Cancer is a large group of diseases that can start in almost any organ or tissue of the body when abnormal cells grow uncontrollably, and go beyond their usual boundaries to invade adjoining parts of the body. According to the World Health Organization (WHO), it is the second most common cause of death globally, accounting for millions of deaths every year. Lung, prostate, colorectal, stomach and liver cancer are the most common types of cancer in men, while breast, colorectal, lung, cervical and thyroid cancer are the most common among women. However, these are not necessarily the deadliest forms of cancer.

What makes cancer the deadliest depends upon how many people have it and what percentage of those people actually survive. Cancer researchers determine this on the basis of five-year relative survival. This is the percentage of people who are expected to survive the effects of a given cancer, excluding their risk of other possible causes of death, for five years past a diagnosis. It is also important to note that what makes cancer really deadly is that practically no cure for it. A cure for cancer would imply that there are no cancerous cells remaining in the body.

Here are the 5 deadliest cancers in the U.S., according to SEER five-year relative survival data for cases diagnosed between 2014 and 2020.

1. Pancreatic cancer occurs when cells in your pancreas, a gland in your abdomen that aids digestion, mutate and multiply out of control, forming a tumour. Major risk factors include smoking, obesity, diabetes, chronic pancreatitis, certain genetic mutations and environmental chemical exposure.

2. Esophageal cancer develops in the oesophagus, which is the tube that connects your throat to your stomach.

3. Liver cancer and intrahepatic bile duct cancer originate in the liver or bile ducts, often linked to hepatitis infections, heavy alcohol use, obesity, and aflatoxin exposure.

4. Lung and bronchus cancer primarily caused by smoking, secondhand smoke, and environmental pollutants, affects the lungs and airways, making it the leading cause of cancer death in the US.

5. Acute myeloid leukaemia (AML) is an aggressive blood and bone marrow cancer that progresses rapidly, often linked to genetic mutations, radiation exposure, and certain chemicals.

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Hundreds of GLP-1 users in the US are suing drugmakers Novo Nordisk and Eli Lilly, alleging they developed a rare form of sudden vision loss called nonarteritic anterior ischemic optic neuropathy (NAION) after taking drugs such as Ozempic, Wegovy and Mounjaro.

The lawsuits allege the companies failed to adequately warn patients about the potential risk, that is often irreversible.

What Is The Controversy?

US law firm Weitz & Luxenberg has filed more than 90 lawsuits in New Jersey state court since 2025 on behalf of people who say they developed NAION while taking Ozempic or Wegovy, according to The Wall Street Journal.

Separate federal lawsuits in Philadelphia accuse Novo Nordisk and Eli Lilly of failing to provide adequate warnings about the potential eye-related risk. The cases are pending.

Regulators in Europe and Australia have required warnings about a possible increased risk of NAION with some GLP-1 medicines after reviewing available evidence.

In the US, vision problems are listed as possible side effects, but the FDA does not currently require NAION to be listed as a specific risk. The FDA's Sentinel Initiative is reviewing the possible safety signal linking GLP-1 drugs to NAION.

"The FDA routinely monitors the safety of drug products post-marketing. The FDA identifies safety signals from a variety of sources, evaluates the available data and takes regulatory actions when appropriate,” an FDA spokesperson said, according to ABC News.

Also read: Ozempic, Wegovy, Mounjaro and Zepbound May Fuel Rare Brain Disorder, Study Finds

What Do The Drugmakers Say?

Novo Nordisk, which makes Ozempic and Wegovy, said it takes “all reports of adverse events very seriously” but called the personal injury lawsuits "without merit."

The company said it is "committed to patient safety and continuously monitors the safety profile of our GLP-1 RA products." It added that if "emerging safety data warrant further action, appropriate measures will be implemented".

Lilly, which makes Zepbound and Mounjaro, said patient safety is its "top priority."

"We actively monitor, evaluate, and report safety information for all our medicines to the FDA," the company said, adding that it continues to review data on potential ophthalmic issues.

What Does The Science Say?

The evidence linking GLP-1 drugs to NAION remains mixed. Some observational studies have found an association, while others have not. Researchers have not established that GLP-1 drugs cause NAION.

What Studies Have Found

• 2025 JAMA study: Among more than 159,000 people with type 2 diabetes, 35 GLP-1 users developed NAION versus 19 in the comparison group. Researchers also found an increased risk of other optic nerve disorders in 93 patients.
• Another 2025 JAMA study: Found no statistically significant association between GLP-1 use and NAION, although it reported a slight increase in diabetic retinopathy.
• 2026 safety analysis: A British Journal of Ophthalmology analysis of more than 30 million FDA adverse-event reports from 2017 to 2024 identified a safety signal linking semaglutide medicines to NAION.
• Wegovy vs Ozempic: The signal was nearly five times stronger for Wegovy than Ozempic, although both contain semaglutide.

The North American Neuro-Ophthalmology Society and American Academy of Ophthalmology said studies have produced mixed results.

"While many report a small possible increased risk of NAION in patients taking GLP-1 RAs such as semaglutide, some studies report no correlation, and the overall magnitude of the risk of NAION remains low,” the groups said.

Read More: Exclusive: GLP-1 Drugs Are The ‘New Statins’, Says University Hospital Birmingham Professor

What Is NAION?

NAION is the most common acute optic neuropathy in people over 50, according to Mayo Clinic. It occurs when blood flow to the optic nerve is suddenly reduced, damaging the nerve that carries visual information from the eye to the brain.

It typically causes painless vision loss in one eye.

Some patients experience partial improvement, but vision loss is often permanent. There is currently no proven treatment to reverse the damage.

