Tamoxifen reduces ipsilateral recurrence risk for certain patients with DCIS
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Key takeaways:
- Patients with DCIS who received tamoxifen had a lower 15-year risk for ipsilateral breast cancer recurrence.
- Tamoxifen had no effect on contralateral breast events.
SAN ANTONIO — Tamoxifen lowered overall and invasive ipsilateral recurrence among women with “good-risk” ductal carcinoma in situ who opted for breast conservation surgery without radiation.
Patients who received tamoxifen exhibited a 44% reduction in risk for any ipsilateral recurrence compared with those who did not receive the agent, findings presented at San Antonio Breast Cancer Symposium showed.
“Previously available data were conflicting about how much impact tamoxifen had on invasive DCIS recurrences among patients with favorable prognostic favors, so this finding, in such a robust data set, is clarifying,” Jean L. Wright, MD, chair of the department of radiation oncology at The University of North Carolina at Chapel Hill and Lineberger Comprehensive Cancer Center, said in a press release. “Tamoxifen, radiation or both, as well as the omission of any adjuvant therapy, are all reasonable options. Now, we have more data to help our patients choose among these. The more information we can provide patients about the impact of specific treatments, the more we can empower patients to make choices that are right for them.”
Background and methods
The impact radiotherapy has on ipsilateral recurrence after breast conservation surgery for patients with DCIS has been the subject of extensive research.
The NRG/RTOG 9804 and ECOG-ACRIN E5194 studies — which assessed outcomes for people with DCIS treated with or without radiotherapy — subclassified patients with DCIS into risk groups following breast conservation surgery based on DCIS size, grade and margin width.
For both trials, the “good risk” group included those who had tumors were no larger than 2.5 cm, they had grade 1 or 2 disease, and they had a margin of at least 3 mm.
Both trials tracked the use of tamoxifen, although it was optional during the studies.
At SABCS, Wright reported data from an ancillary analysis of both trials assessing the role of tamoxifen alone on ipsilateral recurrence among good-risk patients who did not receive radiation therapy.
The cohort of 878 people (median age, 59 years) included 317 people from NRG/RTOG 9804 who did not undergo radiation, as well as 561 people deemed to be good risk from ECOG-ACRIN E5194.
Approximately 98% of patients had a margin width of at least 3 mm or negative by re-excision. About half (48.1%) had tumor size less than 5 mm, and 87.5% of patients had grade 1 or grade 2 disease. Slightly less than half (43.1%) had received tamoxifen.
Results, next steps
After median follow-up of 14.85 years, 117 ipsilateral recurrences, 65 invasive ipsilateral recurrences and 52 DCIS events had occurred.
Patients who received tamoxifen exhibited reduced risk for any ipsilateral recurrence (HR = 0.56; 95% CI, 0.38-0.84) or invasive ipsilateral recurrence (HR = 0.49; 95% CI, 0.28-0.84).
Researchers also observed a lower estimated 15-year ipsilateral recurrence rate among those who received tamoxifen (11.4% vs 19%). Further analysis revealed a statistically significant association between tamoxifen and invasive ipsilateral recurrence (P = .0048) but not ipsilateral DCIS recurrence.
Univariable analysis showed associations between reduced risk for ipsilateral recurrence and pathologic size ( 5 mm vs. > 10 mm) and DCIS grade (1 vs. 2).
Tamoxifen did not affect contralateral breast events.
“I found the result [of the agent not affecting contralateral breast events] a little bit surprising,” Wright during a presentation. “I think the main feature that we want to focus on is that this was a group of patients with a very clear inclusion criteria of this ‘good-risk’ DCIS, and even though the definition of good-risk DCIS included patients with up to 2.5 cm of DCIS, we saw in reality that the patients enrolled had very small DCIS. I’m wondering if maybe that is related to the fact that the patients enrolled into these studies had really low-risk features and perhaps just had a lower risk [for] contralateral breast events as compared with a broader population of patients with DCIS.”
References:
- Adjuvant tamoxifen may reduce recurrence risk for patients with ’good risk’ DCIS who forgo radiation (press release). Available at: https://www.aacr.org/about-the-aacr/newsroom/news-releases/adjuvant-tamoxifen-may-reduce-recurrence-risk-for-patients-with-good-risk-dcis-who-forgo-radiation/. Published Dec. 12, 2024. Accessed Dec. 12, 2024.
- Wright JL, et al. Abstract GS2-02. Presented at: San Antonio Breast Cancer Symposium; Dec. 10-13, 2024; San Antonio.
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Wright JL, et al. Abstract GS2-02. Presented at: San Antonio Breast Cancer Symposium; Dec. 10-13, 2024; San Antonio.
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