Mortality and Resource Use: CKD versus Nonmetastatic Cancer

Chronic kidney disease (CKD) is associated with poor outcomes and high burden of healthcare resources. It has been challenging to communicate the importance of preventing and managing CKD to decision-makers, in part because the clinical outcomes from advanced kidney disease are not well understood, according to Marcello Tonelli, MD, SM, MSC, and colleagues. Conversely, decision-makers and the general public are aware of the risks of mortality and disability associated with cancer, particularly the most common solid malignant tumors.

Dr. Tonelli et al. conducted a cohort study designed to compare clinical consequences of incident severe CKD and the first diagnosis with a solid malignant tumor, focusing on the 10 leading causes of cancer in men and women in Canada. Results were reported online in JAMA Network Open [doi:10.1001/jamanetworkopen.2021.44713].

The study cohort included individuals ≥19 years of age with severe CKD or certain types of cancer between 2004 and 2015 in Alberta, Canada. Data analysis was performed in November 2021. Participants were categorized as having severe CKD (defined as estimated glomerular filtration rate <30 mL/min/1.73 m² or nephrotic albuminuria without dialysis or kidney transplant) or nonmetastatic or metastatic cancer (defined by a diagnosis of lung, breast, colorectal, prostate, bladder, thyroid, kidney or renal pelvis, uterus, pancreas, or oral cancer).

The outcomes of interest were all-cause mortality, number of hospitalizations, total number of hospital days, and placement into long-term care, calculated after diagnosis.

The total cohort included 200,494 individuals; 52.2% (n=104,559) were women, and median age was 66.8 years. The cohort was divided into three groups: severe CKD (n=51,159), nonmetastatic cancer (n=115,504), and metastatic cancer (n=33,831). Median ages were 76.5 years in the CKD group, 63.7 years in the nonmetastatic cancer group, and 65.8 years in the metastatic group. In the CKD group, 56.5% were women; in the nonmetastatic cancer group, 49.6% were women, and in the metastatic group, 54.2% were women.

In the group with nonmetastatic cancer, the most common cancers were prostate (21%) and breast (20%), followed by colorectal, lung, and bladder cancer. In the group with metastatic cancer, lung cancer was the most common (30%).

Comorbidity burden was high in all disease groups; comorbidities were most common in the CKD group and least common in the nonmetastatic group. Of participants in the CKD group, 4.6% (n=2353) developed kidney failure, requiring dialysis or kidney transplant; only 0.1% of those in the cancer groups developed kidney failure. Of those in the CKD group, 7.9% developed a cancer of interest and of those in the cancer groups, 4.0% developed severe CKD.

For patients in the severe CKD group, the Kaplan-Meier 1-year survival was 83.3% (95% confidence interval [CI], 83.0%-83.6%); for patients in the nonmetastatic cancer group, 91.2% (95% CI, 91.0%-91.4%) and for those in the metastatic cancer group, it was 52.8% (95% CI, 52.2%-53.3%). Kaplan-Meier 5-year survival was 54.6% (95% CI, 54.2%-55.1%) for those with CKD, 76.6% (95% CI, 76.3%-76.8%) for those with nonmetastatic cancer, and 33.9% (95% CI, 33.3%-34.4%) for those with metastatic cancer. For participants who entered the study in later years, Kaplan-Meier estimates for 1- and 5-year survival were longer compared with those who entered in earlier years, suggesting small improvements over time for those with CKD or nonmetastatic cancer (P for trend <.001 for both), but not for metastatic cancer (P for trend=.22).

Compared with nonmetastatic cancer, following adjustment for age, sex, and comorbidities, the relative rate of death during the first year of follow-up  was similar for CKD (adjusted relative rate, 1.00; 95% CI, 0.97-1.03). Between years 1 and 5 of follow-up, the adjusted rate of death was higher for CKD (adjusted relative rate, 1.23; 95% CI, 1.19-1.26) than for nonmetastatic cancer (2.95; 95% CI, 2.85-3.05). The most common cause of death among the CKD group was cardiovascular disease; most patients in the two cancer groups died of cancer.

In unadjusted analyses, in the first year of follow-up, the rate of placement into new long-term care was highest for those with metastatic cancer (0.25 per 1000 person-days; 95% CI, 0.23-0.26 per 1000 person-days) compared with those with CKD (0.14 per 1000 person-days; 95% CI, 0.14-0.15 per 1000 person-days) and those with nonmetastatic cancer (0.06 per 1000 person-days; 95% CI, 0.06-0.06 per 1000 person-days). During years 1 and 5, the unadjusted rate was highest for the CKD group.

Following adjustment for age, sex, and comorbidities, the rates of new placement in long-term care during the first year were 0.88 for patients with CKD and 4.02 for patients with metastatic cancer compared with those with nonmetastatic cancer. Between years 1 and 5, the adjusted rate was higher for patients with CKD compared with those with nonmetastatic cancer (adjusted relative rate, 1.36; 95% CI, 1.29-1.43).

During the first year of follow-up, the unadjusted rates of the number of hospitalizations were highest for metastatic cancer (7.97 per 1000 person-days; 95% CI, 7.89-8.05 per 1000 person-days), compared with CKD (2.73 per 1000 person-days; 95% CI, 2.69-2.77 per 1000 person-days) and nonmetastatic cancer (2.98 per 1000 person-days; 95% CI, 2.97-3.00 per 1000 person-days). During years 1 to 5, the rates of hospitalization were highest for CKD followed by metastatic cancer; the rates were lowest for nonmetastatic cancer.

Following adjustment for age, sex, and comorbidities, the rates of hospitalization during the first year were 0.65 for CKD and 2.65 for metastatic cancer, compared with nonmetastatic cancer. Between years 1 and 5, the adjusted rates were higher for CKD compared with nonmetastatic cancer. Findings for length of stay were generally similar to those for the number of hospitalizations.

Limitations to the study cited by the authors included the use of administrative data rather than a prospective cancer registry to identify individuals with cancer, and requiring only a single outpatient measurement of either eGFR or albuminuria to meet the threshold for severe CKD.

In conclusion, the researchers said, “In this cohort study, unadjusted mortality at 1 and 5 years was higher among patients with incident severe CKD than among patients with common forms of nonmetastatic cancer. In unadjusted analyses, the total number of hospital days and the likelihood of lost capacity for independent living were both higher among patients with CKD than those with nonmetastatic cancer. After adjustment for age and comorbidity, mortality, rates of placement in a long-term care facility, and rates of hospitalization remained higher for patients with CKD than those with nonmetastatic cancer at 1 to 5 years, although the magnitude of the excess was attenuated. These data highlight the importance of CKD as a public health problem.”

Takeaway Points

1. Researchers reported results of a study to examine differences in clinical consequences associated with severe chronic kidney disease (CKD) compared with cancer.
2. In the population-based cohort study in Canada, the unadjusted mortality among patients with CKD at 1 year and 5 years was higher than that among patients with nonmetastatic cancer.
3. The findings highlight the importance of CKD as a public health problem.