Impact of timing of adjuvant chemotherapy initiation on survival for elderly patients with stage III colon cancer in Norway - a register-based cohort study

Sep 23, 2026

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Standard treatment for stage III colon cancer is major surgery followed by adjuvant chemotherapy (ACT), yet optimal ACT timing remains uncertain. This register-based retrospective cohort study evaluates how ACT initiation timing affects 5-year overall survival among Norwegian patients aged 70+ after stage III colon cancer resection. Patients were categorized by ACT timing (≤6, 7–8, 9–10, 11–13 weeks) versus resection only, using Kaplan-Meier and Cox models. Findings support initiating ACT within 8 weeks, with subgroup-dependent benefits.

LanguageEnglish

CategoryHealthcare

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Gustavsen et al. BMC Cancer (2025) 25:1578 BMC Cancer [https://doi.org/10.1186/s12885-025-14942-y](https://doi.org/10.1186/s12885-025-14942-y) RESEARCH Open Access Impact of timing of adjuvant chemotherapy initiation on survival for elderly patients with stage III colon cancer in Norway – a register-based cohort study Elin Marthinussen Gustavsen 1,2*, Stig Norderval3,4, Liv Marit Dørum5, Eva Stensland 1,2, Ellinor Haukland6,7, Yohannes Tesfay2 and Beate Hauglann2 Abstract Background Standard treatment for stage III colon cancer is major surgical resection followed by adjuvant chemotherapy (ACT) . Norwegian guidelines recommend initiation of ACT within 4–6 weeks after resection, but consensus regarding optimal timing of ACT is lacking. Objective To investigate the impact of ACT timing on 5-year overall survival (OS) of elderly patients with stage III colon cancer in Norway. Methods This population-based retrospective cohort study included patients aged 70 years or older who underwent major surgical resection for stage III colon cancer diagnosed between 2011 and 2021. Patients were grouped by ACT timing after resection: ≤ 6, 7–8, 9–10, and 11–13 weeks, in addition to those with resection only. The 5-year OS was assessed using Kaplan-Meier analysis and Cox proportional hazards models. Results Among 4 075 patients included, 1 408 were provided ACT. Median timing of ACT was 6.4 weeks after resection. Initiation of ACT in weeks 7–10 after resection was not associated with increased mortality risk compared to initiation within the first 6 weeks. Delaying the initiation of ACT beyond 10 weeks after resection was associated with worse 5-year OS (hazard ratio 1.49, 95% confidence interval 1.04–2. 12) . The association between survival benefit and ACT timing varied based on risk levels: For low risk patients, there was an association of improved survival benefit when ACT was initiated within 8 weeks after resection compared to resection alone, whereas for high risk patients, the association of survival benefit was better for those provided ACT in weeks 9–10 as well. Conclusions Our findings support initiation of ACT within 8 weeks after major resection to maximise survival benefits in elderly patients with stage III colon cancer. However, for certain patient groups, initiation of ACT seems beneficial even up to 10 weeks after resection. The findings suggest greater flexibility in ACT initiation timing, benefiting both patients and health care services. Keywords Colon cancer, Adjuvant chemotherapy, Timing, Survival, Elderly *Correspondence: Elin Marthinussen Gustavsen elin.gustavsen@helse-nord. no Full list of author information is available at the end of the article © The Author(s) 2025. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit [http://creativecommons.org/l](http://creativecommons.org/l)icenses/by/4.0/. Gustavsen et al. BMC Cancer (2025) 25:1578 Introduction Colon cancer is one of the most commonly diagnosed cancers globally. The highest rates occur in developed regions such as Europe, Australia, and Northern America [1]. In Norway, colon cancer is the fourth most common cancer type [2]. Of the 3 536 persons who were diagnosed with colon cancer in Norw

FAQs

What clinical question does the study address?

The study investigates how the timing of initiating adjuvant chemotherapy after surgery affects 5-year overall survival in elderly patients with stage III colon cancer in Norway.

How were patients grouped by adjuvant chemotherapy timing?

Patients aged 70+ who underwent major resection were grouped by ACT initiation time after resection: ≤6, 7–8, 9–10, and 11–13 weeks, plus a comparison group receiving resection only.

What did the results show about starting ACT after surgery?

Initiation of ACT in weeks 7–10 was not associated with higher mortality versus initiation within the first 6 weeks, while delaying beyond 10 weeks was linked to worse 5-year overall survival. The survival benefit also varied by risk level.

Sep 23, 2026

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