Patients have a high risk of developing a second primary tumour (SPT) following definitive radiotherapy for nasopharyngeal carcinoma, particularly for a SPT located within the radiotherapy field, warranting close clinical follow-up according to findings presented at the ESMO Asia 2017 in Singapore, an Annual Congress organised by the European Society for Medical Oncology.
James C.H. Chow, Department of Clinical Oncology, Queen Elizabeth Hospital, Hong Kong, and a team of researchers determined the incidence of SPT and the risk of developing cancer in patients with nasopharyngeal carcinomafollowing intensity-modulated radiotherapy (IMRT) by reviewing the records of 759 patients with non-metastatic nasopharyngeal carcinoma who underwent definitive IMRT between February 2003 and September 2011.
The cumulative SPT incidence and overall survival (OS) after SPT diagnosis were estimated, with associations between clinical characteristics and SPT risk analysed using the Cox proportional hazard model. Standardised incidence ratios (SIR) were calculated using age, gender and calendar-year specific incidence rates from the Hong Kong Cancer Registry to quantify excess cancer risks in patients with nasopharyngeal carcinoma compared with the general population.
High cumulative incidence of SPT observed
At a median follow-up of 7.5 years, 51 (6.7%) cases of SPT had occurred; of these, 22 (43.1%) cases were located within the previous radiotherapy fields. The in-field SPTs most commonly reported were tongue cancers in 31.8%, and sarcomas in 31.8% of patients.
The cumulative SPT incidence was 1.0% at 3 years. The cumulative incidences of SPT at 5- and 8-years were 3.7% and 7.7%, respectively.
Median OS after diagnosis of a SPT was 2.9 years.
The only independent variable that was associated with SPT development was age, hazard ratio [HR] 1.061; 95% confidence interval [CI] 1.029-1.094 (p < 0.001).
Patients undergoing IMRT were found to have an elevated risk of 84% in developing a second cancer (SIR 1.84; 95% CI 1.37-2.42).
Significant excess risk was determined for specific cancers, including sarcoma (SIR 38.10; 95% CI 16.41-75.06), tongue (SIR 33.33; 95% CI 13.36-68.67), oropharyngeal (SIR 25.00; 95% CI 2.81-90.25), prostate (SIR 3.19; 95% CI 1.17-6.95), and liver cancer (SIR 2.80; 95% CI 1.02-6.10).
The excess risks of developing cancer in general and each for specific cancer all were higher beyond 5 years of follow-up.
Following definitive IMRT for nasopharyngeal carcinoma, patients continued to have excess cancer risk and a high incidence of SPT, particularly for tumours arising within radiotherapy fields.
SPT severely limits the longevity of nasopharyngeal carcinoma survivors, necessitating that clinicians have high awareness for this lethal late complication in clinical follow-up.
No external funding was reported.
340O – Chow CHJ, et al. Risk of second primary tumors in patients with nasopharyngeal carcinoma following definitive intensity-modulated radiotherapy.