A 55-year-old female patient with a height of 151 cm and a weight of 55 kg was referred from the hematooncology clinic for left buttock pain caused by right infiltrative ductal breast cancer with left pelvic bone metastasis. The degree of pain on the 1-10 numeric rating scale (NRS) was 8, and it was characterized as a spontaneous tingling and ripping pain. She had received breast conserving surgery for right breast cancer 2 years before, but metastasis to the left pelvic bone had been discovered in an MRI one year before. Chemotherapy with adriamycin, cyclophosphamide, and taxol had been performed 6 times, and radiation therapy had been performed 8 times, but there had been no reduction in tumor size. Metastasis had occurred in the right acetabulum. Hence, palliative chemotherapy of Gemzar and Navelbine had been performed 6 times, and radiation therapy had been performed 6 times. At the time of referral, the patient was only scheduled for palliative care. The patient was having difficulty walking due to the pain in the pelvic area. In the MRI and bone scan of the pelvic area performed before referral, bone metastasis was observed in the left ilium, left ischium, and right acetabulum, in addition to a pathologic fracture in the left iliac wing (Fig. 1). At the time of referral, the patient was administered with fentanyl patch 100 µg/hr, oxycodone IR 10 mg bid, gabapentin 200 mg tid, and carbamazepine 200 mg bid for pain control; however, she was continuously complaining of severe pain (NRS 8/10) that worsened when walking. During hospitalization, fluoroscopically guided caudal epidural injection of 0.125% Chirocaine™ (levobupivacaine hydrochloride, Abbott Korea, Korea) 10 ml and Triam™ (triamcinolone acetonide, Shin Poong Pharm, Korea) 20 mg was performed twice with a one-week interval. However, the pain alleviation effect did not continue for more than one day after the procedure. Hence, scrambler therapy (MC5-A Calmare®) was planned. Because the patient's pain was located at the S1-2 dermatome of the left buttocks, the scrambler electrodes were attached at 4 normal sensory areas above and below the painful area of the S1-2 dermatome for treatment. During the scrambler treatment, the NRS score decreased to 0. The NRS score was maintained at 3 in the ward on the day of treatment. The patient was discharged after 10 sessions of scrambler therapy. During the 10 sessions, the dermatome location of pain did not change, but the area of pain slowly contracted; hence, the painful area of the patient was consulted daily before attaching the electrodes. Pain medications were continually administered without a change in dosage during the scrambler therapy. The pain alleviation effect through scrambler therapy continued for 2 months; on the third month, the pain recurred in the same area. The patient was re-hospitalized, and a second round of scrambler therapy was started. During treatment, the NRS score decreased from 7/10 to 0/10 on the first day, and this was maintained for 3-4 hours after treatment. Subsequently, the NRS score remained at 3.5/10 for 2 months, and pain medication was consistently given without a change in dosage during this period.

A 49-year-old female patient with a height of 152 cm and a weight of 45 kg was referred by her Obstetrics and gynaecology for bilateral sacral area pain caused by uteuterine sarcoma and bilateral sacral bone metastasis. The patient complained of a spontaneous, throbbing pain with an NRS score of 8/10, and it worsened with changes in position or movement. Total laparoscopic hysterectomy had been performed on the patient for uterine sarcoma one year before. Because discomfort in the lower abdomen and symptoms of tenesmus had continued after surgery, a CT scan of the abdomen had been performed one month after surgery. In the scan, a heterogeneously enhancing mass lesion of 14.6 × 7.7 cm in the pelvic cavity and numerous lymph node enlargements in the abdominal cavity had been observed, as well as a soft mass lesion of 3.7 × 2.9 cm in the left pelvic bone and a lesion of 2.5 cm² in the right pelvic bone (Fig. 2). Doxorubicin and cisplatin chemotherapy had been started and further radiation therapy scheduled. At the time of referral, the patient was taking oxycodone PR 20 mg bid, as well as oxycodone IR 5 mg when pain increased, as prescribed by the referring department. However, severe opioid-induced constipation developed, and the patient was refusing an increase in opioids despite the increase in pain level. Thus, scrambler therapy was planned for the patient. As the patient's area of pain was located on the bilateral S3-5dermatome, the scrambler electrodes were attached to 6 normal sensory areas to the left and right of the S3-5dermatome pain area for treatment. Scrambler therapy was performed 10 times for 40 minutes once every day, and oral pain medication was continually administered without a change in dosage. From the first day of treatment, the NRS score of the affected area decreased from NRS 8/10 to 0/10, and the NRS score at home after the procedure decreased to 2.5/10; this was maintained for approximately 2 weeks after treatment. During the 10 sessions of scrambler therapy, the dermatome location of pain did not change, but the painful area slowly contracted; thus, the patient's area of pain was consulted daily before attaching the electrodes. The pain medications were continually administered without a change in dosage during the scrambler therapy. One week after completion of scrambler therapy, the patient developed symptoms of diarrhea as she started radiation therapy. In addition, the pain in the sacral area worsened. The patient was re-hospitalized, as she wanted a second round of scrambler therapy. There was no pain during the subsequent scrambler therapy, and the chronic diarrhea improved. Her pain at home was maintained at around NRS 3/10 for one month. Afterwards, the patient was transferred to another hospital near her hometown.

A 56-year-old male patient with a height of 166.6 cm and a weight of 59.9 kg was referred from the gastroenterology department for right chest pain caused by hepatocellular carcinoma and right chest fifth rib metastasis. The degree of pain was NRS 6/10, and it was characterized as a spontaneous splitting pain. Transarterial chemoembolization (TACE) chemotherapy had been performed on the patient for liver cancer for one year. Five months before visiting the cancer pain unit at our hospital, metastasis to the right chest fifth rib had been discovered, and the patient had received radiation therapy. In the subsequent MRI and bone scan of the thoracic vertebrae, right fifth rib metastasis with extraosseous mass formation had been observed. The patient had the underlying diseases of hepatitis B and liver cirrhosis and, at the time of referral, had been using Ultracet Tab™ (acetaminophen 325 mg tramadol hydrochloride 37.5 mg, Janssen Korea LTD, Korea) 2 tab tid for pain control. However, the right chest pain had gradually worsened and been causing sleep disturbance. Hence, a thoracic epidural injection had been performed during hospitalization, but 3 days after the procedure, the pain had worsened, with the NRS score increasing again to 6/10 from 2/10; thus scrambler therapy (MC5-A Calmare®) was planned for the patient. The patient complained of chest pain in the right fifth rib area, so the scrambler electrodes were attached to 2 normal sensory areas to the left and right of the right fifth rib pain area for treatment. As the 10 sessions of treatment progressed, it was clear that the pain area was gradually contracting, and the location of the electrodes was adjusted accordingly for treatment. After 2 sessions of scrambler therapy, the NRS score decreased to 2/10, and the treatment effect continued until the next morning. The administration of Ultracet Tab™ was stopped accordingly. After 10 sessions of scrambler therapy, the NRS score has been maintained at 2/10, and the pain area maintained at about 80% reduced state, for 2 months.