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Written By: Editorial Team | Published : October 23, 2018 11:33 AM IST
High dose radiation can decrease treatment time for prostate cancer. © Shutterstock
High dose radiation with fewer rounds seems to work well with men who are suffering from low or intermediate prostate cancer risk. This kind of treatment can reduce the length of the treatment and also chances of recurrence suggest a new study. Stereotactic radiation is a form of external beam radiation therapy (EBRT) that delivers substantially larger doses of radiation per treatment session over a much shorter time period than traditional EBRT was used for the study. The subjects were been treated or kept under a watch since 2000. This is a long-term, multi-institutional study. However, this treatment modality isn't widely accepted by experts and doctors as they express concern over the long-term safety and efficacy as high doses of radiation is used which can lead to an overload of toxins in the body. The American Society for Radiation Oncology (ASTRO) and National Comprehensive Cancer Network (NCCN) have issued specific guidelines and called for longer follow-up studies of stereotactic radiation for prostate cancer, including multi-institutional data, to address concerns about potentially worse late toxicities occurring from higher-dose treatments.
Even the lead author Amar U. Kishan, MD, an assistant professor in the department of radiation oncology at the David Geffen School of Medicine at the University of California, Los Angeles (UCLA) said that radiation therapy is typically delivered in small daily doses over a multi-week period because prostate cancer cells appear to be unusually sensitive to higher daily doses of radiation, one can reduce the duration of treatment from as many as 8-9 weeks with 39-45 treatments down to about 1.5 weeks with 4-5 treatments. However, he also expressed the concerns that correct guidelines need to be followed when using radiation therapy.
The study followed 2,142 patients over a period of 6.5 years. Patients were followed for a median period of 6.9 years (interquartile range (IQR): 4.9-8.1). Those who were low-risk were followed for 7.1 years (IQR 5.4-8.8); those with favourable intermediate-risk were followed for 6.2 years (IQR 4.1-7.9), and those in the unfavourable intermediate-risk group were followed for 5.9 years (IQR 3.3-7.1). 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 favourable intermediate-risk disease and 27 patients with the unfavourable intermediate-risk disease.
Researchers measured the safety and efficacy of stereotactic radiation using the following criteria: a cumulative incidence of biochemical recurrence (BCR) marked by rising PSA levels following SBRT; cumulative incidence of distant metastases (DM), i.e., the cancer spreading from the tumor to distant organs or lymph nodes; biochemical recurrence-free survival (BCRFS); and overall survival. They also evaluated the occurrence short-term adverse events within 90 days following completion of SBRT.
None of the patients in the study died from prostate cancer. In all, 100 patients (6 per cent) experienced recurrence and 10 experienced distant metastases (0.6 per cent). In the low-risk group, 95.5 per cent of patients were free from BCR at seven years. In the favourable intermediate-risk group, 91.4 per cent of patients were BCR-free at seven years. In the unfavourable intermediate-risk group, 85.1 per cent were BCR-free at seven years.
