Radiotherapy is one of the main treatment modalities for cancer in which high-energy radiation beams are used to eradicate cancer cells. One of the major issues in radiotherapy treatment planning is to find the desired balance between contradictory goals of delivering sufficient radiation dose to the tumor while sparing the surrounding healthy tissues and critical structures. In this research, a multi-criteria mathematical optimization approach is used to quantify and incorporate the trade-off information between conflicting clinical objectives into the radiotherapy treatment planning process. Furthermore, due to biological and logistical reasons, long treatment times are undesirable and may cause inconvenience to the patient. Thus, the proposed treatment planning approach also takes the trade-off between the plan quality and treatment duration into consideration. The proposed method provides clinicians with valuable information for individual cancer patients to design radiotherapy plans that yield the desired trade-off between clinical objectives and can be efficiently delivered.