"Their body would shrink, the shape of the area we were radiating would shrink and as they subsided and lost weight the position of their head would slightly change and we wouldn't adjust one iota to that, we just carried on the way we were."
In an ideal world, Harrington said, scans would be done every day to create a bespoke programme overseen by a doctor, but this is extremely time and labour intensive, needing up to two hours per session.
The team of researchers at the Institute of Cancer Research, in partnership with the Royal Marsden and funded by Cancer Research UK, sought to find a middle ground between the time-consuming fully customisable method and the antiquated, inflexible approach.
A machine called MR-Linac combines MRIs with X-rays to give a quick and accurate look at the cancer's location and automatically adjusts the aim of the radiotherapy.
This automation of the adjustment process, Harrington says, can cut the treatment down from as two hours to as little as 30 minutes without any drop-off in the quality of care.
"The technique cuts out a very laborious, time-consuming step without any detriment to our ability to target the cancer, as we found it to be 99.9 per cent as good as a fully bespoke programme," Harrington told The Telegraph.
A pioneering new study, published by the team in the journal Clinical and Translational Radiation Oncology, used the method on two patients with head or neck cancer and found that of more than 50 doses of radiation delivered, just one exceeded the acceptable threshold, providing a success rate of 99.9 per cent.
In contrast, the old-school rigid approach scored just 92.4 per cent.
"The failure rate of the old approach was as high as seven per cent, which means that there was a significant risk of either missing the tumour target, and therefore reducing the chance of curing the disease, or overdosing the normal organs and increasing the risk of toxicity," Harrington said.
"We believe the new approach means we maximise the opportunities to cure the cancer while minimising the risk of toxicity."
He added that the technique will likely be used in the future to treat other cancers, including those of the pelvis, prostate, cervix and bladder.