Long-term results of combined interstitial gold seed implantation plus external beam irradiation in localised carcinoma of the prostate

Needle displacement during HDR brachytherapy in the treatment of prostate cancer

PURPOSE

We used clinical patient data to examine implant displacement between high dose rate (HDR) brachytherapy fractions for prostate cancer to determine its impact on treatment delivery.

MATERIALS AND METHODS

We analyzed the verification films taken prior to each fraction for 96 consecutive patients treated with HDR brachytherapy boosts as part of their radiation therapy for definitive treatment of organ-confined prostate cancer at our institution. Patients were treated with 18-24 Gy in 4 fractions of HDR delivered in 40 hours followed by 36-39.6 Gy external beam radiation to the prostate. We determined the mean and maximum displacement distances of marker seeds placed in the prostate and of the implanted needles between HDR fractions.

RESULTS

Mean and maximum displacement distances between fractions were documented up to 7.6 mm and 28.5 mm, respectively, for the implant needles and 3.6 mm and 11.4 mm, respectively, for the gold marker seeds. All displacement of implant needles occurred in the caudal direction. At least 1 cm caudal displacement of needles occurred prior to 15.5% all fractions. Manual adjustment of needles was required prior to 15% of fractions, and adjustment of the CLP only was required in 24%. Most of the displacement for both the marker seeds and needles occurred between the first and second fractions.

CONCLUSIONS

There is significant caudal displacement of interstitial implant needles between HDR fractions in our prostate cancer patients. Obtaining verification films and making adjustments in the treatment volume prior to each fraction is necessary to avoid significant inaccuracies in treatment delivery.

Irradiation of localized prostatic carcinoma with a combination of high dose rate iridium-192 brachytherapy and external beam radiotherapy with three target definitions and dose levels inside the prostate gland

PURPOSE

Localized prostate cancer was treated with combined external beam radiotherapy and high dose rate Ir-192 brachytherapy with the purpose of a high dose. The technical aspects of a modified treatment are described.

METHODS

The brachytherapy was given in two sessions preceded and succeeded by external beam radiation. The radioactive source was temporarily implanted by a remote afterloading device through six to 15 needles inserted transperineally guided by transrectal ultrasound. The entire prostate gland was included in the clinical target volume. The urethra and the tumour volume could be defined and irradiated to different dose levels in more than 90% of the patients.

RESULTS

Fifty-four patients were treated. The total dose to the prostate was approximately 70 Gy and to the tumour volume 80 Gy. By calculating the corresponding dose given by 2.0 Gy fractions, considering the radiobiology by using the LQ formula and assuming an alpha/beta value for prostate tissue of 10, the dose to the prostate was approximately 84 Gy and to the tumour volume 112 Gy. For the late effects to the urethra an alpha/beta value of 3 was used, which corresponds to 85 Gy. The brachytherapy could be given with accuracy except when the dorsal border of the prostate was concave. The dose distribution then tended to be less satisfactory. Post-treatment calculations showed that the maximum dose to the rectum was 67 Gy (radiobiologically corrected to 88 Gy), given in a small volume. The early side effects from the brachytherapy were minimal. The treatment could not be performed as intended in four patients; three patients had a narrow pelvis and in one patient the prostate was unusually resilient, preventing the needles from being positioned properly.

CONCLUSIONS

This modification of a previously reported brachytherapy technique for prostate carcinoma permits a high radiation dose to the tumour and to the prostate gland, which ultimately may improve local control.

Combined treatment with temporary short-term high dose rate iridium-192 brachytherapy and external beam radiotherapy for irradiation of localized prostatic carcinoma

PURPOSE

To evaluate the treatment outcome after radical radiotherapy of localized prostate cancer in 50 patients (38 patients with stage T1-2 and 12 patients with stage T3) after a median follow-up time of 45 months (range 18-92 months).

METHODS

The treatment was given by combination of external beam radiotherapy (50 Gy) and brachytherapy (2 x 10 Gy). The brachytherapy was given using TRUS-guided percutaneously inserted temporary needles with a high dose rate remote afterloading technique with Ir-192 as the radionuclide source. Three target definitions and dose levels inside the prostate gland were used. Local control was evaluated by digital rectal examination, TRUS-guided biopsies and serum PSA evaluations.

RESULTS

Clinical and biopsy verified local control was achieved in 48 of the 50 (96%) patients; for stage T1-2 in 37 of 38 (97%) patients and for stage T3 in 11 of 12 (92%) patients. A posttreatment serum PSA level < or =1.0 ng/ml was seen in 42 (84%) patients, values from >1.0 to < or =2.0 ng/ml were seen in four (8%) patients and values exceeding 2.0 were seen in four (8%) patients. The late toxicity was minimal.

CONCLUSION

The local control results and the minimal toxicity after the combined radiotherapy treatment are promising. However, long term results are necessary before general use.