Mortality in the Portuguese thorotrast study.

Area of Science:

• Radiology and Nuclear Medicine
• Epidemiology
• Oncology

Background:

• Thorotrast, a radioactive contrast agent used diagnostically from 1929-1956, poses potential long-term health risks.
• Previous follow-up of the Portuguese Thorotrast cohort was interrupted, necessitating its reactivation and extended monitoring.

Purpose of the Study:

• To re-evaluate the long-term mortality risks associated with Thorotrast exposure.
• To extend the follow-up of the Portuguese Thorotrast cohort through 1996 and analyze causes of death.

Main Methods:

• Reactivated and extended follow-up for a cohort of Thorotrast-exposed patients and an unexposed control group through December 1996.
• Utilized medical records for initial cohort identification, including contrast agent type and dose.
• Employed standardized methods for follow-up and cause of death ascertainment for both groups.

Main Results:

• Increased all-cause mortality was observed in the Thorotrast group compared to controls.
• Excess mortality risk escalated with time since exposure, peaking around 30 years post-administration.
• Significant increases in mortality were linked to neoplasms (RR=6.04), nonmalignant liver disorders (RR=5.67), and hematological conditions (RR=14.2).
• Specifically, liver cancer risk (RR=70.8) and leukemia risk (RR=15.2) were substantially elevated.

Conclusions:

• Thorotrast administration is associated with significantly increased long-term mortality, primarily due to cancer and liver/hematological disorders.
• The latency period for Thorotrast-induced excess mortality underscores the importance of long-term patient surveillance.
• This study reinforces the understanding of Thorotrast's carcinogenic and toxic effects on human health.