ICHNO-ECHNO 2022 - Abstract Book

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ICHNO-ECHNO 2022

alive, among them 8 (7%) alive with disease; 35 (34%) expired with disease progression and 15 (15%) patients were lost to follow up. All patients completed RT with 18(17%) having unplanned break. In acute toxicities, mucositis [grade II-55(54%) and grade III-14(14%)] and dermatitis [grade II-21(21%), grade III-2(2%)] were common. 24 patients (23.5%) required additional feeding tube insertion during RT due to dysphagia or prophylactic due to weight loss. At 6 months response evaluation (n=74), 55 (77%) patients had complete response (CR), 12 (17%) had a residual disease [7 primary alone (1 OPX, 2 LX, 4 HPX), 2 nodal disease alone, 7 patients had metastasis]. At mean time to recurrence of 9 months, 7 patients (2 OPX, 3 LX, 2 HPX) had recurrence [5 at primary site, 2 nodal]. Four patients had second primary cancers [2 carcinoma lung, 1 carcinoma tongue, 1 carcinoma OPX]. Laryngectomy was done for 8 patients (6 LX, 1 HPX, 1 OPX with supra-glottic extension); 2 for residual disease, 3 for dysfunctional larynx, 3 for recurrence.

Conclusion Outcome and toxicity profile in Indian head & neck cancer patients are similar to the published literature.

PO-0122 The influence of the dose optimisation technique on the dose and LETd distribution in proton therapy

M. Garbacz 1 , J. Gajewski 2 , K. Kisielewicz 3 , P. Olko 4 , A. Rucinski 2 , T. Skóra 5 , R. Kope ć 2

1 Institute of Nuclear Physics Polish Academy of Sciences, Cyclotron Centre Bronowice, Krakow, Poland; 2 Institute of Nuclear Physics Polish Academy of Sciences, Cyclotron Centre Bronowice , Krakow, Poland; 3 National Oncology Institute, National Research Institute, Krakow Branch, Department of Medical Physics, Krakow, Poland; 4 Institute of Nuclear Physics Polish Academy of Sciences, Division of Applications of Physics, Krakow, Poland; 5 National Oncology Institute, National Research Institute, Krakow Branch, Radiotherapy Clinic, Krakow, Poland Purpose or Objective One of the advantages of proton radiotherapy over photon radiotherapy is its higher relative biological effectiveness (RBE). RBE can vary along the beam path and may exceed the clinically accepted constant value of RBE = 1.1 used in clinical treatment planning systems (TPS). The variable proton RBE (vRBE), among others, results from the linear energy transfer (LET) of protons, which rises at the end of their range. Those elevated LET and RBE lead to the biological dose underestimation during treatment planning with clinical TPS. Our goal was to investigate the influence of the dose optimization technique (IMPT vs SFUD) on the dose-weighted LET (LET d ) distribution and therefore on the RBE-weighted dose using Monte Carlo calculations. Materials and Methods The study included patients with brain and skull base tumors treated at Cyclotron Centre Bronowice in Krakow. Original treatment plans were recalculated using the Monte Carlo FRED code (Schiavi et al. 2017) with the McNamara radiobiological model to obtain the LET d , RBE and RBE-weighted dose distributions. Those distributions were compared between different dose optimization techniques - single field uniform dose (SFUD) and intensity modulated proton therapy (IMPT).

Results

Figure 1. LET d and RBE distributions for IMPT (upper row) and SFUD (lower row) proton plans.

We compared patients with 2-fields proton plans. Figure 1 presents LET d distribution for each treatment field and RBE distributions for the whole plan calculated with the vRBE McNamara model. In the IMPT treatment fields (upper row) the high-LETd (over 5 keV/um) values are more spread around the planning target volume (PTV, red contour) compared to the