Radiation Benefits Women with Small Cancers After Lumpectomy

M.F.X. Gnant and others

San Antonio Breast Cancer Symposium, December 8, 2005, Abstract 8

Is this for me? If you have small, early-stage invasive breast cancer and are wondering if you can skip radiation after surgery, you might want to read this article.

Background and importance of the study: Breast-conserving surgery lumpectomy followed by radiation—has become a standard treatment for women with breast cancers that:

• are small to medium in size (usually four centimeters—about two inches—or less in diameter),
• are limited to one place in the breast, and
• can be removed with clean margins.

Radiation to the whole breast after lumpectomy has been recommended for all women who choose breast conservation (instead of breast removal, or mastectomy), regardless of the women's age. This "standard of care" recommendation is based on many large studies that compared lumpectomy plus whole breast radiation to lumpectomy alone. These studies showed that radiation therapy after lumpectomy significantly reduced the risk of the breast cancer coming back in the same breast.

The studies also found that women with node-negative disease lived equally long lives after lumpectomy alone or lumpectomy plus radiation. Women with node-positive disease had an increase in survival. The main benefit from radiation is to lower the risk that cancer might return in the breast, requiring more surgery and possibly other treatments.

Other treatments may be given after surgery. Hormonal therapy is a medicine given after surgery for hormone-receptor-positive breast cancer. Hormonal therapy:

• lowers the risk of the cancer coming back,
• improves survival after surgery, and
• lowers the risk of developing breast cancer in the other breast.

With all these different types of post-surgery treatments, it would be helpful to know who needs radiation treatment and who might do fine with hormonal therapy alone. Several studies have looked at whether hormonal therapy offers enough protection against recurrence after lumpectomy for women with small cancers—eliminating the need for radiation. This could spare some women the inconvenience, side effects, and cost of radiation.

The study reviewed here continues to look at this important question. Keep in mind that ALL of the women in this study had relatively small cancers and no lymph node involvement. They then received hormonal therapy and about half received radiation too. So this study does not address the role of radiation alone without hormonal therapy.

Study design: Austrian researchers used the results of two studies conducted by the Austrian Breast Cancer Study Group (ABCSG) to identify groups of women who had an extremely low risk of recurrence (the breast cancer coming back).

All the women were post-menopausal and had breast cancer that was:

• hormone-receptor-positive,
• smaller than three centimeters, and
• node negative.

All the women had lumpectomy followed by different types of hormonal therapy:

• In ABCSG-6, 698 women took tamoxifen with or without aminoglutehimide (an old-fashioned kind of aromatase inhibitor).
• In ABCSG-8, 875 women took either five years of tamoxifen or two years of tamoxifen followed by three years of Arimidex (chemical name: anastrozole).

About half of the women in each study were randomly assigned to receive radiation after lumpectomy and before hormonal therapy. The other half had lumpectomy followed by hormonal therapy—without radiation.

Results: After about 10 years of follow-up in the ABCSG-6 trial, the cancer came back in

• 3.3% of the women who had radiation, compared to
• 5.2% of the women who didn't receive radiation.

However, this difference was not significant, meaning it could be due to chance rather than due to the radiation.

After about four years of follow-up in the ABCSG-8 trial, the cancer came back in

• 0.24% of the women who had radiation, compared to
• 3.2% of the women who didn't have radiation.

This difference was statistically significant, meaning that it was likely due to the radiation and not just to chance.

There was no difference in overall survival in either trial between women who had radiation treatment and women who did not.

Conclusions: The researchers concluded that radiation therapy to the whole breast can help reduce the risk of recurrence in women with small hormone- receptor-positive breast cancers, even if they receive hormonal therapy after lumpectomy.

Take-home message: After lumpectomy alone with clear margins, chances are that you are cancer-free. But your doctor will talk to you about treatment you can have just in case some cancer cells were left behind.

In this situation, getting the best breast cancer treatment can feel like a balancing act: You want to do as much as you can to get the cancer out and lower the risk of it coming back. But you'd like to avoid uncomfortable side effects that might lower your quality of life.

In this study, the researchers wanted to see if there was a group of women who could get just hormonal therapy after lumpectomy and skip radiation therapy. So they looked at a group of post-menopausal women whose cancers are the type associated with the most favorable outcomes:

• hormone-receptor-positive,
• smaller than three centimeters, and
• node negative.

If you're in this group, you have a very low risk of the cancer coming back.

As these results show, even women with a very low risk of recurrence can benefit from radiation after surgery. This means that so far, no group of women has been found that would NOT benefit from whole breast radiation.

Remember that no single treatment plan is right for everyone. If you want to do everything possible today to lower the risk of ever seeing the cancer again, then radiation after lumpectomy may be a very important step for you. If you have a small cancer that has been removed with wide and clear margins of resection and you're more concerned about how radiation will affect you, you may want to talk to your doctor about skipping radiation and just taking hormonal therapy. Your risk of the cancer coming back in the same area is likely to be higher, but how long you live will probably not be affected.

Instead of having whole breast radiation, you can also talk to your doctor about the potential role of partial breast radiation. Studies are now under way to test the effectiveness of radiation delivered just to the area around the cancer. This is called partial breast radiation. Promising results after four years of using this approach have led to a clinical trial that is now comparing partial breast radiation to whole breast radiation. The trial is called the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-39 study. Talk to your doctor—you may be able to enroll in the NSABP B-39 study.

Juggling risks that may affect your life can be very uncomfortable. You need to talk to your doctors and family, and consider all your options, to decide on the plan that's right for YOU.

The February 2006 Research News section was made possible by an unrestricted educational grant from Genentech BioOncology.