F. Saran

Survival of very young children with medulloblastoma (primitive neuroectodermal tumor of the posterior fossa) treated with craniospinal irradiation

PURPOSE Very young children with medulloblastoma are considered to have a worse prognosis than older children. As radiotherapy remains an important part of the treatment, the adverse prognosis could be due to inadequate radiation treatment rather than biological factors. We analyzed the published literature to examine the impact of radiotherapy on survival in this group. METHODS AND MATERIALS A Medline search was performed and we reviewed studies of treatment of medulloblastoma where radiotherapy was delivered using megavoltage equipment and the minimum follow-up allowed the calculation of 5-year survival rates. RESULTS Thirty-nine studies were published between 1979 and 1996 with a treatment including craniospinal irradiation and boost to the posterior fossa. Eleven studies comprising 1366 patients analyzed survival by age at diagnosis. Eight of 11 studies showed a worse 5-year survival for the younger patient group which reached statistical significance in two. There is also a suggestion of a higher proportion of children with metastatic disease at presentation in the very young age group. The usual policy in younger children was to give a lower dose of radiotherapy to the craniospinal axis (CSA) and posterior fossa (PF) with reduction of dose in the range of 15 to 25% compared to standard treatment. As dose reduction to the posterior fossa is associated with worse survival and local recurrence is the predominant site of failure, the major determinant of worse survival in very young children with medulloblastoma may be suboptimal radiotherapy. Protocols including postoperative chemotherapy with delayed, omitted, or only local tumor irradiation do not reach survival rates of protocols with standard radiotherapy, also suggesting a continued importance for irradiation. CONCLUSION Very young children with medulloblastoma have a worse prognosis than older children. Inadequate radiation dose and technique to the primary tumor region may be a major contributing factor. Current chemotherapeutic regimes alone are not sufficient to compensate for reduced radiation doses and volumes.

In vivo dose increase in the presence of dental alloys during 60Co-gamma-ray therapy of the oral cavity

During irradiation of the mouth cavity, dental metallic materials emit secondary electrons and thus increase the applied radiation dose in their vicinity. Therefore, local destruction of the mucous membrane contacting metallic dental crowns and fillings may be observed. Available data on this dose increase are based on measurements with beam arrangements perpendicular to the metallic surface. Since the dose modification depends on the beam direction in relation to specimen surface, a reliable prediction of dose modification in the close vicinity of dental caps on fillings under complex beam arrangements, as applied in the irradiation of head and neck region from the published data is not possible. Therefore, we measured dose increase in the immediate surrounding of metallic dental material using thermoluminescence dosimetry on the phantom and during routinely applied 60Co gamma ray therapy. Phantom measurements were carried out using several oblique irradiation angles and rotational therapy. In vivo measurements were carried out at alloy specimens containing gold, palladium, and amalgam in six patients and at permanently fixed golden teeth in five patients. In vivo, the following relative dose increase values according to a simultaneously measured reference value were obtained at the surface of different dental materials: 61% for fixed golden caps. 68% for the specimen containing gold, 33% for the specimen of palladium and 61% for the specimen of amalgam. The measured dose increases due to metallic dental material during routinely applied external 60Co beam irradiation are lower compared with those of perpendicular beam arrangements. Although, the extent of dose modification is less than expected, we still advocate protection of the oral mucosa to prevent painful lesion spots.

