3 radiotherapy advances you need to know about

An important trend in modern cancer research (particularly in the UK) is to challenge traditionally held practices to understand if therapy can be safely omitted. By reducing the intensity of treatment, people living with cancer can be assured of similar outcomes and fewer side effects.

The RADICALS study, led from the UK, looked at the use of radiotherapy after curative surgery for prostate cancer. It had been considered a standard to give radiotherapy to patients with high-risk disease after surgery. The study allocated half of its 1396 patients to close surveillance (with blood test PSA monitoring) or to up front radiotherapy.

After average follow up of nearly five years, the disease outcomes were similar in both groups. However, the group that received up-front radiotherapy had more urinary incontinence as a result of the radiation treatment. The trial, published in the Lancet, has established a new standard of care.

The RADICALS trial looked at omission of radiotherapy. However, another way to de-intensify radiotherapy is to shorten treatment schedules.

Radiotherapy treatments are given over courses of divided doses (fractions). A course of radiotherapy may be divided in different ways – just as a cake can be cut into different slices of varying sizes, while still amounting to the same cake. The principle of giving a small number of large fractions is referred to as hypofractionation.

Another UK effort, The FAST-Forward study, looked at the practice of giving breast cancer radiotherapy over fifteen days and shortening this to just five days. The study included over 4000 patients and was due for presentation in the latter half of 2020.

Seeing the likely impact of COVID-19 on radiotherapy services, the team at the ICR sped up the analysis to produce results in the Spring. These showed that for certain low risk breast cancers it was safe and more convenient to receive radiation over the shorter period.

This data was welcomed globally as a way to reduce impact on services and patients during COVID-19, but the legacy of the research will be much longer lasting. You can read the full report in the Lancet.

Another use of radiotherapy is to target highly focused beams at areas of cancer spread and treat these areas to high dose. This is the principle of stereotactic radiosurgery (SRS) or stereotactic ablative radiotherapy (SABR).

The paradigm is a fundamental shift in an oncologist’s thinking, best illustrated by the Dandelion Dilemma, which poses a question: ‘If as a gardener after treating your lawn a single dandelion grows, would you treat the whole lawn with a new weed killer or instead try to weed out the single dandelion?’ Traditionally, oncologists have changed systematic therapies (chemotherapy etc) but SABR offers an opportunity to ‘pluck the weed’.

One criticism of this approach is that the ‘tail was wagging the dog’ and that these technologies were being used without evidence. Now useful evidence has accumulated. The SABR-COMET study looked at 99 patients with metastatic disease from a variety of cancers at centres in Canada, the Netherlands, Scotland and Australia – the survival outcomes in the 2/3rds of patients who received SABR were superior to those treated traditionally.

This evidence is paving the way for larger phase 3 studies. In England, SABR is available in a limited way through the ‘Commissioning Through Evaluation’ program. In January 2021 the results on 1422 patients were published, showing the treatment to be safe and effective. These data endorse SABR as an expanded option for some people with secondary disease.

You can read the full reports for SABR and SABR-COMET in the Lancet.

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