Does partial surgical tumour removal influence the response to octreotide‐LAR in acromegalic patients previously resistant to the somatostatin analogue?

Abstract

To compare the intrapatient response to the same dose of slow-release octreotide (OCT-LAR) before and after noncurative surgery in acromegalic patients who did not attain disease control after primary treatment with OCT-LAR. Prospective clinical study. Eleven acromegalic patients (eight men, aged 42.45 +/- 11.15 years, 10 macroadenomas) received OCT-LAR (20 mg, n = 1; 30 mg, n = 10) every 28 days as the primary treatment (1stOCT-LAR) for 11.3 +/- 4.2 months, without IGF-I normalization. They were subsequently submitted to surgery without cure and were then treated with the same dose of OCT-LAR for 8.0 +/- 6.5 months (2ndOCT-LAR). GH and IGF-I serum concentrations were obtained under basal conditions as well as during treatment. Pituitary tumour volume was assessed by magnetic resonance imaging (MRI) of the sella. IGF-I was also expressed as a percentage of the upper limit of the normal age- and sex-matched range (%ULNR IGF-I). After 1stOCT-LAR, there was a decrease in GH levels (P = 0.003) and %ULNR IGF-I (P = 0.009) compared to baseline (B), but no IGF-I normalization. Tumour shrinkage was observed in eight of 10 patients with macroadenomas (median 63.7%, range 24.5-75.5%). After surgery, mean levels of GH and %ULNR IGF-I were lower than those at baseline (P = 0.0004 and P = 0.003, respectively), but not when compared to values during 1stOCT-LAR (P = 1.000 and P = 0.957, respectively). MRI confirmed surgical tumour removal (median 64%, range 4.9-96.6%) in eight of the 10 patients. Comparing the 2ndOCT-LAR results with postsurgical results, there were no significant decrease in %ULNR IGF-I (P = 0.061) and GH levels (P = 0.414). Nine patients (82%) achieved IGF-I normalization. The degree of surgical tumour reduction did not correlate with IGF-I normalization (P = 0.794). When comparing the results between 1stOCT-LAR and 2ndOCT-LAR, there was a decrease, albeit not statistically significant, in serum GH levels (P = 0.059) and a significant decrease in %ULNR IGF-I (P = 0.011). Using strict criteria (same patient, same drug, same dose) our results strongly suggest that the surgical reduction of tumour mass can improve the outcome of OCT-LAR treatment in acromegalic patients resistant to primary therapy with SA.