Hire a biostatistics CRO when your program involves novel or high-risk regulatory pathways, complex methodologies (e.g., adaptive/Bayesian designs), or surge workload around pivotal trial planning, SAP development, and FDA responses where deep precedent and fast turnaround reduce approval risk. Keep work in-house when you have steady, predictable needs on well-trodden pathways and sufficient internal bandwidth—often best executed as a hybrid model where internal teams handle routine analyses and an external CRO covers specialized expertise and peak capacity.