18F-Fluorodeoxyglucose positron emission tomography (18F-FDG PET) for the early detection of response to neoadjuvant chemotherapy for locally advanced rectal cancer

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.

Early response to upfront neoadjuvant chemotherapy (CAPOX) alone in low- and intermediate-risk rectal cancer: a single-arm phase II trial

BACKGROUND

With local recurrence of rectal cancer continuing to decrease, distant recurrence is becoming a major concern, especially for patients with low- and intermediate-risk stage II/III rectal cancer. Therefore, a new treatment strategy is warranted for these patients. This single-arm phase II trial aimed to assess the effect of neoadjuvant chemotherapy (NCT) in low- and intermediate-risk stage II/III rectal cancer and explore candidate radiological and clinical parameters for early prediction of tumour response after two cycles of CAPOX.

METHODS

Patients with mid-low stage II/III rectal cancer with low and intermediate risk were examined. The primary outcome was defined as a clinicopathological response by integrating tumour longitudinal length reduction (TLLR) on MRI into pathological tumour regression grade (TRG). After completing NCT, patients with TRG0-2 and TRG3 with a TLLR rate greater than 30 per cent were considered to be responders. Secondary outcomes included pathological complete response (pCR), adverse events and local and distant recurrence.

RESULTS

This study enrolled 61 eligible patients. No patient was converted to neoadjuvant chemoradiotherapy owing to tumour progression. The clinicopathological response and pCR rates were 78.7 and 21.3 per cent respectively. After two cycles of CAPOX, TLLR, TRG on MRI, and mucosal lesion regression grade on endoscopy had potential discriminative ability (area under the curve greater than 0.7) for predicting both clinicopathological and pathological response.

CONCLUSION

NCT alone achieves good tumour response rates in patients with low- and intermediate-risk stage II/III rectal cancer, and predicting tumour response to NCT is feasible at an early treatment phase.

REGISTRATION NUMBER

NCT03666442 (http://www.clinicaltrials.gov).

A decade of multi-modality PET and MR imaging in abdominal oncology

OBJECTIVES

To investigate trends observed in a decade of published research on multimodality PET(/CT)+MR imaging in abdominal oncology, and to explore how these trends are reflected by the use of multimodality imaging performed at our institution.

METHODS

First, we performed a literature search (2009-2018) including all papers published on the multimodality combination of PET(/CT) and MRI in abdominal oncology. Retrieved papers were categorized according to a structured labelling system, including study design and outcome, cancer and lesion type under investigation and PET-tracer type. Results were analysed using descriptive statistics and evolutions over time were plotted graphically. Second, we performed a descriptive analysis of the numbers of MRI, PET/CT and multimodality PET/CT+MRI combinations (performed within a ≤14 days interval) performed during a similar time span at our institution.

RESULTS

Published research papers involving multimodality PET(/CT)+MRI combinations showed an impressive increase in numbers, both for retrospective combinations of PET/CT and MRI, as well as hybrid PET/MRI. Main areas of research included new PET-tracers, visual PET(/CT)+MRI assessment for staging, and (semi-)quantitative analysis of PET-parameters compared to or combined with MRI-parameters as predictive biomarkers. In line with literature, we also observed a vast increase in numbers of multimodality PET/CT+MRI imaging in our institutional data.

CONCLUSIONS

The tremendous increase in published literature on multimodality imaging, reflected by our institutional data, shows the continuously growing interest in comprehensive multivariable imaging evaluations to guide oncological practice.

ADVANCES IN KNOWLEDGE

The role of multimodality imaging in oncology is rapidly evolving. This paper summarizes the main applications and recent developments in multimodality imaging, with a specific focus on the combination of PET+MRI in abdominal oncology.

Comparison of 18F-FDG PET/CT and DW-MRI in assessment of neoadjuvant radiochemotherapy response in locally advanced rectal cancer patients

OBJECTIVE

Our aim is to evaluate if different metabolic parameters obtained by ¹⁸F-FDG PET/CT and diffusion weighted magnetic resonance imaging (DW-MRI) can aid in neoadjuvant radiochemotherapy (RCT) response assessment in locally advanced rectal cancer (LARC) patients.

