Relationship of MRI and clinical staging to outcome in invasive bladder cancer treated by radiotherapy

Radiomics-guided therapy for bladder cancer: Using an optimal biomarker approach to determine extent of bladder cancer invasion from t2-weighted magnetic resonance images

Background

Current clinical staging methods are unable to accurately define the extent of invasion of localized bladder cancer, which affects the proper use of systemic therapy, surgery, and radiation. Our purpose was to test a novel radiomics approach to identify optimal imaging biomarkers from T2-weighted magnetic resonance imaging (MRI) scans that accurately classify localized bladder cancer into 2 tumor stage groups (≤T2 vs >T2) at both the patient level and within bladder subsectors.

Method and Materials

Preoperative T2-weighted MRI scans of 65 consecutive patients followed by radical cystectomy were identified. A 3-layer, shell-like volume of interest (VOI) was defined on each MRI slice: Inner (lumen), middle (bladder wall), and outer (perivesical tissue). An optimal biomarker method was used to identify features from 15,834 intensity and texture properties that maximized the classification of patients into ≤T2 versus >T2 groups. A leave-one-out strategy was used to cross-validate the performance of the identified biomarker feature set at the patient level. The performance of the feature set was then evaluated at the subsector level of the bladder by dividing the VOIs into 8 radial sectors.

Results

A total of 9 optimal biomarker features were derived and demonstrated a sensitivity, specificity, accuracy of prediction, and area under a receiver operating characteristic curve of 0.742, 0.824, 0.785, and 0.806, respectively, at the patient level and 0.681, 0.788, 0.763, and 0.813, respectively, at the radial sector level. All 9 selected features were extracted from the middle shell of the VOI and based on texture properties.

Conclusions

An approach to select a small, highly independent feature set that is derived from T2-weighted MRI scans that separate patients with bladder cancer into ≤T2 versus >T2 groups at both the patient level and within subsectors of the bladder has been developed and tested. With external validation, this radiomics approach could improve the clinical staging of bladder cancer and optimize therapeutic management.

Dynamic contrast enhanced magnetic resonance imaging of bladder cancer and implications for biological image-adapted radiotherapy

PURPOSE

To assess the role of image parameters derived from dynamic contrast enhanced magnetic resonance imaging (DCEMRI) in bladder cancer staging, and to investigate the potential use of such parameter images in biological image-adapted radiotherapy (RT).

MATERIALS AND METHODS

High-resolution volumetric interpolated breath-hold (VIBE) DCEMRI of 26 patients diagnosed with bladder cancer was performed. DCEMRI parameters derived from tumor and muscle contrast uptake curves were extracted and subjected to correlation analysis with tumor volume as well as clinical, pathological, histological and T2-weighted MR tumor stage. For parameters showing a significant correlation with tumor stage, 3D malignancy maps were generated. As an initial step towards delivery of biologically adapted intensity modulated radiotherapy (IMRT) it was hypothesized that the malignancy map could be used as a RT dose prescription map. Simulating IMRT delivery with multi-leaf collimators (MLCs), idealized dose distributions, constituted by dose cubes, were adapted to the prescription map. The size of the dose cubes were varied to mimic MLCs of varying leaf width. The difference between the adapted and prescribed dose distributions was quantified by the root mean square deviation (RMSD).

RESULTS

No significant relationships were found between tumor volume and extracted DCEMRI parameters. The normalized area between tumor and muscle contrast uptake curves (nABC) evaluated from 0-180 seconds (nABC(180)) and 0-480 s (nABC(480)) correlated significantly with tumor stage (p=0.047 and p=0.035, respectively). Dose prescription maps for 10 patients were generated from the nABC(480). The RMSD between the prescribed and adapted dose distribution decreased with decreasing size of the dose cubes. Large interpatient variations in the RMSD and in the dependence of the RMSD on different dose cube sizes were found.

CONCLUSIONS

The nABC(180) and nABC(480) may provide added value in staging of bladder cancer. High-resolution IMRT is required for some patients for optimal adapted RT.

Long-term follow up of patients with invasive bladder carcinoma receiving combined cisplatin-based intra-arterial chemotherapy and radiotherapy

OBJECTIVES

Combined cisplatin-based intra-arterial chemotherapy and radiotherapy is an effective treatment for patients with locally invasive bladder carcinoma. We report long-term follow-up data regarding definitive treatment of locally invasive bladder carcinoma, regardless of whether bladder preservation was possible.

