Stereotactic Ablative Radiotherapy Boost to Bladder Tumor for Bladder Preservation in Patients with Muscle-Invasive Bladder Cancer

Abstract

Previous studies showed that selective bladder-sparing approach using TMT is an established therapy of MIBC with outcomes that are comparable to those of radical cystectomy. However, it has been shown that the 5-year local recurrence in the bladder is greater than 40% after TMT. One of the possible reasons was that the RT dose to the bladder tumor or tumor bed was insufficient. Thus, we assessed the effectiveness and safety of Stereotactic Ablative Radiotherapy (SABR) boost to bladder tumor or tumor bed for patients with muscle invasive bladder cancer (MIBC). A total of 59 consecutive patients with cT2-4 bladder cancer underwent transurethral resection of bladder tumor (TURBT). TURBT was visibly complete in 25 cases. Patients received SABR to the tumor or tumor bed in the bladder followed by conventionally fractionated RT (CFRT) to pelvis and total bladder with concomitant weekly radio-sensitizing chemotherapy. During SABR intravesical installation of isovolumetric saline through urinary catheter ensured adequate bladder filling. Response rate was assessed by cystoscopic evaluation and pelvic MRI or CT. Toxicities were reported per the RTOG acute and late Radiation Morbidity Scoring Schema. The median age of all patients was 76 years (35-90 years). All patients completed SBRT boost and 61% patients received concurrent Gemcitabine chemotherapy. After a median follow-up time of 28 months, the rate of local control (LC) at 3 years was 90.0%. The overall survival (OS) and cancer-specific survival (CSS) rates at 3 years were 61.6% and 77.5%, respectively. Of the surviving patients, 84.4% have a disease-free and functioning bladder. Acute grade 3 gastrointestinal (GI) or genitourinary (GU) toxicities occurred in only 1.7% of the patients. Late grade 3 GU toxicity occurred in 5.1% of the patients. No patients experienced grade 4 GI or GU toxicities. SABR boost followed by chemoradiation to the pelvis was found to be a well-tolerated and effective treatment for MIBC patients who are either not candidates for cystectomy or who desire bladder preservation. Randomized study is required to further evaluate this novel tri-modality treatment paradigm.