Optimizing brachytherapy dose on the same day as the implant can control prostate cancer

As is known, brachytherapy is a radiotherapy treatment involving the insertion of radioactive sources within or near the tumour.

Between 2000 and 2006 the research team analysed the cases of 220 patients suffering from low-risk prostate cancer and who had been treated with iodine-125 brachytherapy seed. The researchers aimed to elucidate the parameters that influence curing amongst these patients. In the case of prostate cancer a long period of observation is required in order to obtain results, "because it is an illness in which relapse problems may occur after 5 years subsequent to the treatment," pointed out Doctor Rafael Martínez-Monge, Director of the Department of the Radiotherapy Oncology Clinic.

Twenty percentage points difference in risk of relapse

Thus the research demonstrated that the radiation dose given during brachytherapy influences patient survival. They found a reliable parameter. They observed that on the day of the brachytherapy implant, those patients with a projected dose less than 147 Gy (gray -- Gy -- is the unit of radiation dose) showed a greater risk of relapse than those with 147 Gy or more. In concrete, they achieved control of the illness in 94.4% of those patients with an optimum implant level, compared to 75.5% amongst those who had a dose less than 147 Gy. This represents almost twenty percentage points difference and it should be remembered that an optimum implant means cure in 95% of the cases.

Moreover, another novel aspect of the research was the study on calculating the radiation dose on the same day of the implant. The international recommendation is that this calculation be carried out 30 days after, because the insertion of the radioactive seeds causes inflammation of the prostate and thus may distort the calculation. In most cases this inflammation disappears after a month. "Nevertheless, at the University Hospital of Navarre, we wish to know from the very day of the implant if the dose is suitable; otherwise, we can make an on-the-spot adjustment, both to ensure the efficacy of the treatment as well as to avoid any subsequent displacement to the patient," explained Doctor Martínez-Monge.