36 HOW TO TREAT: COLORECTAL CANCER: TREATMENT
36 HOW TO TREAT: COLORECTAL CANCER: TREATMENT
11 APRIL 2025 ausdoc. com. au is used to accurately stage rectal cancer. This evaluates whether the cancer has spread into the mesorectum( the fatty envelope surrounding the rectum), if lymph nodes are involved or if the surgical margins are threatened. If any of these are likely, then neoadjuvant combined chemotherapy and radiation therapy is indicated.
In this setting, chemotherapy is administered at a relatively low dose to‘ radiosensitise’ the tissues of the pelvis, increasing the efficacy of local irradiation. CT and blood tests are performed as with colonic cancer. If MRI is contraindicated, then endoanal ultrasound is a useful alternative, but there is limited local expertise in Australia.
Neoadjuvant therapy is usually given as‘ long-course’ chemoradiation with generally six weeks of chemoradiation, then a hiatus period of about 6-12 weeks before definitive resection.‘ Short-course’ radiation therapy alone, administered over five days is an option, although this is less commonly performed in Australia.
An emerging area in some instances of locally advanced disease is‘ total neoadjuvant therapy’, where all the chemotherapy is administered up-front, over a three-month period. This offers improved tolerance to chemotherapy compared with traditional adjuvant therapy. However, there is a risk of overtreatment where patients with over-staged disease on initial staging receive chemotherapy they may not have needed based on final pathological staging.
A small percentage of patients will develop a complete clinical response to neoadjuvant chemoradiation, where it appears the cancer has been completely treated. Management of these patients remains contentious. Observational studies have demonstrated that the prognosis for these patients is far better than for patients with a lesser response to chemoradiation. 2 Selected clinical trials are occurring where no definitive resection is performed and patients are treated with a‘ wait and watch’ approach, with careful surveillance. 3 This is not currently the standard of care and should only be considered in the setting of a clinical trial or registry. Nonetheless, it remains an option, but requires intensive surveillance with regular colonoscopy and imaging, with which patients must be compliant.
General medical workup
The Bowel Cancer Outcomes Registry reports inpatient mortality from elective colorectal resection at 1 %. 4 Part of this is as a result of the increased emphasis on the preoperative workup and improved perioperative management. All patients usually require routine investigations, including FBC, EUC, LFTs, CEA and resting ECG. Patients with significant comorbidities, especially cardiovascular and respiratory, require further evaluation, such as functional cardiac testing and lung function tests.
The value of involving a general or perioperative physician or team in formal evaluation and functional testing of patients before admission cannot be overestimated. Where significant reversible risk factors, such as bronchospasm, are found, surgery may be delayed to allow for optimisation of these risk factors.
Box 1. Distant metastatic disease at initial presentation
• Distant metastatic disease that may be surgically resectable:— Patients may present with limited disease in the lung or liver that is potentially completely resectable, leaving sufficient lung or liver to allow acceptable organ function and quality of life postoperatively.— With careful selection, there is good evidence that some of these patients can potentially be cured with removal of the primary and metastatic disease. 5— In these patients, PET scanning is a necessary adjunct to determine the extent of the metastatic disease.— These patients require multidisciplinary team care in a specialist colorectal centre, and if there is sufficient residual organ( liver or lung) to allow for resection, then this should proceed.
— The decision to administer chemotherapy preoperatively and the order of resection( primary first versus metastatic disease versus synchronous resection) is nuanced, with different views and contradictory evidence, and needs to be tailored to the individual patient.
— Patients with borderline sufficient residual organ tissue may be offered preoperative chemotherapy with a view to downstaging the disease to allow sufficient residual organ tissue for resection.— Almost all these patients will require postoperative chemotherapy.— With total gross resection, depending upon other prognostic factors, 20-25 % of these patients achieve longterm remission. 5
• Metastatic disease where gross total resection cannot be undertaken:— Most patients with distant metastatic disease are not able to have all disease resected.— The priority in these patients is extension of their life by treating their metastatic disease with systemic chemotherapy as the mainstay.— Where the primary tumour is likely to, or already is, causing consequences such as obstruction, this will need resection.— It is still unclear whether resection of the minimally symptomatic primary tumour improves prognosis.— The main risk is complications from the surgery, resulting in a delay in starting systemic chemotherapy treatment and allowing growth of distant metastases.— These patients benefit greatly from multidisciplinary care.
DISTANT METASTATIC DISEASE AT INITIAL PRESENTATION
DESPITE growing awareness of colorectal cancer and the impact of the National Bowel Cancer Screening Program, about 20 % of patients will present with advanced disease. Although data are still incomplete, this has anecdotally risen during the COVID-19 pandemic. These patients will require input from multiple clinicians, including their GP. Broadly speaking, these patients fall into two groups( see box 1).
SURGERY
CANCER resection( see figures 2 and 3) follows the principle of removal of the primary colorectal cancer with sufficient margin, together with an en bloc resection of the associated lymph node basin that follows the major vascular supply to that segment. Therefore, segmental resection along vascular supply lines is the primary operation for curative intent. Where patients have a genetic predisposition to future malignancy, extended resection, total colectomy or proctocolectomy may be considered to reduce future risk; however, this does not alter the prognosis of the index cancer. Box 2 contains a summary of the segmental operations( see figure 4) indicated based on the position of the primary lesion.
Preoperative preparation and perioperative care
There is a move towards preoperative bowel preparation for patients before resection. New data show that bowel preparation plus oral antibiotics is likely to significantly reduce anastomotic leak and other infective complications. 6 The American Society of Colon and Rectal Surgeons includes this in their guidelines for colorectal resections, and many surgeons in Australia are following suit. 6 Bowel preparation was previously often omitted because of concerns regarding possible associated dehydration and fluid shifts.
Less widespread is the concept of‘ prehabilitation’ where patients participate in programs to improve their fitness for surgery. This may include exercise physiology, specialised diets and supplements and psychological interventions. Research is still ongoing regarding the specific interventions that improve clinical outcomes.
Most colorectal surgeons now practise some form of enhanced recovery after surgery. Although not standardised, this includes minimal
Figure 1. CT showing liver metastases.
Box 2. Segmental operations
• Right hemicolectomy( caecum to proximal transverse colon).
• Extended right hemicolectomy( proximal transverse to descending colon).
• Left hemicolectomy( distal transverse, splenic flexure and descending colon).
• High anterior resection( sigmoid and upper rectum).
• Low anterior resection( upper to mid rectum).
• Ultra-low anterior resection( low rectum).
• Abdomino-perineal resection( low rectum to anus).
intraoperative and postoperative IV fluids, opioid-sparing techniques such as regional nerve blocks, early feeding and mobilisation, and early catheter removal.
Laparoscopic surgery
Laparoscopic surgery( see figure 5) is an accepted standard of care for the treatment of colonic cancers. Several randomised trials have demonstrated the safety of laparoscopic surgery, with equivalent oncological outcomes compared with open surgery and significant improvements in postoperative recovery. 7 However, technical restrictions to laparoscopy surgery remain, including previous surgery causing adhesions, bowel obstruction that reduces intra-abdominal space, and obesity.
Laparoscopic surgery for rectal cancer is more contentious. While the safety of laparoscopic colonic mobilisation of the splenic flexure to allow for a secure anastomosis is not in doubt, equivalence between laparoscopic and open pelvic dissection for rectal cancer has not been proven.
Two large, randomised controlled trials, one in Australasia and one in the US, failed to prove non-inferiority of laparoscopic rectal surgery. 8, 9 While there are a number PAGE 38