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Seed implantation is a state-of-the-art radiotherapeutic procedure that is used for patients with localized prostate cancer. Under constant ultrasound monitoring, up to 80 short-beam, tiny radiation sources (so-called "seeds") made of iodine are implanted into the prostate under general or partial anesthesia. This is done with the help of puncture needles, which are placed at precisely pre-calculated positions in the prostate using a coordinate targeting system. The seeds are placed at the desired position in the prostate, where they remain to develop their radiation effect on the prostate carcinoma.
In the early stages of prostate cancer, seed implantation is considered to be an equally effective procedure to radical surgery, but is much gentler on the patient. Incontinence is practically non-existent and impotence is much less common (10-30 percent) after three years than after surgery. In addition, erectile dysfunction does not occur immediately as with surgical removal of the prostate, but develops gradually.
According to recent data from the Seattle Prostate Institute, the 15-year survival rate after seed implantation is 94 to 98 percent for low-risk patients and 89 to 97 percent for intermediate-risk patients. As the results of a long-term study on seed implantation by the West German Prostate Center* demonstrate, the biochemical recurrence-free rate after a follow-up of 71 months was 97 and 94 percent for patients with a low and medium risk profile respectively. The results confirm long-term studies from leading European and US institutes. Potters and his colleagues (Potters et al.) achieved a comparable result: out of a total of 733 patients, 84 percent had a PSA of less than 0.5 ng/ml after 7 years. This means that seed implantation for localized tumours is considered an equally effective procedure to prostatectomy (Kupelian et al.), but is considerably less invasive for the patient.
*Neubauer S, Derakhshani P., Weise C., Spira G.: Interstitial low-dose-rate mono-brachytherapy with I125-relapse-free survival and dosimetric outcome for localized prostate cancer in a single european institution Brachytherapy, Vol. 7, Number 2, 2008
According to the current guidelines of the specialist societies for urology and radiotherapy, seed implantation is primarily recommended for low-risk patients with a PSA below 10, a Gleason score below 7b, a tumor stage of T1c or T2a and a prostate volume of less than 50 ml. Patients who have had a transurethral resection of the prostate performed within the last six months are not suitable.
Before the seed implantation
After the urologist and radiotherapist have given the indication for seed implantation, "pre-planning" is carried out six to eight days before the procedure using transrectal ultrasound via the rectum. The resulting images are transmitted to a planning computer. Based on the size, shape and position of the prostate, the radiotherapist determines the number and position of the seeds.
Blood-thinning medication such as aspirin, ASA, Eliquis, Lixiana, Plavix, Xarelto or similar preparations must be discontinued one week before the operation. On the second day before the procedure, an antibiotic and an alpha-blocker should be taken as prescribed by the doctor. The day before the operation, foods that are difficult to digest should be avoided. Do not eat or drink for six hours before the procedure. The evening before the procedure, laxative measures are taken to empty the rectum.
The intervention
During "seed implantation", up to 80 short-beam, tiny radiation sources (so-called "seeds") made of iodine are inserted into the prostate under general or partial anesthesia and constant ultrasound monitoring. This is done with the help of puncture needles, which are placed at precisely pre-calculated positions in the prostate using a coordinate targeting system. The seeds are placed at the desired position in the prostate, where they remain to develop their radiation effect on the prostate carcinoma. In this way, the tumor tissue is destroyed from the inside by high-dose, targeted radiation. Until a few years ago, seed implantation was planned in advance, resulting in a radiation plan that was calculated a few days to weeks before the seeds were actually inserted. This method has been replaced by much more precise online planning. Pre-planning is now only used to order the number and activity of seeds for the procedure date. The actual planning is done "online", i.e. the ultrasound images, which form the basis for the individual radiation plan for each patient, are only created while the patient is under anesthesia. The intended positions of the seeds are constantly compared with the actual location in the ultrasound image. Shifts in the radiation plan can therefore be corrected even more precisely. The precision of brachytherapy increases, which leads to an optimization of the treatment. The procedure takes around 60 minutes. As it is a minimally invasive procedure, this method is not stressful for the body.
After the seed implantation
Approximately four weeks after the procedure, a so-called follow-up planning is carried out. This involves a CT scan to check that the seeds are still in the positions originally planned. If necessary, a correction can be made at this point without any problems.
All other urological follow-up examinations, such as the determination of the PSA value, an ultrasound examination and the determination of erectile function and micturition using standardized questionnaires, are initially carried out quarterly. Please note: Due to an inflammatory reaction of the prostate, a temporary increase in the PSA value may occur. The so-called PSA bounce is therefore not necessarily due to a progression of the cancer, but can be triggered by the effect of radiation on the prostate tissue. Patients can usually resume their professional activities within a few days after the procedure. During the initial period, patients should take it easy physically and pay attention to the following: For the first two weeks, bathing, swimming, sauna visits, sexual activities and heavy lifting are prohibited. Pressure on the prostate and perineum, e.g. from cycling, horse riding or sitting on hard surfaces, should be avoided for around eight to twelve weeks.
Seed implantation - side effects
The side effects of seed implantation are very minor. Acute side effects usually only occur after 2-4 weeks and are characterized by temporary irritation of the bladder and bowel. There may be increased stool frequency and discomfort when urinating. Some patients also report blood in the urine or ejaculate. However, heavy bleeding is very rarely observed. In the long term, 20-30% of patients develop erectile dysfunction, which then requires drug therapy.
In the USA, seed implantation has been practised for more than 25 years and, with 80,000 patients a year, is used more frequently than surgical removal of the prostate. Due to the good cure rates with comparatively minor side effects, the method has now also established itself in Germany as a recognized procedure for the treatment of prostate cancer. For the early stages of prostate cancer, seed implantation is considered an equally effective procedure to radical surgery, but is much gentler on the patient. According to the current guidelines (2021) of the German Society of Urology (DGU), patients undergoing seed implantation are significantly less likely to suffer from impaired potency. Urinary incontinence, which is up to 50 percent* after radical removal of the prostate, is also negligible at 0.3 to 3 percent after seed implantation and actually only occurs after previous transurethral prostate resection (TURP). More and more experts are calling for greater consideration to be given to the side effects of treatment in addition to the cure rate as the most important criterion when choosing a therapy.
*S3 guideline on prostate cancer 2021, German Society of Urology (DGU)
