High dose-rate treatment moulds by afterloading techniques

A modified technique for fabrication of custom-made afterload brachytherapy appliance

Radiotherapy for carcinomas that involve the mouth and its related structures has been improved by the usage of different prostheses known as radiation carriers. These prostheses can accurately position radionuclide such as radium, iridium, cesium, and cobalt to allow adequate transfer of a concentrated radiation dose to a tumor region. At the same time, they minimize the exposure to radiation of nearby tissues due to rapid fall-off the radioactivity and thus minimizing the side effects of radiation. This study emphasizes the usage of a modified technique for the development of afterload mold brachytherapy appliance for squamous cell carcinoma patients of hard palate/soft palate.

GEC-ESTRO ACROP recommendations in skin brachytherapy

PURPOSE

The aim of this publication is to compile available literature data and expert experience regarding skin brachytherapy (BT) in order to produce general recommendations on behalf of the GEC-ESTRO Group.

METHODS

We have done an exhaustive review of published articles to look for general recommendations.

RESULTS

Randomized controlled trials, systemic reviews and meta-analysis are lacking in literature and there is wide variety of prescription techniques successfully used across the radiotherapy centers. BT can be delivered as superficial application (also called contact BT or plesiotherapy) or as interstitial for tumours thicker than 5 mm within any surface, including very irregular. In selected cases, particularly in tumours located within curved surfaces, BT can be advantageous modality from dosimetric and planning point of view when compared to external beam radiotherapy. The general rule in skin BT is that the smaller the target volume, the highest dose per fraction and the shortest overall length of treatment can be used.

CONCLUSION

Skin cancer incidence is rising worldwide. BT offers an effective non-invasive or minimally invasive and relative short treatment that particularly appeals to elder and frail population.

HDR Brachytherapy with Surface Applicators: Technical Considerations and Dosimetry

HDR surface molds offer an alternative radiotherapy modality to electrons for the treatment of skin lesions. Treatment planning and dosimetry are discussed for two types of surface molds used in our clinic. Standard rectangular applicators are used on a variety of sites where surface curvature is minimal. In these cases an idealized planar geometry is used for treatment planning dose calculations. The calculations yield treatment dose uniformity at the prescription depth in tissue as well as skin dose, as a percentage of the treatment dose, and its dose uniformity. The availability of optimization techniques results in superior dose uniformity at depth but the dose at the skin has to be carefully evaluated. We have studied the dependence of these dosimetric parameters on the size of the surface mold and the type of optimization procedure used in the dosimetry calculations. The second type of surface applicator involves the use of a customized silicone rubber mold attached to a thermoplastic mask of the patient. We have used them to treat lesions of the face where surface curvatures are appreciable and reproducibility of setup is more critical. In these cases a CT data set is used for reconstruction of the catheters, activation of relevant dwell positions and dosimetry, including optimization. Towards establishing effective methods for quality assurance of the optimized HDR surface mold planning calculations, we have compared their dosimetry to both a classical brachytherapy system and to one based on an analytical model of the applicator. The classical system yields an independent verification of the integrated activity used in the planning calculations, whereas the analytical model is used to evaluate depth dose dependence on mold size and optimization.

High dose rate brachytherapy using molds after chemoradiotherapy for oral cavity cancer

PURPOSE

The aim of this study was to investigate the role of the combined use of customized molds and a high dose rate (HDR) remote afterloading brachytherapy apparatus with a (192)Ir microsource in the treatment of superficial oral carcinomas after chemoradiotherapy.

MATERIALS AND METHODS

Nine patients with oral squamous cell carcinoma who were treated using this combined technique were analyzed retrospectively. The primary sites of the tumors were the mouth floor, gingiva, and soft palate. For each patient, a customized mold was fabricated in which 2-3 afterloading catheters were placed for the (192)Ir source. Three to eight fractions of 3 Gy, 5 mm below the mold surface, were given following external radiotherapy of 24-50 Gy/2 Gy combined with chemotherapy (peplomycin or taxotere). The total dose of HDR brachytherapy ranged from 9 to 24 Gy.

RESULTS

The 2-year local control probability was 100% and the 2-year cause-specific survival rate was 100%. No serious complications (i.e., ulcer or bone exposure) have been observed thus far during the follow-up period of 29-120 months.

CONCLUSION

HDR brachytherapy using the mold technique after chemoradiotherapy is a safe and excellent method for selected early and superficial oral cavity cancers.

