Which diagnostic tests are recommended for confirming a diagnosis of rectal cancer in primary care?

In primary care, the recommended diagnostic approach to confirm a diagnosis of rectal cancer begins with a thorough clinical assessment including a digital rectal examination (DRE) to detect any rectal mass, which if found, warrants urgent referral via a suspected cancer pathway ¹. Following this, quantitative faecal immunochemical testing (FIT) is advised for patients presenting with symptoms suggestive of colorectal cancer, such as iron-deficiency anaemia or non-iron-deficiency anaemia in those aged 60 and over, to guide the need for further investigation ¹. FIT serves as a non-invasive test to stratify risk and prioritize patients for colonoscopy or other definitive diagnostic procedures ¹. If FIT is positive or if there is a palpable rectal mass on DRE, an urgent referral for colonoscopy or flexible sigmoidoscopy is indicated to visually confirm the presence of rectal cancer and obtain biopsy samples for histological diagnosis ¹.

While DRE remains a cornerstone in initial assessment, its sensitivity and specificity can vary; meta-analyses in related cancer screening contexts (e.g., prostate cancer) highlight that DRE alone is insufficient for definitive diagnosis but valuable as part of the clinical evaluation (Hoogendam et al., 1999). Therefore, DRE should be combined with FIT and prompt referral for endoscopic evaluation to confirm rectal cancer diagnosis ¹ (Hoogendam et al., 1999). Imaging such as CT scanning is generally reserved for staging after diagnosis rather than initial confirmation in primary care ¹.