<title>Abstract</title><sec>
<title>Background</title>
The characterisation of desmoplastic reaction (DR) has emerged as a new, independent prognostic determinant in colorectal cancer. Herein, we report the validation of its prognostic value in a randomised controlled study (SACURA trial).


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<title>Methods</title>
The study included 991 stage II colon cancer patients. DR was classified by the central review as Mature, Intermediate or Immature based on the presence of hyalinised collagen bundles and myxoid stroma at the desmoplastic front. All clinical and pathological data, including DR characterisations, were prospectively recorded and analysed 5 years after the completion of the registration.


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<title>Results</title>
The five-year relapse-free survival (RFS) rate was the highest in the Mature group (<italic>N</italic> = 638), followed by the Intermediate (<italic>N</italic> = 294) and Immature groups (<italic>N</italic> = 59). Multivariate analysis revealed that DR classification was an independent prognostic factor, and based on Harrell’s C-index, the Cox model for predicting RFS was significantly improved by including DR. In the conditional inference tree analysis, DR categorisation was the first split factor for predicting RFS, followed by T-stage, microsatellite instability status and budding.


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<title>Conclusions</title>
Histological categorisation of DR provides important prognostic information that could contribute to the efficient selection of stage II colon cancer patients who would benefit from postoperative adjuvant therapy.


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