It can be difficult to treat malignant tumors using radical particle therapy if the tumor is too close to healthy organs. A team led by Professor Takumi Fukumoto and Professor Ryohei Sasaki (Kobe University Graduate School of Medicine) has collaborated with Alfresa Pharma Corporation to develop a new medical device “Neskeep” to separate tumors from adjacent normal organs during particle therapy. The Neskeep is designed to be placed by surgical procedure.

Neskeep received pharmaceutical approval in December 2018 and is available to purchase from June 27, 2019.

Radiation therapy, which is one of the less invasive and less stressful treatments, has been recognized as an important cancer treatment. Health insurance from the Japanese government covers particle therapies for bone and soft tissue tumors, pediatric malignant tumors, and non-squamous head and neck tumors.

In some cases, it can be difficult to apply particle therapy when malignant tumors are located near digestive tract organs sensitive to radiation (the small and large intestine). Doctors currently use non-absorbent materials such as silicone balloons and Gore-Tex sheets to act as spacers in the abdomen and intestines, or they place the intestine or other organs outside the radiation field using an absorbent mesh. Based on several observations, some patients may then undergo a second surgery to remove the spacer or it may cause serious complications in their bodies for the rest of their lives.

The team succeeded in developing a nonwoven fabric bioabsorbable spacer that can create a space between healthy and cancerous tissues during particle therapy. After that the spacer is safely absorbed by the body.

The Neskeep is available in 5, 10 and 15mm nonwoven fabrics using polyglycolic acid, the same material as polyglycolic acid suture thread (Opepolix N (approval code: 16200BZZ01566000) and Opepolix (approval code: 16200BZZ01566000), both already approved for medical use.

In their preclinical evaluation, the team conducted physical experiments to check that the spacer fulfilled the requirements for isolating cancer from organs and providing a barrier against radiation. After safety studies in animal models, a clinical trial was carried out in Kobe University Hospital and Hyogo Ion Beam Medical Center (HIBMC). The human trial involved five patients with malignant tumors in the abdominal or pelvic region, for whom particle therapy was difficult because of the proximity of normal organs to the cancer.

In all treatments the spacer preserved enough distance between the tumor and healthy tissue during the particle therapy. Having successfully reduced the radiation exposure to the intestines, they were able to use a full dose of radiation therapy. There were no serious complications observed with this treatment, and they confirmed that the spacers safely disintegrated afterwards.

Particle therapy to treat malignant tumors is a promising new radiation treatment, and it is available in a growing number of clinics. Initially this spacer will be used mainly to treat bone tumors that are covered by insurance for particle therapy treatment. The team hopes to expand the use of this spacer alongside the expansion of insurance coverage for particle therapy, ultimately using it to treat conditions such as pancreatic and liver cancers.

About particle therapy

Currently two kinds of treatment are used in clinical settings: proton therapy (using protons) and heavy-ion radiotherapy (using carbon ions).

  • Doses of concentrated radiation in particle therapy:
    Particle beams display a physical trait called the Bragg Peak, which can be used to focus the dose of radiation to target the tumor. This also enables us to reduce the impact on healthy tissue.
  • Biological effects of particle therapy:
    Compared to X-rays, proton beams and carbon ion beams are very effective. If we take the relative biological effect on organisms as 1, the effects of proton and heavy ion beams are 1.1 and 3, and there are high expectations for effective treatment against radiation-resistant tumors.

Journal Information


First-in-human phase I study of a non-woven fabric bioabsorbable spacer for particle therapy: Space-making particle therapy (SMPT)
Ryohei Sasaki*, Yusuke Demizu, Tomohiro Yamashita, Shohei Komatsu, Hiroaki Akasaka, Daisuke Miyawaki, Kenji Yoshida, Tianyuan Wang, Tomoaki Okimoto, Takumi Fukumoto
*Corresponding author
Advances in Radiation Oncology


Preclinical Evaluation of Bioabsorbable Polyglycolic Acid Spacer for Particle Therapy
Hiroaki Akasaka, Ryohei Sasaki*, Daisuke Miyawaki, Naritoshi Mukumoto, Nor Shazrina Binti Sulaiman, Masaaki Nagata, Shigeru Yamada, Masao Murakami, Yusuke Demizu, Takumi Fukumoto
*Corresponding author
International Journal of Radiation Oncology*Biology*Physics