May 22, 2013 - 11:01 pm
Current standards and future directions for prostate cancer radiation therapy, "Beyond the Abstract," by Michael Pinkawa, MD
Published on 03 May 2013
BERKELEY, CA (UroToday.com) - Radical prostatectomy and radiation therapy are curative treatment options with equivalent outcomes as determined by biochemical recurrence-free survival. Therefore, patients and physicians need to especially consider treatment-related toxicity before the decision for a specific treatment modality.
Radiation therapy concepts can vary widely between different institutions. A suitable technique, dose, target volume, and the option of a combination with androgen deprivation therapy need to be chosen for each individual patient. Target volume always includes the whole prostate, with the base of the seminal vesicles for intermediate- and high-risk patients, and pelvic lymph nodes for patients with an invasion risk of > 15%. An optimal standard external-beam radiotherapy to reach favourable tumour control rates with only limited toxicity currently includes intensity-modulated and image-guided radiotherapy techniques with total doses of ≥ 76-78Gy in conventional fractionation. Several different options are available for image-guided radiotherapy, allowing reduced safety margins and treatment volumes: radio-opaque or electromagnetic markers, cone-beam CT, or ultrasound-based systems. Intermediate-risk patients benefit from short-term androgen deprivation therapy, high-risk patients benefit from a longer androgen deprivation therapy of at least 2-3 years, current studies are evaluating if this benefit still exists if higher doses of ≥ 76Gy are used.
Prostate brachytherapy can be alternatively applied as a single modality for low risk and selected intermediate risk patients or as a boost to external beam radiotherapy, especially for patients with significant adverse prognostic factors.
Several new concepts have been introduced in the last years. Promising results of clinical studies indicate the potential to change the radiotherapy strategy for significant patient numbers.
Protons or carbon ions are alternatives available only in specific centres. Experience with proton therapy is increasing with growing availability of proton treatment centres. However, current clinical data do not support a benefit in comparison to photon intensity-modulated radiotherapy. The application of carbon ions is a promising experimental option available only for a few patients.
Hypofractionation concepts with even extreme single fractions of 6-10Gy, as originally known from HDR brachytherapy concepts, are increasingly used. Thus, treatment duration can be shortened substantially, increasing patient convenience. Hypofractionation concepts have a great potential to gain more acceptance in the next 5-10 years.
Progress in molecular imaging methods, specifically positron emission tomography (PET) and multiparametric magnetic resonance tomography/spectroscopy, along with increasing radiotherapy conformality and accuracy, allow the dose escalation to an intraprostatic malignant lesion. The simultaneous integrated boost concept is a dose escalation to the macroscopic tumour with the best possible normal tissue protection. Only limited clinical experience is currently available.
The application of a hydrogel spacer is a well-tolerated procedure to effectively protect the rectal wall. In contrast to the usual direct contact of the prostate and rectal wall, especially in the medial prostate planes, a distance of about 1 cm ensures the exclusion of the rectal wall from the planning target volume and thus the high isodoses. There is a great potential for increasing spacer application within the next few years.
Department of Radiation Oncology, RWTH Aachen University, Pauwelsstr. 30, 52072, Aachen, Germany