It is now known that neoadjuvant radiochemotherapy treatment has established good results in reducing the risk of local recurrences of rectal cancer, when it is followed by TME (total mesorectal excision).
In lower rectum tumors, surgery alone has a rate survival of 30%l at 5 years and a local recurrence rate of 55-65%, with a disease-free interval of 30-35%. Preoperative administration of fluororimidine chemotherapy improved local control over recurrences of 7%.
The time interval between surgery and neoadjuvant treatment, however, is still debated. Retrospective studies have shown in recent years that tumor regression can be slow and not complete even after several months. More recently, some studies have shown an increase in the percentage of complete pathological response related to a longer waiting interval after neoadjuvant treatment, although other experiences have shown no influence on pCR and surgical technical results.
In the LYON trial the percentage of full or almost complete pCR increased from 10.3% to 26% and in other retrospective studies it was 23-30%. These results can be interpreted with the relationship between radiotherapy and tumor regression: DNA damage occurs during irradiation, but cellular lysis occurs within the next few weeks. A recent study compared the full response in 35 neoadjuvated patients suggesting that the greatest effect of downstaging would occur between the ninth and fourteenth week after treatment.
In the Stockholm III trial, a significantly low percentage of postoperative complications were reported in the long group, although not described in other studies where morbidity and complications were similar to the standard treatment.
All these experiences, however, have some biases: absence of randomization, the personal choice of the surgeon on the interval after neoadjuvant treatment, different pathological stages and response to neoadjuvant treatment, which may have influenced the results.