Digital rectal examination in rectal cancer response assessment: clinical performance and the need for standardized...

Accurate assessment of treatment response after neoadjuvant therapy is crucial to select patients with rectal cancer for organ-preserving strategies. Digital rectal examination (DRE) remains a key component of response assessment, but its precise clinical role and the lack of standardized reporting limit its utility. This study aimed to assess variability in DRE reporting and to explore the association between DRE findings at first reassessment and subsequent local oncological outcome within a watch-and-wait pathway, rather than to evaluate DRE as a stand-alone diagnostic test.

In this retrospective cohort study at a Belgian tertiary referral center, all patients with rectal cancer considered for active surveillance between January 2018 and January 2023 were reviewed. DREs at diagnosis and first post-treatment reassessment were classified as normal or abnormal. Clinical outcomes during surveillance, including sustained clinical complete response (cCR), local regrowth, and salvage surgery, were recorded. For the primary analysis, histopathologically confirmed viable tumor at salvage surgery was classified as residual tumor, whereas sustained cCR for at least 2 years or salvage surgery without viable tumor was classified as no residual tumor. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated descriptively as exploratory estimates of clinical performance within this multimodal surveillance pathway.

Among 105 eligible patients, 20 (19.0%) had abnormal DRE findings at first reassessment. Of these, 19 underwent salvage surgery due to clinical suspicion of local regrowth, and 17 (85.0%) had viable tumor confirmed histopathologically. Among the 85 patients with a normal DRE at reassessment, 24 (28.2%) later underwent salvage surgery for suspicion of local regrowth during follow-up, and all had histologically confirmed viable tumor, while 61 (71.8%) maintained a sustained cCR. At the time of later local regrowth or clinical suspicion, 35 of 39 available DRE reports (89.7%) were abnormal. DRE documentation was brief and heterogeneous, typically consisting of one to two free-text sentences.

Within a multimodal watch-and-wait pathway, DRE at first reassessment appears to function primarily as a clinical warning-sign examination rather than as an isolated diagnostic test. A normal DRE does not exclude future residual disease or regrowth, whereas an abnormal DRE should be considered a relevant warning sign within multimodal reassessment. These findings are hypothesis-generating. The marked variability in reporting underscores the need for standardized terminology and structured documentation in rectal cancer response assessment.