Early PSA decrease is an independent predictive factor of clinical failure and specific survival in patients with localized prostate cancer treated by radiotherapy with or without androgen deprivation therapy.

BACKGROUND: The aim was to identify predictors of outcome in patients with localized prostate cancer treated with external beam radiotherapy (EBRT), with or without androgen deprivation therapy (ADT). MATERIALS AND METHODS: A total of 448 patients with prostate cancer received EBRT alone (n = 361, group 1) or ADT followed by EBRT (n = 87, group 2). In group 2, ADT was initiated 3 months before EBRT. After baseline prostate-specific antigen (PSA) determination (PSA(preRT)), PSA was assessed during the 6th week of the EBRT course (PSA(6wRT)) in group 1. In group 2, PSA was measured again 3 months after the start of ADT, before EBRT (PSA(ADT-preRT)). RESULTS: In group 1, median PSA(6wRT)/PSA(preRT) was 0.72 and median prostate-specific antigen velocity (PSAV) was -1.5 ng/ml/month. In the multivariate analysis, prognostic groups and PSA(6wRT)/PSA(preRT) (or PSAV) independently predicted biochemical failure (BF), clinical failure (CF), and prostate cancer-specific survival. In group 2, the median PSA(ADT-preRT) was 1.3 ng/ml. In the high-risk group, an undetectable PSA(ADT-preRT) (< or =0.2 ng/ml) predicted BF (P < 0.01) and CF (P = 0.007). CONCLUSION: A PSA decline 6 weeks after the start of EBRT when used as monotherapy and 3 months after the start of ADT in patients treated with combined ADT and EBRT is predictive of progression and specific survival.

[Prostate localization systems for prostate radiotherapy]. / Dispositifs de repositionnement prostatique sous l'accélérateur linéaire.

The development of sophisticated conformal radiation therapy techniques for prostate cancer, such as intensity-modulated radiotherapy, implies precise and accurate targeting. Inter- and intrafraction prostate motion can be significant and should be characterized, unless the target volume may occasionally be missed. Indeed, bony landmark-based portal imaging does not provide the positional information for soft-tissue targets (prostate and seminal vesicles) or critical organs (rectum and bladder). In this article, we describe various prostate localization systems used before or during the fraction: rectal balloon, intraprostatic fiducials, ultrasound-based localization, integrated CT/linear accelerator system, megavoltage or kilovoltage cone-beam CT, Calypso 4D localization system tomotherapy, Cyberknife and Exactrac X-Ray 6D. The clinical benefit in using such prostate localization tools is not proven by randomized studies and the feasibility has just been established for some of these techniques. Nevertheless, these systems should improve local control by a more accurate delivery of an increased prescribed dose in a reduced planning target volume.

[In vivo dosimetry study of semi-conductors EPD-20 in total body irradiation technique]. / Etude de la dosimétrie in vivo par semi-conducteurs EPD-20 dans les conditions de l'irradiation corporelle totale.

PURPOSE: The objective of this work was the study of in vivo dosimetry performed in a series of 54 patients receiving total body irradiation (TBI) at the Salah-Azaiz Institute of Tunis since 2004. In vivo dosimetry measurements were compared to analytically calculated doses from monitor units delivered. PATIENTS AND METHOD: The irradiation was conducted by a linear accelerator (Clinac 1800, Varian, Palo Alto, USA) using nominal X-rays energies of 6 MV and 18 MV, depending on the thickness of the patient at the abdomen. The dose was measured by semi-conductors p-type EPD-20. These diodes were calibrated in advance with an ionization chamber "PTW Farmer" type of 0.6cm(3) and were placed on the surface of plexiglas phantom in the same TBI conditions. A study of dosimetric characteristics of semi-conductors EPD-20 was carried out as a function of beam direction and temperature. Afterwards, we conducted a comparative analysis of doses measured using these detectors during irradiation to those calculated retrospectively from monitor units delivered to each patient conditioned by TBI. RESULTS: Experience showed that semi-conductors are sensitive to the angle of beam radiation (0-90 degrees ) and the temperature (22-40 degrees C). The maximum variation is respectively 5 and 7%, but in our irradiation conditions these correction factors are less than 1%. The analysis of the results of the in vivo dosimetry had shown that the ratio of the average measured doses and analytically calculated doses at the abdomen, mediastina, right lung and head are 1.005, 1.007, 1.0135 and 1.008 with a standard deviation "type A" respectively of 3.04, 2.37, 7.09 et 4.15%. CONCLUSION: In vivo dosimetry by semi-conductors is in perfect agreement with dosimetry by calculation. However, in vivo dosimetry using semiconductors is the only technique that can reflect the dose actually received instantly by the patient during TBI given the many factors that calculation can not take into account: patient and organs motions and the heterogeneity of the targets.