**3. Usefulness of nonwoven fabric spacers in the treatment of pancreatic cancer**

performance characteristics of these products—which come into close contact with the human body—are driven by their end use, which determines the desired function and barrier, absorption, and strength properties, and the fact that any chemical additives need to be biocompatible. Nonwoven products remain the component of choice for providing appropri‐ ate protection because of their ability to create barriers due to either the structure of the nonwoven material itself or an additional active coating for personal protective apparel. Nonwoven materials are also beginning to play a role in extracorporeal devices, such as artificial lungs, hearts, and kidneys, as well as in ligament repairs and other skeletal scaffolds,

Radiotherapy is one of the strategies used against several cancers, and X-ray or particle beams are mainly used for cancer treatment. Particle therapy, exhibiting more focused effects on target tissues, has emerged as a promising treatment modality. Several systematic reviews associated with proton or carbon-ion beam therapy discuss the extensive use of particle therapy to treat various malignant tumors, including chordoma, ocular melanoma, and prostate cancer [3–5]. Several studies have indicated the efficacy of proton therapy for the treatment of hepatocellular carcinoma or pancreatic cancer [6–9]. However, in certain cases, it is difficult to deliver curative doses of radiation to treat upper abdominal tumors without damaging adjacent radiosensitive organs, such as the duodenum, jejunum, and stomach. To overcome these anatomical difficulties and to deliver effective radiation doses to treat upper abdominal tumors, nonwoven fabric barriers have been applied as spacers to separate tumors

Nonwoven fabric is a fabric-like material manufactured from long fibers bonded together by chemical, mechanical, heat, or solvent treatment. The performance characteristics of nonwoven fabrics vary according to the material components and the manufacturing process. A charac‐ teristic of nonwoven fabrics is not to have directionality for strength or growth. In addition, specific features of nonwoven fabrics include "water absorbency," "chemical resistance," "breathability," "abrasion resistance," and "flexibility." These characteristics of nonwoven fabrics support their use as surgical gowns and hats, masks, drapes, water-absorbing mats, and machine covers. The GORE-TEX sheet is a waterproof, breathable fabric membrane and has been widely used in permanent implants, including the artificial blood vessel, for many years. The GORE-TEX sheet was the first nonwoven fabric to be applied as a spacer in the field of particle therapy [10–12] (Figure 1). The use of this spacer allows the application of particle therapy in cases in which particle therapy may result in severe incurable damage to adjacent organs. However, although the GORE-TEX spacer is useful during the period of particle therapy, it becomes a foreign body after the therapy [12]. Problems related to the ongoing presence of the spacer may be avoided by removal during a second surgery, but repeated

yet these uses are still rare compared with their other uses [2].

**2. Medical application of nonwoven fabric spacers**

and adjacent organs [10, 11].

206 Non-woven Fabrics

operations might be a risk for the patient.

Despite recent progress in treatment options for pancreatic cancer, survival rates have failed to show any significant improvement [13]. Among these modalities, resection is the only curative treatment for pancreatic cancer, but only 10%–15% of patients have operable tumors [14, 15]. The remaining patients cannot undergo resection because of local invasion or distant metastasis at the time of diagnosis [16]. Local invasion is found in approximately 40% of patients with pancreatic cancer at the time of presentation and most commonly includes the superior mesenteric vessels or the celiac trunk [17].

Chemoradiotherapy with concurrent 5-fluorouracil was historically considered the standard therapy for locally advanced pancreatic cancer [18]. Recently, successful results have been reported with the use of a combination of gemcitabine and proton therapy to treat this type of advanced pancreatic cancer. However, reductions of the irradiation doses and target fields were necessary because approximately 10% of the patients subsequently developed Grade 3 or higher gastric ulcers several months after completing the therapy [9]. In such cases, surgical placement of a spacer between the pancreas and the gastrointestinal tract might be an effective option to reduce gastrointestinal toxicity and allow the continued use of high doses of radiation.

Among pancreatic cancers in various regions, good candidates for spacer placement are unresectable pancreatic body and tail cancers. Pancreatic head cancer is not amenable to this treatment strategy because the pancreatic head cannot be separated from the duodenum.

The treatment strategy aims to keep the gastrointestinal tract away from the irradiation field by spacer placement and to allow the application of proton-beam radiotherapy with curative intent. The GORE-TEX sheets and the omentum are superimposed and applied as a spacer to maintain a safety margin of approximately 10 mm from the gastrointestinal tract. The spacer is finely fixed to the retroperitoneum, peritoneum, stomach, and surrounding tissues using 4-0 nylon to avoid hernia formation. The use of absorbable sutures for the fixation must be avoided because it leads to migration of the spacer. In the treatment of pancreatic body and tail cancers, target gastrointestinal tract components to be protected by spacer placement include the stomach, duodenum, small, jejunum, and colon. Of note, the protection of the duodenal bulb and horizontal part of the duodenum in the region of the Treitz ligament is of particular importance. The spacer placement surgery is a first step to allow proton-beam radiotherapy, and no part of the tumor is resected during this procedure.

Until the end of 2013, 8 patients with unresectable pancreatic body and tail cancers were treated by spacer placement and particle therapy as phase I and phase II trials. One-year and 2-year survival rates were 87.5% and 43.8%, respectively. These patients were free from complications associated with the gastrointestinal tract.

We believe that surgical spacer placement can be used to maintain a safety margin around the gastrointestinal tract. In consequence, full-dose particle-beam radiotherapy for pancreatic body and tail cancers can be achieved without serious toxicities.

**Figure 1.** A case of pancreatic body cancer in which a GORE-TEX spacer was placed before the application of protonbeam therapy. The left panels show perisurgical images during the placement of the GORE-TEX spacer. The right pan‐ els show computed tomography images, including tumors, liver, adjacent organs, and the GORE-TEX spacer (arrows) after the surgery.
