Study Overstates Heart Risk From Radiation Therapy for Breast Cancer

GREENBRAE, CA — A 53-year-old breast cancer patient sat in my office last week looking at me nervously.  She had just had a lumpectomy for a Stage I cancer in her right breast. 

“I’m just not sure whether I want to risk radiation,” she said. “I don’t want to be having heart problems because of this 20 years from now.” 

She is one of the millions of women left alarmed and confused about their breast cancer treatment choices because of a recent widely reported study that looked at 2168 women who had radiotherapy for breast cancer between 1958 and 2001. The data showed that a 50-year-old woman with no cardiovascular risk factors has a 1.9 percent chance of dying of heart disease before she turns 80 without radiation therapy, but it rises to between 2.4 percent and 3.4 percent if she has radiation treatment, depending on how much radiation hits the heart. 

Since that study was published, I’ve talked with patients who suddenly are considering forgoing radiation after a lumpectomy, or having a mastectomy instead of lumpectomy, despite having only a small, early stage tumor. I’ve also talked with healthy patients who’ve undergone recent, successful treatment, and now are questioning their choice to have radiation therapy.

Their fear is understandable but misguided—and even dangerous.

The study analyzed data from 1958—practically the Stone Age of radiation therapy—through 2001, 11 years ago. Even at the end point, radiation doses commonly used far exceeded the norm today, and cardiac sparing therapy techniques were not used in the study. To extrapolate the risks found in this study to today’s treatment protocols is an apples-to-oranges comparison that needlessly frightens today’s breast cancer patients. Further, it may lead many women to make decisions that increase their risk of dying of breast cancer significantly, while doing little, if anything, to diminish their risk of dying of heart disease.

The lead investigator even noted some of his study's limitations, saying that “. . . in order to have a long follow-up, we mostly included women who were treated more than 10 years ago. This means that we do not know how today's treatments are affecting women."

That comment should have been highlighted in the news coverage, and with these other important facts:

• With breast conserving surgery alone (without radiation) women have twice the risk of recurrence of their breast cancer within ten years. (Based on a meta-analysis of studies involving more than 10,000 women in the 10 years after surgery, 19.3% who got adjuvant radiation therapy had a cancer recurrence, compared to 35% who didn't have radiation therapy.) 
• By decreasing the risk of a recurrence in the breast, radiation saves lives. For every 100 patients with early breast cancer who decide not to have radiation therapy, three will die needlessly from this cancer. 
• Patients with tumors in their right breasts have almost nothing to worry about, because their hearts get little if any radiation exposure.

Patients need to be told that today’s better equipment and better techniques allow radiation therapy to be equally effective with far lower heart doses than almost any of the patients in the recently published study experienced. The use of heart-sparing radiation techniques (which we helped pioneer here at the Marin Cancer Institute), which are being adopted by more and more cancer centers every year, further reduce this risk. In fact, if this study were repeated starting with women being treated today using heart sparing techniques, I’m confident the cardiac risk would be negligible.

My breast cancer patients face daunting choices, and they are right to consider carefully. But it would be wrong for them to base their decisions on out-of-date information. As even the study’s author concluded, “For now, doctors can tell their patients that radiotherapy is a very important treatment and it should be used. However, they should try to lower the dose of radiation to the heart as much as possible.”

(Dr. Francine Halberg is a radiation oncologist at Marin General Hospital's Marin Cancer Institute and has served on the National Institute of Health's Consensus Development Panel for the Treatment of Early Stage Breast Cancer.)