What are the therapeutic strategies for treatment of lung masses?
Ten percent to 20% of CPAM lesions will decrease in size as the pregnancy progresses. For BPS, ≈66% will decrease in size. For these reasons, if the fetus does not have hydrops or has a CVR well below 1.6, observation with regular monitoring of the mass volume and CVR may be performed.
For masses that approach the CVR 1.6 threshold (typically 1.5) and do not have hydrops, administration of corticosteroids (e.g., betamethasone) to the mother can moderate CPAM growth or cause a reduction in size.
For those lung masses that are very large and cause fetal hydrops, fetal surgery may be performed to remove the mass. In some instances, when the mass has large cystic components, aspiration of the cystic components or placement of a shunt (cyst to amnion) is performed using interventional techniques rather than open surgery. This reduces the size of the mass and can prevent, or reverse, fetal hydrops. These, along with BPS and CPAM masses that are not removed in utero, are recommended for postdelivery removal because of the potential for infection and malignant transformation.
Lung masses that result in fetal hydrops can also produce the “mirror syndrome” (also known as Ballantyne syndrome) in the mother. In these cases, the mother develops symptoms that mirror those of the fetus. These usually include edema (always present) and proteinuria (usually mild). The mirror syndrome can also result from other fetal conditions that result in fetal hydrops.
If the fetal lung mass causes fetal hydrops close to the time of delivery, a therapeutic option is removal of the mass using EXIT. Delivery at centers that can provide neonatal respiratory support is advised for large CPAM and BPS lesions that do not decrease in size but are below the critical CVR ratio.