Author reply

Abstract

We welcome the interesting points raised by Merrie et al. concerning our article on the utilization of polymerase chain reaction (PCR) technology in the detection of solid tumors, published this year in Cancer.1 Merrie et al. point out correctly that we have reported the positivity per sample rather than per patient. As discussed, this can be attributed to the lack of uniformity of the reported data. While all reports clearly stated the reverse transcriptase (RT)–(PCR) positivity per sample, only some also reported on the concurrent positivity per patient. Clearly, the variability of the assay from patient to patient as well as for the same patient at different periods of time is of great interest, as it would more accurately reflect the sensitivity and the reproducibility of the assay. With regard to the t(11;22) translocations, Merrie et al. again correctly indicate that these tumors are now to be regarded as a member of the family of small round cell neoplasms of bone and soft tissue generically known as primitive neuroectodermal tumors (PNETs). However, some authors still prefer the distinction between the various members of the PNET family.2 Because PNET tumors exhibit solidarity in harboring the t(11;22) mutation, they would have a positive RT-PCR assay. This denotes perhaps an absolute requirement for the t(11;22) mutation for tumorigenesis in these tumors. Of note, in an recent article, the t(11;22) mutation was reported to have been detected in 2 of 12 typical neuroblastomas by the PCR assay.3 Thus, we stand by our earlier contention that the t(11;22) mutation, while highly sensitive, is not restricted to PNET tumors, and thus not absolutely specific. We agree that keratins and cytokeratins are the same entity as classified by Moll's catalogue system. We reported them as keratins or cytokeratins based on the original author's description. The utility of various breast tumor markers is under active investigation and still evolving. Clearly, traditional breast tissue markers lack specificity for the disease. We are still not aware of any published data that demonstrate maspin gene expression in normal peripheral blood. Merrie et al. also report their unpublished data on the detection of occult tumors. In our article, we presented a state-of-the-art review of the utility of PCR in the detection of solid tumors. Indeed, in the year since the acceptance of our article, more than 78 additional original articles have been published on the application of this technology for various tumors. This is an exciting area of research, and we strongly feel that these and ongoing studies will clarify the utility of PCR for detecting solid tumors. We appreciate their interest in our research in this dynamic field. Ganesh Raj M.D., Ph.D.*, Jose G. Morena M.D. , Leonard G. Gomella M.D. , * Division of Urology, Duke University Medical Center, Durham, North Carolina, Department of Urology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania