Introduction: Somatostatin analogues (SSA) are a cornerstone in the treatment of neuroendocrine tumours. Two clinical trials have defined the disease control effect of these treatments; the PROMID study of Octreotide LAR vs placebo, median time to tumour progression (TTP) 14.2 m vs 6.0 m, and the CLARINET study (Lanreotide vs placebo), median progression free survival (PFS) 31 m vs 18 m. In every day practice, however, many neuroendocrine tumours commenced on SSA are growing slowly before initiating treatment thus making determination of treatment benefits protracted and difficult, particularly as SSA may simply slow rather than stop tumour growth. In the CLARINET study 95% of cases showed no growth in 3 months pre-treatment. PROMID did not assess pre-treatment growth rates. We have therefore looked at radiological measures of tumour growth rates before and after commencing SSA in a cohort of patients to determine true treatment effects and assess possible factors predictive of response.
Methods: 34 patients with metastatic neuroendocrine tumours commenced on SSA were identified from the West Yorkshire Neuroendocrine Tumour Service database. In all patients 2 pre-treatment CT scans with measurable metastatic lesions were selected and compared to 2 CT scans over a similar time period after initiation of treatment. Tumour diameters and volumes were calculated using imaging software. The rates of change in these parameters over the scan interval was calculated pre and post treatment initiation. Correlation with clinical, radiological and pathological features was investigated.
Results: The median (range) time between pre-treatment scans was 177 days (31903) with 47% showing progressive disease by RECIST. Median post treatment scan interval was 212 days (73752). The median % change in tumour length and volume per day pre-treatment was 0.127 and 0.355. Post-treatment median % change in tumour length and volume per day was 0.025 and 0.073. This slowing of tumour growth rate was statistically significant. No significant association was observed between Ki-67 or Krenning score and tumour growth retardation.
Conclusion: SSA can be shown to slow tumour growth rate even in already very slowly growing NETs. Measurement of rate of change of tumour length/volume may allow better prediction of benefit.
02 Dec 2019
UK and Ireland Neuroendocrine Tumour Society