Comparison of various common whole pelvic radiotherapy (WPRT) and local radiotherapy (LRT) procedures to treat prostate cancer based on dosimetric parameters and radiobiological models

Abstract

Background: Comparing three whole pelvic radiotherapy (WPRT) procedures as well as two local radiotherapy (LRT) procedures with each other for the treatment of prostate cancer patients using dosimetric parameters and radiobiological models: tumor control probability (TCP), normal tissue complication probability (NTCP), and equivalent uniform dose (EUD). Materials and Methods: Two groups of prostate cancer patients underwent WPRT (n=16) and LRT (n=16) procedures. In the WPRT group, the patients treated with two intensity modulated radiation therapy (IMRT+IMRT) procedures at two consecutive phases. Then, two other techniques including a three dimensional (3D) conformal radiation therapy (3DCRT) phase followed by an IMRT phase (3DCRT+IMRT) and also two consecutive 3DCRT procedures (3DCRT+3DCRT) were carried out on the patients' data. In the LRT group, the patients treated with just an IMRT technique. Then a 3DCRT technique was also performed on the patients' data. All the WPRT and LRT procedures compared with each other based on the dosimetric parameters and radiobiological models. Results: The mean of dosimetric parameters did not exceed the specified dose constraints for the bladder and femoral heads in the 3DCRT+ IMRT, and for the bladder in the 3DCRT technique. In the WPRT and LRT procedures, the TCP values for the prostate did not reveal any significant differences (P>0.05). The NTCP results in accordance with the dosimetric results for the organs at risk (OARs) showed a significant decrease in the IMRT+IMRT (WPRT) and the IMRT (LRT) techniques (P<0.05). However, the EUD results were dependent on the type of the procedure and OARs. Conclusion: For selecting the appropriate treatment technique for each prostate cancer patient, a compromise between the dosimetric and radiobiological evaluation of the WPRT and LRT procedures should be considered.

Thyroid function following radiation therapy in breast cancer patients: risk of radiation-induced hypothyroidism

“…2 ) with 50 Gy/25 fractions/5 weeks. The mean and maximum doses of the thyroid and its lobes, as well as thyroid V5, V10, V20, V30, V40, and V50 (percentage of thyroid volume receiving ≥ 5 Gy, ≥ 10 Gy, ≥ 20 Gy, ≥ 30 Gy, ≥ 40 Gy, and ≥ 50 Gy, respectively) were calculated from each patient’s tissue-specific dose-volume histogram (DVH) based on the TPS [ 17 , 18 ]. DVH shows a graphical representation of the radiation dose delivered to any defined volume.…”