Global pattern of Nasopharyngeal Cancer: correlation of outcome with access to radiotherapy

Abstract

Epidemiological data on nasopharyngeal cancer (NPC) from Globocan 2012 showed that the total number of new cases in the world amounted to 86,691 and number of deaths was 50,828. NPC has a uniquely skewed geographic distribution, 81 % of new cases occurred in Asia and 9 % in Africa. The top four countries (China, Indonesia, Vietnam and India) accounted for 64 % of the global burden. China has the largest number of new cases (n = 33,198), but in terms of age-standardized incidence (ASI), China only ranked 19th because only the southern provinces have high incidence.

Radiotherapy (RT) is the primary treatment modality for NPC. We conducted a study on the correlation of outcome with access to RT to evaluate the fundamental requirement for RT facilities. Outcome for each country was calculated by taking [1-(age-standardized modality/incidence)] as a proxy for 5-year relative survival (RS). Information from the IAEA Directory of Radiotherapy Centres (DIRAC) was extracted to calculate the number of RT equipment (linear accelerator and/or Cobalt machine) and radiation oncologists per million populations.

There were 112 countries with both outcome and RT data: the proxy RS rate ranged widely from 0 to 83 % (median 50 %). Countries can be categorized into poor (proxy RS < 50 %), median (proxy RS = 50 %), and good outcome group (proxy RS > 50 %). Among the 53 countries with poor outcome, the top 14 countries accounted for 75 % of the global burden; their proxy RS rate ranged 22-41 %. Univariate linear regression showed a significant correlation between outcome and the availability of RT: proxy RS increased at 3.4 % (p < 0.001) and 1.5 % (p = 0.001) per unit increase in RT equipment and oncologist per million, respectively. Comparison of median similarly showed statistically significant differences in RT indicators among the three outcome groups (p < 0.001). The median number of RT equipment per million populations increased from 0.6 in the poor to 4.5 in the good outcome group; the corresponding number of oncologists increased from 1.1 to 7.1. These findings will be useful in advocating cancer plan by government, particularly those in developing countries.

Nasopharyngeal cancer is a highly treatable cancer. For patients treated with good quality RT in experienced centers, 5-year disease-specific survival exceeds 80 %. Concerted global efforts are urgently needed to improve outcome in countries with poor outcome.