Does quitting cigarettes make an impact on lung cancer?

Lung cancer remains a leading cause of cancer-related deaths worldwide. Smoking is a known high-risk factor for developing lung cancer.

Despite a recent decline in lung cancer rates with a reduction in the number of smokers, survival rates remain alarmingly low with 75% of patients succumbing to the disease within 5 years of diagnosis.

Multiple studies have demonstrated the positive impact of quitting smoking on prolonging survival. However, limited research exists regarding how the timing and duration of stopping cigarettes can change survival rates following a diagnosis of lung cancer.

A study conducted from 1992 – 2022 at Harvard by T.H. Chan School of Public Health, investigated the relationship between pre-diagnosis smoking habits and survival rates among lung cancer patients.

The study involved more than 5500 participants diagnosed with the most common form of lung cancer, non-small cell lung cancer. They were meticulously surveyed about their smoking habits including the start age, quantity smoked,  if & when had they quit smoking or continued to smoke even after their diagnosis. The participants were monitored every 12 to 18 months.

At the start of the study, the largest group were former smokers (3,308), followed by current smokers (1,491), while non-smokers (795) formed a minority. By the time the study was completed nearly three-fourth of the patients passed away due to lung cancer including 79% of current smokers, 67% of former smokers, and 60% of never smokers.

When comparing the death rate among individuals who had never ever smoked, a higher death rate (68%) was found in current smokers, while former smokers had a 26% higher death rate.

To estimate the impact of overall smoking, the researchers calculated the number of cigarette packs the participants had smoked throughout their lives, known as smoking pack years. Doubling the smoking pack years among smokers was, unsurprisingly, linked to shorter survival.

A significant finding in this study was that there was an improved chance for survival when there was a longer duration between quitting cigarettes  and  lung cancer diagnosis. This emphasized the potential impact of quitting smoking on survival rates even among former smokers. The study concluded that quitting smoking early can improve survival rate and this benefit can persist even after an individual is diagnosed with lung cancer in the future.

We need such studies on the Indian subcontinent to draw a correlation between quitting smokeless tobacco and head and neck cancers as well as bidi smoking and lung cancer