A new clinical trial of partial breast radiation is set to begin. Researchers hope it will answer some important questions about this alternative way of delivering radiation therapy to women who have had breast tumors removed.

The Phase 3 study is run by the National Surgical Adjuvant Breast and Bowel Project (NSABP) and the Radiation Therapy Oncology Group (RTOG), and sponsored by the National Cancer Institute. It will include 3,000 women with early stage breast cancer who have had a breast-conserving therapy called lumpectomy.

The women will be randomly assigned (like flipping a coin) into one of two groups. Half of them will be assigned to receive whole breast radiation, the standard treatment after lumpectomy, while the others will be assigned to partial breast radiation. Their patients will be followed for about 10 years to find out if partial breast radiation is just as safe and effective as whole breast radiation.

"We'd like to think they'd be equivalent, based on early information that we have, but this is why we conduct a trial," said Thomas Julian, MD, one of the NSABP protocol officers for the study and associate director of the Breast Care Center at Allegheny General Hospital in Pittsburgh.

He presented information about the trial Friday at the annual meeting of the American Society of Breast Surgeons. The study protocol is identified as NSABP B-39/RTOG 0413.

RESOURCES: Learn more about the trial and how to register from the National Cancer Institute

Whole breast radiation therapy is usually given after a lumpectomy to kill any stray cancer cells that might remain in the breast. Studies have shown that the treatment can reduce the rate of local recurrences and improve long-term survival. Whole breast radiation can be inconvenient, usually requiring clinic visits 5 days a week for 5 to 7 weeks.

Partial breast radiation delivers the treatment only to the tumor site and to a small area of surrounding tissue. It has been used in various forms for about a decade, and has recently grown in popularity. Some women prefer it to whole breast radiation because it takes much less time to complete treatment (1 or 2 weeks). But there are no large studies showing that partial breast radiation is as effective as whole breast radiation.

Some doctors worry that limiting the field of radiation might allow some stray cancer cells in other parts of the breast to survive -- and possibly grow into another tumor later. There has also been opposition from doctors who worry the technique will cause too much scarring in the breast, making it harder to detect any recurrence of cancer.

Several small studies suggest women who get partial breast radiation fare just as well as women who get whole breast radiation; both groups have similar rates of recurrence. But those studies tracked the women for only a few years. There have been no large, long-term studies to see if the outcomes remain the same 10 or more years down the road.

"This is an important study," said Len Lichtenfeld, MD, deputy chief medical officer for the American Cancer Society. "There has been a substantial interest in the last few years in reducing either the amount of radiation, the length of radiation therapy, or the amount of breast that has to be radiated. This trial will help find out whether every woman really needs to have whole breast radiation, and that's important."

It should also help determine which women would be best suited to partial breast radiation.

Previous trials, Julian explained, included only highly-selected patients -- women with small tumors, no lymph node involvement (or minimal lymph node involvement), and cleanly removed tumors that left no suspicious tissue behind. Most of the studies were also conducted in women over age 45.

That was a precaution taken because breast cancer tends to be more aggressive in younger women, said Frank Vicini, MD, a radiation oncologist at William Beaumont Hospital in Royal Oak, Mich. He conducted many of the early trials of partial breast radiation and is lead protocol chair for this new study.

"If you're going to try a new technique, you try it in patients who have a better prognosis," he said. "We've been doing that for many years and we've had good results. As more data accumulate, we're seeing age probably isn't a risk factor."

The current study will include women 18 and older.

The study will compare whole breast radiation to three different types of partial breast radiation: multi-catheter brachytherapy, balloon catheter brachytherapy (MammoSite), and 3-D conformal external beam radiation. After talking with their doctors, the women who are selected for partial breast radiation will choose one of these treatments, and will receive it twice a day for a total of 5 days. Each treatment will deliver the same amount of radiation.

In multicatheter brachytherapy, doctors insert hollow tubes (usually 15-20) into the tumor site. Radioactive pellets are then inserted into the tubes. They are left in the breast for a few minutes, then taken out again. The tubes themselves remain in place for the length of the treatment, which is 1 to 2 weeks.

Balloon catheter brachytherapy is a similar technique, but it uses only one tube with a balloon at the end. The balloon is inserted into the breast and inflated with salt water to fill the cavity left by the removal of the tumor. The radiation pellet is inserted into the center of the balloon for a few minutes at a time. This is done over the course of 1 to 2 weeks.

The final technique, 3-D conformal external beam radiation, is similar to traditional radiotherapy for breast cancer in that the radiation is delivered from outside the breast. But instead of hitting the whole breast, the beams are targeted to hit only the tumor site and a small portion of surrounding tissue.

Another thing the researchers hope to learn from the study is whether partial breast radiation can improve a woman's quality of life.

It may be more convenient for women who live far from a radiation facility because it cuts their treatment time sharply.

The researchers will also compare the cosmetic results of the different radiation types and side effects like fatigue.

Vicini said women who are interested in receiving partial breast radiation should consider joining the study. And Julian said women should only get partial breast radiation in the context of a clinical trial.

"A woman should understand the complexity of this," he said. "Less is not necessarily better, and it may or may not be as good. But the only way to really know is to conduct this randomized Phase 3 trial."