By Kathleen Doheny

HealthDay Reporter

MONDAY, Nov. 9 （HealthDay News） -- After a lumpectomy, women with very dense breasts have a higher risk of cancer recurrence in the affected breast, a new study shows.

Breast density has already been linked with an increased risk of developing breast cancer, and experts have suspected that very dense breasts may also be associated with an increased risk of cancer recurrence at the site of the original cancer after lumpectomy.

The Canadian study, which involved a 10-year follow-up and is published online Nov. 9 and in the Dec. 15 print issue of Cancer, suggests those suspicions are correct.

"This trial is interesting because it is over such a long period of time," said Dr. Christy Russell, an associate professor of medicine at the University of Southern California Keck School of Medicine and spokeswoman for the American Cancer Society. "It's a very interesting study saying if you don't radiate after lumpectomy, density plays a large role in having a recurrence in the same breast."

Currently, radiation is typically given after breast-conserving surgery, or lumpectomy.

But not all of the 335 patients in the latest study had radiation after lumpectomy for their invasive breast cancer. Led by Dr. Steven Narod, a professor at the Dalla Lana School of Public Health, Women's College Research Institute, University of Toronto, the researchers evaluated the medical records of the women, who had undergone lumpectomy from 1987 through 1998. They followed-up with the women for 10 years to see which women experienced a recurrence of the cancer in the same breast.

The researchers categorized the women into three groups depending on breast density: low, intermediate or high. The average age for each group was: 63 years in the low-density group; 58 in the intermediate group; and 55 in the high-density group.

Overall, experts estimate that women with invasive breast cancer treated with breast-conserving surgery and radiation -- the current standard of care -- have a 10 percent risk of recurrence at the same site at 10 years.

In the new study, women with the highest density had the highest risk of recurrence, the researchers found. Over the 10-year follow-up, those in the highest breast-density category had a 21 percent chance of cancer coming back in the same breast, while those who had the least-dense breasts had just a 5 percent chance.

Not all the women in the study had radiation after the lumpectomy. When Narod's team compared recurrence between women who had radiation and those who didn't, overall, 22 percent of those who didn't receive radiation had recurrence, but 10 percent of those who did receive radiation had recurrence.

The women with highly dense breasts who didn't receive radiation had a 40 percent risk of recurrence, but none of the 34 women with low breast density and no radiation treatment had recurrence at the same site.

The results are for local recurrence, "not for distant recurrence or death," Narod noted.

Next, Narod hopes to repeat the findings and "to find out what it is about breast density that explains this phenomenon."

The study results raise two issues, according to Russell. "If you have a lumpectomy and you have very low [breast] density, the question is, 'Can you avoid radiation?'

"The other point [raised by the new findings] is that there are newer techniques of radiation therapy coming along, much more localized [than traditional whole-breast radiation]," she said. Women with high-density breasts may want to strongly consider whole-breast radiation, Russell suggested.

Women in the study all had invasive breast cancer, Russell added, so the findings don't apply to earlier, noninvasive cancers.

Most women probably don't know about the density of their breasts, Narod said. They can ask their physician, although more study is needed on the association, he said.

More information

To learn more about breast density, visit the American Cancer Society.

然而此项研究并没有回答具体原因

11月9日星期一，今日健康新闻（HealthDay News）

一项新的研究显示，乳癌术后的妇女，同侧乳房密度高的乳癌复发的风险性高。乳房的密度与乳癌的复发有着一定的关系，专家认为密度高的乳房在乳癌术后其原发病灶复发的风险性加大。加拿大研究人员经过10年的随访调查于11月9日和12月15日在网上发表了上述见解，他们认为这种怀疑与猜测是正确的。Cristy Russell（南加州Keck医学院医学副教授和美国癌症协会发言人）,他说："这项实验很有意义因为它研究了很长的时间，如果你乳癌术后未曾接受放射治疗，复发与否乳房的密度会起着决定性作用。"目前，放射治疗是乳癌保守治疗及乳癌切除术后采取的主要手段。Steven Narod医生（Dalla Lana公共卫生学院、多伦多大学女子学院研究所的教授）最新研究了335名乳癌患者，并不是所有乳癌切除术后的患者都在患侧乳房接受了放射治疗。研究人员评估了自1987年至1998年接受乳癌手术患者的医疗记录，他们对这些妇女进行了10年的随访表明：癌肿易于在患侧乳房复发。

研究人员根据乳房的密度把这些妇女分为三组：低、中、高，按平均年龄划分：63岁在低密度组，58岁在中密度组，55岁在高密度组。专家全面评估了那些患有乳癌并接受外科保守治疗同时结合放射治疗的患者---都接受标准的护理，在10年中同侧乳房有10%复发的风险。最新研究发现，乳房密度越高乳癌复发的风险就越大，经过10年的随访，那些在高密度组的患者同侧乳房复发率为21%,而低密度组乳癌复发率只为5%.在研究中并不是所有妇女都接受了放射治疗，Narod的研究小组对那些接受放射治疗和未接受放射治疗的患者作比较时发现，未接受放射治疗的复发率为22%,那些接受放射治疗的复发率为10%.妇女乳房密度高而未接受放射治疗复发的风险为40%,34名低密度乳房的乳癌妇女没有接受放射治疗而无一例在同侧复发。Narod表明这相研究结果仅限于局部复发，不包括远处转移和死亡病例，他还希望重复这项研究结果以更好地解释这种现象。

这项研究结果引发两个问题，根据Cristy Russell的观点，如果你做了乳癌切除术且乳房密度低，问题是，难道你就不作放射治疗了吗？另一个问题是，随着新放射治疗技术的进展，大多病人采取局部放射治疗从而替代传统的全乳放射治疗，他还建议那些密度乳房高的乳癌患者可以强烈要求做全乳放射治疗。Cristy Russell又补充说，研究的都是乳癌患者，对非乳癌患者还不能早下此结论。

Narod说，虽然还需要做进一步的相关研究，大多数妇女可能不知道她们自己的乳房密度，她们可以请教自己的医生。