With 50 patients included, this trial would be the largest pilot study evaluating the value of MRI PET in locally advanced rectal cancer. On the other hand, it would be the only pilot study performing several MRI PET during neoadjuvant treatment. Presumably, the response assessed at the 2nd MRI PET (before cycle 4 or induction chemotherapy) would be predictive of the overall response at the end of neoadjuvant treatment. Then, it would be possible to predict precociously the tumor response.
World Health Organization (WHO)/Eastern Cooperative Oncology Group (ECOG) 0 to 2
Histologically proven rectal cancer
clinical tumor classification (cT) : cT3 - cT4 or all T / N+ / M0
Tumor resectable or considered resectable after chemoradiotherapy
Subject with Uncontrolled diabetes
Contraindication to surgery
Contraindication to MRI
Contraindication to PET scan
Patient with histologically proven rectal cancer with an indication for induction chemotherapy followed by neoadjuvant chemoradiotherapy
Case-only
Prospective
PET-MRI
Other interventionEach patient will have a pre-treatment PET-MRI (PET-MRI 1) within 21 days before the start of treatment. Induction chemotherapy may be performed at another center than the investigating center. After 3 cycles of induction chemotherapy and before the 4th cycle, a second PET MRI (PET MRI 2) will be performed. In patients who have received less than 3 cycles of induction chemotherapy, this mid-therapy PET-MRI will not be performed. A 3rd PET-MRI will be performed prior to radiation therapy (PET-MRI 3). A final MRI PET (MRI PET 4) will take place before surgery. A total of 4 PET MRI scans will be performed.
Description of the correlation between the PET-MRI changes after neo-adjuvant treatment and the histological response after surgery in terms of metabolic criteria.
The purpose of this study is to determine predictive parameters for response to the first phase of treatment by accurately identifying the characteristics of tumors that have responded or not to chemotherapy and chemoradiotherapy. Metabolic criteria will be measured with the SUVmax values that will be determined on the 4 PET-MRI scans.
Description of the correlation between the PET-MRI changes after neo-adjuvant treatment and the histological response after surgery in terms of MRI criteria.
MRI criteria will be measured with the Apparent Diffusion Coefficient (ADC) values that will be determined on the 4 PET-MRI scans.
Description of the correlation between the PET-MRI changes after neo-adjuvant treatment and the histological response after surgery in terms of anatomopathological criteria.
Anatomopathological criteria will be measured with the histopathological response to treatment which will be defined according to the tumor regression grade (TRG)
Comparison of the first PET-MRI staging with standard of care imaging, namely pelvic MRI in terms of tumor volumes
Record of tumor volumes on MRI PET 1
Comparison of the first PET-MRI staging with standard of care imaging, namely pelvic MRI in terms of SUVmax values
Record of SUVmax on MRI PET 1
Comparison of the first PET-MRI staging with standard of care imaging, namely pelvic MRI in terms of ADC values
Record of ADC on MRI PET 1
Description of the specific PET-MRI responses at mid-treatment of the neoadjuvant chemotherapy in terms of delta tumor volume
Record of delta tumor volume, compared to baseline (PET MRI 1)
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