Neoadjuvant chemoradiation therapy and pathological complete response in rectal cancer

The management of rectal cancer has evolved significantly in the last few decades. Significant improvements in local dis-ease control were achieved in the 1990s, with the introduction of total mesorectal excision and neoadjuvant radiotherapy. Level 1 evidence has shown that, with neoadjuvant chemoradiation therapy (CRT) the rates of local recurrence can be lower than 6 % and, as a result, neoadjuvant CRT currently represents the accepted standard of care. This approach has led to reli-able tumor down-staging, with 15–27 % patients with a pathological complete response (pCR)—defined as no residual cancer found on histological examination of the specimen. Patients who achieve pCR after CRT have better long-term outcomes, less risk of developing local or distal recurrence and improved survival. For all these reasons, sphincter-preserving proce-dures or organ-preserving options have been suggested, such as local excision of residual tumor or the omission of surgery altogether. Although local recurrence rate has been stable at 5–6 % with this multidisciplinary management method, distal recurrence rates for locally-advanced rectal cancers remain in excess of 25 % and represent the main cause of death in these patients. For this reason, more recent trials have been looking at the administration of full-dose systemic chemotherapy in the neoadjuvant setting (in order to offer early treatment of disseminated micrometastases, thus improving control of sys-temic disease) and selective use of radiotherapy only in non-responders or for low rectal tumors smaller than 5 cm. Key words: rectal cancer; neoadjuvant chemoradiation therapy; pathological complete respons