).