55 Fractionated brachytherapy in cancer of the head & neck

s35 53

54

THE KIEL EXPERIENCE

IN PDR INTERSTITIAL BRACRYTXiBRAPY

AND INTRACAVITARY

PDR

G. ~UJV~CS. P. Kohr, R we. P. Dennut, H.M. Mehdmn’. R. 5 : CA Univenm Rocheb =. B. Krem&. J. Wen~e+ . and D. Wehna of Kiel. Clinics Kiel.

for Radiation

Therapy

(Radiw~cology),

1 Neurosurgery. 2 Ophthalmology.

Suqery.

and 50bsterics

Arnold

3 Surgery

4

Helkr

ORL

btr.9.

and

OPTIMIZED

DOSE

DISTRIBUTIONS

VERSUS

NON-

OPTIMIZED CLDR DOSE DISTRIBUTIONS ON THE BASIS OF CLINICAL EXAMPLES

D-14165

Head & Neck

Bems, Ch., Fritz, P., Hensley, F.W., Wannenmacher, M. Dept. of Radiotherapy, University of Heidelberg, FRG

and Gynecology

There were 21 patients with 22 tumors treated at the Clinic for Radiation Therapy of the CA University of Kiel, by interstitial/intracavitary brachytherapy

alone or in combination

with external beam radiation.

12

patients were irradiated with the PDR unit. and 10 with HDR. The treated tumor sites were: orbits/base (7). presacnl

of skull (6). head & neck (7). biliary duct

(5). panvenebral

(1). parametrium

catheters were fixed intraoperatively hand implantation

wlthout

(1). respectively.

The

in 16 cases. in six cases manual free-

tumor surgery.

Applied brachytherapy

dose

(75-10 Gy) by PDR 5x 1Gy in 10 hours, 5x in a week. as welJ as 2x 2.5 Gy. with an interval Extemd

radiation

of 6 hours.

dose usually

tumor size and aim of therapy. realized and optimized

5x in a week using the HDR unit. 20-46 Gy. The total dose depends

Generally

with a 2D planning

cases a digital-imaging-based

3D planning

the treatment procedure.

planning

on was

In some spmzial

system was used to improve

the accurancy. We observed no significant tissue reactions.

differences

as well as any progress

volumes (Follow-up:

in the acut normal/tumor in prophylactic

irradiated

2-10 months for PDR, 2-14 months for HDR).

Further multicentric

observations

and more follow-up is necessary

to observe acute-. and late effects. The daily comparison

work

with mPDR

is technically

very similar

in

to the HDR unit.

Obiective: For interstitial volume implants (a) and surface moulds (b) optimized treatment plans for PDR-BT with a single stepping Ir source are compared with non-optimized plans for CLDR-BT with Ir wires. Materials and methods: (a) The geometrically optimized and nonoptimized dose distributions of 11 patients who were treated with an interstitial breast implant were analysed by comparing the first smoothly surrounding isodose and the reference volume and by evaluating “natural” dose volume histograms (Anderson). (b) 8 patients have so far been irradiated with a chest wall surface mould. The reference surface, dose profiles and the depth dose curve of the geometrically optimized and the Ir wire dose distributions for a 10 cm x 10 cm irradiation field were analysed. Results: (a) Volume implants: Geometrical volume optimization leads to an improvement of dose uniformity indicated by a mean enhancement of the uniformity and quality indices by 6% and 15% respectively. The reference volume increases by 18% on average, the first smoothly surrounding isodose by an avarage of 4%. (b) Surface mould: Geometrical distance optimization provides an enhancement of the reference surface and an improvement of the dose homogeneity on the skin surface. Conclusion: Irradiation with geometrically optimized PDR-BT substantially changes the dose distribution known from line sources. This must especially be considered in choosing the active lengths. Dose homogeneity and conformation of the reference isodose to the shape of the target geometry are improved. 56

55

PuJ’utsirradiation

FRACTIONATED HEAD & NECK Peter Levendag,

BRACHYTHERAPY

IN CANCER

Andries Visser & Peter Jansen

Departments of Radiation-Oncology and Clinical Physics Dr. Daniel den Hoed Cancer Center, Rotterdam.

HDR and PDR afterloading technology dramatically changed the horizon of Brachytherapy (BT). Although HDR & PDR come with a number of (logistic) advantages, the effects on tumors and normal

tissues are still uncertain

of skin with extended

field afterloading

OF THE

and thus the therapeutic

ratio in comparison to LDR BT has still to be established. If anything, Hl!IR seems “less permissive” as opposed to LDR; however, PDR has been suggested to combine the radiobiological advantages of LDR with the logistic and physical

advantages of HDR. With regard to PDR, confusion has emerged about the optimal fraction size and interval between fractions to be employed. As of aug. 1990 we embarked on a pilot study for cancer in the Head and Neck. All patients eligible for BT were treated by either the microSelectron HDR (“fractionated HDR” regime; fraction size 3 Gy, twice daily with an interval of 6 hours) or the microSelectron PDR (“pulsed-dose-rate” regime; 4-8 fractions per day, 3 hour interval) This paper deals with preliminary results in terms of local control (LC), survival and particularly side-effects using fractionated HDR and PDR. Until may 1993, 111 patients were treated with a minimum follow-up of 10 months. The majority of tumors were located in the tonsil and soft palate (n=30, primary tumors LC: 93%), nasopharynx (n=35, primary tumors LC: 96%) and recurrent-neck (n=lO, LC: 70%). We will present a detailed analysis on side effects. In short: no significant differences were observed in comparison to tumors treated by LDR.

Fritz, P., Hensley, F., Berns, Ch., Schraube, P., Wannenmacher, M. Dept. of Radiotherapy, University of Heidelberg, Germany Objective: For pulsed brachytherapy a flexible, reusable extended field afterloading mould (weight 111 g) was developed. This enables irradiation of skin areas in any shape within a maximum field size of 17 x 23.5 cm. Materials and methods: Irradiations are carried out using geometrical optimization with a 37 GBq 192-Ir source with

hourly pulses bf 1 Gy referring to the s&ace of the skin. The 80% lsodose line is located at 10 mm and the 50% line at 27 mm under the skin surface. Dose inhomogeneities within the mould field are in the range of ~10%. Eight patients with skin metastases at the thoracic wall after ablatlo mammae were irradiated with 1 - 2 applications with total doses tween 25 and 50 Gv. The surface treated was 100 to 752 cmY . Five patients had a pre-exposure of 50 to 60 Gy. Results: Previously irradiatedpatients (n =.5). Remission: CR 4/5, PR l/5. Early reactions: grade II 4/5, grade III l/5. Late reactions after 6 months: grade I l/5 (25 Gy), grade II 3/5 (40 Gy), grade III l/5 (50 Gy). Recurrence-free: 4/4 (40-50 Gy). Non previoustj+mdiatedpatients (n =3). Remission: CR 213, PR l/3. Early reactions: grade II 3/3. Conclusion: PDR brachytherapy is an effective alternative to second-line chemotherapy, laser treatment or photodynamic therapy for the treatment of skin metastases even if the skin was preirradiated and is more economic than an external beam irradiation of several weeks. At the thoracic wall more homogeneous dose distributions can be achieved than with lined-;p electron fields. A pulsed total dose of 40-50 Gy seems to be well tolerated. The skin reactions support the theorv of a LDR-close effect of pulsed brachytherapy: *