The Ten-Year Results of Radiation Therapy at the Juntendo University Nerima Hospital

Ten years have passed since the opening of the Juntendo University Nerima Hospital in July 2005. Radiation therapy started at this facility in September 2005 with one linear accelerator (Linac) considered state-of-the-art at the time. Our facility has only this one treatment device, and using this device, we have performed a lot of conventional irradiation as well as high-precision radiation therapy, such as stereotactic irradiation, intensity-modulated radiation therapy, and image-guided radiation therapy. We present the analyzed results of the past 10 years and introduce the patient characteristics of radiation therapy at the Juntendo University Nerima Hospital.


Introduction
The Juntendo University Nerima Hospital celebrated its 10-year anniversary in July 2015.Radiation therapy was introduced at the hospital in September 2005.This facility has only one treatment device i.e., a high-performance model used for high-precision radiation therapy since 2005.Using this device, we have performed many conventional irradiation and carried out high-precision radiation therapy, such as stereotactic irradiation and intensity-modulated radiation therapy with image guidance using cone-beam computed tomography (cone-beam CT, or CBCT).As of last year, the number of treatment cases has surpassed 3,000.We report the facility radiation systems, results obtained from 10 years of radiation therapy, and patient characteristics of radiation therapy at the Juntendo University Nerima Hospital.

Radiation treatment systems
The radiation treatment systems at the Juntendo University Nerima Hospital are listed in Table -1.
This hospital has one Linac system, one planning CT, and four planning systems.Even though there are four planning system devices, just two systems are currently available ＊＊ (Table -1) by valid license.
The Linac system can be used to perform imageguided radiation therapy (IGRT) using a CBCT device.Current cancer radiation therapy is image guided in the sense that some picture of the tumor region (most often CT) is used to plan the course of external beam irradiation.The Linac machine at the Juntendo University Nerima Hospital incorporates a kilo-voltage x-ray tube and detector (CBCT) orthogonal to the mega-voltage (MV) beam line.When we perform intensity-modulated radiation therapy (IMRT), we are usually treating to correct the motion error of the patient in the day-to-day irradiation by this IGRT system.prostate cancer, and lung cancer account for approximately 70% of the cases.This trend has not changed over the last few years.Four years after the hospital opened, the number of patients needing radiation therapy exceeded 300.Over the last few years, it has remained around 350 patients per year (see Figure -1).This number will be discussed later; it is thought to be close to the maximum number that can be treated by a single irradiation device.
If the patient numbers increase in the future, it will be necessary to shorten the treatment period per patient.For example, the period of recent breast-conserving radiation therapy was shortened from five weeks to around three weeks with unchanged therapeutic effect.This method also has high evidence level by clinical randomized control trial 2) .

High-precision radiation therapy
In general, high-precision radiation therapy (HPRT) supplies a higher dose to the tumor and minimizes the dose to the normal tissue by using a variety of radiation techniques such as stereotactic radiation therapy (SRT), stereotactic radiosurgery (SRS), and IMRT with IGRT.All these highprecision radiation therapies are available at the Juntendo University Nerima Hospital (see Table-3   The number of IMRT cases has reached the maximum that can be treated in one day.According to the document 3) and our experience, the appropriate number of patient treatments per day is around 35 for one Linac system.We think the maximum treatment number for 1 hour is six cases in conventional radiation therapy or four cases in IMRT.The maximum amount of HPRT safely performed has been calculated to be 20% of total treatments in one day.HPRT cases as percentages of the total number of treatments per year since 2009 are shown in Figure -3.We want to maintain this current percentage in the future.

Conclusion
We reported the analyzes of 10 years of radiation therapy at the Juntendo University Nerima Hospital.Conventional radiotherapy and HPRT were performed using just a single radiation treatment device.In recent years, the number of patient treatments has remained at close to the maximum amount for a single treatment device.We would like to continue radiation therapy at this level of safety and high quality in the future.

Figure- 1
Figure-1 Changes over 10 years in the number of new patients.It has remained around 350 patients per year for the last few years

・
). HPRT started in March 2007, and the first case was SRS with brain metastasis.IMRT started in July 2008 with a case of prostatic cancer.In 2015, the number of cases of SRT and IMRT each exceeded 100.The Juntendo University Nerima Hospital has a stereotactic radiotherapy using invasive head fixation at one time.SRT means fractionated brain stereotactic radiotherapy using a Scalpel device.SBRT means fractionated stereotactic body radiotherapy for pulmonary cancer.

Figure- 2
Figure-2 Changes in the number of HPRT cases since 2009

References 1 )Figure- 3
Figure-3 HPRT cases as percentages of the total number of treatments per year

Table - 1
Radiation treatment systems at the Juntendo University Nerima Hospital

Table - 3
The number of HPRT cases from March 2007 to September 2015