What term refers to the effective date for accessioning cases into the registry?

The correct term referring to the effective date for accessioning cases into the registry is the reference date. This date is crucial as it indicates the starting point from which data is collected and utilized for a particular patient in the cancer registry. The reference date is often established as the date of diagnosis, which means it marks the day when the cancer was confirmed or identified.

In contrast, the other options relate to different aspects of patient management and data collection. The date of diagnosis signifies when the tumor is diagnosed, while the date of first contact refers to when the patient first engages with the healthcare system regarding their cancer. The date of last contact indicates when the patient was last seen by a healthcare provider, which is important for follow-up and survivorship data but not for the accessioning of cases. Therefore, the reference date succinctly encapsulates the moment when the case officially enters the registry, making it the precise term for that particular function.