detection: a prospective study. J Urol. doi:10.1016/j.juro.2014.01. 014. [Epub ahead of print]. 3. Rosenkrantz AB, Lim RP, Haghighi M, et al. Comparison of interreader reproducibility of the prostate imaging reporting and data system and Likert scales for evaluation of multiparametric prostate MRI. AJR Am J Roentgenol. 2013;201:W612-618. 4. Robertson NL, Moore CM, Ambler G, et al. MAPPED study design: a 6 month randomised controlled study to evaluate the effect of dutasteride on prostate cancer volume using magnetic resonance imaging. Contemp Clin trials. 2013;34:80-89. 5. Ahmed HU, Berge V, Bottomley D, et al.: Can we deliver randomized trials of focal therapy in prostate cancer? Nat Rev Clin Oncol. doi:10.1038/nrclinonc.2014.44. [Epub ahead of print].

Reply by the Authors We appreciate the comments put forth by the authors and agree that there remains a great need for improved risk stratification of men diagnosed with presumed localized prostate cancer. Multiparametric magnetic resonance imaging was discussed at the workshop held 1 year ago. The sentiment of the panel was that although promising, multiparametric magnetic resonance imaging had not yet been shown to be reliable and reproducible in multicenter trials. In regards to end points, the Food and Drug Administration has a statutory requirement to approve products that are safe and effective for their intended use. Efficacy is most directly demonstrated by an improvement in how a patient feels, functions, or survives. Surrogate or intermediate clinical end points may be used if they are considered “reasonably likely” to “predict” clinical benefit. The consensus of the panel was that development of metastatic disease was an intermediate clinical end point that was reasonably likely to predict overall survival. Time to institution of local salvage or systemic therapy was discussed, but as mentioned by the authors of the letter, was thought to be too greatly influenced by subjective biases despite use of prespecified criteria. Monitoring of local tumor growth within the prostate was not discussed. In regards to comparator (controls) arms, the requirement for regulatory action is that a therapy be shown to be safe and effective. Although in some instances a placebo arm may be appropriate, active therapies are often used because of both practical and ethical reasons. The Food and Drug Administration is receptive to the use of novel trial designs as a basis for regulatory action, and one of the goals of this workshop was to explore these options. Jonathan P. Jarow, M.D. Office of Hematology and Oncology Products U.S. Food and Drug Administration Silver Spring, MD Ian M. Thompson, M.D. University of Texas Health Science Center San Antonio, TX UROLOGY 84 (3), 2014

Re: El-Tabey et al.: Long-term Functional Outcome of Percutaneous Nephrolithotomy in Solitary Kidney (Urology 2014;83:1011-1015) TO THE EDITOR

Treatment of urolithiasis in patients with solitary kidney is one of the most challenging problems in urology practice. In a recent article, El-Tabey et al1 evaluated the long-term renal functional outcomes of percutaneous nephrolithotomy (PNL) in solitary kidneys. They concluded that PNL in solitary kidneys provides significant improvement in renal function at long-term followup. Furthermore, they determined that multiple punctures and severe bleeding are independent risk factors for deterioration of the kidney function. The authors must be congratulated for their work and bringing this debatable topic to our attention. But we think that some issues about this topic need further discussion. Patients with calculi in a solitary kidney can be treated with shock wave lithotripsy, retrograde intrarenal surgery, or PNL depending on stone size and location.2 But despite the relatively noninvasive nature of these modalities, none of them can achieve a 100% stone clearance rate because stone fragments remain in various proportions of the kidney. In patients with solitary kidney, it is very important to remove the stones completely to avoid obstructive potential complications after surgery. Streem et al reviewed the natural history of small residual fragments in 160 patients and observed that 43% of patients required additional intervention because of symptomatic stone events.3 Therefore, patients with solitary kidney should be carefully evaluated in the postoperative follow-up period. Routine imaging after stone surgery has recently been questioned, and studies regarding after these minimally invasive procedures are controversial. Some authors reported that the combination urinary ultrasonography (US) and plain film radiography are safe and effective imaging techniques in postoperative follow-up period.4 But we do not believe that combination of US and plain film radiography is a good choice after stone surgery for patients with solitary kidney. Because compared with noncontrast computed tomography, US has poor accuracy rates for detecting stones in urinary tract.5 For these reasons, noncontrast computed tomography should be the first-choice imaging modality for evaluating renal calculi in this group of patients during postoperative period. Mustafa Resorlu, M.D. Gurhan Adam, M.D. Department of Radiology C ¸ anakkale Onsekiz Mart University C ¸ anakkale, Turkey 733

Eyup Burak Sancak, M.D. Alpaslan Akbas, M.D. Murat Tolga Gulpinar, M.D. Department of Urology C ¸ anakkale Onsekiz Mart University C ¸ anakkale, Turkey

