Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.

Example Input: Abstract: Two patients with metastatic dysgerminoma of the ovary were treated with a combination of etoposide, bleomycin, and cisplatin at The University of Texas M.D. Anderson Hospital and Tumor Institute at Houston. Both patients achieved a complete remission. Patient 1 developed a massive recurrence in the para-aortic lymph nodes 21 months after diagnosis and treatment with right salpingo-oophorectomy alone. She received four cycles of chemotherapy and is free of disease 21 months from the start of chemotherapy. Patient 2 had Stage III dysgerminoma and a lymphangiogram positive for tumor in the para-aortic lymph nodes. After surgery she received three cycles of chemotherapy and is free of disease 20 months from the start of chemotherapy. Both complete remissions were documented with second-look laparotomy. Chemotherapy may be an alternative to radiotherapy for the treatment of metastatic dysgerminoma and should also be considered for selected patients with Stage I disease. A literature review further supports the conclusion that additional clinical trials might expand the indications for chemotherapy in patients with this disease.
Example Output: Adolescence

Example Input: Abstract: A carotid-cavernous fistula recurred 16 years after a Hamby procedure. The recurrence was manifested by subarachnoid hemorrhage originating from dilated draining pial veins. The fistula was closed with a balloon catheter introduced through a patent remnant of the cervical carotid artery. Patients who have previously undergone Hamby trapping and embolization should be reassessed for an occult fistula that could predispose them to intracranial bleeding.
Example Output: Adult

Example Input: Abstract: Adenosine infusion (100 micrograms X kg-1 X min-1) in humans stimulates ventilation but also causes abdominal and chest discomfort. To exclude the effects of symptoms and to differentiate between a central and peripheral site of action, we measured the effect of adenosine infused at a level (70-80 micrograms X kg-1 X min-1) below the threshold for symptoms. Resting ventilation (VE) and progressive ventilatory responses to isocapnic hypoxia and hyperoxic hypercapnia were measured in six normal men. Compared with a control saline infusion given single blind on the same day, adenosine stimulated VE [mean increase: 1.3 +/- 0.8 (SD) l/min; P less than 0.02], lowered resting end-tidal PCO2 (PETCO2) (mean fall: -3.9 +/- 0.9 Torr), and increased heart rate (mean increase: 16.1 +/- 8.1 beats/min) without changing systemic blood pressure. Adenosine increased the hypoxic ventilatory response (control: -0.68 +/- 0.4 l X min-1 X %SaO2-1, where %SaO2 is percent of arterial O2 saturation; adenosine: -2.40 +/- 1.2 l X min-1 X %SaO2-1; P less than 0.01) measured at a mean PETCO2 of 38.3 +/- 0.6 Torr but did not alter the hypercapnic response. This differential effect suggests that adenosine may stimulate ventilation by a peripheral rather than a central action and therefore may be involved in the mechanism of peripheral chemoreception.
Example Output:
Adenosine