PET/MRI as a Predictor of Response to Pre-op Chemoradiation in Resectable Rectal Cancer: a Pilot Study

The primary purpose of this study is to determine the negative predictive value of PET/MRI for determining pathological complete response from neoadjuvant chemoradiation.

Inclusion criteria

• Low-lying, low- to moderate-risk pathologically-confirmed rectal cancer (stage uT3n) or uT1-3N+
• Negative workup for distant disease
• > 18 years of age
• Pre-treatment workup completed including:
• history and physical
• CT or MRI of the abdomen and pelvis
• endoscopic tumor evaluation (biopsy, blood work to assess CEA and hematopoietic, renal and liver function)
• if female of child-bearing age, negative pregnancy test
• Recommendation to undergo preoperative concurrent chemoradiation, as determined by the treating physician
• Informed consent reviewed and signed

Exclusion criteria

• Not deemed a candidate for preoperative chemoradiation for medical reasons, such as uncontrolled infection (including HIV), uncontrolled diabetes mellitus or cardiac disease
• Hemoglobin ≤ 10.0 g/dL (transfusion allowed to achieve or maintain levels)
• ANC ≤ 1,500/cubic mm³
• Platelet count ≤ 100,000/mm³
• ALT and AST ≥ 2.5 times upper level of normal (ULN)
• Alkaline phosphatase ≥ 2.5 times ULN
• Total bilirubin ≥ 1.5 times ULN
• Creatinine clearance < 50 mL/min
• Creatinine ≥ 1.5 times ULN
• Not deemed a candidate for concurrent preoperative chemoradiation for social reasons, such as psychiatric illness
• Not deemed a surgical candidate
• Currently active second malignancy, except non-melanoma skin cancer, non-invasive bladder cancer, low risk adenocarcinoma of the prostate and carcinoma in situ of the cervix
• Previous pelvic radiation therapy
• History of severe reaction to gadolinium
• Inability to tolerate MRI (e.g., inability to lie flat for > 1 hour)
• Presence of a pacemaker, intracranial aneurysm clip, bladder stimulator, cochlear implant or metal near eyes
• Body Mass Index (BMI) > 35
• Pregnant or lactating female