During the period 1999-2005, radiotherapy planning converged on anatomy-guided inverse planning applied across brachytherapy and external-beam modalities, unifying dose distributions through anatomy-based objective functions that align optimization with patient anatomy. Conformity-focused planning and straightforward indices, complemented by early dose-volume and end-user optimization, shaped cross-modality plan quality and comparability. Robustness to geometrical uncertainties became a central concern, with coverage-probability frameworks and explicit margin delineation guiding probability-based guarantees of target coverage and sparing. Image-guided and adaptive radiotherapy emerged as a core methodological direction, linking imaging data to planning adjustments and enabling iterative improvements. Prostate brachytherapy remained a dominant clinical domain, with imaging standards and MR-informed planning for high-dose-rate boosts reinforcing practice. Historical Significance: The era's key breakthroughs integrated geometry with biological targets to yield probabilistic planning assurances, standardizing three-dimensional image-based planning, dosimetry, and quality assurance for prostate seed implants and related techniques. Simple conformity metrics and formal plan-quality assessments provided practical, cross-modality benchmarks that facilitated broader adoption of quantitative planning approaches and set the stage for later advances in adaptive and robust radiotherapy.