Potential impact of controlling opium use prevalence on future cancer incidence in Iran.

Background: The International Agency for Research on Cancer (IARC) recently classified opium consumption as carcinogenic to humans. This study aimed to estimate the potential reduction in incident cancers by 2035 in Iran, which accounts for 42% of global opium consumption, through decreasing opium use prevalence.

Methods: The population attributable fraction (PAF) of opium-related cancers was projected using national cancer incidence, age- and gender-specific opium use prevalence, relative cancer risks associated with opium use, and annual percentage changes in cancer incidence rates in Iran. Opium-related cancers were defined based on IARC monographs as cancers of lung, larynx, bladder, esophagus, stomach, pancreas, and pharynx. The number of preventable cancer cases under different opium prevalence scenarios was determined by subtracting attributable cases in each year based on current prevalence from those in alternative scenarios.

Findings: By 2035, an estimated 3,001,421 new cancer cases are expected in Iran, with 904,013 (30.1%) occurring in opium-related sites. Maintaining the current opium prevalence (5.6%) is projected to cause 111,130 new cancer cases (3.7% of all cancers, 12.3% of opium-related). A 10%, 30%, and 50% reduction in opium prevalence could prevent 9,016, 28,161, and 49,006 total incident cancers by 2035 in Iran, respectively. Reducing opium use prevalence by 10%-50% is projected to have the highest impact on lung cancer (prevention of 2,946-15,831 cases), stomach cancer (prevention of 2,404-12,593 cases), and bladder cancer (prevention of 1,725-9,520 cases).

Interpretation: Our results highlight the significant benefits that can be achieved through effective cancer prevention policies targeting opium use in Iran. Neglecting this risk factor is estimated to pose a significant burden on cancer incidence in the next decade in this population.

Funding: None.