Health related quality of life (HRQOL) and early clinical outcomes of high - very high risk prostate cancer treated with linac based stereotactic body radiotherapy (SBRT) and long term androgen deprivation therapy (ADT).

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Background: Stereotactic body radiotherapy (SBRT) in NCCN high-risk (HR) and very high-risk (VHR) prostate cancer is evolving but limited by long-term oncologic outcome and quality of life (QOL) data. We report early clinical outcomes in terms of biochemical disease-free rate, overall survival (OS) rate, health related QOL (HRQOL) and toxicity in HR and VHR prostate cancer treated by Linac based SBRT and long term androgen deprivation therapy (ADT). Methods: NCCN HR and VHR, treated with uniform protocol of Linac based SBRT (prostate and pelvic nodes - 36.25Gy/25Gy/5 fractions/alternate days) with long term ADT (18-24 months) were included. HRQOL was assessed for urinary incontinence, urinary obstructive, bowel, sexual and hormonal domains by Expanded Prostate Cancer Index Composite for Clinical Practice (EPIC‐CP) questionnaire. Maximum score of 12 for each domain, lower score indicating better HRQOL. EPIC-CP was documented pre SBRT, 6 monthly till 24 months and at 36 months post SBRT. Acute and late genitourinary (GU) and gastrointestinal (GI) adverse events were recorded as per RTOG. Survival curves were calculated by Kaplan-Meier curve. Results: 70 patients were analyzed. Median age was 71 years, majority (55.7%) had moderate pre SBRT International Prostate Symptom Score (IPSS). The median baseline serum PSA was 25.44. HR and VHR category 39 (55.7%) and 31 (44.3%) respectively. Median follow-up (FU) was 21 months, five patients lost to FU and nine died of non-prostate cancer related causes. Three patients had biochemical recurrence and one had metastatic progression. At 3 year biochemical disease-free rate, OS rate was 91% and 81% respectively. The median OS was 26 months. Acute grade 2 GU and GI adverse events were reported in 14 (20%) and 8 (11.4%) respectively. Late grade 3 GI/GU adverse events in one patient each. Pre-SBRT mean HRQOL scores were 1.2 (urinary incontinence), 1.3 (urinary obstructive), 0.3 (bowel), 5.6 (sexual) and 0.78 (hormonal). At 24 months mean urinary incontinence and obstructive scores decreased to 0.68 and 0.72 respectively, indicating probable recovery, while bowel score remained stable at 0.28. Till 24 months mean sexual (7.6) and hormonal (2.19) scores showed increasing trend indicating worsening of QOL followed by a decline at 36 months (6.2 and 1.2 respectively) representing probable recovery. Mean EPIC CP score pre SBRT and at 24 months was statistically significant for sexual domain (p=0.01 by paired t-test). Conclusions: Linac based SBRT with long term ADT achieved encouraging biochemical control and fewer adverse events with favourable urinary and bowel HRQOL in HR and VHR prostate cancer. Overall survival did not emerge significantly owing to shorter follow-up. We are in the process of prospective documentation of long-term outcomes and adverse events.