Radiotherapy Research Today is a free monthly online journal that collates and summarizes the latest research about Radiotherapy, including details on cancer treatment, side effects. | ||||||||
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The impact of dose escalation on secondary cancer risk after radiotherapy of prostate cancer.Schneider U, Lomax A, Besserer J, Pemler P, Lombriser N, Kaser-Hotz B Division of Medical Physics, Department of Radiation Oncology and Nuclear Medicine, Triemli Hospital, Zürich, Switzerland. uwe.schneider@psi.ch PURPOSE: To estimate secondary cancer risk due to dose escalation in patients treated for prostatic carcinoma with three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated RT (IMRT), and spot-scanned proton RT. METHODS AND MATERIALS: The organ equivalent dose (OED) concept with a linear-exponential, a plateau, and a linear dose-response curve was applied to dose distributions of 23 patients who received RT of prostate cancer. Conformal RT was used in 7 patients, 8 patients received IMRT with 6- and 15-MV photons, and 8 patients were treated with spot-scanned protons. We applied target doses ranging from 70 Gy to 100 Gy. Cancer risk was estimated as a function of target dose and tumor control probability. RESULTS: At a 100-Gy target dose the secondary cancer risk relative to the 3D treatment plan at 70 Gy was +18.4% (15.0% for a plateau model, 22.3% for a linear model) for the 6-MV IMRT plan, +25.3% (17.0%, 14.1%) for the 15-MV IMRT plan, and -40.7% (-41.3%, -40.0%) for the spot-scanned protons. The increasing risk of developing a radiation-associated malignancy after RT with increasing dose was balanced by the enhanced cure rates at a larger dose. CONCLUSIONS: Cancer risk after dose escalation for prostate RT is expected to be equal to or lower than for conventional 3D treatment at 70 Gy, independent of treatment modality or dose-response model. Spot-scanned protons are the treatment of choice for dose escalation because this therapy can halve the risk of secondary cancers. Published 4 June 2007 in Int J Radiat Oncol Biol Phys, 68(3): 892-7.
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