Second primary cancer after intensity-modulated radiotherapy for nasopharyngeal carcinoma: A territory-wide study by HKNPCSG

•Cancer risk in nasopharyngeal carcinoma survivors who underwent intensity-modulated radiotherapy was 90% higher than that in the general population.•Significant excess cancer risks were observed for oral cavity, sarcoma, oropharynx, paranasal sinus, salivary gland, thyroid, skin and lung.•Re-irradiation is an independent risk factor for in-field second primary cancer development.•Second primary cancer represents a significant cause of late mortality among NPC survivors.