Some older women with early-stage breast cancer may be able to safely skip radiation treatments, a new study suggests.

The researchers came to this conclusion after comparing two groups of elderly women treated for small cancers. One group was given tamoxifen after undergoing lumpectomy, while the other got tamoxifen and radiation. The finding reported in the New England Journal of Medicine (Vol. 351, No.10: 971-977), means some women may be able to avoid the time and expense of radiation treatment, as well as possible side effects such as breast and arm swelling, breast pain, and poorer cosmetic results.

"If a patient does not need to have radiation therapy, her quality of life can improve significantly," said lead study author Kevin Hughes, MD, of Massachusetts General Hospital Cancer Center. "By showing that radiation therapy has very little impact on outcome for these patients, we can help each woman and her physician decide on the right treatment."

Hughes and his colleagues studied a very specific group of women, though: those 70 or older with very early-stage breast cancer that was hormone-receptor positive.

All 636 women in the study had small tumors (no larger than 2 cm) that were removed by a breast-conserving surgery called lumpectomy, and all were given 5 years of tamoxifen therapy afterward. But about half of the women (317) were also given radiation therapy. Radiation after lumpectomy is considered standard treatment for most women with early-stage breast cancer.

The researchers noted only one significant difference between the 2 groups in 5 years of follow-up. Women who received radiation therapy in addition to tamoxifen were less likely to have their cancer return in the same breast or nearby tissue. Just 2 women in that group (1%) saw their cancer return locally, while 16 women who received only tamoxifen (4%) had a local relapse in that period.

Although that difference was statistically significant, in the real world it may not be, Hughes said.

"The local recurrence risk in both groups was extremely low, and women who have not had radiation have the option of another lumpectomy if they do have recurrence in the same breast," he said. "Once a patient has had radiation, however, she must have a mastectomy if her tumor recurs."

In fact, rates of mastectomy because of a subsequent recurrence were 1% in the group that received radiation, and 2% in the tamoxifen-only group -- a statistical dead-heat. Rates of distant spread were also the same: 7 women in each group saw their cancer return in another part of their body. There was no difference in survival, either: 3 women in each group died of breast cancer, and about equal numbers died from other causes.

This study isn't the first to find that giving radiation after lumpectomy can delay a relapse of breast cancer, even though it does not seem to improve overall survival.

What is new is the possibility of sparing some women radiation altogether, according to outside experts who reviewed the research.

"There are clear advantages in identifying … women who do not require radiotherapy after lumpectomy and tamoxifen," Ian Smith, MD, and Gillian Ross, PhD, write in an editorial accompanying the study.

For one thing, they note, radiation therapy still has the potential to damage the heart, even though modern techniques have made the treatments safer than ever.

And there are the other side effects to consider. In the Hughes study, women who had radiation in addition to tamoxifen reported worse breast pain, swelling, and cosmetic outcomes in the first few years of follow-up compared to women who took only tamoxifen. After about 4 years, though, these effects were about the same in both groups.

For some women, the chance to bypass these side effects might well be worth a small increase in the chance of a relapse, Smith and Ross write. Elderly women already have a low risk of recurrence because their breast cancers tend to be less aggressive. Moreover, elderly women also are more prone to have other illnesses that are more likely to be deadly before breast cancer would be.

And, Smith and Ross note, it may be possible to reduce the risk of relapse even further by adding aromatase inhibitors to treatment. Studies of younger women have shown that these newer drugs can lower the risk of breast cancer recurrence even more when given after a course of tamoxifen.

Unfortunately, there's still no way to guarantee that a specific woman will not have a relapse if she decides to skip radiation. For that to happen, scientists will have to discover genetic markers and other such clues to identify women with less aggressive disease. Until then, Hughes said, women should consider their treatment options carefully.

"In the long run, each woman and her physician should choose a treatment plan by weighing the slightly increased local recurrence risk against the virtually certain costs of radiation -- the patient's time, adverse effects, and financial cost," he said.