Introduction: Therapeutic approaches to lung cancer are evolving, with personalized therapy, based on "molecular analysis" of tumors being developed. Given that approximately 90% of patients will not undergo surgery for their disease, an ability to apply these tests to small samples obtained at the time of initial pathological diagnosis is desirable. Studies in this area have produced variable results, and the minimum area of tumor tissue required for analysis has not been defined. Furthermore, such assays have not been widely applied to cytology specimens, which may be the only source of diagnostic material in many cases.
Methods: Routinely processed biopsy and cytology specimens were microdissected to enrich for tumor cells, followed by RNA extraction using QIAGEN RNeasy kit and cDNA synthesis/reverse-transcriptase polymerase chain reaction for genes including beta-actin, ERCC-1, and RRM-1, according to standard laboratory protocols. Paired biopsy and resection specimens were similarly analyzed.
Results: As little as 1 mm(2) of tumor tissue, from a 10-mu m-thick section, may be used to produce RNA suitable for analysis. RNA of adequate quality and quantity for analysis may be obtained from residual, routinely processed biopsy and cytology specimens. There is good correlation between the result obtained on the tumor biopsy specimen and paired blocks from the surgical resection with respect to clinical decision making.
Conclusion: Routinely processed clinical diagnostic samples provide a suitable source of RNA for polymerase chain reaction-based molecular analyses, potentially providing personalized medicine to all lung cancer patients.