Reply to: Prospective trial comparing full-field digital mammography (FFDM) versus combined FFDM and tomosynthesis in a population-based screening programme using independent double reading with arbitration

by Per Skaane (perska@ous-hf.no)

Skaane P, Bandos AI, Gullien R et al. (2013) Prospective trial comparing full-field digital mammography (FFDM) versus combined FFDM and tomosynthesis in a population-based screening programme using independent double reading with arbitration. Eur Radiol 23: 2061.

Dear Editor,

We thank Ana Rosengurtt for having read our article [1] “with great interest”, and the Editor of European Radiology for giving us the opportunity to respond to this letter.

This letter raises some questions of interest to the breast imaging community regarding our article, and other issues not relevant to our paper. We would comment primarily on those issues of relevance.

First, to make one statement absolutely clear: The Oslo Tomosynthesis Screening Trial OTST (ClinicalTrials.govNCT01248546) was approved by the Norwegian REK (Regional Committee for medical and health ethics research) on February 16th, 2010. All consenting participants in the trial had signed a written informed consent.

Ethical committees in different countries have different review criteria and different thresholds as to what is considered ethical. The cost and risk of each study has to be assessed by the potential benefit to participants and to society as a whole, and we as investigators and all women should be thankful that this is exactly what the committee did and determined that the study is indeed, ethical, worthwhile and has satisfactory risk and cost benefit ratios to approve it.

The concern of Ana Rosengurtt is the doubling of radiation dose which might increase the risk of radiation-induced breast cancer, and would be hard to justify ethically. To avoid any misunderstanding: we absolutely agree that a doubling of the radiation dose to healthy women in a breast cancer screening programme would add some risk but it always has to be reviewed and considered in the context of possible benefit as well.

In our trial, the incremental risk from a very small, one time, additional radiation dose is extremely small compared with the expected benefits including but not limited to mortality reduction achievable through screening. This dose should certainly not be a deterrent from mammography screening taking place at 1- or 2-year intervals [2, 3]. More important, this dose should not be a deterrent from comprehensively assessing new technologies that may significantly improve our practices and as a result screening outcome. Actually, it would have been quite unethical to use clinically new technology (namely, in our study breast tomosynthesis) before it was demonstrated that it is at a minimum equal in diagnostic performance to the current one (namely, full-field digital mammography FFDM). Paired study designs in which participants undergo both procedures are common and extremely efficient in demonstrating effectiveness and efficacy and have been used in this and many other fields in the past. For example, three of the four initial prospective trials carried out more than a decade ago comparing screen-film mammography (SFM) and FFDM had a “paired study design” in which the women underwent both SFM and FFDM [4-6]. Similarly, the first three studies comparing tomosynthesis (“3D mammography”) with the “old standard” FFDM had applied the needed additional radiation exposure [1,7,8]. Only time and experience will tell whether or not synthetic 2D images reconstructed from the tomosynthesis data set would be used in the future rather than the “double exposure”, thus keeping the radiation dose at a similar level to FFDM alone.

Many of the radiation exposure related points by Ana Rosengurtt are general and have little or no relevance to our article: women with breast implants were excluded from our trial as clearly stated in our paper; women with known BRCA mutations are enrolled in a special MRI based screening program in our country; and the risk of ischemic heart disease from mammographic screening is hardly even of theoretical interest. All of these issues have little relevance to our paper.

We do not believe that this screening trial should constitute an opportunity to raise and reassess radiation risk related issues in medical imaging in general and in breast imaging in particular.

If you would like to comment on this letter, please send your comments together with full contact data to office@european-radiology.org. Replies and comments will be reviewed by the Editorial Office and published on this website.