| الوصف: |
Stereotactic ablative radiotherapy (SABR) is an effective non-surgical alternative treatment for early stage, inoperable, non-small cell lung cancer (NSCLC). These patients are often elderly with co-morbidities. UK recommendations have been that treatments can be delivered in 3, 5 or 8 sessions ('fractions') for peripheral targets; often decided on the proximity of the normal tissues to the tumour, with treatments close to the chest wall frequently delivered in 5-8 fractions. For these patients, extra hospital trips and additional radiotherapy resources are required despite the risk of a rib fracture and lung toxicity being low. The purpose of this research was to determine if the calculation of the radiobiological parameters for the chest wall and ribs could be used to personalise the number of treatment fractions whilst maintaining reasonable tumour control. In addition, patient opinion was sought on personalised fractionation via a service evaluation questionnaire. Dose volume histogram (DVH) data obtained from 200 previously treated lung SABR patients was used to determine baselines for publication of tumour control probability (TCP) and normal tissue complication probability (NTCP) for rib fracture and radiation pneumonitis using the software, Biosuite (Version 12.01). The survival data, TCP and NTCP was disaggregated to confirm there was no sex bias. A service evaluation was conducted to obtain the patient perspective on personalised fractionation during the corona virus (COVID-19) pandemic of 2020 -2022. Most patients surveyed thought that they could cope with their previous treatment schedules but would be willing to accept as many as recommended, with few saying it would affect their decision to undergo radiotherapy. Three quarters of those surveyed were willing to consider alternative fractionation schemes. Moving towards alternative fractionation schemes for the purposes of reducing hospital footfall or to capitalise on radiobiological optimised dose schemes may therefore be well tolerated with high patient compliance. This thesis shows that a consideration of TCP and NTCP may prove useful for individual patients to trade off acceptable toxicity and number of visits, instead of resorting to the binary choice currently employed of whether the tumour is in close proximity, or not, to the chest wall. The results suggest that there is potential for improved tumour control whilst maintaining current levels of toxicity, by reducing 8 fraction treatments to 5 fractions for some patients. The overall population risk of both radiation pneumonitis and rib fracture in this cohort is low as compared to some historically reported values for lung SABR and for standard radiotherapy. |