Dataset Information

Stereotactic radiotherapy boost after definite chemoradiation for non-responding locally advanced NSCLC based on early response monitoring ¹⁸F-FDG-PET/CT.

ABSTRACT:

Background and purpose

Prognosis of locally advanced non-small cell lung cancer remains poor despite chemoradiation. This planning study evaluated a stereotactic boost after concurrent chemoradiotherapy (30?×?2?Gy) to improve local control. The maximum achievable boost directed to radioresistant primary tumor subvolumes based on pre-treatment fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT) (pre-treatment-PET) and on early response monitoring ¹⁸F-FDG-PET/CT (ERM-PET) was compared.

Materials and methods

For ten patients, a stereotactic boost (VMAT) was planned on ERM-PET (PTV_boost;ERM) and on pre-treatment-PET (PTV_{boost;pre-treatment}), using a 70% SUV_max threshold with 7?mm margin to segmentate radioresistant subvolumes. Dose was escalated till organ at risk (OAR) constraints were met, aiming to plan at least 18?Gy in 3 fractions (EQD₂ 84?Gy/BED 100.8?Gy).

Results

In five patients, PTV_boost;ERM was 9-40% smaller relative to PTV_{boost;pre-treatment}. Overlap of PTV_boost;ERM with OARs decreased also compared to overlap of PTV_{boost;pre-treatment} with OARs. However, any overlap with OAR remained in 4/5 patients resulting in minimal differences between planned dose before and during treatment. Median dose (EQD₂) covering 99% and 95% of PTV_boost;ERM were 15?Gy and 18?Gy respectively. Median boost volume receiving a physical dose of? ??18?Gy (V18) was 88%. V18 was???80% for PTV_boost in six patients.

Conclusions

A significant stereotactic boost to volumes with high initial or persistent ¹⁸F-FDG-uptake could be planned above 60?Gy chemoradiation. Differences between planned dose before and during treatment were minimal. However, as an ERM-PET also monitors changes in tumor position, we recommend to plan the boost on the ERM-PET.

PROVIDER: S-EPMC7807537 | BioStudies |

REPOSITORIES: biostudies

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