# Incidence patterns of rare cancer in southeast Asian and western Pacific countries (RARECAREnet Asia project): a study using population-based cancer registry data, 2011–2015

## TL;DR

This study estimates the incidence of rare cancers in Southeast Asia using cancer registry data, revealing some cancers are more common there than in other Asian countries.

## Contribution

The study provides the first population-based estimates of rare cancer incidence in Southeast Asia using standardized methods.

## Key findings

- Some rare cancers in Malaysia and Thailand had higher incidence rates than in Japan, Korea, and Taiwan.
- Pediatric cancers like pancreatoblastoma and odontogenic tumors were more common in Malaysia.
- Nasopharyngeal cancer incidence was higher in Thailand and Malaysia compared to Japan and Korea but lower than in Taiwan.

## Abstract

In Southeast Asia (SEA), the understanding of most rare cancers is limited, which sometimes leads to delays in diagnosis, treatment, and care. This study aimed to estimate for the first time the incidence of rare cancers in SEA using population-based cancer registry (PBCR) data from the 2011–2015 period.

This study used data from the nationwide PBCR of Malaysia and two PBCRs in northern Thailand in Chiang Mai and Lampang Cancer registries. The age-standardized incidence rate (ASR) per 100,000 person-year of the rare cancers included in the RARECAREnet list was calculated. All analyses were performed using SEER∗Stat (version 8.3.5). Cancers defined as rare by RARECAREnet in Europe were also rare in Thailand and Malaysia.

The ASR of some rare cancers in Thailand and Malaysia were greater than that in Japan, Korea, and Taiwan, including some pediatric cancers (pancreatoblastoma and odontogenic malignant tumors) in Malaysia, eye and adnexal cancer, and epithelial tumors of the penis in Thailand. ASR of nasopharyngeal cancer was higher in Thailand and Malaysia than in Japan and Korea but lower compared to Taiwan.

Although most rare cancers were also rare in Thailand and Malaysia, some cancers were not considered rare. However, the incidence of some rare cancers in Thailand and Malaysia were higher than that in Japan, Korea, and Taiwan. To enhance understanding, diagnosis, treatment, and care of rare cancers, reliable epidemiological data needs to be generated under the RARECAREnet Asia project by working with countries in Asia with high-quality PBCRs.

This study was supported by a UICC Yamagiwa-Yoshida Memorial International Cancer Study Grant (Award/Grant Number: YY/2022-1477) and Government of Japan Ministry of Health Labour and Welfare Grant numbers: 23EA1033, and was partially supported by 10.13039/501100002842Chiang Mai University, Thailand.