Pulsed dose rate (PDR) brachytherapy of anal carcinoma

With radiotherapy of anal carcinomas, sphincter preservation can be obtained at survival rates similar to those obtained with radical surgery. By combining external beam irradiation with interstitial irradiation, superiority over standard external irradiation has been obtained. With the introduction of pulsed dose rate equipment, where a single high activity source moves through catheters, a more individualized dose distribution and a further elimination of radiation exposure to the staff can be achieved.

Between June 1993 and November 1994, 17 patients with anal carcinoma (T1:4, T2:4, T3:6, T4:3) have been treated at the Finsen Center. The treatment consisted of three-field external irradiation 46 Gy/23 fractions with five fractions a week to the anal canal and regional pelvic lymph nodes. Seven to 33 days after completion of external irradiation, the tumorspace was given 25.2 Gy PDR brachytherapy with 42 pulses of 0.6 Gy, one pulse every hour.

One isolated local recurrence has been noted 13 weeks after implantation. One additional local recurrence was seen in a patient with concomitant hepatic and inguinal recurrence. In three patients inguinal recurrence had occurred, two of these patients were irradiated without any further evidence of disease, and one patient with a primary advanced tumour, had local failure. So far necrosis has been observed in 13 patients within 1-49 weeks (median 16 weeks) after implantation. Eight of these patients required colostomy. No relation was observed between the number of implanted needles and the occurrence of necrosis.

The results indicate that the treatment is highly effective, but with substantial toxicity.