21 Urinary Bladder Cancer

Urinary Bladder Cancer

9

THE GEC ESTRO HANDBOOK OF BRACHYTHERAPY | Part II: Clinical Practice Version 1 - 21/04/2015

Fig 22.15: Three equidistant and parallel catheters in the dorsal bladder wall with the corresponding isodose lines.

10. DOSE, DOSE RATE AND FRACTIONATION

the dose prescription was done on a tumour encompassing iso- dose, without reporting the basal dose points as recommended by ICRU 58. After a short median follow-up time of 14 months, local control was 72% and less than the LDR experience. Five patients developed severe late bladder toxicity. This result was explained by a wrong choice of α/β-ratio when designing HDR schedules from LDR schedules. Radiobiology modelling of clini- cal data proposes a schedule of 40 Gy in 28 fractions of 1.4 Gy in 7 days as the best equivalence between LDR and HDR if the T½ is 1 hour and the α/β−ratio 10-15 Gy (30). Otherwise 56 frac- tions of 0.7 Gy are necessary if the T½ is 0.5 hours. Alternatively, a schedule with a 40 Gy external beam dose followed by 10 frac- tions of 2.5 Gy in three fractions a day has been proposed (25). However, no long-term experience has yet been published with this alternative schedule. After the operation the patient stays for one or two days in the urology department to receive adequate post surgical care. For PDR treatments the patient is transported to the radiotherapy department. If the treatment is by HDR, the patient can stay on the urology ward and be taken to the HDR-unit for each frac- tion. Since the implanted material is very soft and flexible, it is well tolerated by the patient. Urine leakage and wound infections are much less frequent with plastic tube implants than reported after radium or caesium needle implants (23).Patients should re- ceive adequate prophylaxis for venous thrombosis. Urinary an- tiseptics, and if needed appropriate antibiotics, are prescribed as well as analgesics and spasmolytics. Particularly implants close to the bladder neck can cause painful spasms that need to be controlled by spasmolytics. Pre-operatively epidural anaesthesia can also be helpful. After 1-2 days, the patient is admitted to the brachytherapy de- partment for simulation and loading of the plastic tubes. After laparoscopic or robotic surgery treatment can start on the op- eration day. 11. MONITORING

Brachytherapy is usually given as a boost to external beam radio- therapy. External beam radiotherapy of the whole pelvis is given to a dose of 40 Gy in 2 Gy fractions. Subsequently a brachyther- apy dose of 25-30 Gy in continuous LDR or PDR technique with Iridium-192 is given to a total dose of 65-70 Gy EQD2 calculated for an α/β−ratio of 10-15 Gy and T1⁄2 of 0.5-1 hour. It is rec- ommended to report the prescribed dose according to ICRU 58. PDR treatments are used most often nowadays. Recommended PDR schedules are 60 pulses of 0.5 Gy with a time period of 1 hour, 30 pulses of 1 Gy with a time period of 2-3 hours or the office hour schedule of 28 pulses of 1 Gy with 10 pulses per day (27). If a partial cystectomy has been performed, the brachytherapy dose can be lowered with 15-20 Gy EQD2 (14). Alternatively for some patients elective pelvic irradiation can be omitted. This is the case if the pelvic lymph nodes have been surgically dissected or for example in the rare case of a bladder treatment after previous pelvic irradiation. In these cases the whole bladder is irradiated to 3 fractions of 3.5 Gy followed by a brachytherapy dose of 55-60 Gy EQD2. Low dose external beam radiotherapy to the whole bladder is given to prevent implanta- tion of urothelial tumour cells in the surgical wound (28). There is less experience with HDR brachytherapy in the inter- stitial treatment of bladder cancer than with LDR and PDR. The first publication on HDR by Soete et al. describes 15 patients with T1-T3 tumours (29). All patients except one were treated with a fraction size of 3 Gy. In total 15 brachytherapy fractions were given preceded by 3 external beam fractions of 3.5 Gy re- sulting in an EQD2 of 60 Gy. The median follow-up in this small feasibility study was only 23 months. Of the 15 treated patients, 2 experienced a local relapse. Two patients had severe persistent radiation cystitis. The experience with HDR brachytherapy at The Netherlands Cancer Institute was disappointing. The external beam dose to 40 patients was 30 Gy or 29.25 Gy in 2.0 Gy or 2.25 Gy frac- tions. The brachytherapy dose was 10 fractions of 3.2 Gy (Total EQD2 =65 Gy). Exact dose reporting cannot be given, because