[Time-course of plasma testosterone in patients with prostate cancer treated by endocrine therapy]

Parameter identification of a model for prostate cancer treated by intermittent therapy

Adenocarcinoma is the most frequent cancer affecting the prostate walnut-size gland in the male reproductive system. Such cancer may have a very slow progression or may be associated with a "dark prognosis" when tumor cells are spreading very quickly. Prostate cancers have the particular properties to be marked by the level of prostate specific antigen (PSA) in blood which allows to follow its evolution. At least in its first phase, prostate adenocarcinoma is most often hormone-dependent and, consequently, hormone therapy is a possible treatment. Since few years, hormone therapy started to be provided intermittently for improving patient's quality of life. Today, durations of on- and off-treatment periods are still chosen empirically, most likely explaining why there is no clear benefit from the survival point of view. We therefore developed a model for describing the interaction between the tumor environment, the PSA produced by hormone-dependent and hormone-independent tumor cells, respectively, and the level of androgens. Model parameters were identified using a genetic algorithm applied to the PSA time series measured in a few patients who initially received prostatectomy and were then treated by intermittent hormone therapy (LHRH analogs and anti-androgen). The measured PSA time series is quite correctly reproduced by free runs over the whole follow-up. Model parameter values allow for distinguishing different types of patient (age and Gleason score) meaning that the model can be individualized. We thus showed that the long-term evolution of the cancer can be affected by durations of on- and off-treatment periods.

Non-monotonic dose-response relationships and endocrine disruptors: a qualitative method of assessment

Experimental studies investigating the effects of endocrine disruptors frequently identify potential unconventional dose-response relationships called non-monotonic dose-response (NMDR) relationships. Standardized approaches for investigating NMDR relationships in a risk assessment context are missing. The aim of this work was to develop criteria for assessing the strength of NMDR relationships. A literature search was conducted to identify published studies that report NMDR relationships with endocrine disruptors. Fifty-one experimental studies that investigated various effects associated with endocrine disruption elicited by many substances were selected. Scoring criteria were applied by adaptation of an approach previously used for identification of hormesis-type dose-response relationships. Out of the 148 NMDR relationships analyzed, 82 were categorized with this method as having a "moderate" to "high" level of plausibility for various effects. Numerous modes of action described in the literature can explain such phenomena. NMDR can arise from numerous molecular mechanisms such as opposing effects induced by multiple receptors differing by their affinity, receptor desensitization, negative feedback with increasing dose, or dose-dependent metabolism modulation. A stepwise decision tree was developed as a tool to standardize the analysis of NMDR relationships observed in the literature with the final aim to use these results in a Risk Assessment purpose. This decision tree was finally applied to studies focused on the effects of bisphenol A.

[New perspectives in prostate cancer management]

The treatment of prostate cancer is experiencing important innovations. Hormone therapy includes a new class of drugs: LHRH antagonists, which induce a rapid, fast and sustained reduction of testosterone levels. Active surveillance enables to avoid an aggressive treatment without decreasing survival, provided that strict eligibility and follow-up criteria are applied. New imaging techniques and laboratory assays lead to early diagnosis of small size tumors. Lastly, focal therapy has the potential to target localized cancers without deterioration of surrounding structures. These concomitant improvements offer the clinician and the patient attractive options for prostate cancer management. However, they are not devoid of limitations and constraints. Thus, it is crucial to define the most appropriate patient's profile for each therapeutic option, taking into account the objective characteristics of the tumor and the psychological features of the patient.

[First line indications for hormonal therapy in prostate cancer]

The utilization of androgen deprivation therapy in prostate cancer has evolved over time. Unquestionably considered first line treatment in metastatic cancers or in case of lymph node involvement, it is increasingly used in locally advanced and high-risk cancers, combined with radiation therapy. However, the practical modalities of treatment are still controversial (neoadjuvant, concomitant/adjuvant) and should be discussed on a case-by-case basis, taking into account tumor stage and risk level, which depends mainly on Gleason score and PSA levels and kinetics. Hormone therapy is also indicated in case of systemic relapse, especially if PSA doubling time is less than 12 months. LHRH agonists have become the standard care; antiandrogens can be added at the beginning of the LHRH agonist therapy to obtain a complete androgen blockade. Intermittent androgen deprivation therapy has recently proved efficacious and might be more widely used in the future, provided that strict prescription and follow-up recommendations are clearly established.