Assessment of Venous Invasion in Colorectal Cancer
Assessment of Venous Invasion in Colorectal Cancer
Aims Venous invasion (VI) is a known independent prognostic indicator of recurrence and survival in colorectal cancer. The guidelines of the Royal College of Pathologists (RCPath) state that, in a series of resections, extramural VI should be detected in at least 25% of specimens. However, there is widespread variability in the reported incidence, and this may affect patient access to adjuvant therapy. This study aims to clarify the current practice patterns of pathologists regarding the assessment of VI and to identify factors associated with an increased self-reported VI detection rate.
Methods A population-based survey was mailed to 361 pathologists in the province of Ontario, Canada.
Results The overall response rate was 64.9%. Most pathologists were practicing in community-based centres (66.2%) and approximately half had been in practice for over 15 years (53.5%). A subspecialist interest in gastrointestinal (GI) pathology was declared by 27.3% of pathologists. The majority of pathologists (70.2%) reported that they detected VI in less than 10% of resection specimens, with only 9.1% reporting VI detection rates above 20%. Standardised reporting criteria were applied by 62.1%. Special stains were employed by 57.6% if VI was suspected on H&E-stained sections. Practice in a university-affiliated centre, a subspecialist interest in GI pathology and the acceptance of the 'orphan arteriole' sign were all independently associated with a self-reported VI detection rate above 10% on multivariate analysis.
Conclusions Self-reported VI detection rates are low among most pathologists. Even among specialist GI pathologists practicing in university-affiliated centres, few reported a detection rate close to that recommended by the RCPath. Strategies to increase the detection of VI may be required.
Venous invasion (VI) has been shown to be an independent predictor for haematogenous disease recurrence (typically liver and lung metastasis) and decreased survival in colorectal cancer. This has prompted its inclusion as a mandatory element in the College of American Pathologists' (CAP) protocol for the examination of colorectal cancer specimens. The CAP protocol provides the basis for most synoptic pathology reports throughout Ontario.
The identification of VI is subject to widespread variability among studies, with reported detection rates ranging from 9% to 90%. The most recently published dataset for colorectal cancer from the Royal College of Pathologists (RCPath) in the UK states that extramural VI should be detected in at least 25% of all specimens, although anecdotal reports suggest that in routine practice this figure is usually closer to 10%. Detection of adverse prognostic features, such as VI, is of particular relevance in patients with stage II tumours, as it may encourage oncologists to offer adjuvant chemotherapy. Studies of interobserver variation have demonstrated only poor to moderate agreement in the detection of VI, even among subspecialist gastrointestinal (GI) pathologists within the same department. Reproducibility in other centres may be lower, especially if the reporting of colorectal cancer specimens is undertaken as part of a general pathology rota.
Factors believed to contribute to the variation in the detection of VI include: selection bias in centres undertaking more advanced cases, a lack of consensus over reporting criteria, the use of special stains, and the experience or subspecialist interest of the reporting pathologist. The RCPath have suggested that extramural VI is recorded according to Talbot's criteria, where 'tumour is present within an extramural endothelium-lined space that is either surrounded by a rim of muscle or contains red blood cells'. The explanatory notes of the current CAP protocol make reference to VI as an 'independent adverse prognostic factor' with particular emphasis on the prognostic significance of extramural VI. Nevertheless, VI is not recorded as a separate entity in the CAP protocol and is instead incorporated under the collective heading of 'lymph vascular invasion'. VI and lymphatic invasion may have different prognostic implications, although it is often difficult to distinguish between these two features in clinical practice.
Increasing numbers of studies have demonstrated that the use of elastic or immunohistochemical staining greatly facilitates the identification of blood vessels, by highlighting elastin or smooth muscle in vessel walls, and is associated with a higher detection rate of VI. In series where special staining techniques have been employed, VI detection rates of 27–52% have been reported for stage II tumours. As yet, the routine use of special stains is not currently advocated by either the CAP or the RCPath.
Therefore, this survey aimed to (1) clarify the current practice patterns of pathologists regarding the assessment of VI in colorectal cancer resections, and (2) identify the factors associated with an increased self-reported VI detection rate.
