New advances in radiotherapy may allow for improved treatment of colorectal cancer that has spread to lymph nodes

This article summarizes current information on the use of stereotactic body radiotherapy (SBRT) for recurrence of colorectal cancer to lymph nodes. 

Colorectal cancer is a major health problem worldwide and is the third most common cause of cancer-related death globally. Although surgery, chemotherapy, and radiotherapy for colorectal cancer have improved, 20%-50% of patients will develop recurrence after treatment.

Nodal oligo-recurrence indicates that the initial cancer is under control but the cancer has spread (metastasized) to lymph nodes. Due to the relative rarity and high levels of post-surgery sickness, surgery it is not widely accepted for nodal oligo-recurrence. Therefore, other treatment options are needed.

SBRT is one of the newer radiotherapy techniques: it is a very precise method for delivering high doses of radiation to tumors. This article summarizes the initial reports regarding clinical outcomes, dose and toxicity of SBRT for nodal oligo-recurrence.

Clinical outcomes

There is very little published data on colorectal cancer patient outcomes after SBRT for nodal oligo-recurrence. Findings indicate that a substantial proportion of patients, generally over 20%, remain disease-free 4-5 years after SBRT. One study included 31 patients with nodal oligo-recurrence, progression-free survival (time following treatment before the disease progresses) was 25% at 3 years and 19% at 5 years. These findings support the idea that aggressive local therapy could improve patient outcomes.

Dose

Results from 5 different studies were discussed. The dose of SBRT ranged from 30 Gy to 60 Gy and the most promising results were reported in a study that delivered an average dose of 48 Gy. After 5 years 38% of patients in the study were still alive. However, there is no consensus on the optimal dose to deliver and further studies with larger patient numbers are required.

It was also noted that patients who had previously undergone chemotherapy may be more resistant to radiotherapy. Given this resistance to radiotherapy, increasing the SBRT dose may be necessary. However, because lymph nodes are usually surrounded by normal tissue this may increase the risk of toxicity to healthy organs. 

Toxicity

The normal tissue of the gastrointestinal tract is sensitive to damage from radiotherapy. Therefore, when SBRT is aimed at the nodes in the abdominal or pelvic area the gastrointestinal tract is at risk of damage. Across 5 studies 3% to 14% of patients had severe gastrointestinal toxicity (nausea, vomiting and diarrhea) after SBRT for nodal oligo-recurrence. This needs to be considered when planning the dose of SBRT to deliver.

The authors concluded that aggressive local treatments such as SBRT could prevent further spread of the cancer. It may also offer a number of advantages over conventional radiotherapy including delaying more widespread treatment and prolonging patient survival time.