Patients with rectal cancer who respond well to preoperative chemoradiotherapy may be able to skip additional lateral lymph node dissection, according to a new study.
Seoul National University Bundang Hospital said on the 18th that a research team led by surgery Professor Oh Heung-kwon and resident Hwang Sung-seo reached this finding after analyzing data from 844 rectal cancer surgery patients, in collaboration with eight university hospitals including Seoul National University Hospital, Asan Medical Center, Severance Hospital, the National Cancer Center, Kyungpook National University Chilgok Hospital, Korea University Anam Hospital, and Seoul St. Mary's Hospital.
Rectal cancer, which develops in the final part of the colon connected to the anus, tends to spread to the lateral pelvic lymph nodes located on the sides of the pelvis. Removing these lymph nodes alongside standard rectal cancer surgery to lower the risk of metastasis widens the scope of the operation and increases the burden on patients. This is because it not only lengthens surgery time but can also carry risks of complications such as nerve damage related to urinary and reproductive function. Whether to perform lateral pelvic lymph node dissection during rectal cancer surgery has been a longstanding debate in the medical field. In the West, there is a strong tendency toward selective dissection when imaging tests suggest metastasis, whereas Japan has widely recommended bilateral lateral lymph node dissection for mid- and lower rectal cancer. In particular, there has been considerable disagreement over treatment policy for patients whose lymph node size has been reduced through preoperative treatment.
The research team focused on whether treatment outcomes are maintained even when additional dissection is omitted in patients whose lateral lymph node size has been sufficiently reduced after preoperative chemoradiotherapy. The team divided 844 patients—whose lateral lymph node metastasis was suspected on preoperative magnetic resonance imaging (MRI) but whose lymph node size was reduced to less than 5 mm after chemoradiotherapy—into a lateral lymph node dissection group and a non-dissection group, and compared their treatment outcomes.
As a result, while the five-year oncological outcomes of the dissection group and the non-dissection group showed some numerical differences, whether dissection was performed did not show a statistically significant difference. The five-year disease-free survival rates of the two groups were 77.1% and 71.4%, respectively, while the overall survival rates were 87.0% and 86.9%. The five-year disease-free survival rate refers to the proportion of patients who received cancer treatment and remained alive without cancer recurrence or new progression for five years, while the overall survival rate refers to the proportion who survived regardless of cancer recurrence or cause of death. The local recurrence rates were 31.% and 5.3%, and the local recurrence rates at the lateral lymph node site were 1.9% and 3.1%.
On the other hand, the difference was clear in terms of surgical burden. The average surgery time for the non-dissection group was 237.9 minutes, a difference of about 41 minutes from the dissection group's 279.3 minutes. The rate of early complications within 30 days after surgery was also lower in the non-dissection group at 19.6% compared with 27.0% for the dissection group. This suggests that for lateral lymph nodes that responded well to preoperative treatment, additional dissection does not provide a clear benefit in terms of survival or recurrence rates, while it can aggravate the burden on patients due to longer surgery time and higher rates of early complications. However, the study identified the possibility that lateral lymph node dissection may be useful for patients whose CEA level—a marker for colorectal cancer—was high in blood tests before treatment, or for patients with low rectal cancer where preserving the anus is difficult. This means that rather than uniformly reducing dissection, the scope of surgery should be adjusted by considering both treatment response and risk factors together.
"Rather than applying the same surgery to all patients, we presented the basis for 'response-based customized surgery' that adjusts the scope of surgery according to the tumor's response to preoperative treatment," Professor Oh said. "As 'total neoadjuvant therapy,' which involves performing preoperative systemic chemotherapy in advanced rectal cancer, has recently been spreading as an international standard, the approach of determining the scope of surgery based on treatment response will become even more important."
The findings were published in a recent issue of Annals of Surgery, a leading international academic journal in the field of surgery.
