Session Item

Patient-Reported Outcomes Measures (PROMs) are an increasingly important tool to record the patient’s individual perception of toxicity. Understanding the relations between dosimetric parameters and PROMs could help to optimize the treatment. However, these relations are poorly described for cervical cancer patients and the spatial information of dose distributions is usually not included in the analysis. In this study patient-reported acute diarrhea symptoms are evaluated specifically, and their relationship with dosimetric parameters of the bowelbag and rectum, as well as spatial information, is investigated. 

In this prospective study, 103 locally-advanced cervical cancer (LACC) patients treated according to an IMRT/VMAT plan-of-the-day protocol were included. Radiotherapy was combined either with concurrent chemotherapy, or with neo-adjuvant chemotherapy and concomitant hyperthermia. Selected patients had filled in a combined EORTC QLQ-C30 and QLQ-CX24 questionnaire at baseline, and at least one combined questionnaire in the acute phase of the treatment (week 4, week 5, 1 week after RT, 4 weeks after RT or 3 months after RT). Maximum deterioration from baseline was recorded for the question regarding diarrhea symptoms, and was scored as an event when a deterioration of two points or more was registered. Dose-volume parameters were collected for the rectum and bowelbag. Dose Surface Maps (DSMs) were constructed for the rectum, which is a technique to visualize a dose distribution on the surface of a tubular organ in a standardized way. Clinical variables and dose-volume parameters were included in the analysis. Permutation testing was performed for the DSMs to find areas of significance (p < 0.05).

Within the entire cohort, a diarrhea incidence of 59% was found. The use of concomitant chemotherapy resulted in a significant increase in reported diarrhea with an odds ratio of 2.5 (CI: 1.1-5.9). The dose-volume parameters V_5Gy-V_25Gy of the rectum were significantly associated with diarrhea, but no significant relation was found for the bowelbag. Conversely, the PTV volume was significantly related with diarrhea with an odds ratio of 1.17 (CI: 1.01-1.37) per 100 cc increase in PTV volume. The results of the rectal DSMs are shown in Figure 1, where a significantly higher dose to the inferior part of the rectum is visible.

PTV volume and concomitant chemotherapy were found to be significant for acute diarrhea symptoms, possibly attributable to bowel irradiation and chemotherapy-related radiosensitizing effects. Additionally, the results suggest that a reduction of inferior rectum dose could decrease patient-reported diarrhea symptoms. Diarrhea typically originates from the bowel, yet the DSMs in this study indicate that radiation-induced damage to the rectum contributes to these complaints. Further studies are necessary to validate the results.