Management of Colorectal Cancer A Clinical Oncologist’s Perspective

Colorectal cancer is the most common cancer among men in Peninsular Malaysia. The incidence of colorectal cancer in Peninsular Malaysia increased with age with the overall ASR (age-standardized-rates) standing at 18.4 per 100,000 population. (Males: 21.6 per 100,000 and Females: 15.4 per 100,000 population). The incidence of colorectal cancer is highest among Chinese (21.4 per 100,000), while Indians recorded 11.3 per 100,000 and Malays recorded the lowest incidence of colorectal cancer with 9.5 per 100,000 population. According to the first Annual Report of the National Cancer Registry-colorectal cancer 2007-2008, Kuala Lumpur 2010, the incidence was high between the age group of 50-70 years.

The terminology “Colorectal” is given because there is difference in managing colon cancers and rectal cancers. Colon cancers are tumours arising from the caecum, ascending, transverse colon, descending colon and sigmoid colon. Rectal cancers are tumours arising from the rectum (the bottom part of the colon). Anal cancers on the other hand, are totally different from colorectal cancers and are not discussed here.

The diagnosis is usually made after a colonoscopic biopsy. Once the diagnosis is made, investigations such as CT chest abdomen and pelvis, blood tests including liver and renal function tumour markers (CEA) are conducted to stage the disease. A PET CT can be useful in certain cases for staging.

There are four stages in Colorectal Cancer:

Stage 1– Tumour is confined to the mucosa

Stage 2– Tumour is infiltrating all the layers of the colon or rectum but still confined

Stage 3– Tumour has spread to the regional lymph nodes

Stage 4– Tumour has spread to other organs such as liver lung, bones, brain

Though the above-mentioned investigations are helpful in staging the disease pre-operatively to an extent, the staging is correctly done only after surgery. Therefore, the first and best line of treatment in operable cases will be surgery which is indicated in Stages 1, 2, 3 and sometimes in Stages 4. The mainstay of treatment for colorectal cancer is surgery whether curative or palliative.

However, depending on the stage of the disease, additional treatments (radiation therapy/ hemotherapy) may also be prescribed. Surgery can be excision of the tumour with end to end anastomosis in case of colon cancers whereas in low rectal tumours it can be Anterior Perineal Resection (APR) with colostomy.

What we are going to explain is the treatment after surgery in most of the cases because gone are the days where a single modality (surgery) was used to treat cancers. Now it has been found that combined modality of treatment is the main choice for cancers in order to boost survival rates. Combined modality of treatment involves the technique of combining chemotherapy, radiotherapy, targeted therapy with surgery.

Radiotherapy in Colorectal Cancer:

In colorectal cancer, radiotherapy is not used as a modality of treatment after surgery except for rectal cancer and sometimes malignant tumours of the sigmoid colon. Generally, post-operative radiotherapy is administered for stage 3 (sometimes stage 4) rectal cancers- 25 fractions in 5 weeks, 5 days a week using high energy X-rays from linear accelerators. Radiation is generally administered as outpatient treatment and it will typically last for 10 minutes every fraction. You can expect side effects such as nausea, vomiting, diarrhea, and skin changes which are only transient and are reversible on completing the radiation schedule.

Recent developments in radiotherapy techniques such as 3D conformal radiotherapy, Intensity Modulated Radiotherapy (IMRT) and the Image Guided Radiotherapy (IGRT) have minimized these side effects and has enabled minimal exposure to radiation for organs surrounding affected areas.

In inoperable rectal cancers, preoperative radiotherapy is given to debulk and downstage the disease and make it amenable for surgery along with concurrent chemotherapy (Cisplatin or Carboplatin or Oxaliplatin) given once a week or for 5 weeks.

Chemotherapy in Colorectal Cancer:

Chemotherapy is indicated in all Stage 3 and Stage 4 colorectal cancers and even in Stage 2 high risk group of patients. Chemotherapy involves the usage of anti-cancer drugs either in the form of injections or tablets. These drugs can be either taken orally or through intravenous administration. This therapy is usually prescribed after surgery and is known as

“adjuvant chemotherapy”.

When chemotherapy is prescribed before surgery, it is to reduce the size of the tumour for easy surgical removal and is known as “neo-adjuvant chemotherapy”. When the cancer has advanced and metastasized, palliative chemotherapy is prescribed to slow the cancer’s progress, alleviate symptoms and, possibly prolong the lifespan.

Potential side-effects include mild lethargy, nausea, vomiting, numbness of fingers and toes, diarrhea, mouth ulcers, soreness of palms and soles of feet, possible increased risk of infection and of course, the most dreaded-hair loss.

Except for hair loss, all the aforementioned side effects can be adequately managed. Most patients are able to tolerate chemotherapy well and enjoy a good quality of life during treatment and thereafter.

Targeted therapy in Colorectal Cancer:

Combining targeted therapy with or after chemotherapy has shown to improve survival for patients with advanced colorectal cancer. A three-drug regimen combining two chemotherapy agents with a targeted therapy agent is commonly used especially in cases of metatastic colorectal cancer.

In summary of the management colorectal cancer, combined modalities of treatment is the current protocol used to achieve better survival rates. Combining chemotherapy/ targeted therapy, radiotherapy with surgery is the standard of care recommended these days.

Patients suffering from colorectal cancer need to be under close scrutiny of the oncologist even after completion of the treatment schedule in order to catch them early if and when there is evidence of local or metastatic recurrence.