Use of Positron Emission Tomography/Computed Tomography (PET/CT) to Assess Tumor Response to Neoadjuvant Treatment for Distal Rectal Cancer

Study of the Value of the PET/CT in Evaluating the Response of Distal Rectal Cancer to Neoadjuvant Chemoradiation Therapy

Preoperative chemoradiation therapy is the preferred initial treatment option for distal rectal cancers. However, assessing tumor response to preoperative chemoradiation therapy remains a challenge to the colorectal surgeon, especially when determining if there is a complete response, observed in more than 10% of cases. The purpose of this study is to evaluate the use of the PET/CT in assessing distal rectal tumor response to preoperative chemoradiation therapy.

Patients with distal rectal adenocarcinoma will be submitted to an initial whole body PET/CT prior to the preoperative chemoradiation therapy with 5-fluorouracil and 5040 cGy. Six weeks and 12 weeks after the preoperative treatment is finished the PET/CT will be repeated. At 1 and at 2 years after preoperative treatment is concluded another PET/CT will be performed. The colorectal surgeon evaluating the response to chemoradiation therapy will be blinded to the results of the PET/CT, as the radiologist will be blinded to the response assessment. PET/CT results will not be used to determine treatment strategy, unless metastatic disease or other disease is diagnosed. Patients with a complete clinical response at 8 weeks will be rigorously followed while patients with an incomplete clinical response at 8 weeks will be submitted to radical surgery. PET/CT results will be compared to current radiological studies and final pathological reports.

Inclusion Criteria:

• Diagnosis of Rectal Adenocarcinoma
• Location of Tumor less than 7cm from Anal Verge

Exclusion Criteria:

• Pregnancy or Nursing
• Metastatic Disease (Stage IV disease)
• Previous treatment for any cancer
• Patients clinically unable to receive neoadjuvant chemoradiotherapy
• Hypersensitivity to 18FDG