Final answer:
Digital rectal exams are primarily used to screen for prostate cancer, while colorectal cancer is often detected through colonoscopies and other tests that assess the colon and rectum.
Step-by-step explanation:
Digital rectal exams are an effective way of screening for prostate cancer. This is because the procedure allows a healthcare provider to feel the prostate gland for any irregularities or enlargements that may indicate the presence of cancer. In contrast, colorectal cancer screening is more effectively performed through colonoscopy, fecal occult blood tests, and DNA testing of stool samples. A colonoscopy is considered the gold standard for diagnosing colorectal cancer, as it allows direct visual examination of the colon and rectum and facilitates the removal of pre-cancerous polyps, assisting not only in detection but also in prevention.