Determinants of Pre-Surgical Treatment in Primary Rectal Cancer: A Population-Based Study

Abstract

When preoperative radiotherapy (RT) is best used in rectal cancer is subject to discussions and guidelines differ. To understand the selection mechanisms, we analysed treatment decisions in all patients diagnosed between 2010-2020 in two Swedish regions (Uppsala with a RT department and Dalarna without). Information on staging and treatment (direct surgery, short-course RT, or combinations of RT/chemotherapy) in the Swedish Colorectal Cancer Registry were used. Staging magnetic resonance imaging (MRI) permitted a division into risk groups, according to national guidelines. Logistic regression explored associations between baseline characteristics and treatment, while Cohen's kappa tested congruence between clinical and pathologic stages. A total of 1150 patients without synchronous metastases were analysed. Patients from Dalarna were older, had less advanced tumours and were pre-treated less often (52% vs. 63%, p < 0.001). All MRI characteristics (T-/N-stage, MRF, EMVI) and tumour levels were important for treatment choice. Age affected if chemotherapy was added. The correlation between clinical and pathological T-stage was fair/moderate and poor for N-stage. The MRI-based risk grouping influenced treatment choice the most. Since the risk grouping was modified to diminish the pre-treated proportion, fewer patients were irradiated with time. MRI staging is far from optimal. A stronger wish to decrease irradiation may explain why fewer patients from Dalarna were irradiated, but inequality in health care cannot be ruled out.

Keywords: chemoradiotherapy; magnetic resonance imaging; neoadjuvant therapy; population-based; preoperative therapy; radiotherapy; rectal cancer; treatment guidelines.

Figure 1

Flow chart of patient selection. ¹ One patient had a missing cTNM status and was excluded. ² Patients that were too ill to be treated (n = 4), died before initiating treatment (n = 2), carcinoma in situ (n = 2), another metastatic tumour type simultaneously (n = 2), sigmoidal cancer (n = 1), missing information about treatment (n = 1), M1 according to pathology report (n = 1), or no tumour could be seen on MRI (n = 1). Abbreviations: Rectal cancer, RC; short-course radiotherapy, scRT; long-course radiotherapy, lcRT; chemotherapy, CT; chemoradiotherapy, CRT; transanal endoscopic microsurgery, TEM; watch-and-wait strategy, W&W.

Figure 2

(a) Distribution of cN-stage for the time periods during which different treatment guidelines were used (2008 guidelines in 2010–2014, 2016 guidelines in 2015–2018 and 2020 guidelines in 2019–2020) in Uppsala and Dalarna regions. The columns do not add up to 100% since nodal status was not detailed in all patients. The changes in cN positivity for each year is shown in Figure S4; (b) Distribution of risk groups in an alluvial diagram after re-classifying all tumours (that had all necessary data available, n = 1038) according to the different guidelines. With the 2008 guidelines, there was an even distribution of the three risk groups; 26% of the tumours were classified as early/good, 36% intermediate/bad and 38% locally advanced/ugly. With the 2016 guidelines, the number of bad tumours decreased while the number of ugly tumours stayed virtually the same; 38% good, 24% bad and 37% ugly. Major changes in the 2020 guidelines meant that even more tumours should be considered good, and more than half of the ugly tumours should now be considered bad; 50% good, 35% bad and 15% ugly.

Figure 3

Distribution of treatments (immediate surgery, short-course radiotherapy; scRT, chemoradiotherapy/scRT + chemotherapy; CRT/scRT + CT) in (a) both regions and also in each risk group (Good, Bad, Ugly) in (b) Uppsala and (c) Dalarna region for the time periods during which different treatment guidelines were used (2008 guidelines in 2010–2014, 2016 guidelines in 2015–2018 and 2020 guidelines in 2019–2020). The columns do not add up to 100% since some patients were treated with other alternatives than the three dominating ones.