Journal Watch - August 2022 (1)

Diagnostic performance of MRI for staging peritoneal metastases in patients with colorectal cancer after neoadjuvant chemotherapy

Rijsemus CJV, Kok NFM, Aalbers AGJ, Buffart TE, Fijneman RJA, Snaebjornsson P, Engbersen MP, Lambregts DMJ, Beets-Tan RGH, Lahaye MJ

Eur J Radiol. 2022 Apr;149:110225 doi: 10.1016/j.ejrad.2022.110225

Peritoneal metastases (PM) affect up to 30% of colorectal cancer (CRC) patients and remain the second leading cause of death after liver metastases (1,2).

The extent of PM is assessed by the peritoneal cancer index (PCI), which provides a measurement of the volume and extent of metastases. The PCI score combines the distribution of peritoneal implants at 13 abdominal and pelvic regions with the tumor size, being the most important and precise quantitative prognostic factor of peritoneal disease (3,4). Patients are eligible to undergo surgical cytoreduction (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) if PCI score is < 21, taking into account their location (5). Unfortunately, computed tomography (CT) underestimates the extent of PM and therefore it is not an accurate method to select patients who may benefit from CRS. With CT, small peritoneal nodules are often indistinguishable from the adjacent surrounding tissues, resulting in reduced sensitivity for peritoneal carcinomatosis (6).

Recent evidence has shown that abdominopelvic magnetic resonance imaging (MRI), including DW-MRI and gadolinium-enhanced MRI, significantly improves the staging and treatment in patients with PM from colorectal cancer (PM-CRC) due to its high accuracy in assessing PCI, compared to CT (7,8). While the diagnostic performance of DW-MRI to assess the PCI in patients with PM-CRC has been evaluated with good results, there are no studies that aimed to investigate PM-CRC after neoadjuvant chemotherapy (NACT).

This single center retrospective study was conducted at the Netherlands Cancer Institute in Amsterdam, a tertiary referral center for peritoneal surface oncology. The aim of this study was to evaluate diagnostic performance of DW-MRI in reassessing the PCI after NACT for patients with PM from colorectal cancer or appendiceal cancer who are potential candidates for CRS-HIPEC. The study included 47 patients from January 2016 until February 2021.

Two abdominal radiologists evaluated the PCI on restaging DW-MRI (mriPCI) and assessed the peritoneal lesions as suspicious if they were identifiable as solid or mucinous lesions on non-enhanced T2-weighted and gadolinium-enhanced T1-weighted images or as an area with diffusion restriction in DW-MRI imaging. The reference standard was PCI at surgery (sPCI). In all patients, sPCI was established by diagnostic laparoscopy, staging laparotomy or CRS-HIPEC. If CRS-HIPEC was performed, resected peritoneal lesions were evaluated and correlated with final pathological PCI (pPCI).

14 out of 47 patients were excluded because they had undergone surgery more than 42 days after the MRI scan; 33 out of 47 patients were eligible for inclusion. 19 out of 33 patients received 2 to 4 cycles of chemotherapy and 14 out of 33 received more than 4 cycles. Both readers correctly detected all 23 patients with resectable disease; however, the unresectable patients were not all correctly identified. The first reader detected 8 out of 10 unresectable patients (sensitivity 100% and specificity 80%) while the second reader identified 4 out of 10 unresectable patients (sensitivity 100% and specificity 40%).

The correlation between sPCI and mriPCI was 0.82 (0.66-0.91) for the reader 1 and 0.67 (0.43-0.82) for the reader 2. Six patients (26.1%) had pPCI of 0, indicating a complete regression of all resected lesions without any vital tumor remnants; five of these patients with complete response had a mriPCI of 3 or less.

Interestingly, this study corroborates in colorectal cancer the results of Jonsdottir et al. in which a group of patients with ovarian cancer underwent NACT before DW-MRI staging in the absence of significant differences between mriPCI and sPCI (7,9). This study shows that DW-MRI is an accurate diagnostic tool in determining the PCI after NACT because it could accurately select those patients in which a CRS-HIPEC was feasible; all patients with resectable disease were detected with MRI.

In conclusion, MRI appears to be a reliable and promising tool for determining the extent of PM in order to improve patient and treatment selection after NACT. The main limitation of the study is the retrospective design and the small sample size; validation with a greater number of patients receiving NACT for PM is therefore necessary.

References:

1. Cao C, Yan TD, Black D, Morris DL. A systematic review and meta-analysis of cytoreductive surgery with perioperative intraperitoneal chemotherapy for peritoneal carcinomatosis of colorectal origin. Ann Surg Oncol. 2009;16:2152–65.
2. Koppe MJ, Boerman OC, Oyen WJ, Bleichrodt RP. Peritoneal carcinomatosis of colorectal origin: incidence and current treatment strategies. Ann Surg. 2006;243:212–22.
3. Sugarbaker P, Ryan D. Cytoreductive surgery plus HIPEC to treat peritoneal metastases from colorectal cancer: standard of care or an experimental approach? Lancet Oncol. 2012;13:362–9.
4. Cashin PH, Graf W, Nygren P, Mahetme H. Cytoreductive surgery and intraperitoneal chemotherapy for colorectal peritoneal carcinomatosis: prognosis and treatment of recurrences in a cohort series. Eur J Surg Oncol. 2012;38:509–15.
5. Chua T, Esquivel J, Pelz J, Morris D. Summary of current therapeutic options for peritoneal metastases from colorectal cancer. J Surg Oncol. 2013;107:566–73.
6. Koh JL, Tan TD, Glenn D, Morris DL. Evaluation of preoperative computed tomography in estimating peritoneal cancer index in colorectal peritoneal carcinomatosis. Ann Surg Oncol. 2009;16:327–33
7. van 't Sant, I., et al., Diffusion-weighted MRI assessment of the peritoneal cancer index before cytoreductive surgery. Br J Surg. 2019 Mar;106(4):491-498.
8. Low, R.N. and R.M. Barone, Combined diffusion-weighted and gadolinium-enhanced MRI can accurately predict the peritoneal cancer index preoperatively in patients being considered for cytoreductive surgical procedures. Ann Surg Oncol, 2012. 19(5): p. 1394-1401.
9. B. Jonsdottir, M.A. Ripoll, A. Bergman, I. Silins, I.S. Poromaa, H. Ahlstro ̈m, K. Stålberg, Validation of 18F-FDG PET/MRI and diffusion-weighted MRI for estimating the extent of peritoneal carcinomatosis in ovarian and endometrial cancer -a pilot study, Cancer Imag. 21 (1) (2021).

Dr. Sergio Ruggiero is a second-year radiology resident at Sapienza University of Rome and an ESGAR member. He has graduated at the University Campus Bio-Medico of Rome with merit in June 2020. He has a wide range of interests in diagnostic imaging and plans to subspecialize in abdominal and gastrointestinal radiology. As a junior resident, he aspires to continuously learn and consolidate his radiological knowledge.

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