Experience of high-dose-rate brachytherapy for head and neck cancer treated by a customized intraoral mold technique

Radiotherapy of head and neck cancer has become more successful with the advances in treatment modalities and use of a multidisciplinary approach. Higher quality treatment and a team approach to radiotherapy have thus been required for head and neck cancer. This study presents the clinical experience of high-dose-rate (HDR) brachytherapy for head and neck cancer treated by a customized intraoral mold technique. Two patients are reported for whom we created dental prostheses as the radiation carriers for HDR brachytherapy of their head and neck cancers. HDR brachytherapy with the dental prostheses reported here was feasible and effective for eradicating the head and neck cancer. It has been demonstrated that HDR brachytherapy using a customized intraoral technique can be a treatment option for patients who are not candidates for surgery or external irradiation. It is strongly suggested that specialized dentists are needed who are familiar with not only the anatomy and function of the head and neck region but also radiotherapy. Dental radiologists should take responsibility for constructing irradiation prostheses. If they do, they have the potential to improve the quality of life of patients who undergo radiotherapy for head and neck cancer.

Customized mold brachytherapy for oral carcinomas through use of high-dose-rate remote afterloading apparatus

OBJECTIVE

The aim of this study was to investigate the role of the combined use of customized molds and recently available remote afterloading brachytherapy apparatus with more flexible catheters in the treatment of superficial oral carcinomas.

STUDY DESIGN

Four patients with oral squamous cell carcinoma who were treated through use of this combined technique were analyzed retrospectively. The molds were made from transparent acrylic resin through use of a dental technique. The combined approach was applied as a boost therapy after external irradiation.

RESULTS

The 4 patients had had no recurrence of tumor or radiation injury by the end of the follow-up period.

CONCLUSIONS

The combined technique could be an excellent method of treating superficial carcinomas of the oral cavity.

Fractionated high dose rate brachytherapy moulds--a precise treatment for carcinoma of the pinna

BACKGROUND AND PURPOSE

The aim of this paper is to describe a fractionated high dose rate brachytherapy procedure for the treatment of small superficial cancers of the pinna and to report the outcome in a small series of patients.

MATERIALS AND METHODS

Thirteen patients with superficial cancers of the pinna, not invading cartilage, have been treated and in the majority of cases the tumour thickness was determined by a transdermal ultrasound measurement. For the single-plane moulds the prescribed surface dose was 45 Gy in eight fractions over 5 days and the moulds were constructed such that the full thickness of the disease, as determined by the ultrasound measurement, would lie within the 80% isodose surface. One case was treated with a sandwich mould and in this case the dose was reduced to 42.5 Gy. The treatment machine was a high dose rate microselectron, which contains a single stepping iridium source.

RESULTS

The radiation reactions were of moderate severity, but were limited to the high dose volume. In all cases there was complete tumour resolution and rapid healing occurred leaving a barely perceptible scar. There were no recurrences over a minimum follow-up time of 18 months and there were no late radiation complications in this period.

CONCLUSIONS

The treatment of superficial carcinoma of the pinna by means of HDR moulds is a safe and reliable technique. In this small series of patients there was total tumour control with excellent cosmesis.

First experiences with superfractionated skin irradiations using large afterloading molds

PURPOSE

Radiotherapy of cutaneous metastases of breast cancer requires large radiation fields and high doses. This report examines the effectiveness and sequelae of superfractionated irradiation of cutaneous metastases of breast cancer with afterloading molds on preirradiated and nonirradiated skin.

METHODS AND MATERIALS

A flexible reusable skin mold was developed for use with a pulsed (PDR) afterloader. An array of 18 parallel catheters was sewn between two foam rubber slabs 5 mm in thickness to provide a defined constant distance to the skin. By selection of appropriate dwell positions, arbitrarily shaped skin areas can be irradiated up to a maximal field size of 17 x 23.5 cm2. Irradiations are performed with a nominal 37 GBq 192Ir stepping source in pulses of 1 Gy/h at the skin surface. The dose distribution is geometrically optimized. The 80 and 50% dose levels lie 5 and 27 mm below the skin surface. Sixteen patients suffering from metastases at the thoracic wall were treated with 18 fields (78-798 cm2) and total doses of 40-50 Gy applying two PDR split courses with a pause of 4-6 weeks. Eleven of the fields had been previously irradiated with external beam therapy to doses of 50-60 Gy at 7-22 months in advance.

