数字化乳腺断层合成又称三维乳腺钼靶，可将数字化乳腺钼靶二维影像通过计算机合成三维影像，是乳腺钼靶的又一次进步，并且可能克服标准数字化乳腺钼靶的局限性。以往的病例对照回顾研究结果表明，数字化乳腺断层合成与数字化乳腺钼靶相比，乳腺癌筛查检出率显著提高。不过，病例对照回顾研究的说服力不足。
挪威乳腺癌筛查计划自1996年起免费向全国年龄50～69岁女性提供每两年一次的双体位（头足轴位和内外侧斜位）乳腺钼靶筛查，由双人分别读片并统一意见。
该平行分组随机对照研究对2016～2017年卑尔根地区参加挪威乳腺癌筛查计划的全部32976例女性进行入组征询。通过研究专用软件，根据参加者身份证号码，将女性按1∶1进行简单随机化，分入三维组或二维组。女性同意入组后，由门诊放射技师录入身份证号码，由软件按照算法进行随机化。女性同意入组时，女性和放射技师对随机化双盲；入组期间，放射技师对该随机化算法单盲。入组结束后12个月收集分析所需全部数据。主要结局指标为乳腺癌筛查检出率，根据筛查技术（即三维和二维）进行分层。通过对数二项回归模型，计算入组期间筛查女性筛查检出乳腺癌的的未校正风险比和95%置信区间，比较三维与二维的效果。
结果，2016年1月14日～2017年12月31日，卑尔根地区44266例女性被邀请参加乳腺癌筛查计划，其中32976例（74.5%）参加筛查。剔除有乳房植入物的女性和不同意参加研究的女性后，29453例（89.3%）符合条件进行软件随机化。其中，14734例被分入三维组，14719例被分入二维组。随机分组后，剔除有乳腺癌史女性（三维组314例，二维组316例）、黑色素瘤转移女性（三维组1例）以及同意入组后告诉放射技师有乳房症状女性（三维组39例，二维组34例），对其余28749例女性（三维组14380例，二维组14369例）进行分析。
两组筛查女性相比，乳腺癌筛查检出率相似：
三维组：0.66%（95%置信区间：0.53～0.79）
二维组：0.61%（95%置信区间：0.48～0.73）
风险比：1.09（95%置信区间：0.82～1.46，P=0.56）
因此，该大样本随机对照研究结果表明，对于大量女性人口的乳腺癌筛查，数字化乳腺断层合成（包括二维乳腺钼靶合成）与标准数字化乳腺钼靶相比，乳腺癌筛查检出率并未显著提高，故有必要进行经济学分析、间隔癌和连续筛查检出乳腺癌随访研究，以更好地了解数字化乳腺断层合成对于大量女性人口乳腺癌筛查的效果。
对此，瑞典隆德大学斯科讷医院发表同期评论：断层合成用于乳腺癌筛查是否众望所归？
Lancet Oncol. 2019 May 8. [Epub ahead of print]
Two-view digital breast tomosynthesis versus digital mammography in a population-based breast cancer screening programme (To-Be): a randomised, controlled trial.
Solveig Hofvind, Asne S Holen, Hildegunn S Aase, Nehmat Houssami, Sofie Sebuodegard, Tron A Moger, Ingfrid S Haldorsen, Lars A Akslen.
Cancer Registry of Norway, Oslo, Norway; Oslo Metropolitan University, Oslo, Norway; Haukeland University Hospital, Bergen, Norway; University of Bergen, Bergen, Norway; University of Sydney, Sydney, NSW, Australia; University of Oslo, Oslo, Norway.
BACKGROUND: Digital breast tomosynthesis is an advancement of mammography, and has the potential to overcome limitations of standard digital mammography. This study aimed to compare first-generation digital breast tomo-synthesis including two-dimensional (2D) synthetic mammograms versus digital mammography in a population-based screening programme.
METHODS: BreastScreen Norway offers all women aged 50-69 years two-view (craniocaudal and mediolateral oblique) mammographic screening every 2 years and does independent double reading with consensus. We asked all 32976 women who attended the programme in Bergen in 2016-17, to participate in this randomised, controlled trial with a parallel group design. A study-specific software was developed to allocate women to either digital breast tomosynthesis or digital mammography using a 1:1 simple randomisation method based on participants' unique national identity numbers. The interviewing radiographer did the randomisation by entering the number into the software. Randomisation was done after consent and was therefore concealed from both the women and the radiographer at the time of consent; the algorithm was not disclosed to radiographers during the recruitment period. All data needed for analyses were complete 12 months after the recruitment period ended. The primary outcome measure was screen-detected breast cancer, stratified by screening technique (ie, digital breast tomosynthesis and digital mammography). A log-binomial regression model was used to estimate the efficacy of digital breast tomosynthesis versus digital mammography, defined as the crude risk ratios (RRs) with 95% CIs for screen-detected breast cancer for women screened during the recruitment period. A per-protocol approach was used in the analyses. This trial is registered at ClinicalTrials.gov, number NCT02835625, and is closed to accrual.
FINDINGS: Between, Jan 14, 2016, and Dec 31, 2017, 44266 women were invited to the screening programme in Bergen, and 32976 (74.5%) attended. After excluding women with breast implants and women who did not consent to participate, 29453 (89.3%) were eligible for electronic randomisation. 14734 women were allocated to digital breast tomosynthesis and 14719 to digital mammography. After randomisation, women with a previous breast cancer were excluded (digital breast tomosynthesis group n=314, digital mammography group n=316), women with metastases from melanoma (digital breast tomosynthesis group n=1), and women who informed the radiographer about breast symptoms after providing consent (digital breast tomosynthesis group n=39, digital mammography group n=34). After exclusions, information from 28749 women were included in the analyses (digital breast tomosynthesis group n=14380, digital mammography group n=14369). The proportion of screen-detected breast cancer among the screened women did not differ between the two groups (95 [0.66%, 0.53-0.79] of 14380 vs 87 [0.61%, 0.48-0.73] of 14369; RR 1.09, 95% CI 0.82-1.46; p=0.56).
INTERPRETATION: This study indicated that digital breast tomosynthesis including synthetic 2D mammograms was not significantly different from standard digital mammography as a screening tool for the detection of breast cancer in a population-based screening programme. Economic analyses and follow-up studies on interval and consecutive round screen-detected breast cancers are needed to better understand the effect of digital breast tomosynthesis in population-based breast cancer screening.
FUNDING: Cancer Registry of Norway, Department of Radiology at Haukeland University Hospital, University of Oslo, and Research Council of Norway.
DOI: 10.1016/S1470-2045(19)30161-5
Lancet Oncol. 2019 May 8. [Epub ahead of print]
Tomosynthesis in breast screening: great expectations?
Sophia Zackrisson.
Skane University Hospital, Lund University, Malmo, Sweden
DOI: 10.1016/S1470-2045(19)30287-6
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