Within a year of the discovery of X-rays in 1896, physicians started using X-rays to treat breast cancer. However, radiotherapy was not very successful at that time due to insufficient knowledge of how radiation works. As science progresses over the decades, professionals now understand how radiotherapy is best used to treat cancer.
Radiotherapy relies on ionizing radiation, such as X-rays and radioactive materials (e.g., iodine, iridium, lutetium), to kill dividing cells by damaging its DNA. Since cancer cells divide much faster than normal cells, they are more susceptible to radiation killing. Types of radiotherapy commonly used to treat prostate and breast cancer are external-beam radiation and in selected cases brachytherapy. In external-beam radiotherapy, a machine delivers radioactive rays onto the tumour. Brachytherapy involves implanting radioactive materials in the form of small seeds, wires, or catheters inside or near the tumour.
One great benefit of radiotherapy is its versatility; it can be used alone, with chemotherapy or immunotherapy to enhance effectiveness, or after surgery to minimize the risk of cancer recurrence by killing residual cancer cells. Radiotherapy is also relatively safe and painless for the patient, so no anesthesia is required. Nevertheless, radiotherapy has its own set of limitations and risks:
#1. Many follow-ups may be required since radiotherapy is performed over many sessions to gradually kill or shrink the tumour, which may take weeks to months. In certain cases, the patient may need to undergo radiotherapy daily or multiple times weekly for months.
#2. Certain medical conditions and prior radiation treatment may disqualify a patient from receiving radiotherapy.
#3. Radiotherapy may not kill all cancer cells, especially when the tumour has grown rather large or resides in places lacking sufficient oxygen supply.
#4. Side effects include fatigue, skin reactions, swelling and tenderness of breast and hair loss on areas treated for breast cancer. For prostate cancer, side effects involve diarrhea, burning sensation and frequent urination, urinary incontinence, erectile dysfunction and fatigue. These side effects may be experienced during the radiation treatment and may last for weeks or months post-radiotherapy.
#5. There is a risk of triggering new mutations in normal cells that may become cancerous, which may cause another type of cancer years later. Nevertheless, the risk of radiation-induced secondary cancer is low. For prostate cancer patients, it is estimated that 8% will develop secondary cancer (i.e., typically lung and bladder cancers) about 5 years after radiotherapy. For breast cancer patients, about 4% will contract another cancer (i.e., typically digestive tract cancer) about 2 years following radiotherapy.
#6. Radiotherapy imposes stress and selection pressure on the cancer, which may give rise to radio-resistant cancer that resists killing. This phenomenon is an acknowledged problem in radiotherapy for prostate and breast cancers, contributing to cancer recurrence and progression.
Therefore, radiotherapy does not always cure cancer on its own. Often, complementary therapies are required, so patients are always advised to seek professional advice and second opinions.
