Given a passage with a context and an answer, construct a question on the basis of the information present in the passage. Construct the question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) it answer uses text phrases from the passage. Avoid creating questions that (i) can't be answered correctly without actually understanding the passage and (ii) uses the same words or phrases given in the passage.

Context: To investigate a putative increased risk of rectal cancer subsequent to prostatic radiotherapy.', 'In an analysis of the Surveillance, Epidemiology, and End Results registry, we compared men who had radiotherapy for prostatic carcinoma with those treated surgically and those treated with neither modality. Kaplan-Meier analyses for the time to failure from rectal cancer were performed between age-matched subgroups of the three cohorts. Cox proportional hazards analyses were performed to ascertain what influences might affect the incidence of subsequent rectal cancer.', 'In all, 33,831 men were irradiated, 167,607 were treated surgically, and 36,335 received neither modality. Rectal cancers developed in 243 (0.7%) of those irradiated (mean age, 70.7 years), 578 (0.3%) of those treated surgically (68.7 years), and 227 (0.8%) of those treated with neither modality (74.2 years). When age effects and the differences between the surgical and untreated cohorts were controlled for, we were unable to demonstrate any significant increased incidence of rectal cancer in men irradiated for prostatic cancer.
Answer: An increased frequency of rectal cancer after prostatic irradiation, apparent on crude analysis, could be attributed to age confounding and other unmeasured confounders associated with prostate cancer treatment and rectal cancer risk.
Is prostatic irradiation associated with any measurable increase in the risk of subsequent rectal cancer?

Context: Before desflurane is advocated for patients undergoing neurosurgical procedures, it is necessary to determine the effect of desflurane on cerebral blood flow (CBF). In this study, CBF values are compared between desflurane and isoflurane at two doses. In addition, CBF reactivity to CO2 and the effect of prolonged exposure were compared between the two agents.', 'Cerebral blood flow measurements with intravenous 133Xe were performed in 24 patients undergoing craniotomy for mass lesions, randomized to receive either isoflurane or desflurane in oxygen and air. Cerebral blood flow was determined at 1 and 1.5 MAC concentrations at PaCO2 of 25 mmHg in the absence of surgical stimulation. Intraoperatively, with 1.25 MAC anesthesia, CBF was determined at target PaCO2 of 25 and 35 mmHg. In 15 patients, an additional measurement at 1.25 MAC was made before closure.', 'At 1.0 MAC, mean +/- SD CBF values for the desflurane and isoflurane groups were 18 +/- 2 and 20 +/- 3 ml x 100 g-1 x min-1, respectively. At 1.5 MAC, CBF values were the same for the two anesthetics; 17 +/- 3 ml x 100 g-1 x min-1 for isoflurane and 19 +/- 4 ml.100 g-1 x min-1 for desflurane. During 1.25 MAC anesthesia, there were no differences between groups, with CO2 reactivity 1.3 +/- 1.2 ml x 100 g-1 x min-1 x mmHg-1 for desflurane and 1.6 +/- 0.6 ml.100 g-1 x min-1 x mmHg-1 for isoflurane. There was no demonstrable decrease in CBF with prolonged exposure to either agent.
Answer: Desflurane and isoflurane are similar in terms of absolute CBF, the response to increasing doses, and the preservation of CO2 reactivity.
Do desflurane and isoflurane have similar effects on cerebral blood flow in patients with intracranial mass lesions?

Context: There have been many studies suggesting that localized scleroderma has a strong autoimmune background, although the lesions are usually limited to the skin and subcutaneous tissue. Here we summarize previous data on the autoimmunity of localized scleroderma, mostly published in the last two decades, because there has not been a review paper summarizing autoimmunity in this disorder.', 'We classified the previous reports into three categories: antinuclear antibodies; cytokine and soluble receptors; and cell adhesion molecules and cell surface molecules. In each category, we introduce the important investigations.', 'High frequencies of antinuclear antibodies, detected by the indirect immunofluorescence method using cultured cells, are confirmed by many groups. The major autoantigens have been revealed to be histones. Recently, anti-topoisomerase II alpha antibody has been found to be detected highly frequently in localized scleroderma, while anti-topoisomerase I antibody, which is highly specific for systemic sclerosis, has not been detected in any case of localized scleroderma. In other studies, elevated serum cytokines and cell adhesion molecules suggest the immunoactivation of localized scleroderma.
Answer: Many previous studies conclude that localized scleroderma involves autoimmune abnormalities and is one of the organ-specific autoimmune disorders targeting mainly skin, although the types of autoimmune abnormality are different from systemic sclerosis.

Is localized scleroderma an autoimmune disorder?