MR imaging of rectal cancer before and after chemoradiation therapy

Adaptive Individualized high-dose preoperAtive (AIDA) chemoradiation in high-risk rectal cancer: a phase II trial

PURPOSE

To evaluate the pathological complete response (pCR) rate of locally advanced rectal cancer (LARC) after adaptive high-dose neoadjuvant chemoradiation (CRT) based on 18 F-fluorodeoxyglucose positron emission tomography/computed tomography (18 F-FDG-PET/CT).

METHODS

The primary endpoint was the pCR rate. Secondary endpoints were the predictive value of 18 F-FDG-PET/CT on pathological response and acute and late toxicity. All patients performed 18 F-FDG-PET/CT at baseline (PET0) and after 2 weeks during CRT (PET1). The metabolic PET parameters were calculated both at the PET0 and PET1. The total CRT dose was 45 Gy to the pelvic lymph nodes and 50 Gy to the primary tumor, corresponding mesorectum, and to metastatic lymph nodes. Furthermore, a sequential boost was delivered to a biological target volume defined by PET1 with an additional dose of 5 Gy in 2 fractions. Capecitabine (825 mg/m2 twice daily orally) was prescribed for the entire treatment duration.

RESULTS

Eighteen patients (13 males, 5 females; median age 55 years [range, 41-77 years]) were enrolled in the trial. Patients underwent surgical resection at 8-9 weeks after the end of neoadjuvant CRT. No patient showed grade > 1 acute radiation-induced toxicity. Seven patients (38.8%) had TRG = 0 (complete regression), 5 (27.0%) showed TRG = 2, and 6 (33.0%) had TRG = 3. Based on the TRG results, patients were classified in two groups: TRG = 0 (pCR) and TRG = 1, 2, 3 (non pCR). Accepting p < 0.05 as the level of significance, at the Kruskal-Wallis test, the medians of baseline-MTV, interim-SUVmax, interim-SUVmean, interim-MTV, interim-TLG, and the MTV reduction were significantly different between the two groups. 18 F-FDG-PET/CT was able to predict the pCR in 77.8% of cases through compared evaluation of both baseline PET/CT and interim PET/CT.

CONCLUSIONS

Our results showed that a dose escalation on a reduced target in the final phase of CRT is well tolerated and able to provide a high pCR rate.

ACR Appropriateness Criteria® Staging of Colorectal Cancer: 2021 Update

Preoperative imaging of rectal carcinoma involves accurate assessment of the primary tumor as well as distant metastatic disease. Preoperative imaging of nonrectal colon cancer is most beneficial in identifying distant metastases, regardless of primary T or N stage. Surgical treatment remains the definitive treatment for colon cancer, while organ-sparing approach may be considered in some rectal cancer patients based on imaging obtained before and after neoadjuvant treatment. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

MRI for Rectal Cancer: Staging, mrCRM, EMVI, Lymph Node Staging and Post-Treatment Response

Rectal cancer is a relatively common malignancy in the United States. Magnetic resonance imaging (MRI) of rectal cancer has evolved tremendously in recent years, and has become a key component of baseline staging and treatment planning. In addition to assessing the primary tumor and locoregional lymph nodes, rectal MRI can be used to help with risk stratification by identifying high-risk features such as extramural vascular invasion and can assess treatment response for patients receiving neoadjuvant therapy. As the practice of rectal MRI continues to expand further into academic centers and private practices, standard MRI protocols, and reporting are critical. In addition, it is imperative that the radiologists reading these cases work closely with surgeons, medical oncologists, radiation oncologists, and pathologists to ensure we are providing the best possible care to patients. This review aims to provide a broad overview of the role of MRI for rectal cancer.

The value of four imaging modalities in diagnosing lymph node involvement in rectal cancer: an overview and adjusted indirect comparison

Several systematic reviews have investigated the accuracy of imaging modalities for lymph node involvement of rectal cancer, but there are considerable differences in conclusions. This overview aimed to assess the methodological and reporting quality of systematic reviews that evaluated the diagnostic value of imaging modalities for lymph node involvement in patients with rectal cancer and to compare the diagnostic value of different modalities for lymph node involvement. The PubMed, EMBASE, Cochrane Library and Chinese Biomedicine Literature were searched to identify relevant systematic reviews. The methodological quality was assessed using the AMSTAR checklist, and the reporting quality was assessed using PRISMA-DTA checklist. The indirect comparison was conducted to compare the accuracy of different imaging modalities. Seven systematic reviews involving 353 primary studies were included. The median (Range) AMSTAR scores were 6.0 (4.0-9.0); the median (Range) PRISMA-DTA scores were 18.0 (11.0-23.0). Sensitivity of MRI [0.69 (95% CI 0.63, 0.77)] was significantly higher than that of ERUS [0.57 (95% CI 0.53, 0.62)]. Specificity of ERUS [0.80 (95% CI 0.77, 0.83)] was significantly higher than that of CT [0.72 (95% CI 0.67, 0.78)]. Positive likelihood ratio of EUS [3.04 (95% CI 2.75, 3.36)] was significantly higher than that of CT [2.21 (95% CI 1.69, 2.90)]. EUS had better diagnostic value than CT and ERUS in the diagnosis of lymph node involvement. Compared with CT and ERUS, MRI was more sensitive. EUS and MRI had comparable diagnostic accuracy, but no modality was proved to be particularly accurate.

