[Improvements in detection of rectal cancer recurrence by multiplanar reconstruction]

Reliability of Contrast CT and Positron Emission Tomography in Post-Surgical Colorectal Cancer and Its Association with Obesity

BACKGROUND

Post-surgical recurrence of cancer colon occurs in one-third of patients within the first two years, so early detection is important. The assessment of the therapeutic response is important to change protocol strategy. Positron emission tomography/computed tomography PET/CT, a valuable tool gives both metabolic and anatomic information for whole-body regions. Obesity is an important risk factor for colorectal cancer.

AIM

To evaluate post-surgical and therapeutic colorectal cancer by PET/CT and study obesity association to its prognosis.

METHODS

This was a prospective study involved 93 patients with, post-surgical colorectal cancer examined by PET/CT, then follow up after 4-6 months.

RESULTS

There was a statistically significant difference between PET/CT and contrast CT. The sensitivity& the specificity were (96.4%-100% & 92.3%-98.2%) for PET/CT and (84.2%-90.2% & 76.5%-85.4%) for contrast CT respectively. Post-therapeutic follow up showed; progressive course (24.5%), stationary course (26.4%), partial regression (28.3%) and complete regression course (20.8%). Obesity is a risk factor for progression with highly statistically significant to treatment response. Obese patients had a progressive or stationary course of the disease. Also, there was a highly statistically significant association between total abdominal fat & visceral abdominal fat areas with good response of treatment.

CONCLUSION

PET/CT is the most appropriate imaging technique to detect any recurrence or metastases in post-surgical colorectal cancer with high sensitivity and specificity comparing to CT. Obesity is a predictor risk factor for prognosis of the disease, as generally and abdominally (total & visceral fat) had an association with therapeutic response.

What is the most accurate whole-body imaging modality for assessment of local and distant recurrent disease in colorectal cancer? A meta-analysis : imaging for recurrent colorectal cancer

PURPOSE

The objective of this study was to compare the diagnostic performance of positron emission tomography (PET), PET/CT, CT and MRI as whole-body imaging modalities for the detection of local and/or distant recurrent disease in colorectal cancer (CRC) patients who have a (high) suspicion of recurrent disease, based on clinical findings or rise in carcinoembryonic antigen (CEA).

METHODS

A meta-analysis was undertaken. PubMed and Embase were searched for studies on the accuracy of whole-body imaging for patients with suspected local and/or distant recurrence of their CRC. Additionally, studies had to have included at least 20 patients with CRC and 2 × 2 contingency tables had to be provided or derivable. Articles evaluating only local recurrence or liver metastasis were excluded. Summary receiver-operating characteristic (ROC) curves were constructed from the data on sensitivity and specificity of individual studies and pooled estimates of diagnostic odds ratios (DORs) and areas under the ROC curve (AUCs) were calculated. To test for heterogeneity the Cochran Q test was used.

RESULTS

Fourteen observational studies were included which evaluated PET, PET/CT, CT and/or MRI. Study results were available in 12 studies for PET, in 5 studies for CT, in 5 studies for PET/CT and in 1 study for MRI. AUCs for PET, PET/CT and CT were 0.94 (0.90-0.97), 0.94 (0.87-0.98) and 0.83 (0.72-0.90), respectively. In patient based analyses PET/CT had a higher diagnostic performance than PET with an AUC of 0.95 (0.89-0.97) for PET/CT vs 0.92 (0.86-0.96) for PET.

CONCLUSION

Both whole-body PET and PET/CT are very accurate for the detection of local and/or distant recurrent disease in CRC patients with a (high) suspicion of recurrent disease. CT has the lowest diagnostic performance. This difference is probably mainly due to the lower accuracy of CT for detection of extrahepatic metastases (including local recurrence). For clinical practice PET/CT might be the modality of choice when evaluating patients with a (high) suspicion of recurrent disease, because of its best performance in patient based analyses and confident prediction of disease status.

