MRI may predict rectal cancer outcomes
MedWire News: Magnetic resonance imaging (MRI) used to evaluate responses to pre-surgery neoadjuvant chemotherapy or radiation may predict survival among patients with advanced rectal cancer, study findings indicate.
"This is the first time that MRI has been shown to predict outcome for patients with rectal cancer who have completed initial chemoradiation therapy," said lead author Gina Brown from the Royal Marsden Hospital NHS Trust in Sutton, UK.
"MRI staging and reassessment of rectal cancers before and after chemoradiotherapy are not routinely done for all patients. We've shown that using MRI this way can help change the course of patient care, perhaps enabling physicians to choose a more effective chemotherapy drug or even in some cases ultimately avoid surgery."
The researchers explain that high-resolution MRI has been used to assess tumor response before surgical resection, but the relevance of post-treatment MRI assessment in predicting survival outcomes has not been investigated.
Brown and team therefore investigated whether MRI assessment of tumor stage, nodal status, circumferential resection margin (CRM) status, and tumor regression grade (TRG) predicted overall survival (OS), disease-free survival (DFS), and local recurrence (LR) in 111 patients with locally advanced rectal cancer treated by neoadjuvant therapy. The team also measured the same variables pathologically.
Patients with T stage 0, 1, 2, or 3a cancer or no CRM involvement were judged to have good prognosis, while those with T stages 3b, 3c, 3d, or 4, or predicted CRM involvement had poor prognosis.
In addition, a poor MRI-assessed TRG (mrTRG) was defined as predominantly tumor signal intensity with minimal fibrotic low-signal intensity or no fibrosis evident with tumor signal visible, while a good mrTRG was defined as absence of any tumor signal or mixed areas of low-signal fibrosis and intermediate signal intensity present but without predominance of tumor signal.
During the follow-up period, 54 patients died, 40 as a result of cancer-related causes, and 50 patients had disease progression.
The researchers report that patients with poor mrTRG had significantly worse 5-year OS and DFS than patients with good mrTRG, at 27% versus 72% and 31% versus 64%, respectively.
On multivariate analysis adjusted for age, gender, height of tumor from anal verge, type of preoperative treatment, and type of operation, patients with poor mrTRG had a 4.4-fold increased risk for death and a 3.3-fold increased risk for disease progression during follow-up compared with those with good mrTRG.
In addition, MRI-predicted CRM status was independently associated with LR; patients with predicted CRM involvement had a 4.3-fold higher risk for LR than those with a clear CRM.
Histopathologically assessed T stage and CRM involvement also significantly predicted OS, DFS, and LR with respective hazard ratios of 4.6, 5.6, and 9.8 for poor versus good T stage and 3.0, 2.2, and 8.8, for poor versus good CRM.
In real terms, patients with poor post-treatment pathologic T stage had 5-year OS, DFS, and LR rates of 39%, 38%, and 27%, respectively, compared with rates of 76%, 84%, and 6% for patients with good post-treatment pathologic T stage.
The 5-year OS, DFS and LR rates for patients with pathologically assessed involved CRM were 30%, 28%, and 56%, compared with 59%, 62%, and 10%, respectively among patients with no CRM involvement.
Of note, node status assessed by MRI or pathology did not significantly predict any of the outcomes measured.
"Post-treatment MRI TRG and CRM evaluation gives the multi-disciplinary team a window of opportunity to refine treatment plans before definitive surgical treatment," Good and co-authors conclude Journal of Clinical Oncology.
By Laura Dean