Year: 2019
Type: letter
Abstract: Dear Sir, We thank Liu et al. for their interest in our recent study in International Journal of Cancer on statins and pancreatic cancer risk in patients with chronic pancreatitis.1 Liu et al. raises concern about some potential flaws in our study design, to which we would like to reply. Liu et al.suggest that starting follow-up 1 year after chronic pancreatitis is insufficient to account for misdiagnosis of pancreatic cancer as chronic pancreatitis.We agree with Liu et al. that the choice of a 1-year lag period between chronic pancreatitis and pancreatic cancer is arbitrary.There is no consensus on the optimal choice of lag period.Two years may be preferable to 1 year to mitigate the impact of misdiagnosis of pancreatic cancer by chronic pancreatitis, but this comes at the expense of fewer observed outcomes and reduced precision.To investigate if the 2 years suggested by Liu et al. could explain our results, we conducted an additional analysis, restricting to patients who were alive and at risk of pancreatic cancer 2 years after the date of chronic pancreatitis diagnosis (reducing our study population from 8,311 to 7,742).This restriction reinforced our finding of a null association (adjusted HR: 1.03 [95% CI: 0.60-1.76]compared to 0.90 [95% CI: 0.56-1.44] in the original analysis).This was also the case when including diabetes in the multivariable model (adjusted HR: 0.93 [95% CI: 0.54-1.61]compared to 0.74 [95% CI: 0.46-1.19]when using the original 1-year lag period).These estimates suggest that choosing 1 or 2 years as lag periods between chronic pancreatitis and pancreatic cancer could not explain our observed null finding.Liu et al. also suggest that adjusting for a summary score of comorbidity burden, such as the Gagne Comorbidity Index, may be insufficient to account for potential confounding.In our study-setting with relatively few observed outcomes, adjusting for a wide range of comorbidity conditions would be unfeasible.Instead, we chose to adjust for the Gagne Comorbidity Index.We agree that this may be insufficient.Therefore, we also adjusted for diabetes, which we considered to be a strong potential confounder, to further reduce the potential for residual confounding.The remaining concerns are all related to the variables included in the multivariable Cox model in our study.Liu et al. suggest that the multivariable model needs to be adjusted for some covariates that they argue are confounders.A.V.
Source: International Journal of Cancer
DOI: 10.1002/ijc.32349
Language: English
Subfield: Oncology
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
Award: G3750581964
OpenAlex ID: W2964145795