Lung cancer is the most commonly diagnosed cancer in the world, with 2.5 million new cases per year, accounting for 12.4% of all cancer diagnoses. It’s followed by breast cancer (2.3 million cases, 11.6%), colorectal cancer (1.9 million cases, 9.6%), prostate cancer (1.5 million cases, 7.3%), and stomach cancer (970,000 cases, 4.9%). These five cancers make up nearly half of all new diagnoses globally, but they vary widely in how they behave, who they affect, and how treatable they are.
Lung Cancer
Lung cancer reclaimed the top spot worldwide with 2.5 million new cases annually. Smoking remains the single biggest risk factor, but a growing number of cases occur in people who have never smoked, particularly women and younger adults. Exposure to radon gas, air pollution, and workplace chemicals like asbestos also contribute.
What makes lung cancer especially dangerous is that it rarely causes noticeable symptoms in its early stages. A persistent cough, chest pain, shortness of breath, or coughing up blood often don’t appear until the cancer has spread. This is a major reason lung cancer kills more people than any other cancer type despite not always being the most commonly diagnosed one in every country. Low-dose CT scans are now recommended for long-term smokers to catch it earlier, when treatment is far more effective.
Breast Cancer
Breast cancer is the second most common cancer globally and the most frequently diagnosed cancer in women. In the United States alone, an estimated 316,950 new cases will be diagnosed in women in 2025, making up roughly 32% of all female cancer diagnoses. While rare, breast cancer also occurs in men.
Risk increases with age, family history, certain inherited gene mutations, early menstruation, late menopause, and long-term hormone therapy. Obesity and alcohol use are modifiable factors that raise risk as well. The good news is that breast cancer caught early has a high survival rate, which is why screening matters. The American Cancer Society recommends women ages 45 to 54 get mammograms every year, with the option to start at 40. Women 55 and older can switch to every two years. Those with a strong family history or genetic risk may also need MRI screening.
Colorectal Cancer
Colorectal cancer, which includes cancers of the colon and rectum, ranks third worldwide with 1.9 million new cases per year. In the U.S., it’s the third most common cancer in both men and women, with about 71,810 new cases expected in women and a similar number in men in 2025.
One notable trend is that colorectal cancer is rising in younger adults. Rates in people under 50 have been climbing for the past two decades, prompting a change in screening guidelines. The American Cancer Society now recommends regular screening starting at age 45 for people at average risk, continuing through age 75. Screening can be done with stool-based tests that look for signs of cancer or with visual exams like colonoscopy. If a stool test comes back abnormal, a follow-up colonoscopy is needed. For people ages 76 through 85, the decision to continue screening depends on overall health and prior results.
Diet plays a meaningful role. High consumption of red and processed meat, low fiber intake, obesity, heavy alcohol use, and smoking all increase risk. Colorectal cancer is also one of the most preventable cancers because screening can find and remove precancerous growths called polyps before they turn malignant.
Prostate Cancer
Prostate cancer is the fourth most common cancer worldwide, with 1.5 million new cases annually, and it’s the most frequently diagnosed cancer in men in many countries. Age is the strongest risk factor. It’s uncommon before 40, and the majority of diagnoses occur in men over 65. Black men face a significantly higher risk and tend to be diagnosed at a more advanced stage.
Many prostate cancers grow slowly and may never cause serious harm. Some men with low-risk prostate cancer are monitored through a strategy called active surveillance rather than being treated immediately. This involves regular blood tests and periodic biopsies to track whether the cancer is changing. For cancers that are aggressive or have spread, treatment options include surgery, radiation, and hormone-blocking therapies. Screening with a PSA blood test is available, but because it can detect slow-growing cancers that may never need treatment, the decision to screen is typically a conversation between patient and doctor weighing individual risk.
Stomach Cancer
Stomach cancer rounds out the global top five with 970,000 new cases per year. It’s more common in East Asia, South America, and Eastern Europe than in the United States, where rates have been declining for decades. The strongest risk factor is chronic infection with H. pylori, a bacterium that causes long-term inflammation of the stomach lining. Smoking, heavily salted or smoked foods, and obesity also increase risk.
Like lung cancer, stomach cancer often goes undetected until it’s advanced because early symptoms (indigestion, bloating, mild nausea) are easy to dismiss. In countries with high rates, like South Korea and Japan, routine endoscopy screening has helped catch cases earlier and improve outcomes.
How Rankings Differ by Sex
The cancers that affect men and women most frequently differ in important ways. For women in the U.S., breast cancer, lung cancer, and colorectal cancer together account for 51% of all new diagnoses. Breast cancer alone represents nearly a third of female cases.
For men, prostate cancer dominates, followed by lung cancer and colorectal cancer. Lung and colorectal cancers appear on both lists, which is why screening for these two types applies broadly regardless of sex. Cervical cancer, while not in the overall top five, remains a significant concern for women globally and is almost entirely preventable through HPV vaccination and regular screening. The American Cancer Society recommends cervical screening starting at age 25, preferably with an HPV test every five years, continuing until at least age 65.
Childhood Cancers Are Different
The cancers that affect children look nothing like those in adults. The most common types in children ages 0 to 14 are leukemias (cancers of the blood and bone marrow), brain and central nervous system tumors, and lymphomas. These cancers are not driven by the same lifestyle and environmental factors that cause adult cancers. Their causes are largely unknown, though certain genetic syndromes increase risk. The overall survival rate for childhood cancers has improved dramatically, with many types now curable when treated at specialized centers.
The Role of Prevention
Up to 50% of all cancers are linked to modifiable risk factors: tobacco use, physical inactivity, poor diet, alcohol consumption, inadequate sleep, and skipping recommended screenings. That number is striking because it means roughly half of cancer cases have a preventable component.
Tobacco is the largest single contributor, connected not just to lung cancer but to cancers of the bladder, kidney, pancreas, stomach, and several others. Excess body weight increases risk for at least 13 cancer types, including breast cancer after menopause and colorectal cancer. Alcohol raises risk for cancers of the mouth, throat, esophagus, liver, colon, and breast, even at moderate levels. None of this means that people who do everything right can’t get cancer, or that a diagnosis implies fault. But it does mean that population-wide changes in these habits would prevent millions of cases each year.
Screening remains one of the most effective tools available. Breast, colorectal, cervical, and lung cancers all have established screening programs that catch disease early, when treatment is simpler and survival rates are highest. Staying current with age-appropriate screenings is one of the most concrete steps you can take.