Jul 25 2005
Inserting biopsy needles through the skin appears to be a safe and reliable alternative to surgery for obtaining diagnostic samples of a suspected solid tumor in children, according to results of a study by investigators at St. Jude Children's Research Hospital.
The technique, called percutaneous ("through the skin") core-needle biopsy, provides samples of tissue suitable for accurate initial diagnosis of a solid tumor, the researchers say.
In addition, the findings contradict the belief of many pediatric surgeons that this technique is more likely than surgery to dislodge cells from the tumor and cause the cancer to spread. A report on the findings of this study appears in the August 1 issue of Cancer. The St. Jude findings are based on a retrospective ("look back") study of the medical records.
Substituting percutaneous core biopsy for surgery would eliminate the need for children to recover from an operation, which delays chemotherapy for their cancer, according to Fredric A. Hoffer, MD, a member of the Department of Radiological Sciences. And it would eliminate potential complications from surgery, such as infections, he says. "This technique is already commonly used to diagnose solid tumors in adults," says Hoffer. "Our own study now shows that this technique appears to be suitable for children as well." Hoffer is senior author of the Cancer paper.
Hoffer performed the biopsies guided usually by ultrasound or CT scans to obtain images inside the patient as he inserted and manipulated the hollow biopsy needles in order to obtain cores of tumor samples.
The biopsy samples were analyzed using histopathologic techniques (studying the tissue under a microscope and using antibody-based techniques to enhance determination of tumor type), as well as by cytogenetics or molecular pathology (identifying abnormalities in chromosomes).
Obtaining sufficient amounts of fresh specimens for study is essential for the success of this technique, says Hoffer. Biopsies obtained only for cytology studies (studying cell structure) aren't usually sufficient to diagnose childhood cancers, according to Christine Fuller, MD, an assistant member of the Department of Pathology at St. Jude. Having a laboratory available to process fresh tissue for cytogenetics and molecular pathology is also a key to success, she notes. Fuller is a co-author of the paper.
Patients ranged from less than one year in age to 33 years. Adults were included in this study because of suspected recurrence or metastasis (spread) from previously diagnosed childhood cancers. The researchers determined the accuracy of their results by comparing their diagnoses to the diagnoses that were subsequently made using specimens that had been obtained by surgery.
The St. Jude team first analyzed the clinical data obtained from 202 percutaneous core-needle biopsies of solid tumors over 5.5 years (1997 to 2003) in order to determine how many of the individual biopsy samples lead to the correct identification of a cancer. This would demonstrate how likely individual biopsy specimens provided suitable tissue for laboratory analysis, according to Hoffer.
Among the tumors correctly identified using biopsy samples obtained percutaneously were 13 neuroblastomas (a tumor of the nervous system), eight hepatoblastomas (a cancer of the liver), seven Wilms tumors (a cancer that originates in the kidney), four rhabdomyosarcomas (a cancer of the soft tissues), and three osteosarcomas (cancers of the bone), according to Hoffer.
Attempts to diagnose initial cancer for each of the 103 patients produced 62 "true positive" diagnoses out of 64 results that had been judged to be positive for cancer. This meant the sensitivity of this procedure for making initial diagnoses was 97%, according to the report. The technique also correctly identified all 39 patients who were later found to be negative following laboratory examination of tissues removed surgically--or by clinical follow-up--a specificity of 100%. These "false tumors" were caused by inflammatory or infectious processes rather than cancer, the researchers say. In addition, examination of biopsy samples obtained percutaneously led to the incorrect diagnosis of "no cancer" in only two thyroid carcinoma cases, for an accuracy of 98%.
The researchers also determined the ability of percutaneous biopsy to correctly identify cancer in 99 patients who were suspected of having a recurrence of a previously treated cancer. The results showed that percutaneous biopsy was less reliable than for initial diagnosis. Specifically, the sensitivity was 83%; specificity was 100%; and accuracy was 88%.
The follow-up studies of patients medical records provided no evidence that the cancer had spread due to dislodging cells during percutaneous biopsy, the researchers report.
"Overall, our study demonstrated that percutaneous biopsy is useful in diagnosing pediatric solid tumors," Hoffer says. "And this technique is especially useful for sampling tumors that are not easy to access using surgery--for instance in a patient with a large retroperitoneal neuroblastoma that may not be able to be removed surgically until the tumor shrinks from chemotherapy," he adds. "This technique might also be useful for those cases in which new chemotherapy agents are used for suspected recurrent tumor." Retroperitoneal refers to the membrane lining the abdomen that covers the internal organs.
The only disadvantage to this technique is that there is only a small amount of tissue remaining for tumor banking (saving the tumor for future studies) after allocating enough for laboratory analysis, Hoffer says.