What stage II means
The tumour has grown through the muscle layer of the colon (T3) or even to the surface or into neighbouring organs (T4), but no lymph node is involved (N0) and there are no metastases. Stage II has three groups: IIA (T3), IIB (T4a, reaching the outer surface of the bowel) and IIC (T4b, invading a nearby organ).
The good news: surgery alone cures most people. Five-year survival in stage II averages around 80-90 %, higher in IIA and lower in IIC. So the question is not "chemotherapy yes or no" in general, but "how much risk do I have, and how much would chemotherapy take off?".
When chemotherapy is considered
Guidelines (ESMO, NCCN, SEOM) only recommend considering adjuvant chemotherapy in stage II when there are high-risk features:
- T4 tumour (especially T4b): the most important factor.
- Fewer than 12 lymph nodes examined in the surgical specimen: it cannot be confirmed that the disease was truly N0.
- Bowel perforation or obstruction at diagnosis (emergency surgery).
- Lymphovascular or perineural invasion (the tumour had entered vessels or nerves).
- High grade (poorly differentiated) in MSS tumours.
- High tumour budding (clusters of cells at the invasive front) and involved or very close margins.
Without any of these factors, chemotherapy reduces the risk of relapse by only a few percentage points (around 3-5 %) in exchange for 3-6 months of side effects: most guidelines do not recommend it. With one or more factors, the benefit may be larger and it is discussed case by case.
The fact that changes the answer: MSI / MMR
Around 20 % of stage II tumours are dMMR / MSI-H (deficient DNA repair). In these:
- The prognosis is better than in MSS tumours: they relapse less.
- Fluoropyrimidine-only chemotherapy (capecitabine or 5-FU without oxaliplatin) provides no benefit and may even be counterproductive. That is why in stage II dMMR the usual recommendation is surveillance only, unless there is a T4 tumour or other very unfavourable features, in which case oxaliplatin is discussed.
- It means Lynch syndrome must be ruled out (genetic counselling clinic).
If your report does not say whether the tumour is MMR/MSI tested, ask for it: it should be done in every case.
What is recommended if treatment is chosen
With risk factors and an MSS tumour, the options are capecitabine alone for 6 months (tablets) or, in the highest-risk cases (T4, several factors), CAPOX or FOLFOX (with oxaliplatin) for 3-6 months. You can read what they involve in our guides on FOLFOX and oxaliplatin neuropathy. In older people or those with other illnesses, the benefit of oxaliplatin is smaller and it is usually avoided.
Circulating tumour DNA (ctDNA): the new tool
After surgery, tumour DNA can be looked for in the blood. The Australian DYNAMIC study showed that, in stage II, guiding the decision by ctDNA halves the number of people who receive chemotherapy without worsening outcomes: those with negative ctDNA after surgery have a very low risk of relapse and can avoid it; those with positive ctDNA are at high risk and are treated. In Spain this is still done mainly within trials or at specific centres, but it is worth asking about.
A shared decision
In stage II there is no single correct answer: there is an individual risk, a small or moderate benefit, and side effects that you are the one who will live through. It is legitimate to ask for specific numbers ("without chemotherapy my risk of relapse is X, with it Y") and to decide with that information. It is also legitimate to say no if the benefit is minimal.
What to ask at your appointment
- What is my sub-stage (IIA, IIB, IIC) and how many nodes were examined?
- Do I have any high-risk features? Which ones exactly?
- Is my tumour dMMR/MSI-H or MSS? Have I been referred to genetic counselling?
- With and without chemotherapy, what is my estimated risk of relapse at 5 years?
- Can I have a ctDNA test, here or in a trial?