Imaging as a surveillance tool in rectal cancer

Despite advances in diagnosis and treatment, half of patients with treated rectal cancer will die owing to recurrent disease. There is no evidence of benefit on survival from an intensive surveillance program, even if presymptomatic recurrent disease is detected. The aim of this article is to review the results described for the different imaging techniques in diagnosing rectal cancer recurrence in different sites and to discuss their relative clinical impact. The sensitivity of imaging techniques is related to the performance of the machines and the site being examined. Computed tomography is the most used technique owing to its availability, speed, panoramic images and ease of use, while MRI of the pelvis and the liver produces the highest resolution, sensitivity and specificity in these anatomical areas. Owing to its high cost, [(18)F] fluorodeoxyglucose-PET should be used as a third-level examination, a 'problem-solving' method when the site of recurrence is unknown or to rule out other possible sites of recurrence before a second surgery, and, finally, because it offers the possibility to investigate the whole body. The follow-up must be designed for individual patients, taking into account a number of factors. In the near future, whole-body imaging, probably by MRI, that is free from radiation will become the method of choice for screening for recurrent disease.

[Preoperative staging of rectal cancer]

Accurate preoperative staging of rectal cancer is crucial for therapeutic decision making, as local tumor extent, nodal status, and patterns of metastatic spread are directly associated with different treatment strategies. Recently, treatment approaches have been widely standardized according to large studies and consensus guidelines. Introduced by Heald, total mesorectal excision (TME) is widely accepted as the surgical procedure of choice to remove the rectum together with its enveloping tissues and the mesorectal fascia. Neoadjuvant radiochemotherapy also plays a key role in the treatment of locally advanced stages, while the use of new drugs will lead to a further improvement in oncological outcome. Visualization of the circumferential resection margin is the hallmark of any preoperative imaging and a prerequisite for high-quality TME surgery. The aim of this article is to present an overview on current cross-sectional imaging with emphasis on magnetic resonance imaging. Future perspectives in rectal cancer imaging are addressed.

Detection of recurrent rectal cancer with CT, MRI and PET/CT

Computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) all have the potential to directly visualize local and distant relapse of colorectal cancer (CRC). Nevertheless, the role of diagnostic imaging for routine follow-up of CRC patients remains controversial. Although MRI and PET have advantages over CT in the detection of local recurrence, until now only a few surveillance programs recommend the use of annual CT for routine follow-up. The objective of this review is to elucidate the current status of diagnostic imaging for the detection of recurrent rectal cancer based on the recent literature and our own experience. Furthermore, an insight into contemporary surveillance programs and an outlook concerning a novel technical approach to moving-table MRI at 1.5 Tesla for staging purposes are given.

Multi-detector CT in the evaluation of patients with recurrence of rectal cancer

The advantages of multiplanar reconstruction in rectal cancer recurrence diagnostics using medium resolution multi-detector CT are evaluated. We included 40 patients after a rectal cancer operation in this study. During follow-up ten patients developed a recurrence. All patients received a minimum of two CT-examinations in their follow-up program. A total of 131 CT-scans were evaluated. Each examination was reviewed by two experienced radiologists in respect to recurrence. Each examination was presented in axial reconstruction with a slice thickness of 8mm with an increment of 7 mm and a slice thickness of 3 mm with an increment of 2 mm. The thin slices were used for the multi-planar reconstruction. Multi-planar reconstructions showed better results for the detection of recurrence than axial reconstruction. A reduced slice thickness did not lead to better results in axial reconstruction. Multi-planar reconstruction showed a sensitivity of 0.88, a specificity of 1.0 and an accuracy of 0.97. Our axial reconstruction results were: 0.86, 0.96, and 0.93, respectively. Sensitivity and accuracy showed a significant increase after the first and second examinations. Multi-planar reconstructions allow for better detection of rectal cancer recurrence when compared to axial reconstructions. Thinner axial slice thickness shows no diagnostic advantage.

Lokalrezidivdiagnostik des Rektumkarzinoms mittels Kontrastmittelanreicherungsverhalten im Mehrzeilen-Spiral-CT

PURPOSE

The purpose of this study was to evaluate whether the recurrence of rectal cancer could by diagnosed reliably by contrast enhancement.

METHOD

A total of 83 patients were included after surgery and radiotherapy for rectal cancer. All patients received a minimum of three CT-examinations in their follow-up program. The contrast enhancement between the native scan and after admission of 75 ml Iopromid 370 mg/ml was calculated, as was the correlation between muscle enhancement and the enhancement of the suspicious lesion.

RESULTS

The only acceptable results for the diagnosis of recurrence were established by using the difference in the density of the suspicious lesion before and after admission of contrast media. No statistically significant difference was found for any of the enhancement parameters examined.

CONCLUSION

Static contrast enhancement of a suspicious lesion in MD-CT cannot confirm the diagnosis of a recurrence.