Carcinoembryonic antigen directed PET-CECT scanning for postoperative surveillance of colorectal cancer

AIM

During the follow-up of surgically resected colorectal cancer (CRC), positron emission tomography-contrast-enhanced computed tomography (PET-CECT) is indicated for asymptomatic elevation of carcinoembryonic antigen (CEA) > 5 ng/ml and no obvious site of recurrence on clinical examination and basic imaging. As an institutional policy, a PET-CECT scan was performed at our institute whenever (1) CEA levels rose above 5 ng/ml and (2) CEA values were doubled (even if the CEA level was < 5 ng/ml). Our aim was to correlate the range of CEA elevation with recurrence rates and to evaluate the diagnostic utility of PET-CECT scanning in this setting.

METHOD

We retrospectively analysed all cases where a PET-CECT scan was performed for elevated CEA levels during surveillance visits after complete resection of the primary tumour followed by adjuvant therapy. This study was conducted from 1 January 2013 to 31 July 2015.

RESULTS

In all, 104 patients underwent a PET-CECT scan for rising CEA values, and 62 patients (59.6%) were found to have recurrent disease. At CEA levels < 5, 5.1-10, 10.1-15, 15.1-50 and > 50 ng/ml, disease recurred in 10%, 45%, 70%, 94% and 100% patients, respectively. Sensitivity, specificity, positive predictive value and negative predictive value of the PET-CECT scan were 92.7%, 95.2%, 96.2% and 90.9%, respectively. Elevation of CEA levels during follow-up was indicative of recurrence in 68% of the secretors and 45% of the non-secretors (based on baseline CEA status).

CONCLUSION

In the setting of rising CEA levels during follow-up of patients with CRC, a PET-CECT scan is a valuable tool to detect recurrence, irrespective of the baseline CEA secretor status. The likelihood of recurrence of disease was directly proportional to the value of the raised CEA level.

High nodal positivity rates even in good clinical responders after chemoradiation of rectal cancer: is organ preservation feasible?

AIM

Local excision (LE) is emerging as a treatment option for rectal cancer responding well to chemoradiation. However, it does not address the mesorectal nodal burden. We aimed to identify the factors influencing nodal positivity and subsequently defined a low-risk group by including only patients at low risk.

METHOD

A single-centre, retrospective database analysis was carried out of patients with radically resected rectal cancer after neoadjuvant chemoradiation.

RESULTS

This study included 524 patients with predominantly low rectal tumours. Nodal positivity among ypT0, T1 and T2 groups was 14.7%, 28% and 30%, respectively. Multivariate analysis with stepwise logistic regression identified the following low-risk features: age ≥ 40 years, nonsignet ring cell carcinoma (SRCC) histology and pathological complete response (pCR). Sixty-nine patients fulfilling all three criteria were analysed and the nodal positivity was found to be 10.1%, which implies that, if these patients had been selected for LE, one in 10 would have had positive mesorectal nodes.

CONCLUSION

Even in patients with low-risk criteria (pCR, non-SRCC histology and age ≥ 40 years), the residual positive nodal disease burden is 10%. Whether this high incidence of residual nodal disease translates into a similar risk of locoregional recurrence if an organ-preservation strategy is adopted is unclear.

An Improved Technique for the Determination of Isocyanurate and Isocyanate Conversion by Photoacoustic FTIR

Conventional rigid polyisocyanurate (PUIR) foams blown with HCFC-141b often suffer from poorer compressive strengths, dimensional stability and inferior flammability properties when compared to foams blown with CFC-11. It is often hypothesized that these properties can be improved by increasing the isocyanurate (or "trimer") conversion by means of catalyst optimization and increased isocyanate index. A convenient, yet reliable method for the determination of the amount of isocyanurate in a PUIR foam has been missing in this industry for a long time, though several attempts have been documented in the literature. The purpose of this paper is to introduce an improved isocyanurate conversion test by photoacoustic Fourier Transform Infra Red (FTIR) technique. This involves creating a baseline through three anchor points at approximately 1637 cm−1, 1469 cm−1, and 1349 cm−1. The absorbance of the isocyanurate peak at 1410 cm−1 is taken relative to the absorbance of the phenyl peak at 1602 cm−1. The phenyl peak is preferred to the urethane peak because the absorbance of phenyl groups in a foam is inherent to the amounts of polyols and isocyanates used in the foaming reaction, whereas the urethane linkages in the foam are created by a reaction between the two and are, therefore, variable depending on the extent of the reaction in the presence of catalysts and possibly water. In addition, the relative ratios of the absorbances of isocyanate end groups (at 2277 cm−1) and carbodiimide groups (at 2136 cm−1) to the phenyl groups can also be determined by generating a baseline through the anchor points at approximately 2470 cm−1, 2207 cm−1 and 2000 cm−1. This allows one to gain a better assessment of the overall kinetics of the isocyanate reactions and creates opportunities to improve the isocyanurate conversion through formulation optimization. The method is not limited to polyisocyanurate foams, as isocyanate conversion is an important parameter to follow in polyurethane foams as well, especially in all carbon dioxide blown foams. The method was found to be quite reproducible, and further statistical analysis to ensure the validity of this technique is under way.

