Women trying to weigh the pros and cons of different treatment options for breast cancer now have another important piece of information. Those who choose breast-conserving surgery (lumpectomy) plus radiation are not at increased risk for developing lung cancer later on, according to a recent study. However, mastectomy plus radiation does seem to increase risk.

Lydia Zablotska, MD, PhD, and Alfred Neugut, MD, PhD, both of Columbia University in New York, studied the data on more than 250,000 women who had been treated for early stage breast cancer since 1973. They reported their results in the journal Cancer (Vol. 97, No. 6: 1404-1411).

Women with breast cancer that has not spread to distant parts of the body can often choose between mastectomy (surgical removal of the breast) and breast-conserving surgery, such as lumpectomy, followed by radiation therapy. (See Surgery for Breast Cancer)

Radiation therapy is not usually required after mastectomy for early stage breast cancers, although it is sometimes used for larger tumors or those that involve nearby lymph nodes.

At one time, mastectomy was the preferred treatment for all early breast cancers, but large studies have shown it to be no more effective than lumpectomy plus radiation in terms of survival.

Some concerns have been raised, however, about radiation and the development of other cancers later on. Previous studies have shown that women who received radiation along with mastectomy were more likely to develop lung cancer 10 or more years later. This risk was especially high among smokers.

Researchers believed this increased risk was due to the lung being exposed to some residual radiation. This idea was supported by the fact that the increased risk was only in the lung on the side of the body that received the radiation.

Because lumpectomy and radiation is a relatively newer form of treatment, it was not known if it would increase the risk as well.

To determine if there was a risk, the Columbia University researchers went to the National Cancer Institute’s SEER database, which contains information from about 10% of all people treated for cancer in the United States, dating back to 1973.

Almost 200,000 women in the database had had a mastectomy, and about 65,000 had had a lumpectomy. About 14% of women in the mastectomy group and 75% in the lumpectomy group also received radiation.

In the mastectomy group, the risk of lung cancer increased significantly after 10 years in those who also received radiation. The risk of cancer in the lung on the same side as the radiation was more than doubled.

In terms of individual risk, the researchers calculated that 1 in 93 women who received a mastectomy plus radiation would develop lung cancer 11 to 20 years after treatment, compared to 1 in 200 for those who received only mastectomy.

These findings were consistent with previous studies.

In the lumpectomy group, however, those receiving radiation did not have a significantly higher risk of lung cancer compared to those who did not get radiation, even up to 14 years later. (The data did not go back farther because the technique is still relatively new.)

The researchers theorized that the remaining breast tissue in lumpectomy patients probably shielded the lungs from receiving much of the radiation.

For women with locally advanced cancer, such as those with larger tumors or tumors that have spread to the lymph nodes, the benefit of adding radiation to mastectomy generally outweighs the risk. It’s also important to note that the women with the longest follow-up in this study were treated in the 1970s and 1980s, and newer radiation techniques might not pose as much of a risk.

Still, the authors cautioned, patients and their doctors should be aware of the risk and should take it into account, both when making treatment decisions and when following up years later.

Because the SEER database does not contain information on smoking history, it could not be examined in this study. Still, other studies have found it added to the risk of lung cancer. More research on this subject is needed, stated the authors. Until such research allows guidelines to be developed, women with breast cancer should take this into account as well.