The INTERACT Trial: Long-term results of a randomised trial on preoperative capecitabine-based radiochemotherapy intensified by concomitant boost or oxaliplatin, for cT2 (distal)-cT3 rectal cancer

BACKGROUND AND PURPOSE

Capecitabine-based radiochemotherapy (cbRCT) is standard for preoperative long-course radiochemotherapy of locally advanced rectal cancer. This prospective, parallel-group, randomised controlled trial investigated two intensification regimens. cT4 lesions were excluded.

PRIMARY OBJECTIVE

pathological outcome (TRG 1-2) among arms.

MATERIALS AND METHODS

Low-located cT2N0-2M0, cT3N0-2M0 (up to 12 cm from anal verge) presentations were treated with cbRCT randomly intensified by either radiotherapy boost (Xelac arm) or multidrug concomitant chemotherapy (Xelox arm). Xelac: concomitant boost to bulky site (45 Gy/1.8 Gy/die, 5 sessions/week to the pelvis, +10 Gy at 1 Gy twice/week to the bulky) plus concurrent capecitabine (1650 mg/mq/die). Xelox: 45 Gy to the pelvis + 5.4 Gy/1.8 Gy/die, 5 sessions/week to the bulky site + concurrent capecitabine (1300 mg/mq/die) and oxaliplatin (130 mg/mq on days 1,19,38). Surgery was planned 7-9 weeks after radiochemotherapy.

RESULTS

From June 2005 to September 2013, 534 patients were analysed: 280 in Xelac, 254 in Xelox arm. Xelox arm presented higher G ≥ 3 haematologic (p = 0.01) and neurologic toxicity (p < 0.001). Overall, 98.5% patients received curative surgery. The tumour regression grade distribution did not differ between arms (p = 0.102). TRG 1+2 rate significantly differed: Xelac arm 61.7% vs. Xelox 52.3% (p = 0.039). Pathological complete response (ypT0N0) rates were 24.4 and 23.8%, respectively (p non-significant). Median follow-up:5.62 years. Five-year disease-free survival rate were 74.7% (Xelac) and 73.8% (Xelox), respectively (p = 0.444). Five-year overall survival rate were 80.4% (Xelac) and 85.5% (Xelox), respectively (p = 0.155).

CONCLUSION

Xelac arm significantly obtained higher TRG1-2 rates. No differences were found about clinical outcome. Because of efficacy on TRG, inferior toxicity and good compliance, Xelac schedules or similar radiotherapy dose intensification schemes could be considered as reference treatments for cT3 lesions.

ACR Appropriateness Criteria® Pretreatment Staging of Colorectal Cancer

Colorectal cancers are common tumors in the United States and appropriate imaging is essential to direct appropriate care. Staging and treatment differs between tumors arising in the colon versus the rectum. Local staging for colon cancer is less integral to directing therapy given radical resection is often standard. Surgical options for rectal carcinoma are more varied and rely on accurate assessment of the sphincter, circumferential resection margins, and peritoneal reflection. These important anatomic landmarks are best appreciated on high-resolution imaging with transrectal ultrasound or MRI. When metastatic disease is suspected, imaging modalities that provide a global view of the body, such as CT with contrast or PET/CT may be indicated. Rectal cancer often metastasizes to the liver and so MRI of the liver with and without contrast provides accurate staging for liver metastases. This article focuses on local and distant staging and reviews the appropriateness of different imaging for both variants. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Beyond Histologic Staging: Emerging Imaging Strategies in Colorectal Cancer with Special Focus on Magnetic Resonance Imaging

Imaging plays an increasingly important role in the staging and management of colorectal cancer. In recent years, magnetic resonance imaging (MRI) has supplanted transrectal ultrasound as the preferred modality for the locoregional staging of rectal cancer. Furthermore, the advent of both diffusion-weighted imaging and hepatobiliary contrast agents has significantly enhanced the ability of MRI to detect colorectal liver metastases. In clinical practice, MRI routinely provides prognostic information, helps to guide surgical strategy, and determines the need for neoadjuvant therapies related to both the primary tumor and metastatic disease. Expanding on these roles for MRI, positron emission tomography (PET)/MRI is the newest clinical hybrid imaging modality and combines the metabolic information of PET with the high soft tissue contrast of MRI. The addition of PET/MRI to the clinical staging armamentarium has the potential to provide comprehensive state-of-the-art colorectal cancer staging in a single examination.

