Extensive long-term study shows that stereotaxic radiotherapy for the body is as safe and effective as a long-lasting treatment – ScienceDaily

Stereotaxic radiation therapy is a form of external radiation therapy (external beam radiotherapy) that provides much higher doses of radiation per treatment session over a much shorter period of time than conventional radiation therapy. It is also referred to extreme hypofractionation because it produces higher radiation levels per fraction or dose.

The treatment has been studied since 2000 but has not been widely adopted due to concerns about safety and long-term effectiveness. The guidelines published by ASTRO and the National Comprehensive Cancer Network (NCCN) have called for longer follow-up studies on the stereotactic radiation of prostate cancer, including multi-institutional data, to address potential late-life toxicity issues. more severe resulting from higher dose treatments.

"This study must meet these criteria and put patients at ease when they are considering treatment options," said lead author Amar U. Kishan, MD, an assistant professor in the department of Radiation Oncology from the David Geffen School of Medicine at the University of California, Los Angeles (UCLA).

"Radiotherapy is usually given in small daily doses over a period of weeks," said Dr. Kishan. "However, since prostate cancer cells appear to be particularly sensitive to higher daily doses of radiation, you can reduce the duration of treatment from 8 to 9 weeks with 39 to 45 treatments at about 1.5 weeks with 4 to This study should dispel the fears of those who prefer to take a shorter course of treatment that they can safely do and with the same positive results that they would get from a longer course of treatment. "

This multi-institutional consortium study – to date, the largest long-term outcome analysis after SBRT for this patient population – includes data from 10 inpatient trials and two large multi-institutional studies. It examines the long-term safety and effectiveness of SBRT in the treatment of low-risk and intermediate-risk prostate cancer in a cohort of 2,142 men enrolled in Phase II trials in residential settings. the SBRT from 2000 to 2012.

Of the 2,142 patients evaluated, just over half (55.3%, n = 1,185) had low-risk disease; about one-third (32.3%, n = 692) had a favorable intermediate-risk disease; and 12.4% (n = 265) had an adverse intermediate risk disease, that is, they had multiple intermediate risk factors, Gleason primary disease type 4, or 50-positive nuclei. %. The median age of the patients was 67.9 years (range: 41-92).

Most patients were treated daily (47.3%) or every other day (47.4%), while a small percentage (5.3%) were treated once a week. Doses ranged from 33.5 to 40 Gray (Gy) and were administered in four or five fractions (88% of patients received five fractions). A small percentage (5.4%, n = 115) of patients received concomitant antiandrogenic therapy (ADT, also known as hormone therapy), with utilization rates ranging from 3.6% in low-risk patients to 9.4% in adverse intermediate risk patients. The median duration of AD was three months.

Patients were followed for a median of 6.9 years (interquartile range (IQR): 4.9 to 8.1). Those with low risk were followed for 7.1 years (IQR 5.4-8.8); those with a favorable intermediate risk were followed for 6.2 years (IQR 4.1-7.9); and those of the group at intermediate adverse risk were followed for 5.9 years (IQR 3.3 to 7.1). A subset of 305 patients had a minimum follow-up of nine years and a median follow-up of 9.8 years. These included 223 patients with low-risk disease, 65 patients with intermediate-risk disease and 27 patients with intermediate-risk disease.

The researchers measured the safety and efficacy of stereotactic radiation using the following criteria: a cumulative incidence of biochemical recurrence (BCR) marked by an increase in PSA levels after treatment with SBRT; cumulative incidence of distant metastases (DM), that is, cancer spreads from the tumor to distant organs or lymph nodes; survival without biochemical recurrence (BCRFS); and overall survival. They also assessed the occurrence of short-term adverse events within 90 days of completion of SBRT treatment.

None of the patients in the study died of prostate cancer. A total of 100 patients (6%) had recurrence and distant metastases (0.6%). In the low-risk group, 95.5% of patients were free of BCR at seven years. In the favorable intermediate risk group, 91.4% of patients were free of BCR at seven years. In the at-risk-adverse group, 85.1% were free of BCR at seven years.

The overall survival rates of the low risk and intermediate risk groups were 91.4% and 93.7% at seven years after treatment. In the adverse intermediate risk group, the most aggressive form of cancer in this study, overall survival was 86.5% at seven years.

Serious toxicities were rare. Thirteen patients (0.6%) had Grade 3 acute genitourinary toxicity (genitals or urinary or GU) and 42 patients (1.9%) had late Grade 3 GU toxicity. There was just late grade 4 GU (haemorrhagic urethritis) and late grade 4 gastrointestinal toxicity (fistula in ano).

"These numbers are the same, if not better, than other types of radiation techniques more commonly used," said Dr. Kishan. "There is no evidence of more serious toxicity with SBRT. We have shown that this method is both safe and effective and that it should be a standard treatment option for patients with low or intermediate risk prostate cancer. "

Each year, approximately 233,000 men are diagnosed with prostate cancer, the most common cancer in men in the United States. The majority of these are low-risk cancers that are eligible for a wide range of treatments, including external radiotherapy, radical prostatectomy, brachytherapy, tetanus treatment and active surveillance. Radiation therapy is one of the most effective treatment options, with an overall cure rate of 98%.

"Fewer treatments for patients would be more convenient and less expensive," said Dr. Kishan. "This could also reduce the number of missed work days.The health system will save money and patients will also save a lot of time and money.This may offer a benefit. considerable psychological impact, as men can live their lives more effectively. " and put their treatment behind them. "

The abstract "Long-term results of stereotactic radiotherapy for the treatment of low-and intermediate-risk prostate adenocarcinoma: multi-institutional consortium study" will be presented in detail at a conference Press Release and Oral Synthesis Session at the 60th Annual Meeting of ASTRO in San Antonio.