Preoperative radiotherapy for rectal cancer: hypofractionation with multiple fractions (15-25 Gy).

Preoperative radiotherapy lowers local recurrence rates after rectal cancer surgery, as seen in several randomised trials. Postoperative radiotherapy is also effective, although a higher radiation dose is required. In addition, preoperative, but not postoperative (unless combined with chemotherapy) radiotherapy also improves survival slightly. Since the toxicity profile also favours preoperative therapy, this is a more attractive approach. The trials have also shown that a sufficiently high biological dose is required to achieve any influence on local failure rates. If the dose at each radiation fraction is higher (e.g. 5 Gy), the radiation can be given much faster (during one week) than if a 'conventional' fraction size of about 2 Gy is used (4-5 weeks). Surgery can also safely be performed immediately after the end of the short radiation course, but not until several weeks later after conventional radiotherapy. This adds to the practicability of the short schedules. An inappropriate radiation technique was used particularly in one trial using multiple 5 Gy fractions. This resulted in unacceptable acute and late toxicity. However, several other trials have shown that the treatment is safe. Preoperative 5 x 5 Gy is one of the most extensively investigated oncological treatments with proven efficacy. Since the total dose is comparably low (25 Gy), the decreased therapeutic ratio of using fraction sizes above 2 Gy appears to have no clinical relevance. The experience indicates, however, that every therapeutic modality should be used in an optimal way.