Early report on quality of life and dosimetric parameters related to adverse effects in prostate cancer patients following normo-fractionated proton therapy.

Objectives: We report the quality of life (QoL) and the impact of dose-volume-parameters on the gastrointestinal (GI) and genitourinary (GU) toxicities in localized/locally advanced prostate cancer patients treated with definitive normo-fractionated (74-76Gy) proton therapy (PT).
Methods: Twenty-five patients treated in the context of an approved clinical study (Proto-R-Prostata) were selected. Three intraprostatic fiducial markers were placed for daily position verification. A water-filled endo-rectal balloon was placed prior to each fraction. Toxicity and QoL were collected prospectively. The first were graded according to CTCAE v4, the latter by EORTC C30 and PR25 QoL questionnaires. The organs at risk (OARs; rectal wall, whole rectum, whole bladder, bladder wall, anterior and posterior bladder wall) were re-contoured. The dose (Gy) to 5-95% of the volume of OARs (D5-D95%) was reported in 5 % increments, as the volume (cc) receiving an absolute dose of 5-75 Gy (V5-V75Gy). Correlations between dose-volume-parameters to the OARs and toxicities were modelled by logistic regression.
Results: Based on the EORTC-C30, physical functioning and social functioning had a slight worsening after PT, but they improved 3 months after PT, whereas the emotional functioning increased slightly during PT and significantly 3 month after PT (p=0.035). Role functioning showed a statistically significant decrease at the end of PT (p=0.017), but also a subsequent improvement. A correlation was found between GU toxicities during PT and the functional and symptom scale based on the EORTC-PR25 (pain, urinary symptoms and hormonal treatment related symptoms, respectively). Dose-volume parameters V5-V20Gy to the anterior bladder wall and V60–V70Gy to the posterior bladder wall were significantly related to cystitis. V5Gy, V15Gy to the posterior bladder wall and V15-V20Gy to the anterior bladder wall had significant impact on urinary incontinence and urinary frequency, respectively.
Conclusions: QoL during/after PT was reported to be good. The estimated dosimetric parameters can be useful to further plan optimization and to find adequate constraints to PT.