Table 1.

Characteristics of the included studies.

Citation	Study Objective	Type of Cancer	Sample Size	Mean Age	Country	Setting
A. Abd El-Rahman et al. [23]	Compare the postoperative analgesic effect of local ketamine 1 mg/kg instilled in the wound to that of intramuscular ketamine and of placebo after total thyroidectomy.	Thyroid	90	43.4	Egypt	Inpatient
Abd El-Rahman, Mohamed et al. [22]	Investigate the effects of intrathecal morphine, ketamine, and their combination with bupivacaine for postoperative analgesia in major abdominal cancer surgery.	Abdominal	90	41.7	Egypt	Inpatient
Barton et al. [24]	Evaluate a topical baclofen, amitriptyline HCL, and ketamine in a pluronic lecithin organogel (BAK-PLO) to alleviate neuropathic pain, numbness, and/or tingling of chemotherapy-induced neuropathy (CIPN). Secondary goals included the evaluation of function, general pain, and toxicity.	N/A	208	61	USA	Outpatient
Chelly et al. [25]	Assess the effectiveness of a multimodal analgesic approach vs. patient-controlled analgesia (PCA) alone in patients undergoing open prostatectomy and assess the long-term benefit of our treatment modality.	Prostate	55	60	USA	Inpatient
de Kock et al. [26]	Investigate first whether ketamine has a specific effect on NMDA-related postoperative hyperalgesia and whether this drug could represent an efficient constituent of `balanced analgesia’. In addition, to determine ketamine’s preferential route of administration, either systemic or epidural.	Rectal adenocarcinoma	100	67	Belgium	Inpatient
Fallon et al. [27]	Comparison of oral ketamine with placebo for treating neuropathic pain in patients with cancer.	Mixed	214	58	UK	N/A
Gewandter et al. [28]	Investigate the efficacy of 2% ketamine plus 4% amitriptyline cream for reducing CIPN.	Mixed	462	N/A	USA	Outpatient
Hardy et al. [29]	Determine whether ketamine, delivered subcutaneously with dose titration over 5 days, has greater clinical benefit than placebo when used in conjunction with opioids and standard adjuvant therapy, in the management of chronic, uncontrolled pain related to cancer or its treatment.	Mixed	185	64	Australia	Inpatient
Ishizuka et al. [30]	The aim of this study was to evaluate the association of oral S(+) ketamine associated with morphine in controlling oncologic pain	Mixed	30	59	Brazil	Outpatient
Kamal et al. [31]	Investigate the effect of ketamine–bupivacaine in thoracic paravertebral block on acute and chronic pain after breast cancer surgery	Breast	90	49	Egypt	Inpatient
Kang et al. [32]	Test if intraoperative low-dose ketamine without postoperative infusion would reduce persistent postsurgical pain (PPSP) development after breast cancer surgery.	Breast	184	50.3	Korea	Outpatient
Kollender et al. [33]	Compare the effects of a standard morphine dose to a 35% lower dose plus a subanesthetic dose of ketamine for postoperative pain control in patients undergoing bone and soft tissue cancer surgery under standardized general anesthesia.	Bone and soft tissue cancer	60	41.5	Israel	Inpatient
Lauretti, Gomes et al. [34]	Examine analgesia and adverse effects of combination epidural pain therapy consisting of administration of morphine with either a low dose of ketamine, neostigmine, or midazolam in terminal cancer pain patients.	Mixed	48	53.8	Brazil	Inpatient
Lauretti, Lima et al. [35]	Evaluate the potential role of oral ketamine, an NMDA antagonist, or transdermal nitroglycerin, an NO donor, as coadjuvants to oral morphine in cancer pain therapy, compared with oral morphine alone or with the combination of a nonsteroidal anti-inflammatory drug (dipyrone) and oral morphine.	Mixed	60	55.3	Brazil	Inpatient
Lavand’homme et al. [36]	Examine the role and timing of balanced epidural analgesia as preventive treatment after major digestive surgery.	Rectal adenocarcinoma	85	53.4	Belgium	Inpatient/Outpatient
Mahran et al. [37]	Evaluate this assumption and compare the analgesic profile of preoperative pregabalin with ketamine in patients undergoing breast surgery.	Breast	90	53.5	Egypt	Inpatient
Mohamed et al. [38]	Investigate the efficacy and safety of intrathecal dexmedetomidine, ketamine, or both when added to bupivacaine for postoperative analgesia in major abdominal cancer surgeries.	Mixed	90	44.4	Egypt	Inpatient
Nesher et al. [39]	Assess if combining a subanesthetic dose of ketamine with morphine could effectively control pain while reducing postoperative morphine demand and drowsiness with an acceptable level of adverse side effects	Lung	41	59.5	Israel	Inpatient
Othman et al. [40]	Compare the analgesic efficacy and safety of modified Pecs block with ketamine plus bupivacaine versus bupivacaine in patients undergoing breast cancer surgery.	Breast	60	48.3	Egypt	Inpatient
Rakhman et al. [41]	Determine whether ketamine’s effect on acute postoperative pain could be enhanced and prolonged and analgesia consumption reduced if it was administered intramuscularly in repeated and escalating subanesthetic doses many hours before surgery.	Mixed	120	45.4	Israel	Inpatient
Shah et al. [42]	Compare two anesthetic techniques for modified radical mastectomy (MRM)—the conventional opioid-based technique versus an opioid-free and PECS-block-based technique.	Breast	70	51.7	India	Inpatient