Scripties UMCG - Rijksuniversiteit Groningen
English | Nederlands

Long term toxicity after radiotherapy for prostate cancer: generation of multivariable prediction models

(2017) Vreeswijk, N. van (Nick)

Every year, 10.000 men in the Netherlands are diagnosed with prostate cancer, making it the most common cancer among men. Radiotherapy is commonly used as a curative treatment for localised prostate cancer. Normal tissue complication probability (NTCP) models predict the risk of toxicity after radiotherapy. These models are mostly based on patient characteristics, treatment characteristics and radiation dose/volume data within organs at risk (OAR’s). These are organs in or surrounding the treatment area. The purpose of this study is to develop NTCP-models for rectal and urinary toxicity, in order to reduce toxicity in the future.
A prospective study was carried out with 302 men, who were treated in the University Medical Centre Groningen (UMCG), with primary radiotherapy for localised, biopsy proven prostate cancer. After treatment, patients filled in questionnaires and visited their radiation oncologist annually to keep track of disease progression and treatment related toxicity. Using multivariable logistic regression analyses, NTCP models were developed.
Rectal bleeding is associated with rectal wall V70 (Vx is the relative volume of an OAR receiving at least x Gy), anal canal V30 and aspirin use. Faecal incontinence is associated with anal canal V10 and patient age. Rectal pain is associated with anorectum V70 and androgen deprivation therapy. Bladder incontinence is associated with bladder V76, α-blocker use, diabetes, age. Macroscopic haematuria is associated with bladder V76 and diabetes. These models could be used to limit long-term toxicity, by reducing the dose in the OAR’s.

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