High dose rate brachytherapy as a boost after preoperative chemoradiotherapy for more advanced rectal tumours: the Clatterbridge experience.

In a systemic review of 8507 patients from 22 randomised trials, radiotherapy has been shown to reduce the risk of local recurrence and death from rectal cancer compared with surgery alone. Recent large randomised trials confirmed that chemoradiotherapy was better than radiotherapy alone. Contact radiotherapy as a boost after external beam radiotherapy (without chemotherapy) has also been shown to improve local control and sphincter preservation in the Lyon 092 trial. Brachytherapy has now been used as preoperative treatment for rectal cancer and showed similar results. The Swedish and Dutch trial results of short-course preoperative radiotherapy have shown improved local control in favour of the radiotherapy group. Similar to the Scandinavian group, investigators from McGill University in Montreal adopted a short course using brachytherapy instead of external beam radiotherapy. However, surgery was delayed for 4-8 weeks to achieve downstaging. The radiation dose was delivered directly on to the tumour and the surrounding normal tissues were spared the effects of radiation. This approach has been shown to reduce the side-effects seen with external beam short-course radiotherapy, but maintains the benefit of improved local control. The Danish group used brachytherapy as a boost after external beam chemoradiotherapy for more advanced rectal tumours and have shown improved pathological complete remission and R0 resection rates. The Mount Vernon group used a similar rectal applicator for inoperable rectal cancer patients and achieved good local and symptom control. The brachytherapy group at Clatterbridge used the same approach as the Danish group, but reduced the external beam radiotherapy dose and increased the brachytherapy dose to lower the side-effects. All 16 patients (100%) had R0 resection compared with 63% with conventional preoperative chemoradiotherapy using a bolus 5-fluorouracil regimen. Pathological complete remission was achieved in seven (44%) patients compared with 2-12% with conventional chemoradiotherapy. There was no increase in grade 3-4 toxicity from radiotherapy and no delay in wound healing or anastamotic leakage. The inclusion of high dose rate brachytherapy seems to increase the pathological complete remission rates and improves the R0 resection rates with no detriment to the side-effects as the increased dose of radiation from the high dose rate boost is confined mainly to the tumour. This treatment may be particularly suitable for elderly patients where intensive chemoradiotherapy regimens are not suitable. Several trials are planned to define the role of preoperative high dose rate brachytherapy in rectal cancer and the results are awaited with interest.