Brachytherapy for Recurrent Prostate Cancer

Overview

After a curative treatment by radiotherapy for localized prostate cancer, between 20% and 50% of patients may have a biological relapse as a progressive re -rise of PSA. After prostate brachytherapy with low flow, this rate is between 2% and 6%. Depending on risk factors initially present, some patients will have a micro metastatic disease at the time of re-rise, but others will have a true local recurrence purely intra-prostate. Local recurrence after radiotherapy is associated with a high incidence of distant metastatic relapse and poor overall survival. For these reasons, the possibility of offering a local treatment for this selected population of patients can have a major therapeutic interest and allow changing a situation often considered palliative to the possibility of a second curative treatment. Currently, there is no consensus regarding the optimal management of patients with purely local recurrence after prostate irradiation at first intention. When an external radiotherapy or brachytherapy is performed as first choice in a patient with prostate cancer, several remedial treatments have been proposed, with controversial results the decision-making for clinicians and for difficult patients. These main therapeutic options remedial (surgery, cryotherapy and brachytherapy) have the potential for complications such as rectal injury, impotence or incontinence Brachytherapy is a new salvage treatment being evaluated in the United States (Phase II study of the Radiation Therapy Oncology Group No. 0526). Several retrospective trials have shown very encouraging results in terms of acute toxicity and biochemical control in the short term. Thus, a team from Mount Sinai in New York recently published for the first time 10 years retrospective results with this approach. In their experience after treatment failures with external beam radiotherapy or brachytherapy, a dose of 122 Gy was delivered over 90% of the prostate gland. Doing this they observed biochemical control rates and survival specific of 54 % and 96 %, respectively at 10 years, with an hormone treatment associated (median 6 months) in 84 % of cases. Four patients had grade 3 toxicity or higher (11%). To reduce the rate of late toxicities the team from the University Of California San Francisco (UCSF), tested focal brachytherapy guided by functional MRI (MRI spectroscopy) to re-treat local recurrence after initial brachytherapy as monotherapy or boost. By delivering 144 Gy on recidivism objectified on MRI, the authors observed that a minimal dose of 37Gy covered 90 % of the prostate gland to treat the risk of microscopic disease. Doing this, the rate of observed toxicities and biochemical control appeared encouraging, with a median follow-up of 2 years, since no grade 3 toxicity was observed and 74% of patients achieved a PSA nadir \<0.5 ng / mL without associated hormone. In case of external radiation or brachytherapy, several attempts proposed to associate an injection of hyaluronic acid gel to the prostate - rectum interface to spare healthy tissue irradiated and thus reduce the rate of radiation proctitis. The feasibility of implementing this gel has been demonstrated in patients with non- irradiated tissues. No inherent toxicity of the injection of hyaluronic acid gel has been described after prostate brachytherapy first line. The feasibility of this injection remains unproven to date on patients previously irradiated externally or by brachytherapy. We hypothesize that the risk of radiation proctitis and fistulas front prostate could be reduced using this technique in this indication. We propose to carry out a French prospective multicenter phase II trial combining brachytherapy remedial with an injection of hyaluronic acid after surgery to reduce the risk of radiation proctitis and / or recto -urinary fistula in a patient population hyper- selected with a high probability of isolated local recurrence.