Low-dose tamoxifen ‘promising’ for highly endocrine-responsive DIN
MedWire News: Women diagnosed with a highly hormone-responsive breast ductal intraepithelial neoplasia (DIN) have a reduced risk for relapse with tamoxifen treatment, , Italian research shows.
In contrast, women with low-expression estrogen receptor (ER) or progesterone receptor (PgR) DIN do not seem to benefit from tamoxifen, report Andrea Decensi and colleagues from the European Institute of Oncology in Milan.
To determine the best treatment for women with DIN, Decensi and team assessed the effect of low-dose tamoxifen on cancer recurrence according to the level of ER and PgR expression.
A total of 309 patients with DIN received low-dose tamoxifen (either 5 mg/day or 20 mg/week) and were compared with 371 DIN patients who received no systemic treatment after surgery.
After a median follow-up of 66 months, the cumulative incidence of breast events did not differ significantly between patients who received tamoxifen and those who did not (13.2% vs 15.8%).
However, patients with highly positive ER and PgR DIN (defined as more than 50% immunostaining on histology) who did not receive tamoxifen had a significant 76% increased risk for breast events, compared with patients with highly positive ER/PgR DIN who did receive tamoxifen. Untreated patients also had a 72% increased risk for breast events compared with all patients with low ER and PgR expression DIN (below 50% immune staining).
Among untreated patients with highly positive ER DIN, recurrence was higher in those who also had highly positive PgR DIN compared with low expression PgR DIN. Conversely, recurrence rates were similar among women who had low expression PgR DIN against which tamoxifen had no effect.
Of note, the researchers observed no difference in endometrial cancer incidence between the groups.
“Although limited by the lack of a randomized comparison, our results support the need for a ‘preventive’ treatment intervention after surgery in women with DIN with both ER and PgR above 50%,” conclude Decensi and co-authors in the Annals of Oncology.
They add: “A phase III trial comparing tamoxifen 5 mg/day versus placebo is currently ongoing in women with DIN to address this issue more definitely.”
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By Laura Dean