LONG-TERM EFFECTS OF MEGAVOLTAGE RADIOTHERAPY IN ACROMEGALY

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Abstract
The progress of 41 Chinese patients with acromegaly treated with megavoltage radiotherapy was reviewed after a mean follow-up of 4.5 (one-ten) years. Nine received prior surgery. Radiotherapy was delivered by a 3-field technique to a total of 4000-5000 cGy in 25 fractions. By life table analysis successful treatment of growth hormone (GH) hypersecretion, as defined by a mean GH concentration of .ltoreq. 10 mu/L, could be expected in 6, 11, 26, 64 and 67% of the patients after one, two, five, eight and ten years respectively. Median intervals before achieving a mean GH level of .ltoreq. 10 mu/L were 6.6 and 8.6 years following radiotherapy with the higher (4500-5000 cGy) and lower (4000 cGy) doses respectively, suggesting a tendency towards earlier response following radiotherapy with the higher dose. The prevalence of acquired hypopituitarism in patients followed up for over five years was 40% for gonadotrophins, 30% for TSH and 20% for ACTH deficiency respectively. In the majority of patients, acquired hypopituitarism was not apparent within five years after radiotherapy. No mortality or major side effects were noted following radiotherapy. In 34 patients on longterm bromocriptine treatment, mean GH concentrations were normalised in 26.5% of patients. We conclude that with judicious selection of patients and use of adjunctive medical therapy, megavoltage radiotherapy remains a safe and satisfactory form of treatment for acromegaly especially if expert transphenoidal surgery is not readily available.