In 1991, Professor Sten Nilsson and his PhD student Bo Lennernäs realised that the prostate, contrary to prevailing beliefs, is a mobile organ. A study confirmed their observations, and the new findings were included in Bo Lennernäs's doctoral thesis in 1995. The discovery quickly influenced prostate cancer radiotherapy practices across the world. In the papers of the thesis, they also demonstrated that it was possible to track the prostate's movements in a phantom model by inserting a small magnet that transmitted signals to an external receiver. These two findings led to the founding of Micropos Medical AB.

Discovering more about Prostate Cancer

Sten Nilsson, now a retired senior consultant at Karolinska University Hospital and Professor Emeritus at the Karolinska Institute, has dedicated over 40 years of his career to oncology, with a particular focus on prostate cancer. He has been involved in numerous pioneering research projects and developed new, crucial treatment concepts that are now used globally.

Decades of Development

When Sten Nilsson treated his first prostate cancer patients in the late 1970s, very few were cured. The tools and techniques for diagnosing and assessing whether the cancer was local or had spread were insufficient, as was radiotherapy. The available X-ray technology could visualise the pelvic skeleton but not the prostate, meaning its position had to be estimated based on the anatomy of the pelvic bones. Radiotherapy was cumbersome and time-consuming to administer, with limited impact on the tumours.

"Patients whose cancer was assessed as local received radiotherapy with what we called a 'curative intention'. But in practice, most returned after a while, and the disease remained - eventually spreading," says Sten Nilsson.

In the mid-1980s, surgery for localised prostate cancer began delivering better outcomes than radiotherapy. However, radiotherapy also advanced rapidly. Computed tomography (CT) became available, allowing the prostate and sometimes the tumour area to be visualised, which created entirely new conditions for treatment. Subsequently radiotherapy equipment, radiobiological research, and various imaging technologies like CT, MRI, ultrasound and others, also underwent enormous development.

The 1990s saw the introduction of high-dose-rate brachytherapy (HDR-BT), a method to which Sten Nilsson made significant contributions. It involves inserting 15-20 hollow needles through the skin into the prostate, through which radiation is delivered. Today, HDR-BT is often combined with external beam radiotherapy in cases of locally advanced prostate cancer.

A Discovery that Overturned Accepted Knowledge

It was during HDR-BT procedures in 1991 that Sten Nilsson and Bo Lennernäs discovered that the prostate changes position under various conditions.

"We used ultrasound to correctly position the needles in the prostate. We then observed that if a patient was anxious, perhaps coughed, raised an arm to scratch their head or simply spoke, the prostate moved. It was a true 'aha' moment. The common belief around the world was that the prostate is firmly anchored in the pelvis. We immediately realized that we had to find a way to describe and document the movement of the prostate, how much and in which directions the prostate moved", Sten Nilsson explains.

Years earlier, he had treated prostate cancer patients by implanting radioactive gold seeds into the prostate to deliver a strong local radiation dose. The method was abandoned when seed production ceased, but the treated patients retained the seeds (they were not surgically removed) - creating an opportunity to document the discovery of prostate movement.

"The gold seeds, and thus the prostate's position, are visible on X-rays. We called in a number of the former patients and took images under various conditions. For example, while straining versus relaxing, with full versus emptied bladder, and so forth. We found that the prostate frequently moved by ...