Diabetes itself can increase the risk of NAION, regardless of GLP-1 use. Other risk factors include overnight low blood pressure and having a very small optic nerve cup.

The US Food and Drug Administration (FDA) has a step towards reducing animal use in drug research, focusing on technologies like human organoids, organs-on-chips, artificial intelligence and computer modelling that may play a bigger role in deciding whether medicines are safe before they are tested in people.

The move is part of the US Department of Health and Human Services's initiative declared on September 21 to shift biomedical research towards methods that reflect human biology more closely.

As part of the changes, the FDA issued a rule updating its regulations to state that non-animal methods can be used where it is appropriate to assess the safety of drugs before human trials.

“This new rule supports the Trump Administration’s push to explore ways to complement, or where appropriate, replace animal studies with methods that may better predict how medicines will actually affect people,” FDA Acting Commissioner Kyle Diamantas said.

“Our goal is not to replace one rigid approach with another. It is to support rigorous, modern science — including animal studies when they remain appropriate and validated alternatives when they can provide the evidence needed to protect patients,” he added.

Why Is FDA Moving Away From Animal-Based Studies?

Animal testing has always been a central part of drug development for decades. But a drug behaving safely in an animal does not necessarily mean it will behave the same way in humans. This is partly because species differ in their biology, metabolism and immune responses.

The FDA's new approach is built around New Approach Methodologies (NAMs), a term for covering laboratory and computational methods that can provide more accurate evidence without relying entirely on animals.

The agency has already issued guidance on how developers can use and validate these methods. It has also created a database containing examples of NAMs used in FDA reviews.

Also read: HHS Announces US FDA’s First AI Chief: Here’s What It Means For The Future Of Drug Regulation

Organoids May Replace Some Animal Experiments

Organoids are three-dimensional clusters of cells grown from human stem cells. They can replicate the structure and some of the function of organs.

Researchers can grow models resembling parts of the liver, intestine, brain, kidney or other tissues and use them to test experimental medicines. This can allow scientists to study how human cells respond directly to a drug, including side effects.

The HHS initiative includes plans for the NIH Clinical Center to develop a laboratory combining standardised human organoids with robotics, AI and advanced data systems.

Also read: Donald Trump Wants Childhood Vaccines Split Into 5 Shots To Prevent Autism: But Is There Evidence?

What Are Organs-On-Chips?

Organs-on-chips, also called microphysiological systems, are small devices containing human cells that mimic aspects of an organ's structure and environment. Researchers can expose these cells to drugs and observe their responses in a controlled environment.

For example, a liver-on-a-chip can help researchers investigate whether a drug damages liver cells, while other systems can model the interaction between different tissues.

The FDA says newer approaches include human cells, organs-on-chips and computer models, provided they are appropriately suitable scientifically.

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AI & Computational Models

AI and computational models can analyse huge amounts of biological and drug data to predict how a medicine may behave in the human body.

HHS' Advanced Research Projects Agency for Health is investing in computational approaches designed to assess drug safety and reduce dependence on animal experiments.

The FDA's rule, however, does not prohibit animal studies. Instead, it does away with language that imply animal testing is the only acceptable way to test drugs and biomedical products.

Non-animal studues can be used when they are scientifically appropriate for the particular drug and regulatory requirements.

Low levels of vitamin D during pregnancy could be linked with a higher risk of preterm birth. The strongest link were seen among women who delivered very prematurely, according to a recent study.

Researchers from the Medical University of South Carolina studied health data from 15,506 pregnancies in which the vitamin D levels of expectant mothers measured during pregnancy.

The study, published in the Journal of Perinatology, found that women with lower levels of 25-hydroxyvitamin D, the main blood marker used to assess vitamin D status, were more likely to deliver before 37 weeks.

The association was even more pronounced among women who delivered before 32 weeks, a group which is considered very preterm.

What Did The Study Find?

Of the 15,506 deliveries, 13,451 were at term, while 1,652 were moderately preterm and 385 occurred before 32 weeks. The researchers found that women who delivered preterm had lower average vitamin D concentrations than those who delivered at term. The lowest vitamin D levels were seen among women who delivered before 32 weeks.

Nearly 45% of women had a vitamin D level below 30 ng/mL at some point during pregnancy, while about 66% had levels below 40 ng/mL.

The researchers adjusted their analysis for maternal age, race and ethnicity and insurance status, and the association between higher vitamin D levels and lower odds of preterm birth remained same.

But, this was a retrospective observational study, meaning it can identify an association but cannot prove that low vitamin D itself caused an early delivery. Other factors that influence both vitamin D levels and pregnancy outcomes may also play a role.

Also read: Ferritin Face: Can Pale Skin Signal Iron Deficiency?

Vitamin D And Pregnancy

Vitamin D is best known for its role in calcium absorption and bone health, but it also plays a role in immune function, placental development and other processes involved in pregnancy.

Researchers say several biological mechanisms could potentially explain the association with preterm birth, including effects on inflammatory pathways, placental function and fetal growth.

The findings also add to previous research. A 2025 NIH-funded study involving 351 first-time mothers found that women with vitamin D levels below 40 nmol/L during the first trimester had 4.35 times the risk of preterm birth compared with women whose levels were above 80 nmol/L.

Another import aspect is that the new study shows that lower vitamin D levels are associated with earlier delivery, but it does not show that raising vitamin D levels will prevent preterm birth.

A Cochrane review found the evidence for vitamin D supplements reducing preterm birth is not certain or confirmed. The NIH's current guidance notes also state that there is insufficient evidence to recommend routine vitamin D supplementation specifically to prevent preterm birth.

The researchers say randomised clinical trials are needed to determine whether optimising vitamin D levels during pregnancy can actually reduce the risk of preterm birth.