Multidisciplinary management of colorectal adenocarcinoma associated with anal fistula: an Indian series

AIM

Adenocarcinomas associated with anal fistula are rare and often present at an advanced stage. They are often mistaken for commonly occurring benign diseases, leading to delayed diagnosis. Previous reports have predicted inferior oncological outcomes for these cases compared with sporadic rectal cancers. We are presenting our series of patients with colorectal adenocarcinoma associated with anal fistula who were treated with multimodality therapy at a tertiary cancer centre in India.

METHOD

This was a retrospective review of a prospectively maintained database of patients treated at our centre between 1 July 2013 and 31 March 2015. Of the 15 patients included in the study, 11 had prior intervention in the form of seton placement or fistulotomy. Fourteen patients had circumferential resection margin (CRM) involvement at initial workup and hence were given neoadjuvant chemoradiotherapy (NACRT). None of the patients had distant metastasis and only 15% had regional nodal involvement.

RESULTS

All 13 patients included in the final analysis underwent abdominoperineal excision (APE). Ten patients (73%) underwent extralevator APE. Plastic reconstruction in the form of a V-Y advancement flap for perineal closure was required in six patients (46%). On histopathological examination, a mucinous component was found to be present in 11 patients (73%). The quality of total mesorectal excision was complete in 92% patients. The CRM was free in 92% of patients. Median overall survival and disease-free survival were not reached.

CONCLUSION

Colorectal adenocarcinomas associated with fistula are locally aggressive malignancies with a low incidence of lymph node involvement and distant metastasis. NACRT, wider resection in the form of extralevator APE, and liberal use of plastic reconstruction may result in favourable outcomes.

Vaginal displacement during course of adjuvant radiation for cervical cancer: results from a prospective IG-IMRT study

OBJECTIVE

To compare internal target volume (ITV) generated using population-based displacements (ITV_study) with empty and full bladder scan fusion (ITV_EBFB) for organ-at-risk (OAR) doses during adjuvant intensity-modulated radiation therapy (IMRT) for cervical cancer.

METHODS

From January 2011 to October 2012, patients undergoing IMRT were included. CT simulation was carried out after inserting vault markers. Planning target volume (PTV)_EBFB received 50 Gy per 25 fractions. Pre-treatment megavoltage CT (MVCT) was performed. MVCTs were registered using bony landmarks with Day 1 MVCT. Displacement of the centre of mass of markers was measured along each axis. Directional ITV was calculated using mean ± 2 standard deviations (SDs) (ITV_study). Replanning was performed using PTV study, and OAR doses were compared with PTV_EBFB using Wilcoxon test.

RESULTS

A total of 348/386 data sets were evaluable for 16 patients. The median vaginal displacement was 1.2 mm (SD, 1.3 mm), 4.0 mm (SD, 3.5 mm) and 2.8 mm (SD, 3.3 mm) in the mediolateral, superoinferior and anteroposterior directions, respectively. The ITV margins were 4.1, 10.3 and 10.6 mm. ITV_study and ITV_EBFB were 115.2 cm(3) (87.7-152.2 cm(3)) and 151 cm(3) (95.7-277.1 cm(3)) (p < 0.0001), respectively. PTV_study and PTV_EBFB were 814 and 881 cm(3) (p < 0.0001), respectively. Median doses to the bladder were lower with the PTV_study (46.2 Gy vs 43.2 Gy; p = 0.0001), and a similar trend was observed in the volume of the small bowel receiving 40 Gy (68.2 vs 60.1 cm(3); p = 0.09).

CONCLUSION

Population-based PTV margins can lead to reduction in OAR doses.

ADVANCES IN KNOWLEDGE

Population-based ITV may reduce OAR doses while executing adjuvant IMRT for cervical cancer.

Evaluation of internal target volume in patients undergoing image-guided intensity modulated adjuvant radiation for gastric cancers

OBJECTIVE

To evaluate three-dimensional (3D) displacements of gastric remnant during adjuvant radiation.

METHODS

From January 2011 to September 2012, patients undergoing adjuvant image-guided intensity-modulated radiation on tomotherapy were included. Megavoltage CT (MVCT) data sets from daily treatment were coregistered with Day 1 MVCT. Residual stomach remnant was delineated on the data set, while the remaining were blinded to previous day contours. Gastric volume and centre of mass (COM) were determined for all data sets. The 3D deviation of COM was calculated for each fraction. Mean 3D and standard deviation (SD) were calculated for each patient and study population, and a 95% confidence interval (CI) was determined. Also, systematic and random errors for patient population and internal target volume (ITV) margin were calculated using the van Herk formula.

RESULTS

There were 119 images available for 15 patients. Mean volume of remnant was 319 cm(3) (146-454 cm(3)). Gastric remnant expanded in different directions with no specific directional expansion. Average deviations in mediolateral, superoinferior and anteroposterior directions were 9 mm (3-25 mm; SD, 5 mm), 6 mm (3-16 mm; SD, 4 mm) and 5 mm (1-10 mm; SD, 3 mm), respectively, with 95% CI of 18, 15 and 11 mm, and ITV margins of 19.2, 13.5 and 7.8 mm, respectively.

CONCLUSION

There is large variation in gastric remnant volume during the course of radiation. Large displacements observed in the present study necessitate the need to investigate adaptive techniques for optimizing intensity-modulated radiotherapy (IMRT) delivery.

ADVANCES IN KNOWLEDGE

An adaptive strategy needs to be developed to optimize IMRT delivery for adjuvant gastric irradiation.