Background: Stereotactic Body Radiotherapy (SBRT) is an established modality of treatment for low and intermediate risk prostate cancer. It’s role in high-risk category is limited by minimal long-term oncologic outcome and Quality of Life (QOL) data.

We report the early clinical outcomes in terms of biochemical disease-free rate and Overall Survival (OS) rate, Health Related QOL (HRQOL) and toxicity in high and very high-risk prostate cancer treated by Linac based SBRT and Androgen Deprivation Therapy (ADT).

Methods: NCCN high and very high-risk, treated with uniform protocol SBRT to prostate and pelvic nodes (36.25Gy/25Gy/ 5 fractions/alternate days) with long course 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. Acute and late genitourinary (GU) and gastrointestinal (GI) adverse events were recorded as per RTOG. Survival curves were calculated by Kaplan- Meir curve.

Results: 70 patients were included in the study. The median age at diagnosis was 71 years, majority (55.7%) had moderate International Prostate Symptom Score (IPSS). The median baseline serum PSA was 25.44. High and very high-risk category 39 (55.7%) and 31 (44.3%) respectively. Median follow-up (FU) was 21 months, five patients lost to FU, nine died of non-prostate cancer related cause. Three patients had biochemical recurrence and one had progressive disease. At three-year biochemical disease-free rate was 91% and OS rate 81%. The median OS was 26 months. Acute grade 2 GU and GI toxicity were reported in 14 (20%) and 8 (11.4%) respectively. Late grade 3 GI toxicity in one patient. 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 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 recovery. Mean EPIC CP score pre SBRT and at 24 months was statistically significant for sexual domain (p=0.01 by paired t-test).

Conclusion: Linac based SBRT with ADT achieved encouraging biochemical control and low toxicity with favourable urinary and bowel HRQOL in high and very high-risk prostate cancer. Overall survival did not emerge significant owing to short follow-up. We are in the process of prospective documentation of long-term outcome and adverse events.

Trinanjan Basu is a highly accomplished senior consultant and head of department in radiation oncology at HCG Cancer Centre, Mumbai. With

over 15 years of experience, he has treated 5000+ patients specialising in the treatment of diverse cancers, including head & neck, genitourinary,

colorectal, lymphoma, bone & soft tissue sarcoma, and lung cancer. His expertise includes IMRT/VMAT for head & neck cancers and SRS/SBRT

(>300 cases) for brain, spine, lung, and prostate cancers. He is actively involved in professional societies like the Society of Genitourinary Oncology, GI Oncology Executive Committee, ASCO TECAG, and serves on the ASTRO Training and Education Committee. He has more than 35 national and international publications in peer-reviewed journals.