RSF1 and Not Cyclin D1 Gene Amplification May Predict Lack of Benefit from Adjuvant Tamoxifen in High-Risk Pre-Menopausal Women in the MA.12 Randomized Clinical Trial

Most women with estrogen receptor expressing breast cancers receiving anti-estrogens such as tamoxifen may not need or benefit from them. Besides the estrogen receptor, there are no predictive biomarkers to help select breast cancer patients for tamoxifen treatment. CCND1 (cyclin D1) gene amplification is a putative candidate tamoxifen predictive biomarker. The RSF1 (remodeling and spacing factor 1) gene is frequently co-amplified with CCND1 on chromosome 11q. We validated the predictive value of these biomarkers in the MA.12 randomized study of adjuvant tamoxifen vs. placebo in high-risk premenopausal early breast cancer. Premenopausal women with node-positive/high-risk node-negative early breast cancer received standard adjuvant chemotherapy and then were randomized to tamoxifen (20 mg/day) or placebo for 5 yrs. Overall survival (OS) and relapse-free survival (RFS) were evaluated. Fluorescent in-situ hybridization was performed on a tissue microarray of 495 breast tumors (74% of patients) to measure CCND1 and RSF1 copy number. A multivariate Cox model to obtain hazard ratios (HR) adjusting for clinico-pathologic factors was used to assess the effect of these biomarkers on Os and RFS. 672 women were followed for a median of 8.4 years. We were able to measure the DNA copy number of CCND1 in 442 patients and RSF1 in 413 patients. CCND1 gene amplification was observed in 8.7% and RSF1 in 6.8% of these patients, preferentially in estrogen receptor-positive breast cancers. No statistically significant interaction with treatment was observed for either CCND1 or RSF1 amplification, although patients with high RSF1 copy number did not show benefit from adjuvant tamoxifen (HR = 1.11, interaction p = 0.09). Unlike CCND1 amplification, RSF1 amplification may predict for outcome in high-risk premenopausal breast cancer patients treated with adjuvant tamoxifen.多数接受他莫昔芬等抗雌激素治疗的雌激素受体阳性乳腺癌患者，可能无需接受该治疗或无法从中获益。除雌激素受体外，目前尚无可用的预测生物标志物来辅助筛选适合他莫昔芬治疗的乳腺癌患者。CCND1（细胞周期蛋白D1，cyclin D1）基因扩增是一种潜在的他莫昔芬预测生物标志物候选物。而RSF1（重塑与间隔因子1，remodeling and spacing factor 1）基因常与11号染色体长臂上的CCND1发生共扩增。我们在MA.12随机对照研究中验证了这些生物标志物的预测价值，该研究针对高危绝经前早期乳腺癌患者，比较了辅助他莫昔芬与安慰剂的治疗效果。淋巴结阳性/高危淋巴结阴性的绝经前早期乳腺癌患者先接受标准辅助化疗，随后被随机分配至他莫昔芬组（每日20mg）或安慰剂组，治疗时长为5年。研究对总生存期（overall survival, OS）与无复发生存期（relapse-free survival, RFS）进行了评估。对495例乳腺癌组织标本（覆盖74%的入组患者）的组织微阵列实施荧光原位杂交（Fluorescent in-situ hybridization），以检测CCND1与RSF1的拷贝数。采用校正临床病理因素的多因素Cox比例风险模型计算风险比（hazard ratio, HR），以评估这些生物标志物对OS与RFS的影响。共对672例女性患者进行了随访，中位随访时间为8.4年。我们在442例患者中成功检测到CCND1的DNA拷贝数，在413例患者中成功检测到RSF1的DNA拷贝数。其中8.7%的患者存在CCND1基因扩增，6.8%的患者存在RSF1基因扩增，且这两类扩增更常见于雌激素受体阳性乳腺癌患者中。未观察到CCND1或RSF1扩增与治疗存在具有统计学意义的交互作用；不过，高RSF1拷贝数患者并未从辅助他莫昔芬治疗中获益（HR=1.11，交互P=0.09）。与CCND1扩增不同，RSF1扩增或可预测接受辅助他莫昔芬治疗的高危绝经前早期乳腺癌患者的预后结局。