In 1991, the NIH published the first evidence-based guidelines for the use of adjuvant therapy in patients with colon cancer.9
Although systematic review does not support the routine use of adjuvant chemotherapy in patients with stage II disease, it should be considered in patients with high-risk features,12–14
including malignant bowel obstruction or perforation at the time of presentation, T4 disease, perineural/lymphovascular invasion or aneuploidy.
The results of our study show that patients with stage I and III colon cancer were managed according to current recommendations in both provinces. Clearly, guidelines supported by adequate level-I evidence have been acknowledged by the appropriate target audience, including surgeons and medical oncologists, resulting in successful implementation.
Although patients with high-risk stage II disease were significantly more likely to receive chemotherapy than patients with low-risk stage II disease, our data suggest that other information was used in the decision to administer adjuvant chemotherapy in patients with stage II disease. This may reflect a paucity of level-I evidence. It appears that patient age influenced the decision to offer adjuvant chemotherapy in that there was a strong trend in favour of chemotherapy in patients aged 50 years or younger who had stage II disease, independent of high-risk status. This requires further study as younger age tends to be correlated with high-frequency microsatellite instability tumours.17,18
There is evidence that patients with this type of tumour may not derive the same benefit from 5-FU– based chemotherapy.19
Thus the use of age alone as an adverse prognostic factor in the decision to administer 5-FU– based adjuvant chemotherapy may not be sound.
Only 71% of patients with high-risk stage II disease in Newfoundland and Labrador and 68% of these patients in Ontario were referred to medical oncology. It has previously been shown that patients with stage II colon cancer were less likely to be referred for consideration of adjuvant chemotherapy (76% for stage II colon cancer, 92% for stage III colon cancer).20
We cannot comment on whether this reflects a lack of knowledge on the part of surgeons as to the potential benefit for high-risk patients, whether surgeons do not feel that the evidence is strong enough to warrant referral for patients with stage II disease, or whether other factors such as resource allocation are at play. It has been shown that concordance with guidelines develops along a continuum from awareness to acceptance to ability to enforce to successful implementation.21–23
The target audience may be unaware of the existence of the information. Surgeons may be aware of the original guideline that recommended no chemotherapy for patients with stage I and II colon cancer after curative resection. Further refinements, based on less compelling data, may not have been as widely disseminated. Furthermore, even once the recommendation is known, surgeons may not accept the validity of the guideline. Even if surgeons and medical oncologists support the guidelines, local factors such as resource allocation and access to treatment may influence the ability to enforce guidelines. Medical oncology resources may be such that treatment is only readily available where there is good level-I evidence.
This complex process of guideline implementation demands a multidisciplinary focus.24
It has been shown that concordance with guidelines is enhanced when members of the target audience are actively recruited to participate in guideline development and dissemination.21–24
To this end, it would be important to ensure that surgeons become involved in the creation of guidelines. This would apply not only to surgeons in academic centres, but also to community surgeons and other health care workers who are seen to be local opinion leaders.24
These individuals could determine what guidelines are necessary, the best means to make surgeons within their communities aware of and accepting of the guidelines and, most importantly, the resource limitations that might impede the implementation of important guidelines. It has been well documented that CPGs without coordinated dissemination strategies rarely result in consistent changes in physician performance and/or behaviour.25–27
It will become increasingly important to establish successful multifaceted approaches that provide sound rationale for the delivery of adjuvant therapy in the treatment of colorectal and other cancers as the use of molecular markers and microarray analyses28
come to the forefront. The rise of increasingly expensive therapies such as cetuximab29
in the adjuvant setting will require sophisticated targeting strategies to ensure their efficacious, efficient and cost-effective use.
In our study, selection bias may have been introduced as a result of the differing sampling techniques in the 2 provinces and the need to obtain consent. We used medical record audit, rather than patient recall or the use of administrative data, as an objective measure of compliance with CPGs. This method has been shown to result in higher levels of concordance in a recently reported study that evaluated the receipt of recommended adjuvant therapy among patients with stage II and III colon and rectal cancer in the Veterans Affairs setting; 87% of patients with stage II and 71% of patients with stage III colon cancer received the recommended therapy.20
However, we have no reason to suspect that the main outcome measure (receipt of recommended adjuvant chemotherapy) was correlated with participation in the study. Owing to the retrospective nature of our study, we are unable to comment on whether the decision to refer patients to medical oncology or offer adjuvant chemotherapy was influenced by socioeconomic status or proximity to a treatment centre. High concordance with guidelines for stage III disease in both provinces would suggest that guidelines that are developed with strong input from the target audience and on the basis of good level-I evidence will lead to more equitable and standardized treatment protocols, at least in Canada.
In conclusion, it appears that among doctors treating colong cancer there is not universal agreement with and belief in an improved outcome following implementation of the ASCO and CCO recommendations for the adjuvant treatment of stage II colon cancer. Concordance could be improved by multi-faceted approaches that incorporate surgeons, who are members of the target audience and the first point of patient contact, in all aspects of the development and implementation of important CPGs.