Radiotherapy (treatment with ionizing radiation) is one of the most effective current cancer treatments. It works by damaging DNA and other cellular components. In which ways could radiotherapy control or cure cancer, and why does radiotherapy often have significant side effects?

Verified step by step guidance

1. Understand that radiotherapy controls or cures cancer primarily by causing damage to the DNA of cancer cells, leading to cell death or preventing their ability to divide and proliferate.
2. Recognize that ionizing radiation induces DNA double-strand breaks and other types of damage, which, if unrepaired or misrepaired, trigger apoptosis (programmed cell death) or senescence in cancer cells.
3. Consider that radiotherapy targets rapidly dividing cells, which is a characteristic of many cancer cells, making them more susceptible to DNA damage compared to most normal cells.
4. Acknowledge that significant side effects occur because radiotherapy can also damage normal, healthy cells in the surrounding tissues, especially those that also divide rapidly, such as cells in the skin, gastrointestinal tract, and bone marrow.
5. Note that the extent of side effects depends on factors like radiation dose, treatment area, and individual patient sensitivity, which explains why side effects can vary widely among patients.

Key Concepts

Mechanism of DNA Damage by Ionizing Radiation

Ionizing radiation used in radiotherapy causes breaks in DNA strands, especially double-strand breaks, which can lead to cell death or malfunction. Cancer cells, which divide rapidly, are more susceptible to this damage, leading to their destruction or growth inhibition.

Selective Targeting of Cancer Cells

Radiotherapy aims to target cancer cells more than normal cells by exploiting differences like rapid division and impaired DNA repair in tumors. However, some normal cells near the tumor are also affected, which limits the dose and effectiveness.

Side Effects Due to Damage of Normal Cells

Radiotherapy can harm healthy tissues surrounding the tumor, causing side effects such as inflammation, fatigue, and tissue damage. These effects arise because normal cells also experience DNA and cellular damage, especially in rapidly dividing tissues like skin and mucosa.