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SAN ANTONIO -- Radiation therapy after breast conservation surgery cut the risk of breast cancer recurrence in patients with low-risk ductal carcinoma in situ (DCIS), according to a prospective randomized trial.

After a 12-year follow up period, 2.8% of patients who received whole-breast radiation therapy (WBRT) experienced local recurrence (95% CI 1.1-5.6), compared with 11.4% (95% CI 7.7-15.8) of patients in the observation group (hazard ratio 0.26, 95% CI 0.13-0.54, P=0.0001), reported Beryl McCormick, MD, of the Memorial Sloan Kettering Cancer Center in New York City.

The incidence of invasive local recurrence after 12 years was 1.5% (95% CI, 0.4-4.0) in women who underwent WBRT and 5.8% (95% CI 3.2-9.5) in those who did not (HR 0.34, 95% CI 0.14-0.85, P=0.016), she reported at the American Society for Radiation Oncology (ASTRO) meeting.

Patients were also given the opportunity to take a selective estrogen receptor modulator (tamoxifen) for 5 years. In multivariable analysis, only WBRT (HR 0.25, 95% CI 0.12-0.53, P=0.0003) and the use of tamoxifen (HR 0.50, 95% CI 0.27-0.91, P=0.024) were associated with reduced local recurrence, she said.

However, there were no significant differences in the likelihood of survival, disease-free survival, or mastectomy use across treatment and observation arms. Additionally, age and pathologic tumor size were not significant for all forms of local recurrence.

"We really feel that, because this is not a life-threatening disease, the patient and her doctor should really use this information for a meaningful patient-doctor discussion about risks, benefits, and the patient's own degree of comfort, which varies greatly," McCormick said. "For many patients, a recurrence risk of 1% per year is not really worrisome, while other patients would really like to do anything they can to not have this come back, including radiation."

One quarter of all new breast cancers in the U.S. are considered DCIS. The current standard treatment includes lumpectomy and radiation therapy to remove the tumor and reduce the likelihood of recurrence. "Good risk" DCIS has been defined as a form of DCIS often found incidentally during a breast biopsy or mammogram, McCormick said.

This study included data from 629 patients from 1999 to 2006. Low-risk patients had tumors of a low or intermediate nuclear grade, ≤2.5 cm, and with margins ≤3 mm. Of these women, 76% were postmenopausal (ages ≥50; average age 58). The mean tumor size was 0.6 cm and a slight majority (56%) of women were diagnosed with grade 2 tumors. The average follow-up time after treatment was 12.4 years.

Sheryl Green, MD, of Mount Sinai Hospital in New York City, said the patients observed in this study were very similar to the women she sees in her practice. Because the researchers used such a long follow-up period, this data is particularly relevant in demonstrating the increased risk of recurrence over time, she said.

Green also noted that many patients faced with this decision may not want to go through with radiotherapy initially, but it's important for them to know the side effects of the alternative anti-estrogen medications. In this study, although 69% of patients indicated they would use tamoxifen, the number of women who ended up receiving this treatment was lower; 58% in the WBRT group and 65% in the observation arm (P=0.05).

"Tamoxifen and those drugs come with side effects, and you're required to take the drug for 5 years. I think the side effect profile can have a significant impact on quality of life and one might argue that people are better off doing short-course radiation," as it offers protection to the breast and patients don't have to the medication, Green told 番茄社区.

McCormick said that she would like to combine these results with an Eastern Cooperative Oncology Group (ECOG) study, which looked at a similar patient population but did not offer radiation therapy. This could help researchers further understand the small difference in local recurrence at 12 years in both studies, particularly with the use of tamoxifen.

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