Peritumoral malignant cellular foci and nodal risk in pT1 colorectal cancer

Design

Multicentre retrospective cohort with training and validation sets

Population

2,611 patients with endoscopically or surgically resected pT1 colorectal cancer, six Chinese centres

Primary outcome

Lymph node metastasis

Effect

Peritumoral malignant cellular foci independently associated with nodal metastasis in both cohorts (P<0.05); budding and clusters inconsistent

Tumour budding and poorly differentiated clusters are both defined by a five-cell cut-off at the invasive front, and studies of their link with nodal metastasis in pT1 colorectal cancer are inconsistent. This study proposed a simpler feature: any non-glandular focus of one or more tumour cells at the invasive front, called peritumoral malignant cellular foci.

Across 2,611 endoscopically or surgically resected pT1 cancers from six Chinese centres, budding and poorly differentiated clusters were not consistently independent predictors of nodal metastasis. Peritumoral malignant cellular foci were independent predictors in both the training and validation cohorts and across age, sex, site and body mass index subgroups. They were also linked to more involved nodes and more strongly to apical (D3) nodes.

The abstract reports significance but not the size of the effect, and the cohorts are all from one country. Removing the arbitrary cut-off could improve agreement between pathologists, but inter-observer reproducibility needs testing.

For now, reporting standards have not changed. It is reasonable to describe any non-glandular foci at the front in pT1 reports, alongside the established high-risk features, so that the surgical team has the fullest picture.

• Continue to report established high-risk features in pT1 colorectal cancer: grade, lymphovascular invasion, budding, depth and margin
• Consider describing any non-glandular tumour foci at the invasive front, even single cells
• Discuss borderline pT1 cases at the multidisciplinary meeting when deciding on completion surgery
• Reporting guidelines have not changed; this feature needs external validation

Why it matters

It challenges the five-cell cut-off that underpins how budding is scored worldwide.

Don't overread it

The effect size is not reported in the abstract and the feature is not yet validated outside China.

The statistics, in plain English

The study reports P values below 0.05 but, in the abstract, no odds ratios or measures of discrimination, so how much better the new feature predicts nodes cannot yet be judged.

Read the rest in the app

You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.

Get Daily Doctor — free

Scan to keep reading on your phone. No account needed to start.