Understanding the importance of adequate time between each radiotherapy session (rests and exposure to the radiation beam)
By: Dr Rolando Loría
Radiotherapy It is a treatment commonly used in the management of various types of cancer. Radiation is given in fractions (sessions) to maximize damage to cancer cells while minimizing the impact on surrounding normal tissues. The rate of cell death is a crucial aspect in the effectiveness of radiotherapy treatment.
When we talk about the medical term “intra-fraction elongated intervals,” we are referring to the time separation between radiation doses within a treatment. Administration of fractionated doses allows normal cells time to repair damage caused by radiation, while cancer cells, which often have a more limited repair capacity, can accumulate damage and eventually die (Shibamoto, Miyakawa, Otsuka , & Iwata, 2016).
If the times between doses are too short, normal cells may not have enough time to recover, which may increase the risk of side effects. On the other hand, if the intervals are too long, cancer cells may have time to repair some of the damage, reducing the effectiveness of the treatment.
The average times between each radiotherapy session They will depend on the dose and the treatment scheme, however the minimum “rest” time between one session and another is approximately 6 hours in Brain injuries and 8 hours in body injuries.
Maximum “rest” times They will vary between 24 or 48 hours between each session depending on the indicated treatment scheme.
EXHIBITHION TIME
In addition to this, there is another important variable to consider: the times of exposure to radiation during treatments.
The expert Khorramizadeh and collaborators demonstrated that when the exposure time to the radiation beam per session increases from 15 minutes to 45 minutes in each fraction (treatment session), the death of tumor cells is reduced. It seems that the main phenomenon that affects the cellular response is the repair of sublethal damage. The effect of the dose administered over 15 minutes may be greater than that of 30 and 45 minutes (Khorramizadeh, Saberi, & Tahmasebi-Bi, 2017).
High dose equipment such as the Linear Accelerator that the XXI Century Radiotherapy Medical Center, They allow radiosurgery doses to be delivered extremely accurately in the maximum periods indicated in these studies, achieving not only the expected cellular damage but also contributing to the patient's comfort by not being exposed to long periods of treatment as happens in other radiosurgery equipment.
The rate of cell death in radiotherapy depends on several factors, including the sensitivity of the cells to radiation damage, the type of radiation used, the total dose administered, and the dose fraction. The relationship between cell death rate and specific intra-fraction intervals may vary depending on the type of cancer and treatment (Benedict, Lin, Zwicker, Huang, & Schmidt-Ullrich, 1997).
It is important to note that radiotherapy treatment planning is carried out in a personalized manner for each patient, taking into account various clinical and radiobiological factors. Radiation oncologists work to optimize the delivery of radiation to achieve maximum effectiveness against cancer while minimizing side effects on normal tissues.
Bibliography
Khorramizadeh, M., Saberi, A., & Tahmasebi-Bi, M. (September 1, 2017). Impact of Prolonged Fraction Delivery Time Modeling Stereotactic Body Radiation Therapy with High Dose Hypofractionation on the Killing of Cultured ACHN Renal Cell Carcinoma Cell Line. J Biomed Phys Eng(3), 205-216.
Shibamoto, Y., Miyakawa, A., Otsuka, S., & Iwata, H. (2016). Radiobiology of hypofractionated stereotactic radiotherapy: what are the optimal fractionation schedules? J Radiat Res.(57 Suppl 1), 76-i82.
Benedict, S., Lin, P., Zwicker, R., Huang, D., & Schmidt-Ullrich, R. (Mar 1, 1997). The effectiveness of intermittent biological irradiation as a function of overall treatment time: development of correction factors for linac-based stereotactic radiotherapy. Int J Radiat Oncol Biol Phys., 37(4), 765-9.
