Colorectal cancer

Colorectal cancer starts in the colon or rectum. Most cases are adenocarcinomas arising from the bowel lining. The exact site matters: a rectal tumor sits within the pelvis, close to structures important for continence, bladder and sexual function. Its distance from the anus and relationship to surrounding tissue influence the operation and whether treatment should come first.

Blood in the stool, a persistent change in bowel habits, unexplained iron-deficiency anemia, abdominal discomfort or weight loss need assessment. They are not specific to cancer. Severe abdominal pain with vomiting and inability to pass stool or gas, or substantial bleeding with dizziness, requires urgent medical attention.

Risk increases with age, a personal history of colorectal polyps or cancer, inflammatory bowel disease and some inherited syndromes. Younger adults can also develop the disease; persistent symptoms should not be dismissed because of age.

• Colonoscopy and biopsy identify the lesion and its tissue type. The team also checks whether the rest of the colon has been adequately examined.
• Chest, abdominal and pelvic imaging assess spread. Liver MRI can clarify lesions when their nature would change treatment.
• For rectal cancer, a dedicated pelvic MRI evaluates local depth, lymph nodes and the margin around the planned operation. Examination and endoscopy add information MRI alone cannot provide.
• CEA provides a baseline for some patients and may help follow treatment. A normal result neither excludes cancer nor proves it has disappeared.

Tumor testing and inherited-risk testing are different. Loss of mismatch-repair proteins can occur through acquired changes as well as Lynch syndrome. The pattern of protein loss, further tumor tests and the personal and family history guide genetic counseling; an abnormal tumor result alone is not a diagnosis for relatives.

TNM describes the depth of the primary tumor, regional lymph nodes and distant metastases. Stages I–III generally describe disease without distant spread; stage IV indicates distant spread. Clinical staging before treatment and pathological staging after surgery are different assessments, so a changed stage does not automatically mean the cancer worsened.

Ask whether the goal is removal of all known disease, shrinkage to make local treatment possible, or long-term control and symptom relief. Stage IV is not one uniform situation: a few removable metastases and widespread disease require different discussions.

Selected superficial cancers can be removed endoscopically. Others usually require removal of the affected bowel segment and regional lymph nodes. After surgery, the pathology helps decide whether chemotherapy offers worthwhile benefit. It is commonly used for stage III disease; stage II decisions depend on recurrence risk, MMR/MSI status, fitness and the expected benefit and harms.

Radiotherapy has a much smaller routine role in colon cancer than in rectal cancer. If a plan includes treatment before colon surgery, ask which local or molecular feature makes that sequence appropriate.

For many locally advanced rectal cancers, treatment starts before surgery. Total neoadjuvant therapy brings chemotherapy and pelvic radiation-based treatment into the preoperative period. MRI-defined risk, tumor height, MMR/MSI and the person's priorities guide selection; some lower-risk cases can follow a different sequence or avoid radiation.

ASCO recommends immunotherapy for MSI-H/dMMR locally advanced rectal cancer. After a carefully documented clinical complete response, nonoperative management may be discussed with an experienced team. This is active surveillance with examination, endoscopy and imaging, not simply cancelling surgery. Regrowth can occur, and reliable follow-up and a salvage-treatment plan are essential. A guideline recommendation and a drug's locally approved indication must still be checked separately.

Review whether every visible metastasis could be treated locally, particularly in the liver or lungs. Surgery, ablation or selected radiation approaches may be considered alongside systemic treatment. Even when surgery is not possible initially, response to treatment can justify reassessment. An organ-specific surgeon and radiologist should contribute before a potentially treatable pattern is dismissed.

For broader disease, treatment considers MMR/MSI, RAS/BRAF, tumor location, other actionable findings, previous exposure and side effects. In the United States, nivolumab plus ipilimumab is approved for unresectable or metastatic MSI-H/dMMR colorectal cancer in adults and patients aged 12 years or older. This should not be generalized to typical MSS/pMMR disease.

For adults with BRAF V600E metastatic colorectal cancer confirmed by an FDA-authorized test, the current US encorafenib label includes combination with cetuximab and fluorouracil-based chemotherapy. A separate encorafenib–cetuximab indication follows prior therapy. These are combination strategies with defined conditions, not a reason to use a BRAF drug alone.

Bring the exact drugs, dates, best response and reason each treatment ended. Progression, intolerance and a planned break are different situations. The next discussion may involve another chemotherapy or targeted strategy, updated tissue or blood testing when it can answer a specific question, a local treatment for a troublesome site, or a clinical trial.

A trial should be matched to the tumor and previous treatment, not just the disease name. Ask about eligibility, travel, study visits, alternatives and how urgent symptoms will be managed while screening is underway.

CEA-directed CAR T-cell approaches are being studied in early-phase trials, including NCT05396300. They are investigational options rather than an established replacement for standard colorectal treatment. Tumor eligibility, safety and current enrollment must be checked with the study team; a high blood CEA is not by itself a treatment-selection test.

A stoma may be temporary or permanent depending on the tumor and operation. Ask for a stoma nurse consultation before surgery when possible. After rectal surgery, urgency, frequent bowel movements or leakage can occur even without a stoma; urinary and sexual effects also deserve early discussion. Persistent diarrhea, dehydration or difficulty eating should be reported rather than endured.

Follow-up is tailored to the treatment and recurrence risk, with clinical review, selected imaging, CEA and colonoscopy as appropriate. It should also address neuropathy, fatigue, nutrition and return to daily activities. A hereditary syndrome can change surveillance for the patient and family.

• Pathology, colonoscopy and operation reports, including tumor location and margins.
• Original imaging and reports; pelvic MRI for rectal cancer and liver MRI if performed.
• MMR/MSI, RAS, BRAF and other molecular results, plus relevant family history.
• Treatment timeline, current bowel symptoms, stoma details and side effects affecting daily life.

Useful questions include: What is the goal now? Does the rectal location change the sequence? Have liver or lung lesions been reviewed for local treatment? Which test would actually change my next option?