The Impact of Neoadjuvant Radiotherapy on Outcomes in Rectal Cancer Treatment

Abstract

Preoperative radiotherapy plays a crucial role in the treatment of rectal cancer. It is the only method proven to significantly reduce local recurrence rates. Radiotherapy contributes to improved treatment outcomes through three primary mechanisms: (1) downstaging the tumor to facilitate surgical resection, (2) reducing the risk of local recurrence by eradicating microscopic tumor foci in the operative field, and (3) increasing the likelihood of sphincter-preserving surgery, particularly in cases involving invasion of the levator ani or external anal sphincter muscles
Materials and Methods
In this study, we analyzed 289 patients with rectal cancer, 80 (27.6%) of whom received preoperative radiotherapy. Of these, 30 patients (37.5%) underwent short-course radiotherapy and 50 (62.5%) underwent long-course radiotherapy. Among the long-course group, 22 patients (44%) were in the laparoscopic surgery group and 28 (56%) in the open surgery group. Long-course radiotherapy was delivered at 2 Gy per session over four weeks, while short-course radiotherapy consisted of 5 Gy per session over five days. Long-course results were assessed eight weeks post-radiotherapy.
Discussion
Short-course radiotherapy was primarily administered in cases with suspected mesorectal lymph node metastases, followed by total mesorectal excision (TME) surgery within the subsequent week. In patients who received long-course radiotherapy, three distinct response patterns were observed: complete radiosensitivity, partial radiosensitivity, and radioresistance.
In cases of complete radiosensitivity, the tumor underwent total regression; in partially radiosensitive cases, tumor size was reduced but not completely eliminated. In radioresistant cases, no significant change in tumor size was observed following radiotherapy. To quantitatively assess these effects, tumor regression rates were evaluated.
Results
Following long-course radiotherapy, among patients in the laparoscopic group, 4 (18.2%) demonstrated complete radiosensitivity, 15 (68.2%) exhibited partial radiosensitivity, and 3 (13.6%) were radioresistant. In the open surgery group, 5 (17.9%) patients showed complete radiosensitivity, 19 (67.9%) had partial radiosensitivity, and 4 (14.3%) were radioresistant (p = 0.998).
Regarding tumor regression grading, in the laparoscopic group, Grade 1 regression was 19.1 ± 5.7%, Grade 2 was 51.1 ± 7.3%, Grade 3 was 17.0 ± 5.5%, and Grade 4 was 12.8 ± 4.9%. In the open surgery group, the respective values were 23.2 ± 5.6%, 44.6 ± 6.6%, 17.9 ± 5.1%, and 14.3 ± 4.7%.
Conclusion
Long-course radiotherapy demonstrated efficacy in reducing tumor size (including instances of complete tumor regression), minimizing local recurrence, and increasing the feasibility of surgical intervention. No statistically significant differences were observed between the laparoscopic and open surgery groups in terms of radiosensitivity or tumor regression rates (p > 0.05). Notably, Grade 2 regression was the most prevalent outcome, observed in 51.1 ± 7.3% of laparoscopic cases and 44.6 ± 6.6% of open surgery cases.