Treatment strategies and oncological outcomes across national guideline periods in rectal cancer: a population-based cohort study
The shift towards more selective use of preoperative radiotherapy in rectal cancer raises concern that locoregional control may be compromised. The aim was to evaluate whether changes in staging, risk stratification, and treatment across three national guideline periods were associated with differences in oncological outcomes in patients with clinical stage I–III rectal cancer treated with curative intent. 2035 patients from Dalarna, Gävleborg, and Uppsala County with clinical stage I-III rectal cancer were included. Data were obtained from the Swedish Colorectal Cancer Registry and supplemented by review of electronic patient records. Logistic regression with guideline period modelled as an ordinal variable was used to assess differences in treatment over time. Associations between guideline period and oncological outcomes were analysed using unadjusted and adjusted Cox and Fine-Gray models. The proportion of patients staged as cN0 increased over time (OR per period 1.40, 95% c.i. 1.25–1.56), whereas the proportion of patients with cN2 decreased (OR 0.67, 95% c.i. 0.59–0.76). Direct surgery increased (26, 33, and 43%), while overall preoperative treatment (44, 40, and 31%) and short-course radiotherapy (35, 27, 12%) decreased over time. Locoregional recurrence was 3.1% at 5 years and did not differ between guideline periods. No differences were observed in distant metastasis, overall survival, or relative survival after adjustment, although unadjusted analyses suggested lower distant metastasis rates in the most recent period. Reduced use of preoperative radiotherapy was not associated with impaired oncological outcomes. The findings support a more selective radiotherapy use while maintaining oncological safety and reducing treatment-related morbidity.