Abstract 5754: Spatial clustering of sex ratio variations of cancer incidence: A modified Moran's index approach
Authors: Raza Syed-Ahsan 
Published: September 2020

Background: Moran's index (I) is one of the most common correlation measurements to investigate spatial process of geographical evolution of disease development and progression. Geospatial variations of sex ratios (male-to-female age-standardized incidence rates) of cancers can be used to postulate on genetic and environmental underpinnings of cancer etiology. The study explored through improved version of Moran's I whether geographic contiguous regions tend to have similar sex-ratios or not, and how SRs of different types of cancers are geographically clustered.

Methods: A simplified approach of computing spatial autocorrelation through Moran's Index (I) was applied to global cancer incidence data. Detailed data on 28 cancer subtypes were retrieved from the tenth volume (2003-07) of the International Agency for Research on Cancer's ‘Cancer Incidence in Five Continents'. Using a publicly available world geolocation database, we geocoded 102 and 52 cancer registry-based regions in Europe and Asia, and linked these to cancer incidence data. For each type of cancer, the spatial clustering of SR in geographically contiguous areas were ranked according to the degree of clustering based on values of Moran's I (dispersed [-1] to highly clustered [+1]).

Results: In Europe, Moran's I values for SRs of cancer incidence ranged from dispersed patterns such as -0.09 for melanoma, to moderate clustering for esophageal (0.115), liver (0.115), and kidney (0.114) cancers. In contrast in Asia, the SRs for esophageal cancer showed a high degree of spatial clustering (0.597). However, despite these spatial patterns being different in Europe and Asia, the degree of clustering for many of the 28 cancers analyzed were comparable. Among top 10 high incident cancers in Europe and Asia (&gt;5 cases per 100,000), those that have relatively similar clustering include cancers of the esophagus, thyroid, pancreas, rectum and anus, stomach, and kidney. For lung, colon, non-Hodgkin's lymphoma, leukemia, skin melanoma, and brain cancers, we observed different spatial patterns across the two continents. Among the low incident cancers (&lt;2 cases per 100,000) such as nose and sinus, pharynx and gallbladder, there were substantial differences in the degree of geospatial clustering between Europe and Asia, whereas rankings were closer in larynx, eye, multiple myeloma, Hodgkin's lymphoma, and small-intestinal cancers.

Conclusions: The findings may help to generate etiological hypotheses of cancer causation. A spatially clustered pattern of cancer suggests exogenous or avoidable causes of cancers, whereas dispersed patterns suggest endogenous causes. Cancers of the esophagus, liver and stomach showed clustered SR patterns in both Europe and Asia. For cancers in which endogenous causes may be reasonably hypothesized, more of high dispersed patterns of SR are observed in Europe (e.g., cancer of the eye). Secondarily, our findings can also be used to identify spatial anomalies that may be reflective of quality concerns for cancer registries.

Citation Format: Syed-Ahsan Raza. Spatial clustering of sex ratio variations of cancer incidence: A modified Moran's index approach [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5754.