Colorectal cancer is the most commonly diagnosed cancer in Singapore. There has been increased awareness about colorectal cancer and regular screenings, thereby allowing colorectal cancer to be detected early when it is most treatable.
Treatment has also improved over the years, making it even more effective.
Here, we go into further detail on Stages 0, 1 and 2 of early-stage colorectal cancer.
Stage 0 is known as carcinoma in situ, which means that the cancerous cells are only limited to within the inner lining (mucosa) of the colon or rectum.
Such cases may either be treated by a simple polypectomy (removal of a polyp found on the inner lining of the colon or rectum), or a local excision.
Follow-up will be determined by how large the lesion removed and an early repeat scope may be required to ensure no recurrence.
In stage 1 of colorectal cancer, it means that the cancer has already grown through the inner lining of the colon or rectum, or even into the muscle walls, but not beyond that.
The main form of treatment is surgery to remove the cancer (possibly along with some healthy tissue).
Currently the standard of care is still recommended to remove the segment of the large intestine/rectum where the tumour is located. However less invasive options can be considered.
It is important to understand that while local excision may be possible in certain cases, the lymph nodes are not removed. In T1 cancers, there may be the presence of cancerous lymph nodes in 5-8% of these cancers. The cancer is therefore actually a more advanced stage III and not removing the lymph nodes (usually done when intestine surgery is performed), will lead to a higher recurrence risk. The patient will need to understand that this risk if present if only local excision or removal of the cancer is performed.
Close surveillance with frequent PET or CT scans, and colonoscopies will be required if local excision or removal of tumour is performed.
Stage 2 of colorectal cancer occurs when the cancer has already spread into the outer wall of the colon or rectum, or even into surrounding tissues or organs. However, it has not spread to the lymph nodes or distant parts of the body yet.
The main form of treatment is also surgery to remove the cancerous tumour:
Local excision will not be suitable for stage 2 cancers. Chemotherapy is usually not required in early stage 2 colorectal cancers.
Generally speaking, when the cancer is still localised (i.e. it has not spread outside of the colon or rectum), the relative 5-year survival rate stands at around 90%.
When the cancer has progressed to a regional stage (i.e. it has spread outside the colon or rectum to nearby structures or lymph nodes), the 5-year relative survival rate falls to around 70%.