1788 - Prognostic and predictive value of 18F-PET/CT on the response to treatment in locally advanced non-small cell lung cancer (NSCLC)

Background

PET/CT is an essential component in the initial assessment of locally advanced NSCLC. However, the role of PET/CT in the assessment of response to therapies is not well established.

Methods

We reviewed all stage III NSCLC patients assessed at our centre between January 2009 and March 2018, selecting those with PET/CT evaluation at diagnosis and after treatment (chemotherapy and/or radiotherapy). We evaluated the prognostic differences between mayor PET/CT response (reduction of ≥ 50% of initial SUVmax), minor PET response (reduction of < 50%) and absence of response, by Cox regression. We assessed the predictive value of PET/CT for pathological response in both tumour and mediastinal nodes in patients who had undergone surgery after an induction treatment.

Results

We reviewed 249 patients. In 92,3% an initial PET/CT evaluation was carried out. 117 patients (46.9%) had a PET/CT re-evaluation after an initial chemotherapy and/or radiotherapy treatment. We observed a higher risk of disease progression in patients with a minor PET/CT response (HR 1.97; IC95% 1.2-3.2) and without a response (HR 2.3; IC95% 1.4-4.6, p < 0.01). Progression free survival (PFS) at 12 months was 73%, 47% and 32% among patients with a mayor response, a minor response and no response, respectively. Differences in overall survival (OS) did not reach statistical significance (p = 0,06), but a higher risk for death was seen with a minor response (HR 1.7; IC95%, 1-2,9) and no response (HR 2.1; IC95%, 1,2-3,9). 37 patients (14.9%) underwent surgery after an induction treatment. A greater reduction of SUVmax was observed when pathological response was achieved (mean SUVmax reduction of 94% with complete pathological response vs 27% in absence of response). 22 patients with N2 disease pre-induction therapy underwent surgery. SUVmax reduction was higher in patients with a response (60% vs 35%). However, post-induction mediastinal SUVmax > 2.5 presented a sensitivity of only 42.9% and a specificity of 87.5%.

Conclusions

PET/CT response after induction therapy was a good prognosticator for PFS and OS in stage III NSCLC patients. However, response evaluation by PET/CT should be interpreted with caution due to its lack of precision.

Clinical trial identification

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

V. Calvo de Juan: Honoraria (self): BMS; Honoraria (self): MSD; Honoraria (self): AstraZeneca; Honoraria (self): Boerhinger; Honoraria (self): Roche. M. Provencio: Honoraria (self), Research grant / Funding (institution): BMS; Honoraria (self): MSD; Honoraria (self): AstraZeneca; Honoraria (self), Research grant / Funding (institution): Boerhinger. All other authors have declared no conflicts of interest.