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Clinical Observations |
1 Department of Radiology, University of Michigan, 1500 E Medical Center Dr., UH
B1 D530, Ann Arbor, MI 48109.
2 Department of Radiology, Beaumont Hospital, Royal Oak, MI.
3 Department of Biostatistics, School of Public Health, University of Michigan,
Ann Arbor, MI.
Received August 10, 2005;
accepted after revision February 1, 2006.
Address correspondence to S. G. Yarram
(syarram{at}med.umich.edu).
Abstract
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CONCLUSION. Imaging-guided core biopsy of pelvic masses is accurate and safe. The accuracy and sensitivity of biopsy under sonographic guidance are higher than those of CT-guided biopsy, although the difference is not statistically significant.
Keywords: biopsy • CT • pelvic imaging • sonography
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Lidocaine was routinely used for local anesthesia. If a patient needed conscious sedation, IV midazolam and fentanyl were used with pulse oximetry and hemodynamic monitoring. Patients were monitored in the recovery area after biopsy, typically for 4 hours if they were outpatients and for a shorter time if they were inpatients. CT-guided biopsy was performed on a dedicated helical CT scanner (CT/i, GE Healthcare). Sonographically guided biopsies were performed with various sonographic units. Two to four core specimens were obtained with a 17-gauge introducer and an 18-gauge biopsy gun. Core biopsy specimens were examined in the pathology department.
Overall, 111 biopsies were performed on 107 patients. Three patients underwent biopsy of different pelvic masses at different times in the clinical course. One patient underwent two biopsies of the same mass. Forty-nine of the patients were men, and 58 were women. The mean age was 58.6 years, and the age range was 20-87 years. The mean mass diameter was 4 cm (range, 1-10.2 cm) for the CT-guided biopsies and 5.9 cm (range, 2-20 cm) for the sonographic procedures. The locations of the masses varied as follows: deep pelvis (n = 62; CT, 19; sonography, 43), superficial and inguinal (n = 22; CT, 10; sonography, 12), and presacral and perirectal (n = 27; CT, 15; sonography, 12). The most common indication for biopsy was a new pelvic mass in a patient with a history of malignant disease.
In general, the choice of CT versus sonographic guidance for biopsy of a pelvic mass was made in consideration of factors such as location, safe access, and comorbidity. Sixty-seven of the 111 procedures were performed with sonographic guidance and 44 procedures with CT guidance. For each technique, the approach to biopsy varied as follows: anterior (n = 45; CT, 13; sonography, 32), posterior and transgluteal (n = 37; CT, 31; sonography, six), and transvaginal and endorectal (n = 29; CT, none; sonography, 29). For the endorectal approach, our current antibiotic prophylaxis is a single 500-mg oral dose of levofloxacin (Levaquin, Ortho-McNeil) 1 hour before the procedure followed by 500 mg of levofloxacin once a day orally for the next 2 days.
Biopsy was considered successful if the specimen was adequate for pathologic diagnosis. Biopsy results were compared with surgical pathologic or additional procedure results (n = 32) or clinical follow-up findings (n = 79). Length of clinical follow-up ranged from 1 month to 68 months with a mean of 18 months. Fourteen patients had a clinical follow-up period as short as 1 month. Some of these patients died soon after the diagnosis, and others no longer received care at our institution. Seventy-nine (73.8%) of the 107 patients underwent clinical follow-up for at least 3 months. A biopsy result was considered true-positive or true-negative when the pathologic results were concordant with clinical follow-up or surgical pathologic or additional procedure results. A biopsy result was considered false-negative if it was discordant with clinical follow-up findings or results of surgical pathologic examination or additional procedures. A separate category of cases in which the tissue specimen was insufficient also was tracked.
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Of the 111 masses biopsied, 74 yielded true-positive results. Fifty-two of these masses were biopsied under sonographic guidance and 22 under CT guidance. Of the 74 true-positive cases, 65 were malignant neoplasms, two were benign neoplasms (schwannoma and ganglioneuroma), and seven were other benign lesions. Representative cases of true-positive findings are illustrated in Figures 1A, 1B and 2A, 2B.
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There were seven false-negative results. Four of these masses were biopsied with CT guidance and three with sonographic guidance. The mean diameter of these lesions was 3.4 cm (range, 2-5 cm). Six of the final results were determined with additional procedures, including sigmoidoscopic biopsy, cystoscopic biopsy, lung biopsy, bone biopsy, open surgical biopsy, and repeated percutaneous biopsy. One patient died of metastatic disease within 1 month of the procedure. Final diagnoses of the seven false-negative cases were as follows: three cases of invasive squamous cell cancer and one case each of metastatic rectal cancer, urothelial cancer, ovarian cancer, and abscess.
The tissue specimen was insufficient in five cases. CT guidance was used in three cases and sonographic guidance in two. In two of these cases, clinical follow-up of 3 months and of 3 years 11 months showed a benign course. The other three patients underwent additional procedures (two, open surgical biopsy and one, bone marrow biopsy), which led to a diagnosis.
