Hormuzd Katki

PhD

NCI

Senior Investigator

PLCO (Learn more about this study)

PLCO-1309

Sep 5, 2023

Quantifying absolute and relative risks of each smoking-related cancer and cause of death as years since quitting smoking increases

The 2020 Surgeon General’s Report details the reductions in relative-risk of lung cancer due to smoking cessation. Studies involving other smoking-related cancers are cited, but the data is sparse, many cancer sites do not have many cases, quit-years were grouped into coarse time intervals, and some smoking-related cancers have no data by quit-years. For non-cancer causes of death, such as heart diseases, no data was presented on how the relative risk decreases as years since quit increases.

Furthermore, the data presented on risks following smoking cessation in the Surgeon General’s Report focuses on relative risks and not absolute risks. Although risk decreases with increasing quit-years, risk also increases with age. As former smokers accumulate quit-years but also concomitantly age, the effects of time since quitting and aging counteract each other. We have recently shown in PLCO and NLST that absolute risk of lung cancer increases beyond 5 years since quitting smoking, because the effect of concomitant aging counteracts that of increasing years since quitting smoking.

In this proposal, we will quantify how absolute risk varies with years since quitting smoking and concomitant aging, for each smoking-related disease and smoking-related cause of death.

Objectives
1. Calculate relative risks of as years since quit increases, for each smoking-related cancer and smoking-related cause of death, adjusted for outcome-specific risk-factors.
2. Calculate how absolute risk changes with increasing quit-years and concomitant aging, for each smoking-related cancer and smoking-related cause of death.

The smoking-related outcomes of interest are:
1. Smoking-related cancers (both incidence and mortality)
a. Lung
b. Head/Neck
c. Esophagus
d. Pancreas
e. Bladder
f. Stomach
g. Colorectal
h. Liver
i. Cervix
j. Kidney
k. AML
i. Endometrium
ii. Thyroid

2. Smoking-related causes of death (not sure if each of these has been categorized)
a. Cardiovascular mortality
i. Coronary heart disease mortality
ii. Cerebrovascular disease mortality
iii. Venous thromboembolism mortality
iv. Abdominal aortic aneurysm mortality

Risk factors for each outcome, to adjust for, will be specified in communication with IMS.