Phase Ii Study Of Consolidative Intensity-Modulated Radiation Therapy Following First-Line Palliative Systemic Chemotherapy For De Novo Previously Untreated Metastatic (M1) Nasopharyngeal Carcinoma.

6524 Background: The prognosis of de novo previously untreated metastatic (M1) nasopharyngeal carcinoma (NPC) at diagnosis is poor, and the role of consolidative intensity-modulated radiation therapy (IMRT) to the primary tumor and the neck following first-line palliative chemotherapy remains unknown. We report a phase II study of consolidative IMRT after first-line chemotherapy in previously untreated M1 NPC. Methods: Consolidative IMRT was given in prospectively recruited patients whose previously untreated M1 NPC did not progress after 6 cycles of first-line chemotherapy with gemcitabine and cisplatin. The primary study objective was overall survival (OS). Secondary objectives included progression-free survival (PFS), local relapse-free survival (LRFS), regional relapse-free survival (RRFS), response and toxicity. Results: Sixty-nine consecutive patients were enrolled. Sixty-four (92.8%) patients received first-line chemotherapy, of which 8 (12.5%) developed progressive disease and another 8 (12.5%) did not receive IMRT despite non-progression to first-line chemotherapy. The remaining 48 patients whose disease controlled after chemotherapy received IMRT, including 18 (37.5%) who received concurrent chemoradiation. OS was significantly better in those who received IMRT (35.1 versus 14.2 months; P < 0.001), after a median follow-up duration of 3.40 years (range 0.43 years to 12.14 years). PFS, LRFS, and RRFS were also significantly longer in those who received IMRT. Multivariable analyses revealed that IMRT was the only prognostic factor of all survival endpoints. Grade 3 adverse events were observed in 10 (20.8%) patients, mainly mucositis, dysphagia and desquamation. Conclusions: Consolidative IMRT was associated with an OS benefit and favorable tolerability among previously untreated M1 NPC patients who had non-progressive disease following first-line chemotherapy. These results support the rationale to further investigate IMRT as part of the initial treatment in this setting. Clinical trial information: NCT02476669 .