Impact of neoadjuvant androgen deprivation therapy on toxicity in intensity-modulated radiation therapy for prostate cancer.

This study aimed to compare toxicities, prostate volume and dosimetry, between patients who underwent intensity-modulated radiation therapy (IMRT) combined with ≥3 months of neoadjuvant androgen deprivation therapy (NADT) and those without NADT for prostate cancer. In total, 449 patients with intermediate- and high-risk prostate cancer received 78 Gy IMRT in 39 fractions, of which 129 were treated without any ADT (non-ADT group) and 320 with NADT ≥3 months (NADT group). Adverse events and dose-volume indices were compared between the two groups retrospectively. The NADT group had a lower rate of acute grade 2 gastrointestinal (GI) toxicities (17% vs 25%, P = 0.063) and late grade 2 GI toxicities (P = 0.055), including a significantly lower rate of late grade 2 rectal hemorrhage (P = 0.033), compared with the non-ADT group. There were no cases of late grade 3 or higher GI toxicities. The average volume of the prostate in the NADT group was 38% smaller than that in the non-ADT group (43.7 vs 27.0 cm3, P < 0.001). Bladder V40Gy and V50Gy, and rectum V40Gy, V50Gy, V60Gy and V70Gy were significantly smaller in the NADT group. In the NADT group, no significant difference was observed in adverse events or dosimetry between the subgroups with NADT ≥12 and <12 months. Acute and late rectal toxicities were reduced by NADT within ≥3 months in accordance with reduced prostate volume and improved rectal dosimetry. This suggests a merit of administering neoadjuvant ADT ≥3 months for reducing rectal toxicities.