Phesi’s report of the world’s most-studied diseases has become a holiday tradition, and this year’s list features few surprises. Breast cancer took the top spot for the fifth year in a row, and the rest of the top five were unchanged from 2024.
Following breast cancer are solid tumors, stroke, prostate cancer and non-small cell lung cancer, Phesi announced on Dec. 30. Obesity ranked sixth, just barely missing out on a top-five spot.
The clinical data company came up with its list by analyzing 65,892 recruiting trials. That breast cancer held the top spot again was no surprise to Gen Li, Ph.D., Phesi’s president and founder.
Breast cancer is one of the most common cancers in the world, and is a “dire disease” with many different subtypes, Li said. Triple-negative breast cancer (TNBC) also had a high rate of phase 2 trial terminations, he added, another focus of Phesi’s report.
Triple-negative breast cancer is defined by its lack of HER2 and estrogen and progesterone receptors. Ultimately, the “negative” in the name “doesn’t mean anything,” Li said. Instead, research should focus on finding what receptors and proteins are actually present in TNBC.
Li has paid extra attention to the rate of trials that fizzle out in phase 2 since the Covid-19 pandemic, during which the attrition rate spiked to 30% in 2022. For 2025, the rate of phase 2 terminations is 26%, a decline but still higher than pre-pandemic levels.
Many phase 2 trials are stopped because unimpressive phase 1 data comes in, Li said, or sponsors design a trial for a patient population that doesn’t exist in large enough numbers to recruit. This is where he wishes companies would use the reams of available clinical data to optimize their trials beforehand.
Related
Phesi’s database includes information on 300 million patients, Li said, which clients can use to simulate the outcome of their trial designs before ever spending a cent to recruit patients at real-world sites.
“We actually have practical, workable tools to further reduce the attrition rate among phase two trials,” he explained.
Another trend highlighted by Phesi’s report China’s continued growth. While the country’s rapidly advancing biotech innovation has been well-documented, China has also seen continued growth in the clinical trial space. The country posted a 51% increase in site number from 2023 to 2025, compared to a 42% growth rate for the U.S.
While the U.S. is a “very competitive place” for clinical trial sites, Li said, it is also uneven, with “some of the most well-known names so much in demand.”
In China, though, patients are easily recruited into trials from hospitals, where most people go for all their medical needs; no need to visit a primary healthcare provider first, as in the U.S.
“The whole hospital is like a mall in Christmas time,” Li said. “The investigators tend to have access to a very large number of those patients.”
China’s biopharma rise is ultimately “good news for humankind,” he added, but he wants to see the U.S. do more to secure its leadership position in the sector.
“I do want this country to continue to be on top,” he said. “It is not to suppress others, it’s more getting ourselves to be more advanced.”