Abstract and Introduction
Abstract
Aims Venous invasion (VI) is a known independent prognostic indicator of recurrence and survival in colorectal cancer. The guidelines of the Royal College of Pathologists (RCPath) state that, in a series of resections, extramural VI should be detected in at least 25% of specimens. However, there is widespread variability in the reported incidence, and this may affect patient access to adjuvant therapy. This study aims to clarify the current practice patterns of pathologists regarding the assessment of VI and to identify factors associated with an increased self-reported VI detection rate.
Methods A population-based survey was mailed to 361 pathologists in the province of Ontario, Canada.
Results The overall response rate was 64.9%. Most pathologists were practicing in community-based centres (66.2%) and approximately half had been in practice for over 15 years (53.5%). A subspecialist interest in gastrointestinal (GI) pathology was declared by 27.3% of pathologists. The majority of pathologists (70.2%) reported that they detected VI in less than 10% of resection specimens, with only 9.1% reporting VI detection rates above 20%. Standardised reporting criteria were applied by 62.1%. Special stains were employed by 57.6% if VI was suspected on H&E-stained sections. Practice in a university-affiliated centre, a subspecialist interest in GI pathology and the acceptance of the 'orphan arteriole' sign were all independently associated with a self-reported VI detection rate above 10% on multivariate analysis.
Conclusions Self-reported VI detection rates are low among most pathologists. Even among specialist GI pathologists practicing in university-affiliated centres, few reported a detection rate close to that recommended by the RCPath. Strategies to increase the detection of VI may be required.
Introduction
Venous invasion (VI) has been shown to be an independent predictor for haematogenous disease recurrence (typically liver and lung metastasis) and decreased survival in colorectal cancer. This has prompted its inclusion as a mandatory element in the College of American Pathologists' (CAP) protocol for the examination of colorectal cancer specimens. The CAP protocol provides the basis for most synoptic pathology reports throughout Ontario.
The identification of VI is subject to widespread variability among studies, with reported detection rates ranging from 9% to 90%. The most recently published dataset for colorectal cancer from the Royal College of Pathologists (RCPath) in the UK states that extramural VI should be detected in at least 25% of all specimens, although anecdotal reports suggest that in routine practice this figure is usually closer to 10%. Detection of adverse prognostic features, such as VI, is of particular relevance in patients with stage II tumours, as it may encourage oncologists to offer adjuvant chemotherapy. Studies of interobserver variation have demonstrated only poor to moderate agreement in the detection of VI, even among subspecialist gastrointestinal (GI) pathologists within the same department. Reproducibility in other centres may be lower, especially if the reporting of colorectal cancer specimens is undertaken as part of a general pathology rota.
Factors believed to contribute to the variation in the detection of VI include: selection bias in centres undertaking more advanced cases, a lack of consensus over reporting criteria, the use of special stains, and the experience or subspecialist interest of the reporting pathologist. The RCPath have suggested that extramural VI is recorded according to Talbot's criteria, where 'tumour is present within an extramural endothelium-lined space that is either surrounded by a rim of muscle or contains red blood cells'. The explanatory notes of the current CAP protocol make reference to VI as an 'independent adverse prognostic factor' with particular emphasis on the prognostic significance of extramural VI. Nevertheless, VI is not recorded as a separate entity in the CAP protocol and is instead incorporated under the collective heading of 'lymph vascular invasion'. VI and lymphatic invasion may have different prognostic implications, although it is often difficult to distinguish between these two features in clinical practice.
Increasing numbers of studies have demonstrated that the use of elastic or immunohistochemical staining greatly facilitates the identification of blood vessels, by highlighting elastin or smooth muscle in vessel walls, and is associated with a higher detection rate of VI. In series where special staining techniques have been employed, VI detection rates of 27–52% have been reported for stage II tumours. As yet, the routine use of special stains is not currently advocated by either the CAP or the RCPath.
Therefore, this survey aimed to (1) clarify the current practice patterns of pathologists regarding the assessment of VI in colorectal cancer resections, and (2) identify the factors associated with an increased self-reported VI detection rate.
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