According to a detailed trends examination there are considerable differences between the main subtypes of bladder cancer. Due to this, investigators are being asked to make a distinction between both types of the disease when they conduct studies.

In the January edition of the urology journal BJUI, a large investigation of almost 128,000 cases of bladder cancer in the U.S., revealed that the disease showed a 9% overall decrease between 1973 and 2007.

However, when investigators examined the two main subtypes, which accounted for 94% of the bladder tumors, they discovered that between 1973 and 2007, papillary transitional cell carcinoma (PTCC) rose by 56% and that non-papillary transitional cell carcinoma (NPTCC) decreased by 53%.

Dr. Yawei Zhang, from the School of Public Health and School of Medicine at Yale University, USA, explained:

“These two subtypes of bladder cancer are normally categorized as a single disease called transitional cell carcinoma in research studies, but our findings highlight major trend differences over more than three decades.

This is a significant finding that underlines the importance of future research differentiating between these two subtypes.”

In the U.S., bladder cancer is the fifth most prevalent cancer. In addition, around 70,000 individuals are diagnosed with the bladder cancer each year, while 15,000 individuals die from the disease. It is believed that occupational exposure to arylamines – organic chemicals – and cigarette smoking are responsible for over half of the cases in the United States.

In order to examine trends in bladder cancer by subtype, disease stage and grade, the investigators use data from the National Cancer Institute’s Surveillance and Epidemiology and End Results data for 1973 to 2007. The analysis revealed the different trends between non-papillary tumors, which grow inside of the bladder, and papillary tumors, that grow on the outside surface of the bladder.

Vital discoveries from the investigation included:

  • Between 1973 and 2007, the overall age-adjusted incidence rates for the disease decreased by approximately 9% from 16.7 per 100,000 to 15.2. Comparable trends were observed in both men and women and racial groups.
  • The data included 127,614 first primary bladder cancer cases. Most of the patients were white (92%) and male (74%). 29% of the tumors were TCC, while 65% were PTCC. The remaining 6% included adenocarcinoma, squamous cell, and small cell carcinoma.
  • When the investigators examined the two main subtypes, considerable differences emerged. While the age-adjusted rates for NPTCC decreased by approximately 53%, from 7.9 per 100,000 in 1973 to 3.7 per 100,000 in 2007, PTCC rose by 56% from 6.8 per 100,000 in 1973 to 10.6 per 100,000 in 2007. Similar trends were observed in both males and females, racial groups as well as in various stages of the disease – localized, regional and distant.
  • Between 1998 and 2007, the researchers found a significant increase in the incidence rates of grade 4 tumors. While incidence rates for grade 1, 2 and 3 tumors decreased. This is likely a result of alterations in the grading system introduced in 1998, however, the insufficient reduction in more aggressive bladder cancer is of considerable concern. The team observed similar increases for PTCC and NPTCC, racial groups, different stages of the disease and genders.

Dr. Zhang concludes:

“The striking differences in the trends between PTCC and NPTCC suggest that they may be two disease entitles with different causes. Recent survival analysis has also shown that survival rates are substantially higher for PTCC than NPTCC.

Despite this, no epidemiological studies have investigated the risk factors of these two subtypes separately. Our study suggests that future research must make clear distinctions between PTCC and NPTCC and not just treat them as subtypes of transitional cell carcinoma.”

Written by Grace Rattue