Final answer:
A new standard data item for a cancer registry typically goes into effect at the beginning of a diagnosis year for a central registry.
Step-by-step explanation:
The new standard data item for a cancer registry typically goes into effect at the beginning of a diagnosis year for a central registry. This ensures that accurate and up-to-date information is being collected and recorded for each newly diagnosed cancer case. By implementing the standard at the beginning of the diagnosis year, the registry can capture all relevant data for that year and have a comprehensive record of cancer cases.