Radiotherapy is a cheap and effective method of cancer treatment, which despite its heavy use, follows a largely standard dose protocol. Human genome sequencing allows us to personalize medicine, including determining the minimum amount of beneficial, but potentially harmful, radiation for each individual.


Radiotherapy is a commonly used, effective and cheap method of cancer treatment. It is used in almost two thirds of cancer patients in the USA and is responsible for 40% of cancer cures and only 5-10% of cancer-related costs. Despite its effectiveness, radiotherapy research is underwhelming and radiotherapy doses are independent of the individual. Using genomic sequencing, scientists aim to personalize radiotherapy to minimize the patient’s radioactive exposure.

Radiotherapy is a result of high doses of radiation that are focussed on cancer-affected areas to kill cancer cells. While improved technology has enhanced our ability to focus on the cancerous areas and preserve healthy tissue, the high energy waves can also damage tissue surrounding the affected area. The side effects from residual radiation range depending on the area of treatment and can include skin problems, fatigue and in rare cases, a secondary cancer. Thus it is in a physician’s best interest to limit radiotherapy dosage to as little as possible.

Scott et al. investigated using a model to determine the genomic-adjusted radiation dose (GARD) in a new study published in The Lancet. The researchers created an algorithm to calculate the minimum dosage required to effectively treat an individual’s cancer dependent on their genes. It has been proven that radiosensitivity differs between patients and thus, different patients require different levels of radiation. The researchers collected tissue samples from patients enrolled in the Total Cancer Care (TCC) protocol to calculate GARD scores and determine differences between tumour types. Retroactive data was also taken from five clinical cohorts to determine if GARD was clinically effective.

The study showed that GARD can range widely within a population and between tumour types. GARD was highest (most sensitive) in cervical cancers and throat cancers and lowest in sarcomas (connective tissue cancer) and gliomas (cancer originating in the brain or spine). GARD was also proven clinically effective when, despite uniform dosages, tumours with higher GARD and patients with higher GARD and the same tumour type had better patient outcomes. These findings suggest that using genomic data, radiotherapy can be personalized to minimize side effects and improve patient outcome. It should be stressed that more variables can be included, such as additional tumour and healthy tissue parameters to better adjust dosage levels.




Written By: Wesley Tin, BMSc

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