Purpose: In this prospective study we evaluated the safety and efficacy of concurrent radiotherapy and panitumumab following neoadjuvant/induction chemotherapy and pelvic lymph node dissection as a bladder preserving therapy for invasive bladder cancer.
Materials and methods: Patients with cT1-4N0-2M0 bladder cancer were treated with pelvic lymph node dissection and 4 cycles of platinum based induction chemotherapy followed by a 6½-week schedule of weekly panitumumab (2.5 mg/kg) and concurrent radiotherapy to the bladder (33 × 2 Gy). As the primary objective we compared concurrent radiotherapy and panitumumab toxicity to a historical control toxicity rate of concurrent cisplatin/radiotherapy (less than 35% of patients with Grade 3-5 toxicity). A sample size of 31 patients was estimated. Secondary end points included complete remission at 3-month followup, the bladder preservation rate, EGFR (epidermal growth factor receptor) expression and RAS mutational status.
Results: Of the 38 cases initially included in this study 34 were staged cN0. After pelvic lymph node dissection 7 cases (21%) were up staged to pN+. Of the 38 patients 31 started concurrent radiotherapy and panitumumab. During concurrent radiotherapy and panitumumab 5 patients (16%, 95% CI 0-31) experienced systemic or local grade 3-4 toxicity. Four patients did not complete treatment due to adverse events. Complete remission was achieved in 29 of 31 patients (94%, 95% CI 83-100). At a median followup of 34 months 4 patients had local recurrence, for which 3 (10%) underwent salvage cystectomy. Two tumors showed EGFR or RAS mutation while 84% showed positive EGFR expression.
Conclusions: Concurrent radiotherapy and panitumumab following induction chemotherapy and pelvic lymph node dissection has a safety profile that is noninferior to the historical profile of concurrent cisplatin/radiotherapy. The high complete remission and bladder preservation rates are promising and warrant further study.