Providing Suggested Rules for Multiple Primary Cancer Recording, Coding and Registering in Population-based Cancer Registry

BACKGROUND: Multiple primary cancers (MPC) present many coding difficulties, while a distinction should be made between new cases and those with metastasis and/or extension and recurrence of the primary ones. We aimed to reflect on the experiences and results of data quality control of the East Azerbaijan/Iran Population-Based Cancer Registry and present our suggested rules for reporting, recording and registering multiple primary cancer. METHODS: Comparability, validity, timeliness, and completeness of data assessment were performed. As a result, we created a consulting team including expert oncologists, pathologists, and gastroenterologists to discuss for multiple primary tumors recording, identifying, coding and registering. RESULTS: In case of confirmed Blood malignancies with definite BMB results, Brain and/or Bone involvements are always metastatic. In most cases of multiple cancers with the same morphological types, the earlier should be registered as primary tumor. In most of the synchronous multiple cancers, familial cancer syndromes should be considered and rules out. In case of two tumors diagnosed at the same time in colon and rectum, primary site should be detected by T stage or tumor sizes. In case of multiple tumors in Recto-sigmoid, Colon , and Rectum the earlier history of tumor should be considered as primary site. This rule was applied for Female Genital tumors, as earlier site is always the Primary cancer and other tumors should be registered as metastatic sites. Conclusion: Given the complexity of coding MPCs, we suggested some additional rules for identifying, recording, coding, and registering multiple primary cancers in the context of the EA-PBCR program.