By Lynda Williams, medwireNews Reporter
medwireNews: Research indicates that women with triple-negative breast cancer (TNBC) might benefit from low-dose tamoxifen to reduce the risk of recurrent or new primary disease.
“Although SBE [subsequent in-breast event] incidence is low, the findings suggest that chemoprevention may be reasonable for patients with TNBC because approximately one-third (30.1% in this cohort) of the neoplasms will be HR [hormone receptor]-positive”, report Lisa Newman (Weill Cornell Medicine, New York, USA) and co-workers in JAMA Surgery.
The team questioned the assumption that TNBC patients will not benefit from the adjuvant endocrine therapy to prevent subsequent malignancies because further events “are expected to recapitulate the biomarker expression of the first cancer regardless of whether the SBE represents a new primary tumor (in either breast) or a true local recurrence.”
The team collated medical records for 597 women aged a median 56 years who were diagnosed with nonmetastatic TNBC between 1998 and 2017 at their institution. Among the 552 patients with data available, most were White (71.2%) or Black (15.6%), and 30.1% of the 229 patients who had undergone genetic testing were diagnosed with a BRAC1/2 mutation.
Overall, 91.4% of 570 primary tumours were invasive ductal carcinoma, 87.8% of 458 were stage T1 or T2, and 75.7% of 457 were node negative. Data for 559 patients showed that 74.8% underwent primary surgery and 23.6% received neoadjuvant chemotherapy, with 64.8% of patients initially aiming for lumpectomy and 42.2% ultimately undergoing mastectomy; 21.2% underwent contralateral prophylactic mastectomy.
Adjuvant therapy consisted of chemotherapy for 65.3% of 476 patients and radiation for 69.9% of 468 patients.
Over a median 5.88 years of follow-up, 16.3% of 582 women were documented to have an SBE a median 2.74 years after their original diagnosis, and 17.9% of the SBEs were contralateral. The 5-year overall survival rate was 93.5%.
Newman and co-authors report that the risk of SBE in the women was not related to their race or ethnicity, their tumour histology, or the sequence of treatment they received.
Of 93 SBEs assessed, 68.4% were negative for both oestrogen and progesterone receptors, 24.2% were oestrogen receptor positive and 19.0% were progesterone positive. Just six of 94 SBEs were ductal carcinoma in situ but four of these were HR-positive.
The researchers note that the median time to develop an HR-negative SBE was 2.37 years versus 3.60 years for an oestrogen receptor-positive SBE and 4.48 years for a progesterone-positive SBE.
The 5-year incidence of SBE was 15% overall, 10% for HR-negative disease and 4% for HR-positive SBE, they calculate.
“Studies of low-dose tamoxifen for chemoprevention suggest preserved risk-reducing benefits with favorable tolerance”, the authors comment.
“Furthermore, the TNBC phenotype is based on lack of expression for ER α”, they say, and “ongoing translational research suggests tamoxifen therapy may be associated with improved outcomes in TNBC expressing ER β.”
The team concludes: “These findings are hypothesis-generating”, adding that “[a]dditional studies of HR expression in SBE after TNBC are warranted.”
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JAMA Surg 2025; 12 March