Radiation therapy (RT) is more effective for older women with ductal carcinoma in situ (DCIS) in preventing recurrence of ipsilateral breast cancer, according to an article published in the January issue of Lancet Oncology.
In a randomized trial with 1,694 participants, breast cancer recurrence occurred in only 9.9% of women older than 50 who received radiation therapy, compared with 27% of those younger than 50. These findings were among the 10-year outcomes reported in an update of the U.K., Australia, and New Zealand ductal carcinoma in situ (UK/ANZ DCIS) trial, which began in 1990 to evaluate the effectiveness of radiation therapy and tamoxifen in preventing new incidents of breast cancer (Lancet Oncology, Vol. 12:1, pp. 21-29).
More than 1,700 women who received treatment in the U.K., Australia, and New Zealand initially enrolled in the trial, one of the first to compare the effectiveness of postsurgical treatment with radiation therapy only, tamoxifen only, radiation therapy and tamoxifen, or no adjuvant treatment. Patients who underwent radiation therapy received 50 Gy in 25 fractions over five weeks, with no boost at the excision site. Tamoxifen was prescribed at a dose of 20 mg daily for five years.
Initial outcomes of the clinical trial, which closed its enrollment in August 1998, were reported in 2003 at a median of slightly more than four years (52.6 months) (Lancet, 2003, Vol. 362:9378, pp. 95-102). The new update reports on outcomes through September 2008, at a median follow-up of almost 13 years (144.7 months), or more than a total of 18,000 person-years.
New breast incidents in total patient cohort
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The annual rate of breast events as of 2008 was 3.2% for patients who received no adjuvant therapy, 2.2% for those who received tamoxifen only, 1.2% for radiation therapy only, and 0.9% for tamoxifen and radiation therapy together, according to lead author Jack Cuzick, MD, a professor at Cancer Research U.K. Center for Epidemiology, Mathematics, and Statistics in London.
Radiation therapy reduced the incidence of all breast events (hazard ratio, 0.41) both five and 10 years after treatment for ipsilateral invasive disease (hazard ratio at five years, 0.45; hazard ratio at 10 years, 0.32) and ipsilateral DCIS (hazard ratio at five years, 0.36; hazard ratio at 10 years, 0.38). It had no effect on the occurrence of contralateral disease at any time.
Eighty percent of the women enrolled were ages 50 to 64 at the time of treatment, and only 9% were younger than 50. The positive impact of radiation therapy 10 years following treatment was statistically significant for women in both the 50- to 60-year age group and the older-than-60 age group. For each of these older groups, only 9% developed a new breast cancer, compared with 25% of women 50 to 60 years of age and 20% of women older than 60 who did not receive radiation therapy.
The long-term benefit of tamoxifen in reducing local and contralateral new breast cancers was also confirmed with 10-year outcomes, in contrast to the five-year outcomes report, which stated that there was little evidence for the use of tamoxifen by these patients. The authors reported that tamoxifen reduced the incidence of both ipsilateral DCIS and contralateral tumors, but it had no effect on ipsilateral invasive disease. Patients who took tamoxifen had an absolute 10-year reduction of 6.5% for all new breast cancers.
Patients enrolled in the combined treatment arm of both radiation therapy and tamoxifen had the lowest breast cancer recurrence rates, at 3% for ipsilateral DCIS, compared with 5% for patients only receiving radiation therapy and 11% for patients only taking tamoxifen. Rates for invasive ipsilateral breast cancer were 3%, 4%, and 9%, respectively.
By Cynthia E. Keen
AuntMinnie.com staff writer
January 14, 2011
Related Reading
Elderly early-stage breast cancer patients don't need RT, May 21, 2010
Changes in breast density an earlier indicator of tamoxifen efficiency, December 12, 2008
Radiotherapy reduces recurrences after breast-conservation surgery for DCIS, August 30, 2007
Radiotherapy benefits patients with DCIS, July 11, 2003
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