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.

    然而此項研究并沒有回答具體原因

    11月9日星期一，今日健康新聞（HealthDay News）   

一項新的研究顯示，乳癌術后的婦女，同側乳房密度高的乳癌復發的風險性高。乳房的密度與乳癌的復發有著一定的關系，專家認為密度高的乳房在乳癌術后其原發病灶復發的風險性加大。加拿大研究人員經過10年的隨訪調查于11月9日和12月15日在網上發表了上述見解，他們認為這種懷疑與猜測是正確的。Cristy Russell（南加州Keck醫學院醫學副教授和美國癌癥協會發言人）,他說："這項實驗很有意義因為它研究了很長的時間，如果你乳癌術后未曾接受放射治療，復發與否乳房的密度會起著決定性作用。"目前，放射治療是乳癌保守治療及乳癌切除術后采取的主要手段。Steven Narod醫生（Dalla Lana公共衛生學院、多倫多大學女子學院研究所的教授）最新研究了335名乳癌患者，并不是所有乳癌切除術后的患者都在患側乳房接受了放射治療。研究人員評估了自1987年至1998年接受乳癌手術患者的醫療記錄，他們對這些婦女進行了10年的隨訪表明：癌腫易于在患側乳房復發。

    研究人員根據乳房的密度把這些婦女分為三組：低、中、高，按平均年齡劃分：63歲在低密度組，58歲在中密度組，55歲在高密度組。專家全面評估了那些患有乳癌并接受外科保守治療同時結合放射治療的患者---都接受標準的護理，在10年中同側乳房有10%復發的風險。最新研究發現，乳房密度越高乳癌復發的風險就越大，經過10年的隨訪，那些在高密度組的患者同側乳房復發率為21%,而低密度組乳癌復發率只為5%.在研究中并不是所有婦女都接受了放射治療，Narod的研究小組對那些接受放射治療和未接受放射治療的患者作比較時發現，未接受放射治療的復發率為22%,那些接受放射治療的復發率為10%.婦女乳房密度高而未接受放射治療復發的風險為40%,34名低密度乳房的乳癌婦女沒有接受放射治療而無一例在同側復發。Narod表明這相研究結果僅限于局部復發，不包括遠處轉移和死亡病例，他還希望重復這項研究結果以更好地解釋這種現象。

    這項研究結果引發兩個問題，根據Cristy Russell的觀點，如果你做了乳癌切除術且乳房密度低，問題是，難道你就不作放射治療了嗎？另一個問題是，隨著新放射治療技術的進展，大多病人采取局部放射治療從而替代傳統的全乳放射治療，他還建議那些密度乳房高的乳癌患者可以強烈要求做全乳放射治療。Cristy Russell又補充說，研究的都是乳癌患者，對非乳癌患者還不能早下此結論。

    Narod說，雖然還需要做進一步的相關研究，大多數婦女可能不知道她們自己的乳房密度，她們可以請教自己的醫生。