We agree with the authors of the letter that NCCT is the most acceptable method for detection of residual fragments after PNL in patients with solitary kidneys. Ahmed R. EL-Nahas, M.D. Nasr A. EL-Tabey, M.D. Ahmed M. EL-Assmy, M.D. Department of Urology Urology and Nephrology Center Mansoura University Mansoura, Egypt

References 1. El-Tabey NA, El-Nahas AR, Eraky I, et al. Long-term functional outcome of percutaneous nephrolithotomy in solitary kidney. Urology. 2014;83:1011-1015. 2. Resorlu B, Unsal A, Tepeler A, et al. Comparison of retrograde intrarenal surgery and mini-percutaneous nephrolithotomy in children with moderate-size kidney stones: results of multi-institutional analysis. Urology. 2012;80:519-523. 3. Streem SB, Yost A, Mascha E. Clinical implications of clinically insignificant stone fragments after extracorporeal shock wave lithotripsy. J Urol. 1996;155:1186-1190. 4. Resorlu B, Kara C, Resorlu EB, et al. Effectiveness of ultrasonography in the postoperative follow-up of pediatric patients undergoing ureteroscopic stone manipulation. Pediatr Surg Int. 2011;27:1337-1341. 5. Ray AA, Ghiculete D, Pace KT, et al. Limitations to ultrasound in the detection and measurement of urinary tract calculi. Urology. 2010;76:295-300.

References 1. El-Tabey NA, El-Nahas AR, Eraky I, et al. Long-term functional outcome of percutaneous nephrolithotomy in solitary kidney. Urology. 2014;83:1011-1015. 2. Osman Y, Harraz AM, El-Nahas AR, et al. Clinically insignificant residual fragments: an acceptable term in the computed tomography era? Urology. 2013;81:723-726. 3. Osman Y, El-Tabey N, Refai H, et al. Detection of residual stones after percutaneous nephrolithotomy: role of nonenhanced spiral computerized tomography. J Urol. 2008;179:198-200. 4. Brenner DJ, Hall EJ. Computed tomography—an increasing source of radiation exposure. N Engl J Med. 2007;357:2277-2284. 5. Jin DH, Lamberton GR, Broome DR, et al. Effect of reduced radiation CT protocols on the detection of renal calculi. Radiology. 2010; 255:100-107.

Reply by the Authors We appreciate the interest and congratulations of the authors of this letter to the editor. The aim of our study was evaluation of long-term renal functional outcome of percutaneous nephrolithotomy (PNL) for calculi in solitary kidneys by measuring the differences in preoperative estimated glomerular filtration rate (eGFR) values and those during follow-up.1 The authors of this letter are raising another important question. What is the best imaging protocol for evaluation of the stone-free status after PNL in patients with solitary kidneys? This is crucial in patients with solitary kidneys because it was reported that residual fragments of 5 mm or less after PNL should be expected to require active intervention in one-third of the patients at intermediate follow-up.2 The answer was a matter of debate because some authors prefer a combination of ultrasonography with plain x-ray or tomography, whereas others prefer noncontrast computed tomography (NCCT). The first option had the advantages of lesser radiation exposure and cost but the sensitivity is not as high as NCCT.3 In some cases, it was difficult to see radio-opaque residual stones in plain films if there was gaseous distention. It was also difficult to differentiate a radiolucent residual stones from the nephrostomy tube or ureteral stent using ultrasonography. The second choice (NCCT) had the advantages of high sensitivity in detection of residual stones whatever their size, location, or opacity,3 but its cost is more and it carries a risk of increased radiation exposure especially if repeated many times.4 This risk can be overcome by applying low-dose protocols for NCCT.5 734

Re: Zhu et al.: The Expression and Evaluation of Androgen Receptor in Human Renal Cell Carcinoma (Urology 2014;83:510.e19-24) TO THE EDITOR

We read with great interest the study by Zhu et al demonstrating the frequency of androgen receptor expression in human renal cell carcinoma.1 Urologists and pathologists should keep this observation in mind when a differential diagnosis between prostate cancer and renal cell carcinoma is required. One of our patients underwent retropubic radical prostatectomy for a Gleason 3þ4 ¼ 7 prostate cancer. Intraoperatively, the peritoneum was opened for lymphocele prevention. On this occasion, a cecal mass with adenocarcinomatous differentiation was found, which was initially classified as metastatic prostate cancer because of strong androgen receptor expression (Fig. 1). Because of the history of the patient (local recurrence of right-sided ruptured renal cell carcinoma was removed 2 years earlier), the uncommon site of metastatic involvement and the undetectable postoperative prostate cancerespecific antigen level, the metastatic tissue and the primary renal tumor were re-evaluated. Finally, the diagnosis of peritoneal spread of androgen receptorepositive renal cell carcinoma was established. UROLOGY 84 (3), 2014

Re: El-Tabey et al.: Long-term functional outcome of percutaneous nephrolithotomy in solitary kidney (Urology 2014;83:1011-1015).

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