|
Brachytherapy is a type of radiotherapy, or radiation treatment, offered to certain cancer patients. There are two types of brachytherapy – high dose-rate (HDR) and low dose-rate (LDR). LDR brachytherapy is the type that is most commonly used to treat prostate cancer; it may sometimes be referred to as ‘seed implantation’ or it may also be called ‘pinhole surgery’. In LDR brachytherapy, tiny radioactive particles the size of a grain of rice (see ) are implanted directly into the site of the tumour. These particles are known as ‘seeds’, and they can be inserted linked together as strands, or individually. Because the seeds are inserted or implanted directly into, or very close to, the tumour, they deliver high doses of radiation to the tumour without affecting the normal healthy tissues around it. This means that the procedure is less damaging than conventional radiation therapy, where the radioactive beam is delivered from outside the body and must pass through other tissues before reaching the tumour. LDR prostate brachytherapy (seed implantation) is a proven treatment for early, localised prostate cancer (when the cancer is contained within the prostate).〔Kupelian PA, Potters L, Khuntia D et al. Radical prostatectomy, external beam radiotherapy less than 72 Gy, external beam radiotherapy ≥72 Gy, permanent seed implantation, or combined seeds/external beam radiotherapy for stage T1-T2 prostate cancer. International Journal of Radiation Oncology Biology Physics 2004;58:25–33〕〔Potters L, Morgenstern C, Calugaru E et al. 12-year outcomes following permanent prostate brachytherapy in patients with clinically localized prostate cancer. The Journal of Urology 2005;173:1562–1566〕 Under a general anaesthetic, the radioactive seeds are injected through fine needles directly into the prostate, so that the radiotherapy can destroy the cancer cells. The seeds are permanently implanted, so they remain in place but gradually become inactive as the radioactivity decays naturally and safely over time.〔The American Brachytherapy Society: www.americanbrachytherapy.org〕 Unlike traditional surgery, LDR brachytherapy requires no incisions and is normally carried out as a day case procedure. Sometimes a single overnight stay in hospital is required. Patients usually recover quickly from LDR brachytherapy, which means that most men can return to work or normal daily activities within a few days. As described below, LDR brachytherapy has a good side-effect profile with less risk of incontinence or impotence than other treatment options,〔Frank SJ, Pisters LL, Davis J et al. An assessment of quality of life following radical prostatectomy, high dose external beam radiation therapy and brachytherapy iodine implantation as monotherapies for localized prostate cancer. The Journal of Urology 2007;177:2151–2156〕 and is becoming an increasingly popular alternative to major surgery (conventional radical prostatectomy or laparoscopic (keyhole surgery) radical prostatectomy). Isotopes used include iodine 125 (half-life 59.4 days) palladium 103 (half-life 17 days) and cesium-131 (half life 9.7 days).〔https://books.google.com/books?id=ewDNqCQ52S8C&pg=PA191#v=onepage&q&f=false〕 ==Procedure== When LDR prostate brachytherapy (seed implantation) is carried out, an ultrasound probe is inserted into the back passage (rectum), and images from this probe are used to assess the size and shape of the prostate gland. This is done so that the doctor can identify how to best deliver the right radiation dose for each patient. Then the seeds are inserted in the exact locations identified at the beginning of the procedure. This usually takes 1–2 hours.〔Salembier C, Lavagnini P, Nickers P et al. Tumour and target volumes in permanent prostate brachytherapy: a supplement to the ESTRO/EAU/EORTC recommendations on prostate brachytherapy. Radiotherapy and Oncology 2007;83:3–10〕 No surgical incision is required; instead, the radioactive seeds are inserted into the prostate gland using needles which pass through the skin between the scrotum and the rectum (the perineum) and an ultrasound probe is used to accurately guide them to their final position. The needles are put into the target positions and between 70 and 150 seeds are placed into the prostate. The needles are then removed. shows the grid-like device used to guide the needles into the perineal area; co-ordinates or ‘map references’ on this grid or template are used to pinpoint the exact positions in the prostate where the seeds are to be placed. shows how the seeds are positioned to target the tumour. The doctor uses ultrasound and X-ray pictures to make sure the seeds are in the right place. A special computer software program is used to make sure the prostate gland is completely covered by just the right dose of radiation (see ) to ensure that all cancer cells present in the prostate have been completely treated. Once in place, the seeds slowly begin to release their radiation. While the seeds are active, the patient must observe some basic precautions. Travel and contact with adults are fine; however, for the first two months following seed implantation, small children and pregnant women should not be in direct contact with the patient for prolonged periods – for example children should not sit on the patient’s knee for any length of time. Sexual intercourse can start again within a few weeks. Very occasionally a seed can be expelled in the semen on ejaculation; if this does happen, it will usually occur in the first few ejaculations, so it is advisable to use a condom for the first two or three occasions of intercourse following LDR brachytherapy.〔Ash D, Flynn A, Batterman J et al. ESTRO/EAU/EORTC recommendations on permanent seed implantation for localized prostate cancer. Radiotherapy and Oncology 2000;57:315–321〕 Patients can usually get back to normal activities and work within a few days. They should expect to be seen for follow-up after four to six weeks, and then every three months for a year, six-monthly up to five years, then annually.〔Salembier C, Lavagnini P, Nickers P et al. Tumour and target volumes in permanent prostate brachytherapy: a supplement to the ESTRO/EAU/EORTC recommendations on prostate brachytherapy. Radiotherapy and Oncology 2007;83:3–10〕〔Ash D, Flynn A, Batterman J et al. ESTRO/EAU/EORTC recommendations on permanent seed implantation for localized prostate cancer. Radiotherapy and Oncology 2000;57:315–321〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「prostate brachytherapy」の詳細全文を読む スポンサード リンク
|