This prospective observational study will evaluate the efficacy and adverse effects of a "simple hydromorphone PCA pump model", which is a rapid titration followed by a convenient maintenance technique, to treat home cancer patients with severe or critical cancer pain or refractory cancer pain.

This is a single-arm multicenter study that will involve 8-10 centers and 50 cases in total. A better pumping mode was discovered through repeated optimization and adjustment of PCA pump parameters, ensuring the unity of convenience, safety, and flexibility: on the one hand, it is convenient for clinicians to set up and adjust the pump quickly; on the other hand, it is also convenient for patients to control at home; thus, it solves the complex pumping and dosing problems. Nearly 20 patients with severe cancer pain or a cancer pain crisis were treated using this model, and the control satisfaction rate was 100% in each case.

The purpose of this study is to:

1. Main objective: To explore the efficacy and adverse effects of a simple hydromorphone PCA pump model, i.e., rapid titration followed by maintenance, for the treatment of patients with severe cancer pain or cancer pain crisis or refractory cancer pain in home cancer patients.
2. Exploratory purpose: To screen sensitive indicators for cancer pain assessment and efficacy monitoring by Ella fully automated microfluidic ELISA system, and to explore the mechanism of action of pain-causing substances in cancer pain initially.

Inclusion Criteria:

1. Age ≥ 18 years.
2. Patients with pathologically confirmed malignant solid tumors; patients with advanced metastatic cancer assessed by imaging
3. Patients with persistent cancer pain and an NRS score of ≥7 in the past 24 hours; or patients with refractory pain
4. Patients who have not received radiation therapy within 7 days prior to randomization and trial
5. Patients without cognitive impairment or mental illness.
6. the patient is able to complete the survey form
7. Patients can correctly understand and cooperate with the healthcare provider's medication instructions.
8. ECOG-PS ≤ 3 points.
9. Subjects voluntarily and signed the informed consent form.
10. Failure of antineoplastic treatment or refusal of antineoplastic treatment at home or community hospital.

Exclusion Criteria:

1. Patients with a diagnosis of non-cancerous pain or pain of unknown origin.
2. Patients receiving inpatient antineoplastic therapy.
3. patients with paralytic intestinal obstruction
4. patients with opioid allergy.
5. abnormal and clinically significant laboratory results, such as creatinine ≥ 2 times the upper limit of normal, ALT or AST ≥ 2.5 times the upper limit of normal (≥ 5 times the upper limit of normal in patients with liver metastases or primary hepatocellular carcinoma), or grade C liver function Child
6. Uncontrollable nausea and vomiting.
7. Use of monoamine oxidase inhibitors within 14 days prior to randomization.
8. pregnant or lactating women; subjects with a planned pregnancy within 1 month of trial (also includes male subjects)
9. Patients with alcohol abuse.
10. Other diseases and conditions that, in the opinion of the investigator, preclude enrollment.