Lung, colon, breast, and prostate cancers are the most common and deadliest cancers in the United States. Together they account for around 55% of all cancers in men and women and cause around 50% of all cancer-related deaths. But in 2004, researchers from around the world reported progress against all of these diseases. Most of the advances came in the form of new drugs, many of which can help people with advanced stages of cancer. Here is a look back at some of the breakthroughs of the past year.

Lung cancer kills more men and women in the United States than any other cancer. American Cancer Society estimates put the number of lung cancer deaths in 2004 at 160,440. One of the reasons lung cancer is so deadly is that it often has spread to lymph nodes or other organs before it is diagnosed. In these cases, surgery alone cannot cure the disease, and chemotherapy and radiation eventually fail also.

But patients in this desperate situation now have new options. In November, 2004, the US Food and Drug Administration (FDA) approved the drug Tarceva (erlotinib) for patients with non-small cell lung cancer (the most common type) that has not responded to other treatments.

Tarceva helped these patients live 2 months longer than similar patients who did not take the drug. And it did it without most of the difficult side effects that are common with chemotherapy. Tarceva is a targeted treatment that has little effect on other normal cells in the body. Its main side effects are rash, diarrhea, nausea, and vomiting, though in rare cases it can cause a serious lung problem called interstitial lung disease.

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Tarceva is similar to another drug approved in 2004 to treat advanced lung cancer: Iressa (gefitinib). Although they work in much the same way, recent study results suggest that Iressa does not help patients live longer. That has led the FDA to reconsider whether the drug should remain on the market.

Still, about 10% of people who take Iressa do seem to get better, at least for a while. Doctors have discovered a certain gene mutation that makes people more likely to respond to Iressa, and a test for the mutation is available.

Doctors also made important discoveries about the most effective way to use chemotherapy in patients with lung cancer.

A large study in the New England Journal of Medicine (Vol. 350, No. 4: 351-360) showed that chemotherapy with the drug cisplatin helped patients live longer after surgery. These results were confirmed by other studies that were presented at the annual meeting of the American Society or Clinical Oncology in June. And the drug Alimta (pemetrexed) was approved for patients with advanced non-small cell lung cancer that hasn't responded to other chemotherapy. Although Alimta didn't improve survival, it was just as effective and had fewer side effects than the standard drug for these patients, docetaxel.

Doctors found a new use for the drug docetaxel, as a treatment for men with advanced prostate cancer that no longer responds to hormone therapy. Two large studies published in October, 2004, showed that men given docetaxel (sold as Taxotere) lived about 2 months longer than men given standard chemotherapy. Even before the studies were published, the FDA used the data to approve docetaxel for this use.

The discovery was especially important because docetaxel is the first chemotherapy drug that actually helps men with this advanced disease live longer.

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Prostate cancer strikes more than 230,000 men in the United States each year and kills nearly 30,000. When caught early, prostate cancer is highly treatable with surgery and radiation. In later stages, however, these treatments may not work as well and men may need hormone therapy. Hormone therapy lowers levels of the male hormones (like testosterone) that help prostate cancer grow.

Although this therapy can be very helpful, it eventually stops working and the cancer begins to grow again. When that happens, chemotherapy can be used to help relieve some of the pain from the widespread cancer. But before docetaxel, no chemotherapy drug improved survival.

The finding is likely just a first step in improving treatments for men with advanced prostate cancer, said Len Lichtenfeld, MD, deputy chief medical officer for the American Cancer Society.

"Hopefully, with further study and possibly in combination with other drugs, there will be continued improvement in survival data," he said.

People with advanced colon cancer also got some new treatment options in 2004 that could improve their outlook. The FDA approved 2 drugs, Avastin (bevacizumab) and Erbitux (cetuximab).

Erbitux can shrink tumors in some patients and delay tumor growth by more than 4 months. Studies to see if the drug can also help people live longer are still ongoing. It was approved for people who are not responding to or can no longer take the chemotherapy drug irinotecan.

Avastin, however, does help patients with widespread disease live about 5 months longer when given along with standard chemotherapy. The improvement is significant because advanced colon cancer is very difficult to treat.

Only about 66% of people whose colon cancer has spread to lymph nodes or nearby organs survive 5 years. Once the colon cancer has spread to distant parts of the body, 5-year survival drops to 9%. Colon cancer is the third most common cancer in both men and women, and kills nearly 57,000 people a year.

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In addition to the new drugs, doctors have found better ways to use older drugs against advanced colon cancer. Early in 2004 researchers reported that the chemotherapy drug oxaliplatin improved survival when given along with standard chemotherapy on a particular schedule.

These small steps have combined to produce major results against advanced or relapsed colon cancer, Lichtenfeld said.

"This disease had no effective therapy 30 years ago," he explained. "Now, median survivals of 20 months or more are being reported with new treatment regimens."

New treatments also hold promise for women with breast cancer. Two studies reported in 2004 found that drugs called aromatase inhibitors can delay a relapse in post-menopausal women with early-stage disease. In fact, they probably work better than tamoxifen, the standard drug given to these women.

In early December, researchers reported that women who took the drug Arimidex (anastrozole) for 5 years after surgery had fewer recurrences than women taking tamoxifen, and a longer time to recurrence. In March, another group of researchers said the drug Aromasin (exemestane) delayed recurrence when given after 2-3 years of tamoxifen.

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The studies followed on the heels of a paper in late 2003 that showed Femara (letrozole) also cut the number of recurrences when women took it after completing 5 years of tamoxifen therapy.

The challenge now facing researchers is to determine whether all 3 of these aromatase inhibitors are equally effective, and the best schedule for taking the drugs. Should they be given instead of tamoxifen? Before? After? How long should women take the drugs?

Answering those questions will require more studies, Lichtenfeld said.