Feasibility and safety of shortened hypofractionated high dose palliative lung radiotherapy – A retrospective planning study

Objective: Assess the safety and feasibility of shortened hypo-fractionated high dose palliative lung radiotherapy. Methods: Fifteen palliative lung radiotherapy patients previously treated with the standard 36 Gy in 12 fractions (12F) schedule were non-randomly selected to achieve a representative distribution of tumour sizes, volumes, locations and staging. Plans were produced using 30 Gy in 5 fractions (5F) and 30 Gy in 6 fractions (6F) using a 6MV FFF co-planar VMAT technique. These plans were optimised to meet dose constraints for both PTVs and OARs where established OAR constraints were expressed as BED. The potential safety of the delivery of these plans was assessed using these BEDs and also with reductions of 10% and 20% to account for effects of chemotherapy or surgery. Results: For all 5F and 6F plans the mandatory constraints using the full BED were met, as with all 6F plans with 10% BED reductions, but reduced to 6 patients using 5F. Three of 15 5F and 6 of 15 6F plans met the 20% BED reductions. Conclusion: It is potentially safe and feasible to deliver high dose palliative radiotherapy using the 5F or 6F regimes described, when carefully planned to comparable OAR BEDs as for 12F standard. It appears that the toxicity from either of these regimes should be within acceptable limits provided that the dose constraints described can be adhered to. A Phase II study would be required to fully assess the safety and feasibility. The outcomes from such a study could potentially reduce the number of patient hospital visits for radiotherapy, thus benefiting the patient and the clinical service by optimising resource utilisation. Advances in Knowledge: Shortened hypo-fractionated high dose palliative lung radiotherapy is technically feasible provided OAR constraints are respected.

Assessing The Clinical Application Of The Van Herk Margin Formula For Lung Radiotherapy

In radiation therapy treatment planning, margins are added to the tumour volume to ensure that the correct radiation dose is delivered to the tumour in the presence of geometrical uncertainties. The van Herk margin formula (VHMF) was developed to calculate the minimum margin on the target to provide full coverage by 95% of the prescribed dose to 90% of the population. However, this formula is based on an ideal dose profile model that is not realistic for lung radiotherapy. The purpose of this study was to investigate the validity of the VHMF for lung radiotherapy with accurate dose calculation algorithms and respiratory motion modeling. Ultimately, the VHMF ensured sufficient target coverage, with the exception of small lesions in soft tissue; however, the derived PTV margins were larger than necessary. A novel planning approach using the VHMF was tested indicating the need to account for tumour motion trajectory and plan conformity.

Assessing The Clinical Application Of The Van Herk Margin Formula For Lung Radiotherapy

In radiation therapy treatment planning, margins are added to the tumour volume to ensure that the correct radiation dose is delivered to the tumour in the presence of geometrical uncertainties. The van Herk margin formula (VHMF) was developed to calculate the minimum margin on the target to provide full coverage by 95% of the prescribed dose to 90% of the population. However, this formula is based on an ideal dose profile model that is not realistic for lung radiotherapy. The purpose of this study was to investigate the validity of the VHMF for lung radiotherapy with accurate dose calculation algorithms and respiratory motion modeling. Ultimately, the VHMF ensured sufficient target coverage, with the exception of small lesions in soft tissue; however, the derived PTV margins were larger than necessary. A novel planning approach using the VHMF was tested indicating the need to account for tumour motion trajectory and plan conformity.