Outpatient Therapeutic ¹³¹I for Thyroid Cancer

MATERIALS AND METHODS

Forty-eight thyroid cancer patients, who were between 14 and 88 y old, were treated with ¹³¹I as outpatients. The administered doses ranged from 3,034 to 9,250 MBq (82–250 mCi). The nuclear physician and radiation safety officer discharged patients on the basis of total effective dose equivalent (TEDE) calculations (using retained activity, an occupancy factor of 0.25 at 1 m, and effective and physical half-lives of thyroidal fraction), assessment of an individual patient’s living conditions, and the patient’s willingness to comply with limitations needed to keep the occupancy factor less than 0.25. Patients whose exposure levels were less than 5 mSv and who agreed to follow radiation safety instructions were discharged after treatment. Three patients, treated with 3,700, 5,500, and 7,400 MBq (100, 150, and 200 mCi), were surveyed at home on the fifth day after treatment. Exposure was measured at 0.3 and 1 m (1 and 3 ft) with a 3450P probe (Victoreen Co.). Radiation in the living room, bedroom, bathroom, and kitchen was surveyed using an E-120 with HP 360 probe (Eberline) (Table 1). The surveys and exposure levels were compared with levels obtained from hospitalized patients treated with the same doses. The costs of outpatient and inpatient treatments were compared. Patient acceptance was assessed by surveys performed when the patient returned for scanning at 7–10 d after therapy.

RESULTS

Radiation exposure and contamination surveys in the patients’ homes found no levels of contamination greater than regulatory levels. The exposure of household members ranged from 0.6 to 2.5 mR/h at 0.3 m (1 ft) and from 0.15 to 0.79 mR/h at 1 m (3 ft) (Table 1). Contamination levels ranged from undetectable to 183.6 disintegrations per minute (Table 2). One area of slight contamination was found in the home of a patient treated with 9,250 MBq (250 mCi). The area was decontaminated, and a wipe test then showed no removable contamination (Table 3). Survey results on the third posttreatment day in the home were compared with those in the hospital room for patients treated with 3,700, 5,500, or 9,250 MBq (100, 150, or 250 mCi). The exposure levels were within regulatory levels in both instances, with most contamination (still below regulatory levels) occurring in the bathroom.

The costs of inpatient treatment were compared with the costs of outpatient treatment at the same doses (Table 4). The average daily cost was $550 more for inpatient treatment than for outpatient treatment. With most inpatients remaining in the hospital for 2 d, costs amounted to $1,100 more for inpatients than for outpatients.

Patients were surveyed when they returned for posttherapy scanning. Most reported no difficulties, and even complaints of nausea and sialoadenitis appeared to be less frequent. The contact information for the nuclear physicians had been given to patients in case they had questions, and 10% had called with minor concerns. No difficulties in complying with regulations were reported. Many patients had made arrangements for young children or pets to live apart for a few days and kept the occupancy factor to at least 0.25. All patients were pleased with the procedure and commented that they would choose outpatient treatment again.

DISCUSSION

Our retrospective analysis demonstrated that outpatient treatment with high doses of ¹³¹I is safe and cost effective. The levels of contamination were less than regulatory limits. Patients had no difficulty complying with requirements for radiation safety. Concerns about patients actually following regulations will always exist, but our surveys showed that if patients are selected with caution, there should be no problems with exposure of the public to radiation (6). Patient acceptance was high, and patients appeared to prefer this way of receiving radioiodine therapy.

Our criteria for release were based on state regulations and included calculations of TEDE and surveys of patients’ living conditions and ability to understand and follow safety directions. Our calculations assumed that patients treated with ¹³¹I for thyroid cancer had already undergone thyroidectomy and had no remaining thyroid tissue. Unfortunately, a small group of patients may have a significant amount of remaining thyroid tissue secondary to surgical difficulties. In these patients, thyroidal uptake is more than the standard 5%, markedly affecting the calculated TEDE. We believe that this group of patients needs to be studied further and probably should be treated within the hospital.

CONCLUSION

Outpatient radioiodine treatment is safe and cost effective and improves patient satisfaction. Thyroid cancer patients receiving large doses of ¹³¹I much prefer to be treated as outpatients, and they can be if state and federal criteria for release are followed, if their living conditions are adequate, and if they are willing to follow safety guidelines.