Reply to Letter to the Editor: The Outcome of Expectant Management of Congenital Cystic Adenomatoid Malformation of the Lung

To the Editor,

We thank [the contributors] for their interest in our study into what is widely acknowledged to be a controversial issue. The letter highlights some of the practical difficulties inherent in studying the topic of conservative management of asymptomatic CCAM and we will attempt to address each issue in turn.

With conservative management there is no histopathological confirmation possible and hence, to avoid the possibility of studying those with an incorrect diagnosis, only cases confirmed by CT imaging or those with histopathological confirmation (following resection or post-mortem examination) were included. CT has previously been demonstrated to have a 100% sensitivity for CCAM compared to the much lower sensitivity of traditional chest X-ray, which tended to be employed in the region during the first epoch [1]. This is a difficulty inherent to a retrospective study over a period when there has been a change in imaging practice. If we had included those cases ‘confirmed’ postnatally only by chest X-ray, then we could have rightly been criticized for drawing conclusions about the antenatal diagnosis and expectant management of lesions which may well have not been CCAM. Indeed, if those cases had been included, the estimate of the population-based incidence of CCAM would have been significantly higher (about 1 in 11 000 live births) and hence the percentage of live-born children with CCAM remaining asymptomatic without resection would also be significantly greater – effectively increasing the number needed to treat to avoid each complication resulting from leaving the lesion in situ (i. e. expectant management).

It is well recognised that some lesions identified antenatally as CCAM may regress or remain asymptomatic throughout life. Others, however, present with symptoms despite apparently unremarkable antenatal scans. Multiple databases covering the Northern region were therefore searched to ensure that case ascertainment was optimized and that we were not only examining cases presenting to surgeons. We were therefore able to include cases of pre- and perinatal deaths identified at post-mortem examination and cases not referred to the surgical service, thereby giving a fuller picture of the natural history of CCAM. It is self-evident that a retrospective review of surgically-treated cases, as reported by Conforti et al., would fail to identify any cases of pre- or perinatal mortality as these cases do not reach surgery [2]. Nonetheless, we recognise that in our region the rate of termination of pregnancy is greater than in some others. In terms of antenatal counselling, we agree that the evidence does not support medical termination of pregnancy in most cases with antenatally diagnosed CCAM.

Our study attempted to retrospectively evaluate the sensitivity of prenatal ultrasound in detecting CCAM. All cases with an antenatal diagnosis of CCAM were included (n=26; true positive) and there were also symptomatic cases diagnosed in the postnatal period in whom antenatal scanning had failed to identify a CCAM (n=8; false negative). Contrary to the contributors’ letter we believe this allows the sensitivity to be calculated as 76%. We accept that if those cases diagnosed by chest X-ray had been included, then this would have increased the numbers available for study, but this modality is inadequate to confirm the diagnosis. Despite the suggestion to the contrary, we specifically included cases which had been diagnosed antenatally as CCAM but were postnatally demonstrated to be CDH (n=5), BPS (n=1), CLE (n=2) or no abnormality (n=5). The contributors are correct to point out that those cases without an antenatal or postnatal diagnosis of CCAM were excluded, as these were not the conditions being studied and there had never been any suggestion clinically that these lesions represented CCAM.

Conforti et al. suggest that resecting asymptomatic, compared with symptomatic, CCAMs is associated with fewer complications and that this justifies subjecting these babies to surgical resection [2]. In our study, 45% of live-born children with CCAM were managed non-operatively and hence any perioperative complication in these individuals is potentially avoidable. In our series of symptomatic resections, the rate of perioperative complications was comparable to that of other published series. If the same argument was applied to all those with small asymptomatic multicystic dysplastic kidneys, many children would be subjected to unnecessary surgery.

Lastly, we would like to emphasize that the conclusion to our study was that an assessment of the number needed to treat to prevent each malignant/infective complication must involve large prospective studies of asymptomatic neonates with an antenatal diagnosis of CCAM, particularly when postnatal imaging shows the lesion to be small. These studies are currently ongoing and we would encourage clinicians to recruit patients so that with time a clearer evidence base will inform our practice [3]. However, until then we would advocate having an honest discussion with parents on the lack of definitive evidence to support expectant or pre-emptive management.

Yours sincerely,

P. Hammond, J. Devdas, B. Ray, M. Ward-Platt, M. Barrett, M. McKean

References

• 1 Calvert JK, Boyd PA, Chamberlain PC. et al . Outcome of antenatally suspected congenital cystic malformation of the lung: 10 years experience 1991–2001.  Arch Dis Child Fetal Neonatal Ed. 2006;  91 F26-F28
• 2 Conforti A, Atul I, Trucchi A. et al . Asymptomatic congenital cystic adenomatoid malformation of the lung: Is it time to operate?.  J Thorac Cardiovasc Surg. 2009;  138 826-830
• 3 http://www.bpold.co.uk

Correspondence