In France, as in most countries, strict strategies were implemented in cancer hospitals to reduce the spread of coronavirus , but to maintain as much as possible the capacity of oncology health services [1,2]. These strategies included the reduction of elective services, an emphasis on remote visits, and the use of personal protective equipment [3][4][5][6][7]. International radiation therapy (RT) academic societies proposed to restrict the indications for treatment [8], to delay as long as possible the start of nonurgent treatments and to prefer hypofractionated regimens [9][10][11][12][13][14][15][16]. To our knowledge, none of these recommendations anticipated how to handle the load of delayed treatments after the lockdown. However, the successful management of cancer treatments during lockdown undoubtedly correlates with the successful management of post-lockdown activity overload.The Institut Curie has one of the largest RT departments in Europe. It is spread over three separate sites in the Paris area and has a total of eleven LINACs (six in Paris, four in Saint-Cloud and one in Orsay) and three treatment rooms for proton therapy in Orsay. In 2019, 5,860 patients were treated and the average number of treatment essions per month delivered was 8931, comprising 4183 sessions in Paris, 3303 in Saint-Cloud and 1445 in Orsay. In order to comply with the international recommendations mentioned above, several measures had to be applied in our department to protect both patients and operators from the risk of contamination. The challenges of post-crisis management following the COVID-19 pandemic therefore had to be anticipated. Here, we propose some key considerations to prepare for the post-lockdown period by pre-
An experimental approach for modeling the lateral penumbra of a proton beam has been investigated. Measurements were made with a silicon diode in a water tank. Several geometrical configurations (phantom position, collimator-to-surface distance, collimator diameter, bolus thickness, air gap, etc.) and beam characteristics (range, modulation, etc.) have been studied. The results show that the lateral penumbra is almost independent of the beam modulation and the diameter of the collimator. The use of scaled variables for depth and penumbra allows us to represent the increase in penumbra with depth for any configuration with a second order polynomial function, provided that the penumbra at the entrance of the medium and at the depth of the range are known.
Background
Proton minibeam radiation therapy (pMBRT) is a new radiotherapy approach that has shown a significant increase in the therapeutic window in glioma‐bearing rats compared to conventional proton therapy. Such preclinical results encourage the preparation of clinical trials.
Purpose
In this study, the potential of pMBRT for treating clinical indications candidates for the first clinical trials (i.e., brain, lung, and liver metastases) was evaluated.
Methods
Four clinical cases, initially treated with stereotactic radiotherapy (SRT), were selected for this study. pMBRT, SRT, and conventional proton therapy (PT) dose distributions were compared by using three main criteria: (i) the tumor coverage, (ii) the mean dose to organs‐at‐risk, and (iii) the possible adverse effects in normal tissues by considering valley doses as the responsible for tissue sparing. pMBRT plans consisted of one fraction and one–two fields. Dose calculations were computed by means of Monte Carlo simulations.
Results
pMBRT treatments provide a similar or superior target coverage than SRT, even using fewer fields. pMBRT also significantly reduces the biologically effective dose (BED) to organs‐at‐risk. In addition, valley and mean doses to normal tissues remain below tolerance limits when treatments are delivered in a single fraction, contrary to PT treatments.
Conclusions
This work provides a first insight into the possibility of treating metastases with pMBRT. More favorable dose distributions and treatment delivery regimes may be expected from this new approach than SRT. The advantages of pMBRT would need to be confirmed by means of Phase I clinical trials.
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