METHODS

Out of 20 LARC patients, who were planned to receive neoadjuvant RCT, 19 were included in this prospective study. Patients had ¹⁸F-FDG PET/CT and DW-MRI at initial staging, interim (2 weeks after onset of RCT) and after completion of RCT (post-therapy). Standardized uptake value (SUV) parameters (SUVmax, SUVmean, SUVpeak, SULpeak), metabolic tumor volume (MTV) and tumor lesion glycolysis (TLG) detected on PET images and apparent diffusion coefficient (ADC) values (for b=400 and b=1000s/mm²) obtained from DW-MRI were recorded. Postoperative tumor regression grade (TRG) was used as gold-standard, except for 2 patients who were under complete remission with non-operative management 19 months post-therapy and scored as responders.

RESULTS

On interim PET/CT, no significant difference was found among PET parameters between responders and non-responders, whereas post-therapy SUVmax, SUVpeak, MTV, SULpeak, TLG (P=0.02, P=0.014, P=0.025, P=0.007, P=0.02, respectively) and initial MTV (P=0.034) were significantly lower in responders. ADC response index (RI) was higher in responders (interim P=0.026; post-therapy: P=0.018) and ROC analysis revealed that a threshold of ADC RI>41.6% for interim MRI and >44.6% for post-therapy MRI had sensitivity and specificity of 75.0% and 90.9%, respectively.

CONCLUSIONS

While interim ¹⁸F-FDG PET/CT failed to predict therapy response during RCT, post-therapy PET could accurately differentiate responders. DW-MRI was found to be more promising in interim detection of RCT response.

Phase II trial of capecitabine plus oxaliplatin (CAPOX) as perioperative therapy for locally advanced rectal cancer

PURPOSE

The standard strategy for locally advanced lower rectal cancer is chemoradiotherapy followed by total mesorectal excision (TME) in Western countries and TME followed by adjuvant chemotherapy without preoperative treatment in Japan.

METHODS

This phase II trial evaluated the efficacy of a preoperative CAPOX chemotherapy regimen without radiation therapy for patients with locally advanced rectal cancer. The primary endpoint was 2-year disease-free survival.

RESULTS

The trial enrolled 45 patients from 9 institutions between 2012 and 2014. The mean age was 63.5 (29-74) years; 31 patients were male. Most patients (n = 41) received preoperative chemotherapy (CTx), and the preoperative CTx completion rate was 95.2%. R0 resection after CTx was performed in 41 patients. The pathological complete response rate was 7.3% (3/41). After surgery, 35 patients (85.3%) received adjuvant CTx, and 22 of 35 completed the protocol treatment. The follow-up period ranged from 0.71 to 4.68 years (median 2.86 years). There was recurrence in 13 of 40 patients who underwent R0 resection, and the 2-year disease-free survival rate and overall survival rate were 71.6 and 92.7%, respectively.

CONCLUSIONS

Here we report the completion rates for neoadjuvant CTx and adjuvant CTx, the pathological complete response rate, and the mid-term prognosis. The results indicate that CAPOX followed by TME may be a safe treatment strategy for locally advanced rectal cancer.

The potential usefulness of the Response Index in positron emission tomography assessing the therapeutic effect of pre-operative chemotherapy for advanced colorectal cancer

BACKGROUND AND PURPOSE

Pre-operative chemotherapy is an option for patients with local advanced rectal cancer, but the response rate to pre-operative chemotherapy with oxaliplatin is still low. If the therapeutic effect of pre-operative chemotherapy could be assessed, we may be able to convert to surgery early. The purpose of the present study was to validate the correlation between the maximum standardized uptake value (SUV_max) in 18F-fluorodeoxyglucose positron emission tomography-computed tomography (PET-CT) of the primary tumor and the therapeutic effect of pre-operative chemotherapy in advanced colorectal cancer.

PATIENTS AND METHODS

Retrospective cohort study from January 2011 to October 2015. We examined 28 patients with pathologically confirmed sigmoid or rectal cancer that underwent pre-operative chemotherapy and surgery. The correlation between Response Index (RI), calculated as (SUV_max after chemotherapy)/(SUV_max before chemotherapy), and the therapeutic effect on the primary tumor in advanced colorectal cancer.

RESULTS

The degree of differentiation (p = 0.04), SUV_max in the primary tumor after chemotherapy (p = 0.02), and RI (p = 0.008) were significant predictors of the therapeutic effect in univariate analysis. The areas under the ROC curve constructed with RI and therapeutic effect was 0.77. The optimal cut-off values for the RI in the responder group was < 0.32.

CONCLUSION

RI calculated as (SUV_max after chemotherapy)/(SUV_max before chemotherapy) in the primary tumor significantly correlated with the therapeutic effect of chemotherapy on advanced colorectal cancer. Thus, RI is potentially useful for predicting the therapeutic effect in advanced colorectal cancer.