2.2. Endpoint

Three hundred and ninety five routine xerostomia toxicity follow-up reports between 6 months and 2 years after RT were analyzed. We aimed to predict moderate-to-severe xerostomia defined as grade 2 or higher (G2) according to the Common Terminology Criteria for Adverse Effects (CTCAE) (32). Two hundred and eighty five reports (72%) included quantitative information according to CTCAE¹. In case only descriptive information was provided, the scores were consistently assigned in retrospect, according to a set of rules together with Heidelberg University Hospital clinicians. According to the time intervals defined by Gabryś et al. (4), late (6–15 months) and long-term (15–24 months) follow-up reports were pooled together in order to increase the patient number. In case there were multiple follow-up reports available for individual patients, the final toxicity score was calculated as the arithmetic mean rounded to the nearest integer with x.5 being rounded up. No patients with xerostomia grade higher than 2 were observed in this cohort. Therefore, positive and negative groups comprised grade 2 and grade 0 to 1 xerostomia patients, respectively.