Magnetic Resonance Imaging (MRI)-Guided Rectal Cancer Preservation Program

HYPOTHESIS

The implementation of Magnetic Resonance Image Guided Radiotherapy (MRgRT) into a TNT Program renders improved TME-free rates due to the better visualization and online dose-adaptation of the Gross Tumor Volume (GTV).

Rationale In the radiation setting, MRI provides superior soft tissue contrast compared to standard onboard X-ray imaging improving inter- and intra- observer delineation variation. MRgRT offers the opportunity to adapt the plan at each fraction to the anatomical changes seen. This is especially important in rectal cancer where the rectum is subject to interfractional position changes, volume shrinkage and intrafractional shape and size variation due to the variability in rectal filling.

Primary Objectives

A. To achieve 3-year TME-free survival of 75% while keeping 3-year DFS rates of 75%.

B. To achieve a CTCAE v5 grade 2-3 proctitis of less than 10% and grade 2-3 rectal bleeding rate of <2% at 2 years.

C. To achieve a Wexner Continence score of at least 90% over baseline at 2 years.

Secondary Objectives

A. Determination of blood and urine biomarkers of treatment response and toxicity .

B. Determination of radiomics biomarkers of treatment response and toxicity . C. Determination of rectal functionality with the Wexner Continence Score.

Inclusion criteria

• Patients aged 18 or older with primary Stage II (T3-4, N0) or Stage III (any T, N1-2) biopsy-proven rectal cancer
• No prior radiation therapy to the target areas;
• ECOG 0-2 with medical status not contraindicating treatment with radical intent including TNT and TME (if required) and with basal laboratory values as follows:

• Absolute neutrophil count (ANC) ≥ 1,000 cells/mm3
• Platelets ≥ 50,000 cells/mm3.
• Hemoglobin ≥ 8.0 g/dl.
• Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) < 4 x upper limit of normal.
• Total bilirubin < 2 x upper normal mg/dL.
• Alkaline phosphatase < 4 x upper limit of normal.

Exclusion criteria

• Patient unable to undergo an MRI examination