Courtesy of Dr. Martijn Intven, UMC Utrecht, NDL

Overview

Patient with a small clinical T2N1 rectal adenocarcinoma 6 cm from the anal verge.

Rational for using Elekta Unity:

To be able to clearly visualize tumor and surrounding normal tissues and consequently optimally adapt the treatment field to the daily anatomy changes in the pelvis such as differences in rectal and bladder filling.
 

CT image
CT image
CBCT image
CBCT image

 

Difficult-to-visualize tumor and normal tissue on CT or CBCT; tumor and surrounding structures clearly visible on MR imaging.

 

Beams

The team evaluated what would have happened if the reference plan had been applied to each fraction.

At fraction #5 the anterior wall of the rectum, which should have been irradiated, would have been missed.

With Elekta Unity, the team was able to adapt the plan delivered at every fraction. As seen below, due to this daily adaptation, the entire target volume was irradiated as planned.

Technical planning comments

As one of the first rectal cancer treatments performed, standard margins (10 mm) were used around CTV mesorectum and elective lymph node regions to gain confidence. The patient was treated in five fractions of 5 Gy, with a five-field IMRT delivery.

Report

Re-staging eight weeks after treatment showed a clinical complete response, and the patient entered a wait-and-see study.