Abstract 879P
Background
Adaptive replanning leads to decrease dose to normal tissues and improves the target volume coverage. We conducted this study to determine the volumetric and dosimetric changes during the treatment course and observe the optimum timing of replanning in locally advanced head and neck carcinoma (LAHNC).
Methods
Twenty patients completing the inclusion and exclusion criteria were enrolled in the study. Pre-treatment planning scans were acquired and a single plan (OPLAN) was generated and executed for the entire treatment. Adaptive replanning (RPLAN) was taken after 20 fractions (4th week) of radiotherapy and dose distribution with and without replanning compared to remaining fractions. Dosimetric and volumetric parameters between OPLAN and RPLAN were compared.
Results
Comparative volumetric analysis showed a reduction of the planning target volume (PTV), ipsilateral and contralateral parotid after four weeks of radiotherapy, which was statistically significant (P <0.05). RPLAN showed reduced PTV D2, which was statistically significant in only PTV HR (p=0.0001), D50 was significant in PTV HR and IR (p=0.0154 and 0.025 respectively), and D98 significant in PTV HR, IR, LR (p=0.046, 0.0035 and 0.014 respectively). Interim replanning significantly improved conformity of the treatment plan. The mean percentage change in conformity index of HR, IR and LR was 1% (p=0.007), 1% (p=0.018) and 1.03% (p=0.008) respectively. Mid-treatment replanning reduced doses to the spinal cord (Dmean), which is statistically significant (P=0.0002). Mean doses to ipsilateral and contralateral parotid of RPLAN (19.91 Gy and 19.92 Gy, respectively) were significantly reduced compared to OPLAN (24.37Gy and 22.05 Gy, respectively).
Conclusions
The use of a mid-treatment planning scan and adaptive replanning improves the target volume coverage and normal tissue sparing in LAHNC.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
A. Pandey.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.