JOURNAL CLUB: Preoperative MRI Evaluation of Primary Rectal Cancer: Intrasubject Comparison With and Without Rectal Distention

OBJECTIVE

The aim of this study was to determine whether rectal distention influences the accuracy of MRI for tumor staging and for measuring of maximal extramural depth of tumor spread and distance between tumor and mesorectal fascia (MRF).

SUBJECTS AND METHODS

Fifty patients with rectal carcinoma underwent MRI before and after rectal distention. Both sets of MR images were reviewed by two radiologists. The scores for depiction of the mass (1-4 scale), T and N category, distance from normal rectal wall to MRF, maximal extramural depth of tumor spread, and distance between tumor and MRF were evaluated.

RESULTS

The visualization scores on MR images obtained with the rectum distended were significantly higher than those on images obtained without distention (90% vs 58% for score 4, p < 0.001). The accuracy of T category assessed on distended images was slightly higher than the accuracy on nondistended images (88.6% vs 84.1% for observer 1, 84.1% vs 81.8% for observer 2), but the accuracy of N category was stable. The distance between normal rectal wall and MRF was significantly less on distended images than on nondistended images (p < 0.05). However, there was no significant difference between nondistended and distended images for maximal extramural depth and distance between tumor and MRF (p > 0.05).

CONCLUSION

Rectal distention significantly improved visualization of tumors on MR images. It also improved T category assessment to some extent. Although the distance between normal rectal wall and MRF was significantly less with rectal distention than without rectal distention, maximal extramural depth and the distance between tumor and MRF did not vary significantly with or without rectal distention.

Oncologic Outcomes according to the Treatment Strategy in Radiologic Complete Responders after Neoadjuvant Chemoradiation for Rectal Cancer

OBJECTIVE

This study aimed to compare the oncologic outcomes between treatment strategies for rectal cancer [radical surgery, local excision (LE), and the wait-and-see approach] in radiologic complete responders after neoadjuvant chemoradiation (nCRT).

METHODS

We retrospectively reviewed rectal cancer patients and included 52 radiologic complete responders after nCRT defined as no residual tumor or residual fibrosis and no suspicious metastatic lymph nodes on magnetic resonance imaging (MRI). Clinicopathologic features and oncologic outcomes were compared according to the treatment strategies.

RESULTS

The median follow-up period was 41 months (range, 6-80). Twenty-eight patients underwent radical surgery, whereas 16 underwent LE, and 8 were closely monitored without initial surgery. The pathologic complete response rate was 40.9%. Patients who underwent radical surgery showed better prognosis compared to those who underwent LE or wait-and-see (3-year disease-free survival: radical surgery 85.0% vs. LE 62.5%, wait-and-see 75.0%, p = 0.019; 3-year local recurrence-free survival: radical surgery 96.4% vs. LE 67.0%, wait-and-see 75.0%, p = 0.009). After recurrence, patients who underwent salvage surgery showed a relatively good oncologic outcome.

CONCLUSION

Pursuing LE or the wait-and-see approach instead of radical surgery in rectal cancer patients undergoing nCRT may bring about a detrimental oncologic outcome if clinical complete response is solely determined by MRI.

MRI of Rectal Cancer: An Overview and Update on Recent Advances

OBJECTIVE

MRI is the modality of choice for rectal cancer staging. The high soft-tissue contrast of MRI accurately assesses the extramural tumor spread and relation to mesorectal fascia and the sphincter complex. This article reviews the role of MRI in the staging and treatment of rectal cancer. The relevant anatomy, MRI techniques, preoperative staging, post-chemoradiation therapy (CRT) imaging, and tumor recurrence are discussed with special attention to recent advances in knowledge.

CONCLUSION

MRI is the modality of choice for staging rectal cancer to assist surgeons in obtaining negative surgical margins. MRI facilitates the accurate assessment of mesorectal fascia and the sphincter complex for surgical planning. Multiparametric MRI may also help in the prediction and estimation of response to treatment and in the detection of recurrent disease.

Magnetic resonance imaging in rectal cancer: A surgeon’s perspective

Magnetic resonance imaging (MRI) in rectal cancer was first investigated in 1999 and has become almost mandatory in planning rectal cancer treatment. MRI has a high accuracy in predicting circumferential resection margin involvement and is used to plan neoadjuvant therapy. The accuracy of MRI in assessing mesorectal lymph nodes remains moderate, as there are no reliable criteria to assess nodal involvement. MRI seems to be good in assessing peritoneal involvement in upper rectal cancer; this however has been assessed in only a few studies and needs further research. For low rectal cancers, mesorectum is thin at the level of levator ani especially in relation to prostate; so predicting circumferential resection margin involvement is not easy. However high spatial resolution coronal imaging shows levator muscles, sphincter complex and intersphincteric plane accurately. This is used to stage low rectal tumors and plan plane of surgery (standard surgery, intersphincteric resection, Extralevator abdominoperineal resection). While most centres perform MRI post chemoradiotherapy, its role in accurate staging post neoadjuvant therapy remains debatable. THe role of Diffusion weighted MRI post neoadjuvant therapy is being evaluated in research settings.