Clinical and Dosimetric Comparison Between Non-image Guided Radiation Therapy and Fiducial-Based Image Guided Radiation Therapy With or Without Reduced Margin in Intensity Modulated Radiation Therapy for Prostate Cancer

Abstract

Purpose

This study aimed to compare the outcomes and toxicities between patients treated with image guided radiation therapy (IGRT) using fiducial markers and non-IGRT in intensity modulated radiation therapy (IMRT) for prostate cancer.

Methods and Materials

In total, 518 patients with intermediate- and high-risk prostate cancer received IMRT with 78 Gy in 39 fractions after neoadjuvant androgen deprivation therapy for at least 3 months. Of these patients, 371 were in the non-IGRT group and 147 in the IGRT group, including the IGRT-A group using the same margins as the non-IGRT group and the IGRT-B group using reduced margins. The median follow-up periods for the non-IGRT, IGRT-A, and IGRT-B groups were 99 months, 88 months, and 63 months, respectively.

Results

The 5-year biochemical recurrence-free survival rates in the non-IGRT, IGRT-A, and IGRT-B groups were 88%, 95%, and 98% (non-IGRT vs IGRT-A, P = .396; IGRT-A vs IGRT-B, P = .426), respectively. Those for intermediate- and high-risk patients were 94%, 93%, and 96% (non-IGRT vs IGRT-A, P = .916; IGRT-A vs IGRT-B, P = .646), respectively, and 87%, 96%, and 100% (non-IGRT vs IGRT-A, P = .500; IGRT-A vs IGRT-B, P = .483), respectively. For the non-IGRT and IGRT-A groups, the rates of acute grade ≥ 2 gastrointestinal toxicities and late grade ≥ 2 genitourinary toxicities were 17% and 7% (P = .019), respectively, and 28% and 16% (P = .028), respectively. In the IGRT-A and IGRT-B groups, the rates of acute grade ≥ 2 genitourinary toxicities were 45% and 21% (P = .003), respectively. All V60_Gy = the volume at least received 60Gy and V70_Gy = the volume at least received 70Gy values of the bladder and rectal walls in the IGRT-B group were smaller than those in the IGRT-A group.

Conclusions

IGRT with fiducial markers results in lower acute and late toxicities compared with non-IGRT in IMRT for intermediate- and high-risk prostate cancer. Moreover, the toxicities are further decreased by reducing the margins in the treatment planning under IGRT. These processes do not decrease the biochemical recurrence-free survival rates.