**2. Description and features of the web application**

The development of the application was carried out by specialists in the field of radiobiology, medical physics, and practicing radiation oncologists on the basis of the International Sakharov Environmental Institute of Belarusian State University and N.N. Alexandrov National Cancer Centre of Belarus. The source code of the program was written by an IT developer, a specialist in applied mathematics and actuarial sciences, using JavaScript (52.2%) and HTML (47.8%) programming languages. The technical requirement for the user is to have a browser that supports JavaScript. The program is accessed *via* the Internet link https://hypo-calc.github.io/.

Web application features:


The application is divided logically into three areas. These are the data entry area, the area of calculated values, and the treatment schedule. In the data entry area, the user sets the parameters he needs. The following cells are required to be filled in: *Dose per Fraction*, *Number of Fractions*, *Fractions proceed*, *α/β ratio*. Fields *Start of treatment*, *Recovery halftime T*1/2, and *Use D*prolif are filled in when it is necessary to take into account the duration of the course, interruptions, and incomplete reparation with multifraction irradiation per day. The *Use D*prolif field becomes active when the number of days of the RT course exceeds 21 days. The appearance of the application is shown in **Figure 1**.

In the area of calculated values, the values of *Overall treatment days*, *Total dose*, *Biological Effective Dose (BED),* and *Equivalent dose EQD*2 depend on the entered values of the *Dose per fraction* and the *Fractions*. The values in the cells *Factual gap days* and *Factual treatment days* depend on the changes made to the *Treatment Schedule*. The *Equivalent dose owing to proliferation* is calculated on condition that the cell *Use D*prolif is filled.

The *Treatment schedule* is filled in automatically if the input fields are filled in correctly. Clicking on filled cells makes them empty; clicking on empty cells adds fractions. With a forced change in the number of fractions, a dose per fraction is recalculated inside the calendar cells. If the number of already treated fractions is


### **Figure 1.**

*Appearance of the web-application.*

set, they are displayed in the *Treatment schedule* in gray. The dose in these cells is not recalculated when the number of remaining fractions changes. When pointing to a cell with the mouse cursor, it becomes available to add several factions per day by clicking on the "+" inside the cell. By clicking on t, the time interval between fractions can be set.

A digital copy of the application, as well as the necessary documents and materials about it, are registered and transferred for storage to the National Center for Intellectual Property of the Republic of Belarus (certificate of voluntary registration and deposit of the copyright object No. 1487-KP, act No. d20220013 dated 03/25/2022; the authors are Orgish A.N., Batyan A.N., Dziameshka P.D., Hancharova K.V., Haida A.V.).
