A Retrospective Statistical Analysis of Second Primary Cancers in the Delmarva Peninsula, U.S.A.

(1) Bennett Middle School, Fruitland, MD, (2) Department of Mathematics and Computer Science, Salisbury University, Salisbury, MD

A significant percentage of cancer survivors develop a second primary cancer. Using data of deceased patients provided by the Peninsula Regional Medical Center, a retrospective statistical analysis was conducted to investigate whether the type of the first cancer affects the occurrence time and type of the second primary cancer. Cancer patients were stratified according to the first cancer type, and the time elapsed between the first and second cancer diagnosis was examined to see if there are statistically significant differences. Histograms of second cancer occurrence times for lung and bronchus, breast and melanoma-skin cancers are strongly skewed right while those for prostate and urinary bladder cancers have lower right skewness. Both one-way analysis of variance test and Kruskal-Wallis test show a p-value below the significance level of 0.05, confirming that the first cancer type affects the second cancer occurrence time. For each first cancer type, the most common types of the second primary cancer are identified. About 40% of breast cancer and lung and bronchus cancer survivors develop a second primary cancer of the same type. 25% of melanoma-skin cancer survivors develop the same cancer again and 17% of them develop a second melanoma cancer. In contrast, less than 1% of prostate cancer survivors develop a second prostate cancer and only 14% of urinary bladder cancer survivors develop the same cancer again. Lung and bronchus cancer is one of the most prevalent second cancer types regardless of the first cancer type.

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