Imaging methods for staging and definition of target volumes for neoadjuvant radiotherapy of locally advanced rectal carcinoma
- Radeva, E. Encheva
Colorectal cancer is the third most common tumor in the world. The imaging methods play an important role in the diagnosis, staging, planning, and delivering of radiotherapy in patients with locally advanced rectal carcinoma. Imaging modalities for staging rectal carcinoma include endorectal ultrasound, MRI, CT, PET/CT. Proper tumor staging enables the best therapeutic approach and help to define the patients indicated for surgical treatment first or after neoadjuvant radiotherapy. Neoadjuvant radiotherapy, followed by surgery, is a standard treatment for patients with locally advanced rectal cancer. The main purpose of modern radiotherapy is to deliver a maximum dose in the tumor and a minimal dose in the surrounding healthy tissues. Radiotherapy techniques used in rectal cancer are 3D conformal radiotherapy, itensity modulated radiotherapy (IMRT), image guided radiotherapy (IGRT), simultaneous integrated boost (simultaneous integrated radiation- SIB). The hybrid image between MRI or PET/CT and the localization CT during radiotherapy planning improves the ability to determine the exact margin of gross tumor volume, organs at risk and involved lymph nodes. This paper summarizes the main imaging modalities used in target volume definition for radiotherapy treatment planning for rectal carcinoma, their role, advantages and disadvantages.
Key words: LOCALLY ADVANCED RECTAL CARCINOMA. IMAGING MODALITIES. STAGING. MRI. PET/CT. RADIOTHERAPY PLANNING