Most Studied Disease? Still Breast Cancer

Breast cancer continues to dominate the global research agenda. According to a new report from clinical data company Phesi, breast cancer was the most studied disease in the world for the fifth year in a row.

Phesi analyzed nearly 66,000 actively recruiting clinical trials to determine which conditions received the most research attention. Breast cancer again claimed the top spot, followed by solid tumors, stroke, prostate cancer and non small cell lung cancer. Obesity ranked just outside the top five.

According to Phesi president and founder Dr. Gen Li, the result is not surprising. Breast cancer remains one of the most common cancers worldwide and includes many distinct subtypes that require different treatment approaches. One area drawing particular focus is triple negative breast cancer, which continues to see a high number of clinical trials that fail to move past Phase 2.

According to Li, triple negative breast cancer is often misunderstood. The term refers only to the absence of three common receptors, not the biology that actually drives the disease. He argues that research needs to focus less on what the cancer lacks and more on identifying the proteins and pathways that are present and actionable.

The report also highlights a lingering challenge in drug development. According to Phesi’s data, Phase 2 clinical trial termination rates remain elevated compared to pre pandemic levels. While the rate has declined since its peak in 2022, more than a quarter of Phase 2 trials in 2025 still ended early.

According to Li, many of these failures could be avoided. Trials often stall when early data is underwhelming or when studies are designed for patient populations that are too small to recruit efficiently. He points to the growing availability of large scale clinical data as a way to simulate and refine trial design before patients are ever enrolled.

Another major trend in the report is the continued expansion of clinical research in China. According to Phesi, the number of clinical trial sites in China grew by more than 50 percent between 2023 and 2025, outpacing growth in the United States. Centralized hospital systems in China allow researchers to recruit patients more efficiently, which accelerates trial timelines.

According to Li, this growth is ultimately positive for global health, but he also believes the United States must invest more aggressively to remain competitive in biomedical innovation.

After five consecutive years at the top, breast cancer’s position on the list reflects both the scale of the disease and the urgency to improve outcomes. The volume of research underscores how much progress has been made and how much work remains, especially for aggressive subtypes that still lack reliable treatment options.