RESULTS

For preirradiated fields (n = 10) the results were as follows: follow-up 4.5-28.5 months (median 17); local control (LC): 8 of 10; acute skin reactions: Grade 2 (moist desquamation) 2 of 10; intermediate/late skin reactions after minimum follow-up of 3 months: Grade 1 (atrophy/pigmentation): 2 of 10, Grade 2-3a (minimal/marked teleangiectasia): 7 of 10, Grade 4 (ulcer): 1 of 10; recurrencies: 2 of 10. For newly irradiated fields (n = 7) results were: follow-up: 2-20 months (median 5); LC: 6 of 7; acute reactions: Grade 1: 4 of 7, Grade 2: 3 of 7; intermediate/late skin reactions after minimum follow-up of 3 months (n = 5): Grade 2-3a: 2 of 5; recurrencies: 0 of 7. Local control could be achieved in 82% of the mold fields. Geometric optimization was mandatory to achieve a homogeneous dose distribution on the skin.

CONCLUSION

Superfractionated brachytherapy with skin molds is an effective alternative for the treatment of skin metastases of breast cancer even if the skin is preirradiated. This method is economically advantageous compared to external beam therapy, which would require several weeks. At the curved chest wall, optimized molds can provide better dose homogeneity than abutted electron fields. Skin reactions are comparable to the sequelae of orthovolt irradiation. In preirradiated areas, PDR doses should be restricted to 40-45 Gy. PDR doses of 50 Gy seem to be the limit for tolerance even in previously unirradiated fields.

Use of the afterloading technique for intraoral radiation carriers

A method for fabrication of a radiation carrier with an adaptation of the afterloading technique has been described. The use of the afterloading technique allows for quick and easy placement of multiple radioactive sources; thus time and exposure to the radiotherapist and the patient are minimized during the period of placement and activation of the prosthesis at the time of therapy.

Postoperative vaginal radiation in endometrial cancer using a remote afterloading technique

Carcinoma of the endometrium is the most common malignancy of the female genital tract. In early stage endometrial cancer, surgery remains the primary mode of treatment while radiation therapy plays an adjuvant role. Prophylactic vaginal radiation has been shown to reduce significantly the incidence of vaginal recurrences. Between the years 1969-1976, 330 patients with FIGO Stages I and II endometrial cancer were treated according to a standard departmental policy in which 40 Gy of external radiation was given to high risk Stage I and all Stage II patients in combination with surgery and intravaginal radiation. Stage I was considered high risk if the tumor was of high grade or exhibited deep myometrial invasion. Vault radiation was delivered with a remote afterloading technique to a point .5 cm from the surface of the applicator; a total dose of 21 Gy was delivered in three fractions spaced two weeks apart over four elapsed weeks. With this regimen, the mucosal surface received a total equivalent dose of 40 Gy. These treatments were given on an outpatient basis without the need for any sedation or analgesics. All patients, regardless of stage, grade, or depth of myometrial invasion received adjuvant post-operative vaginal radiation. The minimum follow-up was 5 years, with a median follow-up of 8.5 years. The overall pelvic and/or vaginal recurrence rate was 2.7%. The incidence of vaginal complications was 3.7%. It appears that the remote afterloading treatment (RAT) for vaginal radiation is a very cost-effective therapeutic alternative, which produces minimal early or late complications and gives complete protection from radiation exposure to the medical staff. The advantages of a remote afterloading technique in delivering vaginal vault radiation in endometrial cancer are discussed in this paper.

High-dose rate intracavitary radiation therapy for advanced head and neck tumors

Fifty-seven treatments were performed on 27 head and neck pateints with recurrent or residual tumors on a high dose rate, remote controlled afterloading unit: There were 16 cases of maxillary sinus tumors, 6 epipharynx, 3 alveolar ridge, 1 hard palate and 1 floor of mouth. All patients have been followed up more than 2 years except one. Five patients are alive without local recurrence for more than 2 years. In 13 patients local tumors disappeared once and normal mucosa covered the tumor sites. Two patients died from local bleeding. In six patients this method failed to destroy tumors. Our prupose was palliative local control: therefore, in two-thirds of cases treated we were successful with this easy method of nonfractionated acute intracavitary radiation. This result is favorable, considering that all cases treated here were failures following full dose external radiation, although the treatment had to be repeated more than twice in 15 cases. Relief of symptoms is excellent when this therapy is used.

Clinical radiobiology of low dose-rate radiotherapy

Investigative irradiations of human skin have shown that the total dose required to obtain a dry desquamation does not increase with the duration of the irradiation as rapidly as it would be expected from the kinetics of repair of the sublethal injuries. This suggests that an additional mechanism, probably accumulation of the cells in a sensitive phase, occurs during a continuous irradiation with dose-rate higher than 150 rads/hour. This effect seems to vanish at smaller dose-rates.