Top Line: You may recall from the recent PROSPECT trial the exceedingly low rate of local recurrence, which was <2% in both arms.
The Study: Folks from the MERCURY and OCUM camps might argue that such a low risk of recurrence questions the need for any neoadjuvant therapy in lower risk patients. They argue that the use of traditional cT and cN staging to guide treatment of rectal cancer leads to over- and under-treatment of many patients. OCUM was a prospective study that sought to use preoperative MRI to identify 1) patients with high chance of cure with TME alone and 2) patients at high risk of recurrence after TME who benefit from neoadjuvant chemoradiation. There was no comparator arm, and the study wasn’t meant to compare the two arms as they obviously have much different recurrence risks. It included 884 patients with cT2-4 cN-any rectal cancer within 16cm of the anal verge. Risk stratification was performed using preoperative MRI, and there were 3 categories of patients considered high risk: those with cT4 tumors, those with cT3 tumors located in the lower third of the rectum, and those with middle or lower third tumors who had primary tumor, suspicious lymph nodes, or mesorectal tumor deposits 1mm or less from mesorectal fascia. High risk patients (40%) received neoadjuvant chemoradiation and low risk patients (60%) went straight to surgery. In the low risk group, 35.7% received adjuvant therapy (mostly chemo), whereas 77% received adjuvant chemo in the high risk group. The pCR rate in the high risk group was 11.9%. At 5 years, the overall local recurrence rate was 4.4%: 2.9% in the low risk group and 5.7% in the high risk group. The rate of distant metastasis was nearly twice as high in the high risk group (30.5% v 15.9%). In other words, MRI can effectively categorize patients with cT2-3 rectal cancer who are at low or high risk of local recurrence. Such an approach may help us better identify patients who truly benefit from neoadjuvant therapy.
TBL: OCUM underlines the importance of using MRI to stage and risk stratify patients with rectal cancer. Carefully selected patients with a clear circumferential margin may do well with primary surgery. Those with high risk features on MRI or low-lying tumors benefit from neoadjuvant chemoradiation and may derive further benefit from TNT. | Rupert, J Clin Oncol 2023
The Study: Folks from the MERCURY and OCUM camps might argue that such a low risk of recurrence questions the need for any neoadjuvant therapy in lower risk patients. They argue that the use of traditional cT and cN staging to guide treatment of rectal cancer leads to over- and under-treatment of many patients. OCUM was a prospective study that sought to use preoperative MRI to identify 1) patients with high chance of cure with TME alone and 2) patients at high risk of recurrence after TME who benefit from neoadjuvant chemoradiation. There was no comparator arm, and the study wasn’t meant to compare the two arms as they obviously have much different recurrence risks. It included 884 patients with cT2-4 cN-any rectal cancer within 16cm of the anal verge. Risk stratification was performed using preoperative MRI, and there were 3 categories of patients considered high risk: those with cT4 tumors, those with cT3 tumors located in the lower third of the rectum, and those with middle or lower third tumors who had primary tumor, suspicious lymph nodes, or mesorectal tumor deposits 1mm or less from mesorectal fascia. High risk patients (40%) received neoadjuvant chemoradiation and low risk patients (60%) went straight to surgery. In the low risk group, 35.7% received adjuvant therapy (mostly chemo), whereas 77% received adjuvant chemo in the high risk group. The pCR rate in the high risk group was 11.9%. At 5 years, the overall local recurrence rate was 4.4%: 2.9% in the low risk group and 5.7% in the high risk group. The rate of distant metastasis was nearly twice as high in the high risk group (30.5% v 15.9%). In other words, MRI can effectively categorize patients with cT2-3 rectal cancer who are at low or high risk of local recurrence. Such an approach may help us better identify patients who truly benefit from neoadjuvant therapy.
TBL: OCUM underlines the importance of using MRI to stage and risk stratify patients with rectal cancer. Carefully selected patients with a clear circumferential margin may do well with primary surgery. Those with high risk features on MRI or low-lying tumors benefit from neoadjuvant chemoradiation and may derive further benefit from TNT. | Rupert, J Clin Oncol 2023