Concurrent radiotherapy/panitumumab safe, noninferior to concurrent cisplatin/radiotherapy
Radiotherapy in parallel with panitumumab use following induction chemotherapy and pelvic lymph node dissection appears to be well tolerated and is noninferior to the historical profile of concurrent radiotherapy and cisplatin, a study has shown.
Participants included patients with cT1-4N0-2M0 bladder cancer who were treated with pelvic lymph node dissection and four cycles of platinum-based induction chemotherapy followed by a 6 ½-week schedule of weekly panitumumab (2.5 mg/kg) and concurrent radiotherapy to the bladder (33 x 2 Gy).
Concurrent radiotherapy/panitumumab toxicity was compared to a historical control toxicity rate of concurrent cisplatin/radiotherapy (<35 percent of patients with grade 3–5 toxicity). Thirty-one patients were analysed. Secondary endpoints were complete remission at 3-month follow-up, bladder preservation rate, epidermal growth factor receptor (EGFR) expression and RAS mutational status.
Thirty-four of the 38 patients initially included were staged cN0, of which seven (21 percent) were up staged to pN+ after pelvic lymph node dissection. Of the 38 patients, 31 initiated concurrent radiotherapy/panitumumab.
Systemic or local grade 3–4 toxicity occurred in five patients (16 percent; 95 percent CI, 0–31) during concurrent radiotherapy/panitumumab. Four patients ceased treatment due to adverse events.
Twenty-nine of 31 patients (94 percent; 83–100) achieved complete remission. Four patients had local recurrence, for which three (10 percent) underwent salvage cystectomy, at a median follow-up of 34 months. Furthermore, two tumours had EGFR or RAS mutation, while 84 percent showed positive EGFR expression.
“The high complete remission and bladder preservation rates are promising and warrant further study,” the authors said.