Why the rectum is different
The rectum is the last 12-15 cm of the bowel, tucked into the pelvis and surrounded by the bladder, the reproductive organs, nerves and the sphincter. Operating there is harder, the risk of the tumour coming back in the pelvis is higher, and the after-effects (bowel, urinary and sexual function, a stoma) weigh more heavily. That is why, in locally advanced rectal cancer (growing through the wall or involving lymph nodes, without metastases), treatment usually starts before surgery rather than after it, as in colon cancer. A pelvic MRI is the key test for that decision: it measures how far the tumour has grown, whether there are suspicious nodes, and the distance to the margin (the "mesorectal fascia").
Early rectal tumours (T1-T2 without nodes) are operated on directly, sometimes endoscopically or through the anus.
The building blocks of treatment
- Short-course radiotherapy: 5 sessions in one week. Long-course radiotherapy: 25-28 sessions over 5-6 weeks with daily capecitabine to boost it (chemoradiotherapy). Both are valid; the choice depends on the tumour and the centre.
- Consolidation or induction chemotherapy: FOLFOX or CAPOX for 3-4 months, also before surgery.
- Surgery (total mesorectal excision, TME): the rectum is removed together with the fatty tissue around it. If the tumour is very low, an abdominoperineal resection with a permanent stoma may be needed; in other cases the bowel is reconnected, often with a temporary protective stoma for a few months.
- Chemotherapy afterwards: now less common if it was all given beforehand.
Total neoadjuvant therapy (TNT)
This means giving all the radiotherapy and chemotherapy before surgery, instead of splitting it before and after. The RAPIDO trial (short-course radiotherapy followed by chemotherapy) and PRODIGE 23 (FOLFIRINOX chemotherapy followed by chemoradiotherapy) showed fewer distant metastases and more tumours disappearing completely before surgery. It is now the standard for high-risk tumours. It takes about 5-6 months before reaching the operating theatre; that is long, but it has a purpose.
"Watch and wait": when the tumour disappears
In a proportion of patients (around 25-30 % with TNT, more in small tumours) the tumour can no longer be seen or felt after treatment: this is a clinical complete response, confirmed by digital examination, endoscopy and MRI. In that case, in experienced centres, it is possible to propose not operating and monitoring instead (watch and wait), preserving the rectum and avoiding a stoma. The OPRA trial showed that with this strategy half of patients keep their rectum at 3 years without losing survival.
What you should know before choosing it:
- The tumour regrows locally in 25-30 % of cases, almost always within the first 2 years. In the great majority it is caught in time and operated on with the same results as if surgery had been done at the start.
- It requires very close follow-up: digital examination and endoscopy every 3-4 months and MRI every 6 months for the first 2-3 years, then somewhat less often for at least 5 years. If you cannot commit to that schedule, it is not the best option.
- Not every hospital offers it, and not all have the same experience. That is a legitimate reason to ask for a second opinion.
If the tumour is dMMR / MSI-H
About 2-3 % of rectal cancers are dMMR. In these, immunotherapy alone (dostarlimab for 6 months) achieved, in a small but very consistent study, that practically all tumours disappeared, with no radiotherapy or surgery. It is still done within specific protocols or trials, but it is essential that your MMR status has been tested before starting any treatment. More on MSI-H/dMMR.
Life afterwards: bowel and sexual function
After rectal surgery, low anterior resection syndrome is common: urgency, fragmented bowel movements, difficulty telling gas from stool. It improves with time (up to 1-2 years) and with pelvic floor physiotherapy, diet, scheduled loperamide or transanal irrigation. Radiotherapy and surgery can affect sexual function (erections, vaginal dryness, pain) and fertility: if you want to have children, ask to discuss egg or sperm preservation before starting. These are subjects that sometimes nobody raises in clinic; raise them yourself.
What to ask at your appointment
- What stage am I on the MRI, and how far is the tumour from the sphincter and from the margin?
- Are you proposing total neoadjuvant therapy? With short- or long-course radiotherapy?
- If the tumour disappears completely, do you offer "watch and wait" here? How many cases have you managed?
- Is my tumour dMMR? Was it tested before deciding?
- Will I need a stoma, temporary or permanent? Can we talk about fertility and sexual function before starting?
