Over the past several decades, two paradigms have emerged in the preoperative treatment of rectal cancer: a short course of radiation therapy (RT) often utilized in centers across Northern Europe and longcourse chemoradiation (CRT) in other parts of Europe and the US. The short-course technique was validated by randomized trials comparing this technique to surgery alone. The majority of these trials included patients with resectable, nonmetastatic rectal cancer, both early and advanced stages, with surgery 1 week following treatment completion. By contrast, long-course therapy is typically offered to patients with more advanced disease (cT3-4, N+) to improve local control, R0 resection rates, and potentially increase rates of sphincter-preserving surgery. Randomized studies have compared long-course CRT followed by surgery to upfront surgery and postoperative CRT. Multiple studies have attempted to optimize the long-course CRT platform with the addition of oxaliplatin. Two randomized trials have compared short-course RT to long-course CRT; however, significant debate still exists regarding the optimal neoadjuvant approach in patients with rectal cancer.
In early trials of preoperative short-course RT from Sweden, patients were randomized to preoperative RT (25 Gy in five daily fractions over 5–7 days) or underwent surgery alone. The incidence of pelvic recurrence was significantly reduced with RT at the expense of increased postoperative morbidity.1,2 A similar follow-up trial with improved RT techniques showed reduction in both locoregional and distant recurrence as well as improvement in overall survival (OS) with the short-course regimen.3 The rate of postoperative morbidity was reduced with the improved RT technique and postoperative mortality was low in both groups. These trials set the stage for the Swedish Rectal Cancer Trial, which randomized patients to the short-course regimen followed by surgery 1 week later versus surgery alone. After a median follow-up of 13 years, RT significantly reduced local recurrence (LR) rates (9 versus 26 %; p<0.001) and improved OS (38 versus 30 %; p=0.008).4 Subset analyses found statistically significant reductions in LR for all stage groups. However, these LR and OS benefits were not without potential toxicity. With long-term follow-up, patients treated with RT were more likely to develop small bowel obstruction.5,6
The Swedish Rectal Cancer Trial was undertaken prior to widespread adoption of the total mesorectal excision (TME) surgical technique. Compared with the conventional surgical techniques at that time, TME significantly reduced LR rates.7 To determine the value of preoperative RT in the TME era, investigators from The Netherlands initiated a multicenter trial randomizing 1,861 patients to preoperative short-course RT with TME compared with TME alone. The RT dose/fractionation and surgical timelines were similar to the Swedish trials. The most recent update with median follow-up of 12 years demonstrated a persistent reduction in the 10-year cumulative incidence of LR (5 versus 11 %; p<0.0001).8 Compared to the Swedish Rectal Cancer Trial, overall LR rates were substantially lower with TME. The 10-year risk of LR with TME alone for stage I and III rectal cancers was 3 % and 19 %, respectively. While there was no improvement in 10-year OS with RT (48 versus 49 %; p=0.86), OS was improved in stage III patients with negative circumferential radial margins (50 versus 40 %; p=0.03). The benefit in local control was at the expense of impaired bowel function and incontinence.9