Possible side effects
In general the side effects were not serious, and most patients can accept some discomfort in order to avoid hair loss. The most common side effects experienced by patients using conventional scalp cooling methods are headaches, complaints of coldness, aversion to ice, dizziness, and claustrophobia. Uncomfortable cold sensations and headaches were especially pronounced in studies where pre-cooled caps which are usually chilled to –15°C to –25° were used (SUB report, 2006–2006). In addition, patients experienced neck pain due to the heavy weight of some cooling caps (Batchelor 2001). Such side effects are less pronounced with the DigniCap system.

In the studies with the DigniCap™ system, the number of patients who discontinued treatment because of discomfort is less than 2%. A possible reason for the good patient compliance may be the light weight of the cap (250 g) as compared to other caps that usually weigh more (70 g – > 2 kg). Another reason may be the gradual lowering of cap temperature which provides ample time for patients to get used to the cold temperature. An added safety feature is the security sensor that ensures that the scalp/cap temperature never goes below 0°C, to avoid frostbite.

Severity and distress associated with hair loss were reported to be less for those who use scalp cooling (Protière et al, 2002). In fact, the majority of patients in scalp cooling studies considered that the psychological comfort related to its use far outweighs minor physical difficulties.

Scalp metastases
A clinical concern with scalp cooling has been the potential incidence of skin scalp metastases. Though the risk has appeared to be remote, it is an important consideration and deserves further discussion. Theoretically, it has been suggested that if blood flow to the scalp is reduced, delivery of chemotherapeutic agents is reduced, which may increase the likelihood that cancer cells seeded in the scalp may survive. In the early 80s, a few cases of skin scalp metastases were found in patients treated with scalp cooling. However, these patients had advanced recurring metastatic disease at the time of treatment and the scalp metastases may still have occurred in the absence of scalp cooling.

In fact, there are many more studies that reported little or no increased risk in incidence of scalp metastases and at follow-up (Parker et al, 1987; Giacconne et al, 1988, Ron et, 1997; LeMenager, 1997; Christodoulou et al, 2002; Protière et al, 2002; Ridderheim et al, 2003). A systematic literature report on scalp cooling conducted by Tollenaar (1994) reviewed 25 publications (1973–88) with a total of 1282 patients. No case of scalp metastases was reported in scalp cooled patients receiving adjuvant chemotherapy. In recent years, more data on the incidence of scalp metastases in non-treated versus scalp-cooled treated patients were collected. In an extensive literature review by Grevelman and Breed (2005), 9 cases of skin scalp metastases out of 2500 patients treated with scalp cooling were reported. Seven of the 9 cases were patients who developed generalized metastasic diseases and 2 other had hematological malignancies. A recent multicenter study in France on 911 patients (Spaëth el al, 2008) treated with scalp cooling concluded that the incidence of scalp metastases is not higher than in non-treated patients. In Scandinavia, the data of 2249 patients treated with DigniCap™ in various hospitals were collected and followed up since 2001, with only one reported case of scalp metastasis, and this was a patient who has metastases in most parts of the body. Similarly, none of the 74 patients (including 8 patients with Hodgkin’s lymphoma) in a study (Ridderheim 2003) on the DigniCap™ system with an average follow-up of 15 months developed skin scalp metastases.

Scalp cooling is discouraged where is the possibility of circulating cancer cells, e.g., in cases of leukemia and lymphoma (Witman et al. 1981; Ron et al, 1997; Grevelman & Breed, 2005). Yet in spite of this, scalp cooling has been used successfully in patients with relapsed lymphoma (Purohit et al, 1992). In a study by Christodoulou (2002), a patient was successfully treated for her scalp metastases but still managed to preserve her hair from scalp cooling treatment.

The need for hair preservation far outweighs the risk and the fear of scalp metastases is not justified (Breed, 2004). The implementation of routine scalp hypothermia as a part of adjuvant chemotherapy treatment was recommended by the authors, especially in a wide variety of solid tumors without tendencies to bone metastases.