Abstract
Background and PurposeBladder radiotherapy is a management option for carefully selected patients with muscle-invasive bladder cancer. However, the inability to visualize the tumor site during treatment and normal bladder movement limits targeting accuracy and increases collateral radiation. A means to accurately and reliably target the bladder during radiotherapy is needed.Materials and MethodsEighteen consecutive patients with muscle-invasive bladder cancer (T1–T4) elected bladder-preserving treatment with maximal transurethral resection (TUR), radiation and concurrent chemotherapy. All underwent endoscopic placement of 24-K gold fiducial markers modified with micro-tines (70 [2.9×0.9 mm.]; 19 [2.1×0.7 mm.) into healthy submucosa 5-10 mm. from the resection margin, using custom-made coaxial needles. Marker migration was assessed for with intra-op bladder-filling cystogram and measurement of distance between markers. Set-up error and marker retention through completion of radiotherapy was confirmed by on-table portal imaging.ResultsBetween 1/2007 and 7/2012, a total of 89 markers (3–5 per tumor site) were placed into 18 patients of mean age 73.6 years. Two patients elected cystectomy before starting treatment; 16/18 completed chemo-radiotherapy. All (100%) markers were visible with all on-table (portal, cone-beam CT), fluoroscopy, plain-film, and CT-scan imaging. In two patients, 1 of 4 markers placed at the tumor site fell-out (voided) during the second half of radiotherapy. All other markers (80/82, 98%) were present through the end of radio-therapy. No intraoperative (e.g. uncontrolled bleeding, collateral injury) or post-operative complications (e.g. stone formation, urinary tract infection, post-TUR hematuria >48 hours) occurred. Use of micro-tined fiducial tumor-site markers afforded a 2 to 6-fold reduction in bladder-area targeted with high-dose radiation.DiscussionPlacement of the micro-tined fiducial markers into the bladder was feasible and associated with excellent retention-rate and no complications. All markers were well-visualized during radiotherapy with all imaging modalities. Bladder fiducial markers improve targeting accuracy, and may increase treatment efficacy and reduce morbidity from collateral radiation.
Highlights
Radical cystectomy with urinary diversion remains the goldstandard treatment for localized muscle-invasive bladder cancer
Despite the absence of direct randomized trials comparing bladder preserving treatment and radical cystectomy, tri-modality treatment with maximal transurethral bladder tumor resection followed by different regimens of combined radio and chemotherapy has, among patients with the aforementioned disease features, achieved results comparable to radical cystectomy in some trials [3]
More than 3 markers were placed at the tumor site if it was felt that one or more of the first 3 markers was at risk of falling-out prematurely- usually due to deployment too close to the mucosa needle-entry hole
Summary
Radical cystectomy with urinary diversion remains the goldstandard treatment for localized muscle-invasive bladder cancer. Bladder preservation with tri-modality therapy (maximal transurethral resection, and combined chemo and radiotherapy) remains an alternative for patients who have been thoroughly counseled regarding the attendant risks and benefits of all management options, including radical cystectomy [1]. Despite the absence of direct randomized trials comparing bladder preserving treatment and radical cystectomy, tri-modality treatment with maximal transurethral bladder tumor resection followed by different regimens of combined radio and chemotherapy has, among patients with the aforementioned disease features, achieved results comparable to radical cystectomy in some trials [3]. Two key challenges to radiotherapy targeting accuracy and precision are that the location of the bladder moves constantly, and, that the tumor-site cannot be identified using CT-scan imaging or on-table imaging. The inability to visualize the tumor site during treatment and normal bladder movement limits targeting accuracy and increases collateral radiation. A means to accurately and reliably target the bladder during radiotherapy is needed
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