Relationships between dose to the gastro-intestinal tract and patient-reported symptom domains after radiotherapy for localized prostate cancer

Abstract

Background Gastrointestinal (GI) morbidity after radiotherapy (RT) for prostate cancer is typically addressed by studying specific single symptoms. The aim of this study was to explore the interplay between domains of patient-reported outcomes (PROs) on GI morbidity, and to what extent these are explained by RT dose to the GI tract. Material and methods The study included men from two Scandinavian studies (N = 211/277) who had undergone primary external beam radiotherapy (EBRT) for localized prostate cancer to 70–78 Gy (2 Gy/fraction). Factor analysis was applied to previously identified PRO-based symptom domains from two study-specific questionnaires. Number of questions: 43; median time to follow-up: 3.6–6.4 years) and dose-response outcome variables were defined from these domains. Dose/volume parameters of the anal sphincter (AS) or the rectum were tested as predictors for each outcome variable using logistic regression with 10-fold cross-validation. Performance was assessed using area under the receiver operating characteristic curve (Az) and model frequency. Results Outcome variables from Defecation urgency (number of symptoms: 2–3), Fecal leakage (4–6), Mucous (4), and Pain (3–6) were defined. In both cohorts, intermediate rectal doses predicted Defecation urgency (mean Az: 0.53–0.54; Frequency: 70–75%), and near minimum and low AS doses predicted Fecal leakage (mean Az: 0.63–0.67; Frequency: 83–99%). In one cohort, high AS doses predicted Mucous (mean Az: 0.54; Frequency: 96%), whereas in the other, low AS doses and intermediate rectal doses predicted Pain (mean Az: 0.69; Frequency: 28–82%). Conclusion We have demonstrated that Defecation urgency, Fecal leakage, Mucous, and Pain following primary EBRT for localized prostate cancer primarily are predicted by intermediate rectal doses, low AS doses, high AS doses, or a combination of low AS and intermediate rectal doses, respectively. This suggests that there is a domain-specific dose-response for the GI tract. To reduce risk of GI morbidity, dose distributions of both the AS region and the rectum should, therefore, be considered when prescribing prostate cancer RT.

Hydrogel rectum-prostate spacers mitigate the uncertainties in proton relative biological effectiveness associated with anterior-oblique beams

“…However, the study was retrospective and limited to one year of follow-up for 86 patients treated using stereotactic body radiation therapy. Other work suggests that complete rectal DVHs are important in determining patient-reported outcome [31]. Thus for a cohort with hydrogel spacers, it is not clear whether the additional rectal sparing offered by AO protons (relative to IMRT or SB protons) is likely to prove clinically meaningful or not.…”

Urinary bladder dose–response relationships for patient-reported genitourinary morbidity domains following prostate cancer radiotherapy

“…Given the level of detail in the two PROs and to avoid subjective grouping of symptoms from various GU-specific symptom domains, factor analysis was applied to the 12 and 23 questions of potentially RT-related GU injuries in DK and SW, respectively [15]. Factor analysis is a statistical method to investigate the relationship between items in a dataset (Appendix).…”

Temporal patterns of patient‐reported trismus and associated mouth‐opening distances in radiotherapy for head and neck cancer: A prospective cohort study

“…Temporally robust symptom domains were identified from our factor analysis methodology, which was previously applied to group radiation-induced patient-reported items for prostate cancer 14 . A detailed description of this approach can be found in the Appendix S1 [14][15][16][17][18][19] .…”

“…Temporally robust symptom domains were identified from our factor analysis methodology, which was previously applied to group radiation‐induced patient‐reported items for prostate cancer. A detailed description of this approach can be found in the Appendix . Exploratory followed by confirmatory factor analysis was carried out in R using the Psych and Lavaan packages with the comparative fit index used as a measure of factor model agreement.…”