Author response: Tumour deposit count is an independent prognostic factor in colorectal cancer—a population-based cohort study

The authors express concern that all patients lacked full 5-year survival due to the inclusion period of the 1st of January 2016 to the 31st of December 2019. However, as final follow-up data collection was performed on the 23rd of January 2024, full 5-year survival and outcome data were available for all patients except those diagnosed in 2019. Additionally, the vast majority of recurrences in colorectal cancer occur within the first three years after surgery, as illustrated by our Kaplan–Meier curves. Thus, the lack of full 5-year data in a small subset of patients is unlikely to affect the study’s conclusions.

The authors raise concerns regarding potential differences in treatment strategies across centres. While we acknowledge this possibility, it is important to note that all centres in Sweden adhere to national guidelines for colorectal cancer management. In our cohort, 91.4% of patients were discussed at a preoperative multidisciplinary team meeting, which supports consistent treatment planning and guideline adherence. Additionally, Swedish patients routinely undergo postoperative multidisciplinary discussion as per the national guidelines.

The authors correctly identified a discrepancy between our text and Table 1. The statement should read: “While both TD-positive and TD-negative tumors were more commonly left-sided, the proportion of right-sided tumours was higher among TD-positive cases compared to TD-negative cases.”

Molecular markers such as MSI, MMR, KRAS, and BRAF were not included in our analysis for two main reasons. First, systematic molecular profiling was not consistently implemented across Swedish centres until recent years and were therefore not available for our study cohort. Second, genetic markers were outside the scope of this study, which aimed to investigate the prognostic impact of the number of TDs. As molecular testing becomes more routine, future research will undoubtedly explore the interplay between TDs and molecular characteristics.

The authors reflected on the low prevalence of TDs in our cohort, which only accounted for 12%. While previous research has shown a prevalence between 10-40%, these estimations are based on older cohorts (1964-2013) and prior TNM editions1. Since then, major strides have been taken in the definition of TDs. Most lately, TNM 8 introduced the exclusion of nodules that contains lymphatic, vascular or neural tissue. As most patients were assessed using TNM 8, and nearly all were discussed in a preoperative multidisciplinary conference, 12% likely represents the true TD prevalence in a national sample, rather than being an under-reported figure. Indeed, in currently unpublished material where a pathological re-review was conducted on approximately 50 patients with TDs and 50 without, only a few cases have been revised.