METHODS

The follow-up data from 24 patients (18 males and six females; aged, 31-85 years; median, 73 years) with invasive bladder carcinoma, between 1993 and 2003, was examined. The clinical stages of the patients ranged T2-T4, all N0M0, and involved 13 patients at T2 (T2a, T2b), seven patients at T3 and four patients at T4. Combined cisplatin-based intra-arterial chemotherapy and radiotherapy was performed.

RESULTS

The 5-year overall survival rate and cancer-specific survival rate for all patients were 81.6% and 85.6%, respectively. When the patients were divided into complete response (CR) of 10 patients and non-CR groups of 14 patients, the 5-year overall survival rate for the CR group was 87.5%, while that of the non-CR group was 78.6% (P = 0.58). The tumor grade of the CR group was significantly lower than that of the non-CR group (P = 0.01). When the non-CR group was divided into radical cystectomy and non-radical cystectomy groups, the 5-year overall survival rate for the radical cystectomy group (100%) was higher than that of the non-radical cystectomy group (70%).

CONCLUSION

This combined chemo-radiotherapy was effective for local invasive bladder carcinoma, leading to the possibility of bladder preservation using this therapy.

Muscle-Invasive Urothelial Carcinoma of the Bladder

Muscle-invasive urothelial (transitional cell) carcinoma is a potentially lethal condition for which an attempt at curative surgery is required. Clinical staging does not allow for accurate determination of eventual pathologic status. Muscle-invasive urothelial carcinoma is a highly progressive disease, and initiation of definitive therapy within 3 months of diagnosis is worthwhile. Age is not a contraindication for aggressive surgical care, and surgical candidates should be evaluated in the context of overall medical comorbidity. In those patients who undergo surgery, clinical pathways may streamline care. Radical cystectomy remains the "gold standard" of therapy, providing 5-year survival rates of 75% to 80% in patients with organ-confined disease, yet organ-sparing procedures demonstrate clinical effectiveness as well. Cystectomy should be undertaken with the intent of performing complete pelvic lymph node dissection and attaining surgically negative margins. In younger female patients, the preservation of reproductive organs may be achieved in many cases. Prostate- and seminal vesicle-preserving cystectomy has been performed, yet the long-term safety and efficacy of such a procedure remains to be determined. Laparoscopic and robotic cystectomy procedures continue to be explored by several investigators. The role of "radical transurethral resection" in muscle-invasive disease is limited to a small cohort of patients, and, when it is performed, cystectomy may be required to consolidate therapy. Postoperative follow-up after cystectomy should occur over short intervals during the first 2 years and can be extended, but not discontinued, beyond that time. Currently, no tumor markers have been prospectively validated to help guide clinical decision making, and prospective trials incorporating marker data should be encouraged.

The management of hydronephrosis in patients undergoing TURBT

OBJECTIVE

Previous studies have shown the negative prognostic correlation of hydronephrosis in bladder cancer; however, practical uncertainties remain regarding the management of these patients.

METHODS

We retrospectively reviewed the notes of patients undergoing TURBT over a three year period and recorded the management and outcome of patients with hydronephrosis.

RESULTS

Six percent with bladder cancer had hydronephrosis. Nearly all the cases had muscle invasive disease. At TURBT, the ureteric orifice was seen in 41%; in the remaining 59% of patients, the ureteric orifice was involved and resected. This resolved the hydronephrosis in only one patient (who had superficial disease).

CONCLUSIONS

Hydronephrosis in bladder cancer is associated with a poor prognosis. The hydronephrosis does not resolve with resection alone. As awaiting it's resolution may delay definitive treatment, we suggest aggressive management of hydronephrosis from the time of initial diagnosis with ureteric stenting in order to protect renal units and optimize renal function prior to further definitive treatment of bladder cancer.

Radiation Therapy for Muscle-invasive Bladder Cancer: Treatment Planning and Delivery

Radiation therapy allows organ preservation therapy in selected patients with muscle invasive bladder cancer. This review sets out to explore the role of radiation therapy in the management of muscle invasive bladder cancer. It describes and assesses the potential benefits provided by technological advances in radiation delivery in optimizing the therapeutic ratio.

MR imaging of the bladder

MR imaging of the bladder can now be routinely and easily performed with consistent quality. The latest techniques provide high-resolution images of the soft tissue contrast and the ability to perform dynamic contrast imaging and functional pelvic floor studies. MR imaging fits in as a complimentary tool to cystoscopy and to conventional pelvic floor dynamic studies and can provide a unique imaging perspective of the bladder. It is important, however, to remain cognizant of the limitations of its use in tumor detection and discrimination.