False-Positive hCG Tests The concept of false-positive hCG tests caused by heterophile antibodies is critical to remember when following patients with molar gestation or GTN. Some assay systems used by commercial laboratories are particularly vulnerable to false-positive tests resulting from the presence of heterophilic antibodies in the test kits they were using (89). For the most part this problem was corrected by adding blocking antibodies to the test systems. Since the hCG molecules in GTN are significantly more degraded or heterogeneous than in normal pregnancy, with higher proportions of free B-hCG, nicked hCG, and B-core fragments, it is important to use an assay that detects both intact hCG and its metabolites and fragments in order to accurately assess the tumor burden (90–92). Additionally, cross-reactivity with luteinizing hormone (LH) can cause confusion when dealing with women in the perimenopausal age group whose hCG level may plateau above assay even when there is no longer active tumor. The use of hormone suppression will suppress LH and prevent unnecessary treatment. False-positive hCG tests caused by heterophile agglutinins or LH release may cause confusion in the diagnosis of early pregnancy, ectopic pregnancy, and so-called phantom choriocarcinoma. When there is concern about the possibility of a false-positive serum hCG test, a urine sample should be tested, because patients with phantom hCG generally have no measurable hCG in a parallel urine sample.
Some patients with molar pregnancy and GTN have persistent (weeks to months) very low levels of real hCG (usually <500 mIU/mL). In these women, extensive radiologic and clinical evaluations fail to reveal any lesions, and chemotherapy is usually not effective. This condition of “real” low-level hCG, where hCG is not hyperglycosylated, is called “quiescent GTN.” These patients should be managed with careful follow-up, because 6% to 10% ultimately will relapse into active disease and rising hCG levels. The risk of relapse to active disease is correlated with the amount of hyperglycosylated hCG. If relapse does occur, chemotherapy usually proves effective (93).
Pregnancies After GTN Patients with GTN who are treated successfully with chemotherapy can expect normal reproduction in the future. Patients who were treated with chemotherapy at the NETDC from 1965 to 2007 had 631 subsequent pregnancies that resulted in 422 term live births (66.9%), 42 preterm deliveries (6.7%), 7 ectopic pregnancies (1.1%), 9 stillbirths (1.4%), and 9 repeat molar pregnancies (1.7%) (94). First-and second-trimester spontaneous abortions occurred in 114 (18.1%) pregnancies. Major and minor congenital malformations were detected in 10 infants (2.1%). Primary cesarean delivery was performed in 81 (21.8%) of 371 subsequent term and preterm births from 1979 to 2007. The frequency of congenital anomalies is not increased, although chemotherapeutic agents have teratogenic and mutagenic potential.
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