Lung cancer contributes to a poor prognosis in patients with idiopathic pulmonary fibrosis (IPF), a new study indicates.
The finding suggests that healthcare professionals should monitor the development and progression of cancer in patients with IPF, given its negative impact on prognosis.
The study, “Prognostic impact of malignant diseases in idiopathic pulmonary fibrosis,” was published in the journal Nature Scientific Reports.
IPF patients often have comorbidities — other medical conditions — that can negatively influence their quality of life and prognosis. Lung cancer is one of the most common comorbidities in IPF patients and has been shown to reduce the survival rate among these patients.
However, limited data is available on extrapulmonary cancer (that is, other cancers besides lung cancer) in patients with IPF.
Researchers at the Seoul National University Hospital, in South Korea, decided to investigate the impact of extrapulmonary cancer in IPF prognosis.
Every five years, they analyzed the medical records of 579 adult patients diagnosed with IPF from January 2001 to December 2015. Patients were divided into three groups based on their diagnosis: IPF without cancer (440 patients, 76%); IPF with lung cancer (69 patients, 11.9%); and IPF with extrapulmonary cancer (70 patients, 12.1%).
Of the 579 patients with IPF (median age at diagnosis of 68 years), 72.4% were men, 63.9% were smokers and the group had a mean body mass index (BMI) of 23.9 — considered a normal weight. Some patients in the cohort had a history of hypertension (33.9%), diabetes mellitus (26.6%), or tuberculosis (16.6%).
The five most common types of cancer in the cohort analyzed were lung (11.9%), gastric (2.4%), colorectal (1.9%), hepatocellular carcinoma (1.9%), and prostate (1.0%) cancers. Cancer comorbidities in IPF patients were more common in men and smokers.
Regarding the type of lung cancer, the most common was squamous carcinoma (24 patients, 34.8%), followed by adenocarcinoma (23 patients, 33.8%), unclassified non-small-cell lung cancer (12 patients, 17.4%), small-cell lung cancer (seven patients, 10.1%), and large-cell lung cancer (three patients, 4.3%).
Researchers started by evaluating the prognostic impact of cancer in IPF patients.
During the study, a total of 382 patients died (66%, median survival time of 4.89 years). The mortality rate was 63.4% in patients without cancer (median survival time of 5.45 years), 82.6% in patients with lung cancer (median survival time 2.93 years), and 65.7% in patients with extrapulmonary cancer (median survival time 4.84 years).
Among IPF patients without cancer, 92.0% survived at one year, 51.7% at five years and 27.1% at 10 years. In the IPF group with lung cancer, the survival rates were 81.2%, 35.7%, and 12.2%, respectively. In the IPF group with extrapulmonary cancer survival rates were 92.9%, 49.0%, and 19.6%, respectively.
These data showed significant differences in survival. Overall, IPF patients with lung cancer have significantly worse survival than patients without cancer or with extrapulmonary cancer.
When dividing patients by cancer stage, with a higher stage corresponding to more advanced disease, the breakdown was: stage I (30.4% of the cohort); stage II (14.5%); stage III (27.5%); and stage IV (27.5%). Researchers found that IPF patients with early-stage lung cancer and those without cancer or with extrapulmonary cancer had comparable survival rates, whereas patients with advanced stage lung cancer had a worse survival rate.
Researchers also analyzed the results of pulmonary function tests including diffusing capacity of the lung for carbon monoxide (DLCO) — a measure of the lungs’ ability to transfer oxygen to the blood — as well as forced vital capacity (FVC).
The data showed that the annual rates of decline in FVC and DLCO did not differ significantly among the groups.
By analyzing variables separately (univariate analysis) or multiple variables at the same time (multivariate analysis), researchers found that lung cancer comorbidities, male sex, older age at IPF diagnosis, lower BMI and percent predicted FVC, and DLCO lower than 80% were associated with poor survival in patients with IPF.
Even after multivariable adjustment for other known predictors of poor survival (namely age, sex, BMI, predicted FVC and DLCO), IPF patients with advanced lung cancer had significantly poorer survival than other groups.
The overall rates of emergency room visits, all-cause hospitalization, and intensive care unit admission were significantly higher among IPF patients with cancer than in those without cancer. The rate of hospitalization for cancer-related complications was significantly higher in IPF patients with lung cancer than in those with extrapulmonary cancer.
These findings suggest that the higher incidence of cancer-related complications and the accompanying rate of respiratory hospitalization may account for survival differences among the groups.
Researchers noted some limitations to their study’s findings, namely the fact that the data was obtained from a single hospital, the sample size was relatively small, and the cause of death could not be determined in some patients.
Nonetheless, the team concluded that “lung cancer comorbidity was an independent prognostic factor for poor survival in patients with IPF, regardless of age, sex, BMI, percent predicted FVC, and percent predicted DLCO. However, extrapulmonary cancer comorbidity was not associated with poor survival in patients with IPF,” they wrote.
“From these results, physicians should pay attention to the development and progression of cancer and its prognostic impact in patients with IPF. Further population-based studies are needed to validate these results,” the researchers advised.
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