Verbesserte Reproduzierbarkeit und erhöhter Komfort durch standardisierte Lagerungshilfe bei der Bestrahlung der weiblichen Brust

ZusammenfassungHintergrundLagerungs-und Fixationstechniken sind Voraussetzung für eine präzise Radiotherapie. Die angebotenen standardisierten Lagerungshilfen sind unzureichend. Daher wurde von uns eine neue, allgemein anwendbare Lagerungshilfe aus Hartschaumstoff zur Mammabestrahlung entworfen und in einer prospektiven Studie auf klinische Eignung geprüft.Patienten und MethodeBei 55 Patientinnen, die nach brusterhaltender Operation bei Mammakarzinom adjuvant radiotherapiert wurden, erfolgte die Bestrahlung in freier Lagerung (n=27) bzw. mit der von uns entwickelten Lagerungshilfe (n=28). Es wurden die zur Lagerung benötigte Zeit, der subjektive Liegekomfort und aus dem Vergleich der Verifikations- mit den Simulationsaufnahmen die Reproduzierbarkeit der Lagerung ermittelt.ErgebnisseDie Reproduzierbarkeit der Bestrahlung konnte signifikant verbessert werden (mittlere Abweichung ohen Lagerungshilfe: 8,4 mm, mit Lagerungshilfe: 6,1 mm, p<0,001). Der zusätzliche Zeitaufwand zur Patientenlagerung betrug im Mittel 19 s (mit Lagerungshilfe: 74 s, ohne: 55s). Signifikant mehr Patientinnen (72%) empfanden die Lagerung mit der untersuchten Lagerungshilfe als angenehm, während nur 46% die freie Lagerung als angenehm beurteilten.SchlußfolgerungenDie von uns entworfene Lagerungshilfe trägt zur Qualitätssicherung bei der Mammabestrahlung bei und erhöht deutlich den Liegekomfort. Im Vergleich zu üblichen Lagerungs- und Fixationshilfen ist sie bei geringem Kostenaufwand schnell und einfach anwendbar. Daher ist ihr Einsatz zu empfehlen.BackgroundPositioning and immobilisation techniques are essential for precise radiotherapy. The currently available standardised positioning devices are insufficient. For this reason, we designed a new and generally usable hard foam positioning support cushion for the breast irradiation and tested its usefulness in a prospective study.Patients and MethodsFifty-five female breast cancer patients receiving adjuvant radiotherapy following breast conservative surgery were irradiated either without immobilisation (n=27) or with the developed positioning support cushion (n=28). The time necessary for patient set-up, the subjective lying comfort and — comparing portal images with simulator images — the reproducibility of the set-up were determined.ResultsIt was possible to improve irradiation reproducibility significantly (average deviation without positioning support cushion: 8.4 mm, with positioning support cushion: 6.1 mm, p<0.001). The additional time required for the positioning of the patient was in average 19 s (with positioning support cushion: 74 s, without cushion: 55 s). A significantly higher proportion of patients (72%) found the position with the hard foam cushion was pleasant, whereas only 46% of patients were pleased with the position without cushion.ConclusionThe positioning support cushion designed in our department seems to play an important role in quality assurance of external beam irradiation of the breast and significantly increases the patients’ comfort in a supine position. Compared to conventional positioning and fixation devices it may be quickly and easily applied at low cost. Therefore, its use can be recommended.

INCREASE OF SURFACE DOSE USING WOUND DRESSINGS DURING PERCUTANEOUS RADIOTHERAPY WITH PHOTONS AND ELECTRONS

Different wound dressings are used for the supportive treatment of patients with radiation-induced skin lesions. Depending on beam quality and energy, an increase of the dose administered to the skin and thus an aggravated skin reaction is to be expected during percutaneous irradiation. The increase of the skin dose during irradiation with photons (Co60, 6 MV, 42 MV) and electrons (7 MeV, 20 MeV, 42 MeV) was determined using thermoluminescence dosimetry. The use of wound dressings during electron irradiation and during soft irradiation therapy does not significantly increase the dose administered to the skin and does not therefore cause any problems. During irradiation with high energy photons only extremely thin dressings should be used; if there is an aggravated skin reaction, the dressing should be taken off before irradiation commences.

HIV-associated cutaneous Kaposi's sarcoma--palliative local treatment by radiotherapy.

