Hypofractionated Accelerated Post-Operative Radiation Therapy for Prostate Cancer (pHART 4)
There is strong evidence that the immediate use of radiation therapy (“adjuvant”) for patients who have disease extending outside the capsule or edge of the prostate at the time of surgery (radical prostatectomy) improves a number of outcomes including overall survival. Conventional radiation treatment delivers small amounts of radiation for 30-35 business days over 7-7.5 weeks. Higher doses of radiation (known as hypofractionation) can be delivered in fewer visits using a more accurate technique (image guided radiation therapy). This technique has the potential to better control prostate cancer with equal or less side effects and requires fewer visits. Forty post-prostatectomy patients who require adjuvant radiation after surgery will be treated with 51 Gy in 17 fractions (3 Gy per day) over 3.5 weeks using highly accurate and precise radiation treatments. Patients will be followed weekly while receiving radiation treatment, at 3 months after the start of radiation and then every 6 months until 5 years
The primary objectives are to determine the acute and late toxicity to the rectum and bladder after treatment and to measure the interfraction motion of the prostate bed during the course of radiation therapy. Quality of Life and bloodwork (PSA and testosterone) will be assessed every 6 months until 5 years.
Due to positive results, immediate post-operative radiation therapy to the prostate bed for patients with extracapsular extension of prostate cancer and/or positive is gaining general acceptance and many patients are being referred post-operatively for adjuvant radiation therapy. This is creating an increasing burden on radiation therapy departments. A strategy that could decrease the number of treatments, yet maintain its efficacy, would be well embraced as long as the toxicities were acceptable. Conventional post-operative radiation treatment involves delivering small amounts of radiation to the prostate for 30-33 business days over a period of 6-6.5 weeks. There is growing evidence that prostate cancer cells may be killed more effectively if higher doses of radiation are delivered everyday (known as hypofractionation). However, if the higher daily dose were delivered in the conventional manner, this could cause more side effects to the neighboring organs (rectum and bladder). Intensity modulated radiation therapy (IMRT) is a new technique which has the ability to deliver radiation more conformally, meaning that radiation dose can be “sculpted” to the prostate gland, while minimizing the amount of radiation to the bladder and rectum. A certain amount of movement of the prostate normally occurs within the body. When using a more conformal approach, one has to make sure that the prostate will not be missed. The most reliable way to ensure the prostate is targeted using IMRT is to insert tiny gold seeds into the prostate/prostate bed, which can be seen using a special type of X-Ray camera during treatment (called a portal imager). By using gold seeds in conjunction with IMRT, there is the potential to safely deliver a more intensive dose of radiation to the prostate gland without increasing the amount of side effects. In other studies where shorter and more intense courses of radiation have been given using similar high-precision techniques, the side effects of treatment have indeed been no worse or even better than the usual techniques.
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