Moderately hypofractionated dose escalation radiotherapy for localized prostate cancer, ESHYPRO: Results of a retrospective single-centre series evaluating safety and efficacy

Purpose- Prostate cancer is the most frequent cancer among men and radiotherapy hypofractionation regimens have become standard treatments for the localized stages, but the absence of increased risk of acute and late genitourinary or gastrointestinal toxicity of the dose escalation still must be demonstrated. Material and methods- The study population included all patients with localized prostatic adenocarcinoma treated at the institut Curie from February 2016 to March 2018 by external radiation delivered by a linear accelerator using an image-guided conformal intensity modulation technique at a total dose of 75 Gy in 30 fractions of 2.5 Gy in the planning target volume that included the prostate and the proximal seminal vesicles, and could be paired with a prophylactic lymph node radiotherapy at 46 Gy in 23 fractions with simultaneous integrated boost. Results- A total of 166 patients were included. Among them, 68.6% were unfavourable intermediate or (very) high risk. The median age and follow-up were 71.4 years and 3.96 years. One hundred and forty-nine patients received prophylactic lymph node radiotherapy (89.8%). One hundred and thirty-one patients received hormonotherapy (78.9%). Genito-urinary toxicity events of grades 2 or above during radiotherapy, at 6 months, 1 year and 5 years were respectively 36.7%, 8.8%, 3.1% and 4.7%. Two patients had late grade 4 toxicity at 5 years (1.6%). Grade 2 gastrointestinal toxicity events during radiotherapy, 6 months, 1 year and 5 years were respectively 15.1%, 1.9%, 14.6% and 9.3%. Of these, eight patients had grade 3 toxicity (6.2%). There was no grade 4 toxicity. Analyses did not reveal any predictive factor for toxicity. The 5-year overall, progression-free, and specific survival rates were respectively 82.4%, 85.7%, and 93.3%. Serum prostate specific antigen concentration and cardiovascular risk factors were found to be predictive factors of deterioration in overall survival (P = 0.0028 for both). Conclusion- External radiotherapy for localized prostatic cancer with our moderately hypofractionated dose escalation regimen is well tolerated. In the absence of increased late toxicity, the analysis of the modes of long-term relapses will be interesting to determine the benefit of this dose escalation on local and distant relapses.