Monday, September 16, 2013

Diagnosis of Colorectal Cancer in Texas

Wan, Neng and F. Zhan, Bin Zou, J Wilson (2013). Spatial Access to Health Care Services and Disparities in Colorectal Cancer Stage at Diagnosis in Texas,The Professional Geographer. 65 (3), 527-541.

 Colorectal cancer (CRC) is treatable and survival rates are high, if the diagnosis takes place at an early stage. The time of diagnosis is key to survival. There is a 90% survival rate if diagnosed in the beginning and only 10% if diagnosed in an advanced stage. The four cancer stages are situ, localized, regional and distant.

While it is treatable, there are many disparities in diagnosis of CRC. Many believe the diagnosis is influenced by socioeconomic status, race, ethnicity and geographic location. To closer examine this, Wen, Zhan, Zou and Wilson conducted a study to examine if spatial access to medical services contributes to disparities of late stage diagnosis of CRC in Texas.
They chose Texas because it is large (area wise) and racially and ethnically diverse. Further, it has the second largest hispanic population in the U.S.A. Spatial factors in the study included: location of the at-risk population, the location of cancer service facilities and the transportation system. Non-spatial factors were: insurance status, medical cost, patient/physician interaction, cultural barriers.

Data was collected between 1995-2003 by the Texas Cancer Registry and includes: race/ethnicity, stage at diagnosis, sex, date of diagnosis, age at diagnosis, residential address, and the address of Texas hospitals and clinics with CRC screening . Cases were geocoded with ArcGIS 9.3 based on their residential addresses. They also referenced residential address with the locations of the hospitals and clinics

They found the southern and western Texas residents had limited spatial access, while central/western Texas residents had to drive the farthest for screening. Non-Hispanic black and Hispanics are at a significantly higher risk of late stage diagnosis than Non-Hispanic whites. Further, spatial access to primary care physicians had a strong association with late stage diagnosis. This highlights the importance of timely, professional medical advising.

The study confirmed their hypothesis that there are indeed significant disparities in CRC stage of diagnosis in regards to race or ethnicity, geographic location and spatial access. The study  also supported previous studies that show low socioeconomic status contributes to higher risk of late stage diagnosis.

Note: Higher spatial access indicuates better access.


  1. The study is an example of GIS displaying spatial relationships in public health, which is what I reviewed in my blog post. I wonder what the maps would like if these methods were applied to other forms of cancer, such as breast cancer or skin cancer, or in other states with smaller surface areas?

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