A comparison of treatment outcome between fiducial-based and bone-based image guided radiotherapy in prostate cancer patients.

Background And Purpose: To compare the clinical outcome in prostate cancer patients treated with radiotherapy using two forms of image guidance: bone-based (BB) or fiducial-based (FB).

Material And Methods: This retrospective study consisted of 180 patients treated with kV-kV image-guided radiotherapy (IGRT) between the years 2008 and 2011. A total of 89 patients were aligned to pelvic bone (Group BB) and 91 patients to the fiducial implanted into prostate for image guidance (Group FB). Patients were treated to a total dose of 76 Gy in 38 fractions. The Cox Regression Model was used to evaluate the influence of clinical and treatment-related parameters on overall survival, biochemical progression and progression-free survival. Acute and late toxicity were evaluated based on the RTOG/EORTC criteria. Sexual function was assessed with QLQ PR-25 (EORTC QLQ forms). An assessment of the differences in patient daily set-up from the time of simulation was performed.

Results: The incidence of acute G2/G3 genitourinary (GU) and gastrointestinal (GI) toxicity was similar between groups. In the BB group, 34 patients had G2 and 5 had G3 GU acute toxicity - compared to 40 patients with G2 and 2 with G3 in the FB group. G2 and G3 GI acute toxicity was observed respectively in 24 patients and in 1 patient in the BB group compared to 18 patients with G2 and 1 patient with G3 toxicity in the FB group. The five-year incidence of late ≥G2 GU toxicity was 12% in both groups (p = 0.98) and ≥ G2 GI toxicity 19% (BB) vs 15% (FB, p = 0.55), respectively. The five-year progression-free survival rate was 87% in BB and 81% in the FB Group (p = 0.15). The 5-year Overall Survival rate (OS) was 80% (BB) vs 91% % (FB, p = 0.20), but the difference was most pronounced in the intermediate-risk group: 5-year OS of 93% (FB) and 75% (BB), respectively (p = 0.06). No significant changes were observed in sexual or erectile functioning as compared to that specified at the beginning of radiotherapy and between the FB and BB Groups.

Conclusion: When comparing bone-based to fiducial-based techniques, no differences in clinical outcomes or late toxicity were seen in this population. However, intermediate risk prostate cancer patients are those who might benefit most from implementation of fiducial-based IGRT.