The increasing number of HIV-infected patients makes palliative treatment of HIV-associated Kaposis sarcoma more common. We retrospectively evaluated a reduced fractionated radiotherapy with 20 Gy in respect to response rates and acute side-effects. From January 1992 to January 1995, 52 patients with HIV-associated Kaposis sarcoma were treated with 133 single portals. Six weeks after the end of radiotherapy 42 patients with 124 portals were evaluable with respect to response rates and side-effects. Of the treated portals 32% were judged as complete responses (CR), 55% as partial responses (PR) and 12% as no change (NC). Skin reactions RTOG, grade 1 were seen in 74% of the patients. Compared with literature data the reduced overall dose of 20 Gy in 10 fractions led to a reduction of CRs by approximately 50% while the overall response rate remained equal. The success of radiotherapy for the nodular component of Kaposis sarcoma can be improved, if a dose exceeding 20 Gy in 10 fractions is applied but at the cost of increasing side-effects in case that non-conventional fractionation schemes are used.

1212 Protection of irradiated human skin by self-adhesive, silicone-coated polyamide net dressing

There is no established biological or pharmacological procedure to prevent acute skin reactions during irradiation. Mechanical protection of irradiated skin during treatment is therefore essential. Some silicone coated materials developed for skin transplants may be beneficial to irradiated patients in this respect. In a prospective study, the tolerance of silicone-coated polyamide net was tested in 21 patients receiving radiotherapy due to malignant disease. In 7 patients the portal skin was intact and in 14 patients the portal included an epitheliolysis and a skin ulcer. The ability of silicone-coated net strips to adhere to irradiated skin and the local skin irritation under the adherent net was evaluated. Patient tolerance of dressing strips was good. There were no reactions to the adherent dressing net by non-irradiated skin. No additional skin irritation due to the tested material was observed in the irradiated region. The ulcers covered by silicone-coated dressings re-epithelialized quickly during radiotherapy. There was no injury to new epithelium during changes of dressing. Our results demonstrate that silicone-coated polyamide net dressings could be used for skin protection during irradiation. We expect that this material will facilitate the intensification of percutaneous radiotherapy.

190 TLD-measurements of the increase of surface dose due to wound dressings during percutaneous irradiation

Objective Since any prolongation of overall radiotherapy time mayaffect the outcome of treatment, skin protection promises to improve the results of percutaneous irradiation. Different non-irritant dressing materials have been tested in the treatment of radio induced skin lesions. However, the increase of skin dose caused by wound dressings may enhance skin reaction. Therefore we measured the dose due to different wound dressings. Material and methods Dose increase at the skin covered by wound dressings was measured during therapeutic irradiation. The investigated materials were a silicon-coated polyamide net (Mepitel, Molnlycke), a hydrocolloid dressing (Varihesive, Merck&Co.) and an alginate dressing (Kaltostat, Convatec). Measurements were carried out by thermoluminescent dosimetry during irradiation with electrons (5 MeV to 40 MeV) and photons (6MV and Co60). Results Dose increase depended on quality and energy of beam and on the beam arrangement. For electrons absolute values at the surface were relatively high for all materials (85–96%), but there was only a small dose increase (5–10% compared to uncovered skin). For photons dose increase depended also on the material. The lowest dose increase was measured for Mepitel, the thinnest coating. During irradiation with a single stationary field perpendicularly to the skin dose values of 32% (6MV) and 43% (Co) related to the maximum dose and a dose increase of 39% and 65% were measured. For tangential fields (e.g. irradiation of the breast, head and neck) absolute dose values were higher (up to 60% (6MV) and 75% (Co)), but dose increase was much lower (up to 20%). The other coatings caused dose increase up to 156% related to the uncovered skin. Dose values of 85% of the maximum dose (Co) are possible. Conclusions Wound dressings need not be removed during irradiation with electrons, thin dressings like Mepitel need not be removed during irradiation with photons, but thicker coatings like Varihesive or Kaltostat should be taken away during photon therapy.