"SpaceOAR reduces rectal bleeding…major shift in radiation therapy"

Prostate cancer is the most common cancer diagnosed in men…treatment demand increases among elderly patients

Samsung Medical Center has accumulated 1,000 cases…patients in early and mid-stage undergo treatments five times

Adopted a system that increases CT visibility…wider adoption depends on equipment and medical department collaboration

Radiation therapy for prostate cancer is evolving in a way that enhances therapeutic efficacy while also reducing adverse events and the burden of hospital visits.

As hypofractionated radiotherapy is expanding, protecting the rectum adjacent to the prostate has become a challenge. This is because radiation exposure to normal organs must be minimized to shorten the overall treatment duration.

Professor Won Park of the Department of Radiation Oncology at Samsung Medical Center recently met with Daily Pharm to discuss shifts in prostate cancer radiotherapy and the SpaceOAR System's role in reducing rectal toxicity.

Prostate cancer cases increase… Critical role of radiation in the elderly

According to the 2023 National Cancer Registry statistics from the Ministry of Health and Welfare (MOHW), prostate cancer was the most frequently diagnosed cancer among Korean men, with 22,640 cases recorded.

Professor Won Park of the Department of Radiation Oncology at Samsung Medical Center

The clinical setting has also changed. While urological cancers accounted for less than 10% of the patients Professor Park treated 15 to 20 years ago, that figure has now grown to approximately 80%. Among these, 70% to 80% are prostate cancer cases, reaching nearly 80% when looking solely at newly diagnosed patients.

Prostate cancer treatment is chosen from active surveillance, surgery, radiation therapy, or hormone therapy based on disease stage, grade of malignancy, patient age, and comorbidities. For early-stage patients with low-grade disease, clinicians sometimes monitor progression through follow-up examinations.

For localized prostate cancer requiring active treatment, surgery and radiation therapy are the primary options. In cases where the disease has progressed or exhibits high-grade malignancy, radiation therapy and hormone therapy may be administered concurrently.

Professor Park explained, "For early-stage disease, patients can choose between surgery and radiation therapy. While the therapeutic outcomes are equivalent, the procedures and side-effect profiles differ, requiring patients to make an informed choice."

Professor Park added, "Radiation can be applied from very early stages up to relatively contained prostate cancer without widespread metastases. As population aging continues, the role of radiation therapy will only expand."

Reducing rectal toxicity has led to fewer treatment sessions

The primary challenge of prostate cancer radiation therapy is that the prostate is located near the rectum and bladder. Delivering an adequate radiation dose to the tumor while avoiding exposure to adjacent normal organs is difficult, and rectal bleeding can occur post-treatment.

According to Professor Park, an analysis conducted by Samsung Medical Center on patients who previously underwent 28 fractions of radiation therapy revealed that approximately 20% experienced Grade 2 or higher rectal toxicity requiring interventions such as hemostasis or blood transfusions. To reduce this risk, the Samsung Medical Center adopted the SpaceOAR System approximately four years ago.

The SpaceOAR System creates a temporary separation by injecting a biodegradable hydrogel between the prostate and the rectum before radiation therapy. This decreases the radiation dose delivered to the rectum. However, patients whose cancer has invaded the rectum are excluded from this procedure.

In a follow-up analysis of approximately 280 early-stage patients monitored for more than two years, only one or two patients had Grade 1 rectal bleeding requiring no medical intervention, and no cases of Grade 2 or higher bleeding were identified.

Professor Park noted, "In the past, roughly two out of ten patients required additional intervention due to rectal bleeding," and added, "Since implementing the SpaceOAR System, observing bleeding that requires clinical intervention has become exceedingly rare."

Rectum protection also provided the clinical foundation for reducing treatment fraction frequency. Samsung Medical Center currently delivers radiation therapy in five fractions over a single week for a substantial proportion of early- to intermediate-stage patients. For patients who do not receive the SpaceOAR System or are ineligible because of rectal invasion, the dose per fraction is lowered, and the total number of treatment sessions is extended.

Professor Park explained that "Creating space between the prostate and the rectum allows the rectum to be protected even when administering high radiation doses per fraction," and added, "Patients can reduce their hospital visits, and the hospital can treat a larger volume of patients utilizing the same equipment."

Experience built based on 1,000 cases…Expanding application to complex cases

Samsung Medical Center recently surpassed 1,000 cumulative SpaceOAR System procedures. After acquiring dedicated equipment, weekly procedural volume increased from an initial two cases to up to 15 cases.

Professor Park attributed the significance of the 1,000-case milestone to gaining experience across a broad spectrum of patient profiles, accumulating clinical indications and limitations. The procedure was attempted even in patients presenting with tissue adhesions from recurrence following previous radiation therapy, adhesions posterior to the prostate following rectal cancer surgery, and recurrence after High-Intensity Focused Ultrasound (HIFU) therapy.

If adhesions are severe, the space between the prostate and rectum may fail to expand sufficiently, leading to procedural failure. Accumulated clinical experience now allows clinicians to assess feasibility accurately and counsel patients on procedural limitations beforehand.

Regarding the milestone of 1,000 cases, he reflected, "Extensive and varied experience has been established. It has instilled the confidence to attempt the procedure even when presented with highly challenging cases."

The SpaceOAR Vue System, introduced last year, incorporates an iodine tracer that allows hydrogel visualization via computed tomography (CT) and MRI. Unlike the conventional product, it enables more precise demarcation between the prostate and rectal boundaries and facilitates pre-treatment alignment.

Regarding this, Professor Park noted, "Patients do not need to undergo the insertion of gold fiducial markers, and clinicians can precisely target treatment areas," and added, "Verifying target positioning during actual treatment sessions has also become significantly more streamlined."

Equipment, interdisciplinary collaboration, and guidelines are the key

Patient access improved after National Health Insurance reimbursement for biodegradable material injection for prostate cancer radiotherapy was granted in 2023. However, reimbursement eligibility alone does not guarantee that every medical institution can implement the procedure.

The procedure requires transrectal ultrasound (TRUS) to visualize the trajectory of the needle relative to the prostate, along with a skilled clinical team. Samsung Medical Center also used equipment and procedural suites in the Department of Urology while acquiring specialized ultrasound techniques through the Department of Radiology.

Depending on the hospital, either the Department of Urology or the Department of Radiology may perform the procedure. Rather than which clinical department leads, wider adoption is dependent on securing the requisite equipment and expertise and building a multidisciplinary collaborative effort.

To increase introduction, Professor Park suggested, "It is challenging for a radiation oncology department to launch this program independently without equipment and prior procedural experience," adding, "Proactive efforts must be made to introduce the system through collaboration with urology or radiology departments."

Establishing standardized domestic clinical guidelines remains an unmet need. Although relevant procedural guidelines have been incorporated into international treatment standards and textbooks, this procedure was introduced in Korea approximately four years ago.

Professor Park emphasized, "Once clinical guidelines are firmly established in Korea, the number of adopting institutions will expand significantly," adding, "Expectations are high, as clinicians can alleviate concerns regarding rectal toxicity, while patients can complete their courses of treatment more rapidly with minimized adverse effects."