AsianScientist (Feb. 18, 2019) – A research group in Japan has revealed that cervical cancer rates in Japan have risen in recent years owing to a low cancer screening rate and a cessation of government-recommended vaccination against the human papillomavirus (HPV). They published their findings in the journal Cancer Research.
Two strains of HPV account for more than 70 percent of all cervical cancer cases. Fortunately, there are vaccines against HPV that have been shown to drastically reduce the onset of cervical cancer. Coupled with early screening techniques like the pap smear, cervical cancer is a largely preventable and treatable disease.
However, the incidence of cervical cancer in Japan has been increasing, say researchers led by Professor Yutaka Ueda of Osaka University, Japan, who examined data from 1976-2012 which included over 50,000 cervical and related cancer cases extracted from the Osaka Cancer Registry.
“The Osaka Cancer Registry gives us especially valuable insight on cancer trends because it’s a large and accurately recorded cohort,” said Ueda. “Osaka prefecture accounts for about 10 percent of Japan’s population, so the data are quite representative of the country.”
The researchers retroactively classified the cases by stage, age group, diagnosis period and histological type using multiple imputation, a reliable method for estimating missing values to yield more comprehensive data. They then calculated the age-adjusted (equal to those in a normally distributed population) incidence rates, and 5- and 10-year survival rates.
They found that, from 1976 to 2000, Japan’s age-adjusted rate of cervical cancer dropped profoundly. However, in the 21st century, it reversed course and started climbing. Japan’s cervical cancer screening rate is a very low 40 percent. Although HPV vaccination was introduced in 2009, after just four years, the government had stopped recommending it amid reports of supposed adverse events. Nevertheless, cervical cancer survival rates have mostly risen, thanks to more effective treatment.
The current findings are somewhat confounding, noted the researchers, as the rising survival rates offset the increasing incidence. These survival rates likely owe to the success of concurrent chemotherapy and radiation therapy (CCRT) in place of radiation alone, and the official recommendation of CCRT’s use.
Additionally, the researchers highlighted that age may negatively correlate with radiation therapy resistance. Predictably, younger people had better overall survival rates, but for localized cervical cancers, which are commonly treated with surgery or radiation, older people (60 years and above) had better survival rates than younger individuals (40-59 years) when undergoing radiation.
“Increased survival rates are certainly a good sign, yet the increasing age-adjusted incidence is concerning,” said lead author Dr. Asami Yagi of Osaka University. “The finding that radiation may be less effective in younger patients with localized cervical cancer is surprising, but could prove useful. Our results should serve as a strong indicator that better preventive measures are needed, and these results can also provide guidance on treatment choices.”
The article can be found at: Yagi et al. (2019) Epidemiological and Clinical Analyses of Cervical Cancer Using Data From the Population-based Osaka Cancer Registry.
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Source: Osaka University; Photo: Pixabay.
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