Abstract T062

A priori estimation of mediastinal toxicities after radiotherapy for Hodgkin Lymphoma - A secondary analysis of the HD16/17 Trial by the German Hodgkin Study Group using normal tissue complication probability calculations

Background: Treatment-associated cardiopulmonary toxicities are main causes for long-term mortality of Hodgkin lymphoma survivors. Concerning radiotherapy, disease extent, field design and setup of radiation treatment may alter the dosimetric exposure and therefore the individual risk profile. Previous works of our group could elaborate an overall low-risk profile for pulmonary toxicities which is modulated by treatment techniques. The following analysis aims at a pre-treatment estimation of relevant mediastinal toxicities after radiotherapy in modern trials for first line treatment of Hodgkin lymphoma.

Methods: Normal tissue complication probability calculations (NTCP) were used to evaluate the toxicity rates for the heart, lungs and female breast of patients undergoing radiotherapy for early-stage Hodgkin lymphoma. Overall, 45 randomly selected patients from the HD16 and HD17 trials by the German Hodgkin study group were included and risks were calculated using the Lyman–Kutcher–Burman model.

Results: Median RT doses to the heart, lungs, left breast and right breast were 6.4 Gy, 5.4 Gy, 18.4 Gy and 16.2 Gy in the HD16 cohort, and 20.6 Gy, 11.0 Gy, 26.2 Gy and 24.6 Gy in the HD17 cohort. Consequently, median NTCP values for pericarditis, pneumonitis and fibrosis of the left or right breast were 0.0%, 0.0%, 0.7% and 0.6% in the HD16 cohort, and 0.0%, 0.1%, 1.1% and 1.0% in the HD17 cohort, respectively. In accordance with these numbers, none of the included patients displayed any of the evaluated toxicities during clinical follow-up. The use of higher doses (30 Gy) in the HD17 cohort led to an increase in toxicity compared to the HD16 cohort (20 Gy) concerning pneumonitis (p<0.01) and breast fibrosis (p=0.02 and 0.01, respectively). No significant influence of the planning target volume size or the radiation technique could be found in this study.

Conclusion: In summary, the clinically observed and NTCP-calculated toxicity rates corroborate the overall low-risk profile of radiotherapy for Hodgkin lymphoma. Further treatment individualization will be attempted in the future.