During the period 1968-1980, radiotherapy research embedded time-dose relationships into clinical planning. Time-Dose-Fractionation factors provided a practical, source-insensitive framework unifying planning across brachytherapy and external radiotherapy, enabling consistent interpretation of schedule and dose-rate effects. Clinically, prostate cancer radiotherapy shifted from cobalt teletherapy to external-beam and regional-field approaches, guided by survival and local-control data. Breast cancer studies tested altered fractionation schedules, while field design and extended-field strategies in prostate radiotherapy aimed to improve disease control through better lymphatic and pelvic coverage. Historical Significance: Pivotal developments included extending the time-dose paradigm to brachytherapy, simplifying NSD-based planning with Time-Dose-Factors and promoting standardized fractionation strategies. Foundational dosimetry work established how to determine absorbed dose across beam qualities, underpinning dose prescriptions and quality assurance. By formalizing fractionation and dose-rate considerations, this era laid groundwork for modern cross-modality radiobiological planning.