Colorectal cancer
cancer, also known as bowel cancer, cancer, or rectal cancer, is the development of cancer from the colon or . It is the consequence of uncontrolled growth of colon cells that can invade/spread to other parts of the body. Signs and symptoms may include blood in the , a change in bowel movements, weight loss, pain and . Most colorectal cancers are due to lifestyle factors and disorders. Risk factors include diet, , smoking, and lack of physical activity. Dietary factors that increase the risk include red meat, processed meat, and alcohol. Another risk factor is bowel disease, which includes disease and . Some of the inherited genetic disorders that can cause colorectal cancer include adenomatous and non-polyposis colon cancer; however, these represent less than 5% of cases. It typically starts as a tumor, often in the form of a polyp, which over time becomes cancerous.
Underlined words are explained — tap any of them.
Symptoms — what it feels like
- ·Blood in
- ·change in bowel movements
- ·unintentional weight loss
- ·vomiting
- ·
Causes — why it happens
- ·Lifestyle factors and disorders
Prevention
- · from age of 45 to 75
Treatment
- ·
- · therapy
- ·
- ·targeted therapy
The sections below are general education drawn from public guidelines (NHS, Mayo, CPIC, WHO, ICMR). They are not individually reviewed by a clinician and are not medical advice — always talk to a doctor about your own health.
When to see a doctor
See a doctor if you have a lasting change in bowel habits, blood in your stool, ongoing belly pain or bloating, unexplained weight loss, or tiredness that could be from low iron. Most causes are not cancer, but lasting changes should be checked.
Get prompt care for heavy rectal bleeding, severe belly pain, or being unable to pass stool or gas with a swollen, painful tummy. If bowel cancer runs in your family, ask when screening should start.
General guidance, not a diagnosis. When in doubt, see a doctor.
Questions to ask your doctor
- ?Which tests, like a stool test or colonoscopy, do I need?
- ?Given my family history, when should screening start for me?
- ?How long should I watch a symptom before coming back?
- ?Which symptoms need urgent attention?
- ?What lifestyle changes lower my risk?
- ?How often should I be screened going forward?
What to note before your visit
- ·when bowel changes started and what they are
- ·any bleeding or change in stool colour
- ·family history of bowel cancer or polyps
- ·unexplained weight loss or tiredness
Genes that change how certain drugs work — and that differ in South Asians. This is education, not a dosing tool; genotype-guided prescribing is a clinician decision.
5-FU and capecitabine are powerful cancer drugs your body normally breaks down quickly with the DPD . People born with a weak version can't clear the drug, so a standard dose becomes a poisoning - which is why a doctor may lower the dose or choose another plan.
South Asian signal: The classic European risk variant DPYD*2A (c.1905+1G>A, rs3918290) is markedly rarer in Indians (~0.05% allele frequency) than in Europeans (~0.3-0.5%), so a European-only variant panel will miss most at-risk Indian patients; population-specific and broader DPYD variant coverage is needed. South Asian populations may carry different or under-catalogued DPYD variants, and DPD-deficiency phenotype testing remains relevant.
Prescriber note: Where DPYD testing is used before fluoropyrimidine chemotherapy, ensure the panel is not limited to European variants (DPYD*2A is rare in Indians); consider broader genotyping and/or phenotype (DPD activity) assessment, and reduce or avoid dosing per the DPYD activity score. CPIC recommends reducing the fluoropyrimidine starting dose (guided by DPYD activity score) for DPYD intermediate metabolisers and avoiding fluoropyrimidines in poor metabolisers, because reduced DPD activity sharply raises the risk of severe or fatal toxicity.
Not a dosing tool. Genotype-guided prescribing is a clinician decision; genotyping access in India is limited.
Test yourself
0/4 answered4 quick questions on Colorectal cancer. Tap an answer to check it.
Across the cancer gene set (BRCA1, BRCA2, MLH1, MSH2, TP53), 108 -'' are actually seen in South Asians () - many European-absent and still clinically 'uncertain'. For cancer, that's a pool of computationally-damaging, India-relevant, clinically-unresolved variants no one has systematically characterised.
A study that would help: Take the South-Asian-observed, European-absent, ClinVar-uncertain in BRCA1, BRCA2, MLH1, MSH2, TP53 and them for cancer: functional or family segregation to move them from 'uncertain' to a real call. Each is a usable diagnostic result.