Restaging Locally Advanced Rectal Cancer with MR Imaging after Chemoradiation Therapy

Abstract

In recent years, preoperative therapy has become standard procedure for locally advanced rectal cancer. Tumor shrinkage due to preoperative chemotherapy-radiation therapy (CRT) is now a reality, and pathologically complete responses are not uncommon. Some researchers are now addressing organ preservation, thus increasing the demand for both functional and morphologic radiologic evaluation of response to CRT to distinguish responding from nonresponding tumors. On magnetic resonance (MR) images, post-CRT tumor morphologic features and volume changes have a high positive predictive value but a low negative predictive value for assessing response. Preliminary results indicate that diffusion-weighted MR imaging, especially at high b values, would be effective for prediction of treatment outcome and for early detection of tumor response. Some authors have reported that the use of apparent diffusion coefficient values in combination with other MR imaging criteria significantly improves discrimination between malignant and benign lymph nodes. Sequential determination of fluorodeoxyglucose uptake at positron emission tomography/computed tomography has proved useful in differentiating responding from nonresponding tumors during and at the end of CRT. However, radionuclide techniques have limitations, such as low spatial resolution and high cost. Large studies will be needed to verify the most effective morphologic and functional imaging modalities for post-CRT restaging of rectal cancer. Supplemental material available at http://radiographics.rsna.org/lookup/suppl/doi:10.1148/rg.303095085/-/DC1.

Tumor volume reduction rate is superior to RECIST for predicting the pathological response of rectal cancer treated with neoadjuvant chemoradiation: Results from a prospective study

“…These results appear to be an improvement on previous reports (3,5,27). The high sphincter-preserving rate observed in the present study may be associated with the fact that the majority of patients underwent a novel treatment strategy termed two-stage TME (20). The PTRs of patients in the present study were consistent with a previous study by Fokas et al (9); a good TRG was determined in 54 (51.4%) The results of the present study identified no significant association between patient demographics and TVRR and RECIST.…”

“…The patients were treated according to the institutional protocol of Sun Yat-Sen University, as previously described (20). Pre-operative radiotherapy of 46 GY in 23 fractions was delivered to the pelvis, followed by an optional boost of 4 GY in two fractions to the primary tumor.…”

Accuracy of multidetector-row CT for restaging after neoadjuvant treatment in patients with oesophageal cancer

“…The result of our study that MDCT is of limited value for restaging of patients with oesophageal cancer following neoadjuvant treatment is in line with the results of the studies which assessed the value of morphologic imaging (including MDCT, MRI and EUS) for restaging of rectal or gastric cancer following neoadjuvant treatment. The reason for the limited value of MDCT in our study might be explained by the fact that changes due to fibrosis, inflammation and residual, viable tumour cannot be reliably distinguished [50,51] and micrometastasis in normal sized lymph nodes cannot be excluded by morphological imaging [52].…”

Usefulness of Perfusion CT to Assess Response to Neoadjuvant Combined Chemoradiotherapy in Patients with Locally Advanced Rectal Cancer

“…Predicting which tumors will respond well to this therapeutic approach remains a challenge because morphological imaging criteria are unreliable in this regard (9)(10)(11). As it is becoming increasingly important that preoperative imaging may noninvasively select high-risk patients who could truly benefit from more aggressive multimodality treatment approaches in the preoperative setting (12,13), there is a growing interest on functional imaging techniques that can help monitor treatment effects.…”