There were no false-positive results. The overall success rate, defined as sufficient specimen for diagnosis, was 95.2%. The success rate for sonographic guidance was 97% and that for CT guidance was 93.2%. Table 2 summarizes the accuracy, sensitivity, specificity, positive predictive value, and negative predictive value. Statistical analysis showed the sensitivity of CT was 84.6% and that of sonography was 94.5%. These results were not statistically significant (p = 0.14, Fisher's exact test) owing to the low power of the study sample.
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There were three cases of complications among the 111 procedures, for a complication rate of 2.7%. All of the complications were infectious in nature and occurred in patients who underwent biopsy by the endorectal approach with sonographic guidance. One patient was hospitalized for 7 days after endorectal biopsy for IV antibiotic management of urosepsis. Another patient was admitted with bacterial infection and hospitalized for 7 days because of comorbid conditions. The third patient had a small perirectal abscess that necessitated incision and drainage and was hospitalized for 2 days.
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During the 6-year period, more masses were biopsied with sonographic guidance (n =67) than with CT guidance (n = 44). Not only were more biopsies performed with sonographic guidance but also the technique had a higher success rate, accuracy, and sensitivity than CT guidance with equivalent specificity, although the differences were not statistically significant (p = 0.14). More masses in the deep pelvis were biopsied with sonographic guidance than with CT guidance (n = 62; CT, 19; sonography, 43) because sonography is better suited for reaching deep pelvic masses through the transvaginal and endorectal approaches. These masses are not safely accessible with CT guidance. Real-time imaging with sonography facilitates manipulation of the biopsy needle into difficult locations. Other advantages of sonographic guidance are the absence of ionizing radiation and a lower cost.
The overall results with both techniques in our study are similar to the results obtained by other authors. For example, Welch et al. [4] used only CT guidance for biopsy of pelvic masses and masses in other locations. These authors reported a success rate of 100%, sensitivity of 91.8%, and specificity of 98.9% compared with 95.2%, 91.4%, and 100%, respectively, in our study. Welch et al. may have had a higher success rate because their study was a prospective one in which an on-site cytopathologist was present to advise about the adequacy of the biopsy specimen and the need for additional specimens [4]. Our results also are similar to the results obtained by Memel et al. [7] in a study of sonographically guided biopsy of abdominal, pelvic, and retroperitoneal lymph nodes. In that study, adequate tissue for histologic evaluation was obtained in 21 (91%) of 23 of the sonographically guided procedures compared with 97% in our study.
Our study had several limitations. Although it is to date and to our knowledge the largest study to evaluate the accuracy of imaging-guided core biopsy of pelvic masses, the sample size was small (n = 111). In the study in which the number of pelvic biopsies was closest to ours, Welch et al. [4] biopsied 94 pelvic masses. Another limitation was that follow-up methods varied and were not standardized given the retrospective nature of the study. In some cases, pathologic findings from surgery and additional procedures were used for follow-up (n = 32); in other cases (n = 79), only clinical follow-up findings were used. Fourteen patients had clinical follow-up periods as short as 1 month, some because they died soon after the diagnosis and others because they no longer received care at our institution. Seventy-nine (73.8%) of the 107 patients underwent clinical follow-up for at least 3 months. Another limitation was the small number of biopsies of benign masses in this study. Ours is a tertiary care center with strong emphasis on evaluation of oncology patients; therefore, we see a large number of malignant pelvic masses.
All complications in our study occurred in biopsies performed through the endorectal approach under sonographic guidance, and all of these complications were infectious. No deaths were caused by the procedures. The data in the urology literature on the endorectal approach to biopsy of the prostate indicate this approach is largely safe and effective but that there is a small risk of infectious complications, the incidence ranging from 1.7% to 3.5% [10, 11]. In our study, antibiotic prophylaxis varied for the three patients with complications. One patient did not receive any antibiotics, one patient received antibiotics after the procedure, and the third patient received antibiotics before the procedure. Because of the incidence of infectious complications of endorectal biopsy, we have standardized antibiotic prophylaxis before this procedure.
In conclusion, imaging-guided core biopsy of pelvic masses is safe, accurate, and effective. The accuracy and sensitivity of biopsy with sonographic guidance are higher than those of CT-guided biopsy, but the difference is not statistically significant. Sonographic guidance offers alternative transvaginal and endorectal approaches to deep pelvic lesions, which are not accessible with CT guidance. Sonography also has the advantages of realtime imaging, lack of ionizing radiation, and lower cost, as reported [12, 13] in the diagnosis of masses in locations such as the liver and mediastinum. In those studies, the cost of biopsy with sonographic guidance was approximately 25-50% less than that of CT guidance.
At our center we use sonographic guidance for biopsy of pelvic masses whenever feasible. CT guidance is reserved for cases in which the lesion is not seen with sonography or when a safe pathway to the lesion in question is not found with sonographic guidance. Although imaging-guided biopsy of pelvic masses is largely safe, caution should be exercised with use of the endorectal approach because of the higher incidence of infectious complications. At our institution, all patients undergoing endorectal biopsy receive antibiotic prophylaxis before and after the procedure.
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