Session Item

Main objective: to compare acute toxicity between a cohort treated with standard fractionation and a cohort treated with hypofractionated radiotherapy.

Secondary objectives: to compare acute toxicity grade between cohorts. To compare acute toxicity and acute toxicity grade in a subgroups analysis: concomitant vs. no concomitant chemotherapy; Small-Cell Lung Cancer (SCLC) vs. Non-Small-Cell Lung Cancer (NSCLS); stage; age >65 vs. ≤65 years old, radiotherapy technique 3D-CRT vs. IMRT. To evaluate if there is any association between different variables and acute toxicity in the whole sample.

Acute toxicity assessed by Common Terminology Criteria for Adverse Events version 4.0 (CTCAE v4.0) was retrospectively compared between two cohorts of non-metastatic lung cancer patients. Cohort 1 (treated between April 2020 and April 2021): hypofractionated radiotherapy (NSCLC: 55Gy/20 fractions, concurrent chemotherapy; 52,5Gy/15 fractions without concurrent chemotherapy; SCLC: 40,05Gy/15 fractions). Cohort 2 (treated between March 2019 and March 2020): standard fractionation (60-66Gy, 1,8-2Gy/fraction with or without concurrent chemotherapy). Chi-square, Fisher exact test, Student-t test, relative risk and logistic regression were used in the statistical analysis.

77 patients were included. Median age was 67,88 years (±8,26). 64,9% of patients were men and 35,1% were women. The most frequent histology was NSCLC (61%) and most patients were stage III at the diagnosis (IIIA 39%; IIIB 31,2%; IIIC 19,5%) (Table 1). In cohort 1, 24 patients had grade 1-2 toxicity, 3 patients had grade 3 toxicity and 1 patient presented grade 5 toxicity (pneumonitis). In cohort 2, 27 patients had grade 1-2 toxicity, 2 patients had grade 3 toxicity and there were no grade 4-5 toxicities. There were no statistically significant differences neither in acute toxicity between the two cohorts (RR 0,884 (95% CI 0,512-1,529; p=0,651)) nor in the toxicity grade presented (RR 0,878 (95% CI 0,560-1,379; p=0,576)). No statistically significant differences were observed in the subgroups analysis (Table 2). The logistic regression showed that treatment on ≥3 nodal regions was independently associated with acute toxicity.

In our study there were no statistically significant differences in acute toxicity incidence between fractionation regimens. No differences were observed in terms of acute toxicity grade neither between the two cohorts nor in the subgroups analysis. This is concordant to the results obtained in other retrospective studies. However, clinical trials are needed to prospectively compare standard fractionation vs. hypofractionation and also to compare different hypofractionated regimens. Late toxicity and efficacy are needed to be evaluated. This and other international studies may lay the foundations to develop clinical trials