Patients With Chronic Conditions In Addition To Colon Cancer Still Benefit From Chemotherapy

Main Category: Colorectal Cancer
Also Included In: Cancer / Oncology;  GastroIntestinal / Gastroenterology
Article Date: 29 Sep 2007 - 1:00 PDT

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Patients with chronic conditions such as diabetes and heart failure benefit just as much from adjuvant chemotherapy after surgery for colon cancer than patients without these conditions - although they are less likely to receive this extra treatment, according to an analysis of drug treatment and outcomes in patients with colon cancer, published in Cancer this month.

Most patients who are diagnosed with colon cancer have at least three different chronic conditions in addition to their cancer diagnosis because they are generally at an age when chronic conditions are more prevalent. These diagnoses are important because patients with comorbidities are less likely to survive for a long time after cancer than those without, and evidence also suggests that physicians are less likely to recommend chemotherapy for such patients, believing it might adversely affect outcomes. However, while this assumption is often made in clinical decision-making, accurate information about how specific conditions affect choices of care or outcomes is scarce.

The only available evidence is from studies that look at comorbid conditions as a single group, rather than teasing out how specific disorders affect outcomes. This information dearth leaves physicians unable to assess the real risks and benefits of adjuvant treatment in individual patients. Evidence from clinical trials suggests that adjuvant chemotherapy is associated with a 34% reduction in mortality and this benefit does not diminish with increasing age. However, increasing age---which equates to increasing prevalence of chronic conditions---is associated inversely with the receipt of adjuvant therapy.

To investigate how patients with colon cancer are affected by non-cancer illness, Cary Gross and colleagues from Yale University School of Medicine did a population-based study of older patients with stage III colon cancer. "Specifically, we determined the degree to which specific conditions affected the probability of receiving adjuvant chemotherapy from 1995 to 1999 as well as the risks and benefits of therapy," the authors explain.

Using the US SEER (Surveillance, Epidemiology, and End Results) database, which is a tumour registry linked into records of patients who receive government-financed treatment in the USA , the researchers identified all patients older than 67 years who were diagnosed with primary adenocarcinoma of the colon between 1993 and 1999. After excluding patients who did not receive adjuvant chemotherapy because of a very poor prognosis, the team was left with a sample size of 5330 patients. They identified the presence of comorbid conditions by tracing claims through Medicare, the US insurance programme for older people, for any comorbid conditions made from 2 years before a cancer diagnosis up to 30 days afterwards.

Of the final study sample, 60.3% of patients had received adjuvant therapy, and, as expected, the probability of a patient being offered this treatment decreased with increasing age and the total number of comorbid conditions. The total number of chronic conditions was related strongly to the receipt of chemotherapy. Overall, 69.1% of patients with no conditions received treatment compared with just 38.6% of patients with greater than three conditions received treatment.

When these figures were broken down by the three most common comorbid disorders---heart failure, which affected 16% of the group, chronic obstructive pulmonary disease (18%), and diabetes (17.8%)---the researchers found that heart failure was most significantly related to receipt of chemotherapy: 36.2% of patients with this condition got the extra drugs compared with 64.9% of those without. The effects were more modest for the other two chronic conditions: 55.2% versus 61.5% for patients with and without chronic obstructive pulmonary disease, respectively and 58.3% versus 60.7% for patients with and without diabetes, respectively. There was no consistent relation between chronic conditions and completion of chemotherapy.

Adjuvant therapy was associated with a significant reduction in mortality in all groups, but patients who received chemotherapy and did not have heart failure had the highest survival probability. Patients who did not receive chemotherapy and did have heart failure had the lowest probability of survival. However, while chemotherapy increased the risk of hospitalisation for gastrointestinal, infectious or haematological complications for patients without heart failure, it did not do the same for patients with heart failure, suggesting that chemotherapy may increase the risk of chemotherapy-related toxicity in heart failure patients to a lesser extent that it does in patients without this disorder.

The researchers concluded that although comorbidity was associated with an increased risk of death, it did not diminish the relative survival benefit associated with treatment. What is more, the observed differences between use of chemotherapy and associated outcomes with the different conditions "emphasizes the importance of moving beyond a comorbidity index when investigating the care and outcomes of older cancer patients," say the authors. "Simply counting the number of conditions with which each patient has been diagnosed may overlook important distinctions between conditions."

The impact of chronic illnesses on the use and effectiveness of adjuvant chemotherapy for colon cancer.
Gross CP, McAvay GJ, Guo Z, Tinetti ME.
Cancer 2007; 109: 2410-19.

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