understanding of a long sentence

Total mastectomy means the complete removal of the breast, in a woman with breast cancer. I find this sentence rather badly written. However, it is speaking of a comparison of treatment methods for patients who undergo complete mastectomy (the removal of the entire breast) and those who have breast-conserving surgery (attempting to cut out just the cancerous tissue, while leaving the breast otherwise intact, i assume for cosmetic reasons).

The sentence says that randomize trials (selecting data at random, and not by a pattern or criterion) demonstrated that there were similar survival rates (i.e., women who did not die from cancer) even though there was an expectation that there would be a higher survival rate with additional surgery and radiation therapy.

It is a needlessly complex sentence, and badly written. It might have made more sense to have written it as two sentences. This is the sort of nonsense which makes the eyes of native English-speakers glaze over if they have to read to much of it. Many people who write technical descriptions seem to think that it will look more impressive or convincing if they write long, complex sentences.

Short, simple sentences are best for conveying ideas.

Thank you Setanta! You explanations are very helpful!
(I hate unnecessarily long sentences too. Unfortunately, I have to read them often. )

Your English is very good, Blue. I wish you the best of luck in your studies.

Thanks for your encouragement!
I'll try my best!