Purpose: To investigate the impact of reducing planning target volume (PTV) margins on patient reported quality-of-life (QOL) for patients with localized prostate cancer after radiation therapy (RT)
Methods: A cohort of 20 patients were included in a single institution IRB-approved prospective study, out of which 9 were planned with reduced margins (5 mm uniformly except 4 mm at prostate/rectum boundary), while 11 were control patients with standard margins (10/6 mm). At time points pre-treatment, post-treatment, and at 2, 6, 12, 18, 24, 36, 48, and 60 months follow-ups, EPIC-26 based patient reported QOL data was collected. Validated EPIC-26 methodology was used to baseline correct and standardize all post-RT QOL scores to five separate EPIC QOL domains on a [0-100] scale. Correlations between QOL scores and dosimetric parameters were investigated, and the overall QOL differences between the two groups (QOL(M-R)-QOL(control)) were calculated for each time point.
Results: Age, Gleason score, and PSA level differences between the two groups were statistically insignificant (p>0.2). Median QOL follow-up length for the 20 patients was 48 months at the time of reporting. At 48 months post-RT, standardized and baseline-corrected mean QOL(M-R)-QOL(control) were improved for “Urinary Incontinence”, “Urinary Irritative/Obstructive”, “Bowel”, and “Sexual” EPIC domains by 3.5,14.8,10.2, and 16.1, respectively. QOL differences between groups were clinically significant for the last 3 domains, while statistically significant for only “Urinary Irritative/Obstructive” domain (p=0.03). PTV/rectum (p=0.03) and PTV/bladder (p=0.14) intersection volumes were larger for the control group (7.2±5.8, 18.2±8.1 cc) compared with the margin-reduced group (2.6±1.8, 12.5±8.3 cc), while the dose to these intersection volumes did not reach statistical significance (p>0.1) between the groups. PTV/rectum intersection volume showed a moderate correlation (R=-0.6, p=0.01) to “Bowel” EPIC domain.
Conclusion: Margin-reduced group exhibits clinically meaningful improvement in Urinary, Bowel, and Sexual QOL domains. More patients are needed to draw unequivocal conclusions.