Reply to Letter to the Editor: Six-year prospective evaluation of second look US with volume navigation for MRI detected additional breast lesions.

by Alfonso Fausto and Maria Antonietta Mazzei (afausto@sirm.org)

Six-year prospective evaluation of second-look US with volume navigation for MRI-detected additional breast lesions

Dear Editor,

We were very interested to read the letter from Dr. Erkin Aribal comprising an intriguing comment on our article [1]. Nevertheless, we feel it is important to note several inaccuracies of interpretation in it.

Firstly, we should like to stress the fact that, as shown in Table 2, in our study 76% (549/722) of the additional lesions detected with contrast-enhanced breast MRI proved visible on second-look US, while for 21% (151/722)—and not 87.3% as stated in Dr. Aribal’s letter—the performance of second-look US with MRI Volume Navigation (V Nav) was required to obtain the histological proof.

Moreover, in the course of the follow-up, the administration of contrast medium three times before obtaining diagnostic definition was required in only one patient: hence in 0.7% of the cases, 1/151, and not 12.7% of patients as reported in the letter. We do not feel that this frequency—namely 1 lesion in 1 patient in 6 years—can be considered relevant.

It should also be stressed that the rate of re-biopsy of US-guided biopsy was 0.5% of the cases, 3/549, which, compared with that of the US-guided biopsy with V Nav, proves insignificant (p=ns).

As regards the question of MRI-guided biopsy, it is important to clarify what is reported in our article: that 3% (22/722) of all additional lesions detected with breast MRI, negative at second-look US, were subjected directly to MRI-guided biopsy since they were cases of breast hypertrophy.

Finally, the hypothesis of performing a supplemental supine sequence (i.e. T1-weighted without fat suppression or without the chance to obtain a subtraction) after the dynamic study in prone position, could seem reasonable, irrespective of the number of cases verified in our study. However, in our opinion, this could present two different problems:

  1. This sequence would be performed more than 10’ after the administration of the contrast medium. This would make it impossible to detect lesions with wash-out, especially if situated in the mammary gland, which is highly enhanced by the contrast medium only in a delayed manner, as demonstrated in other studies [2-4].
  2. It would be necessary to place fiduciary markers in all the patients undergoing breast MRI examination, since it is impossible to know in advance which have to undergo supine reassessment for the V Nav biopsy. Moreover, the suggested absence of fat subtraction or suppression would prevent visualisation of nuanced impregnations of contrast medium in the breast tissue and adipose tissue.

As reported in our study [1], US-guided biopsies with V Nav were performed both when the lesions were visible in the US and MRI images and when they were visible only in the MRI images.

We should like to conclude this letter with a last consideration stemming from these interesting observations. Perhaps a complete change of perspective could be useful: performing the breast MRI with contrast medium directly in a supine position, as suggested by Siegler P et al [4]. Such a change of paradigm would definitely save MRI room time and save on the administration of contrast media.

Only further studies will tell us whether the two MRIs are equivalent in terms of diagnostic efficacy and feasibility.