Are Benign and Borderline Brain Tumors Underreported?

Area of Science:

• Neurology
• Oncology
• Epidemiology

Background:

• Primary benign and borderline (BB) brain tumors have been reportable by US cancer registries since 2004.
• Underreporting of BB brain tumors is a concern due to clinical diagnosis in non-hospital settings.
• Magnitude and geographic variations in BB brain tumor underreporting remain unknown.

Purpose of the Study:

• To assess variations in BB brain tumor incidence rates by registry and trends compared to malignant brain tumors.
• To identify factors associated with the completeness of BB brain tumor reporting.
• To understand geographic disparities in BB brain tumor surveillance.

Main Methods:

• Utilized the North American Association of Central Cancer Registries (NAACCR) Cancer in North America (CINA) Deluxe 1995–2012 Analytic File.
• Analyzed data from 47 US population-based cancer registries.
• Calculated age-adjusted incidence rates and average annual percent change (APC); used correlation coefficients to assess relationships between incidence and clinical factors.

Main Results:

• Overall age-adjusted incidence rate: 14.2 per 100,000 for BB tumors vs. 6.6 per 100,000 for malignant tumors.
• BB tumor incidence rates varied significantly by registry (9.8–19.9 per 100,000), unlike malignant tumors (4.1–7.7 per 100,000).
• BB tumor incidence increased 2.3% annually (2004–2012), while malignant tumor rates decreased 0.9%; higher BB rates correlated with less microscopic confirmation or surgery.

Conclusions:

• BB brain tumor incidence rates substantially differ across US registries and are higher than malignant brain tumors.
• Variations in BB brain tumor incidence likely stem from differences in identifying clinically diagnosed cases.
• The increasing trend in BB brain tumor incidence may reflect improved case ascertainment, not necessarily a biological increase.