The incidence of AWS was 18% in our study, which was lower than in other studies [5, 9, 12]. As Koehler LA et al concluded, 47.2% of BC women developed AWS [15], and Ryans K found that AWS occurred in 30% of BC survivors[12]. Our result was due to the more rigorous definition of AWS in our study -- AWS was defined as not only palpable or visible bands, but also limitations of the affected shoulder ROM. Koehler LA defined participants as having AWS when a palpable or visible cord was present in the upper extremity or trunk during maximal shoulder abduction, but such cords did not have to be associated with restriction of shoulder ROM[9, 15]. Fukushima KF [11] reported an AWS incidence of 28.86%, due to their longer follow-up period and having more patients that received MRM (71% vs 30.6%). However, Wernicke AG reported a rate of AWS in ALND patients of only 5.2% in their retrospective review of early-stage BC patients[4]. In our study, 30% of patients had advanced BC, which might have contributed to an increase in the incidence of AWS beyond Wernicke’s result.
We found that younger age, a higher number of removed lymph nodes, and receiving neoadjuvant chemotherapy were associated with an increased risk of developing AWS. Fukushima KF[11] and O'Toole J [10] also reported that younger patients had an increased risk of developing AWS. Fukushima KF found that the average age of patients with and without AWS was 50.5 and 57.6 years, respectively. Fukushima’s result is similar to our finding[11]. But Ryans K had a different finding -- they reported that the chances of developing AWS were 73% greater for participants over the age of 60[12].
Our result revealed that the mean number of removed lymph nodes was 12 in the AWS group and 9 in the non-AWS group. We concluded that a greater number of removed lymph nodes was associated with the risk of developing AWS, similar to the findings of a review article [2] and O'Toole J[10]. Many articles have reported a higher incidence of AWS in patients undergoing ALND compared to SLNB[2, 4, 5]. However, Huang HC found there was no difference in the number of removed lymph nodes between the AWS and non-AWS groups -- it may be that more lymph nodes were dissected in Huang’s study (17.3/14.7 in the AWS/non-AWS groups) than in our patients[16].
Undergoing neoadjuvant chemotherapy was associated the highest risk of developing AWS in our study, by a factor of 2.96. Ryans K reported that neoadjuvant chemotherapy increased the risk of AWS, and they also found that women with AWS had a 44% greater risk of developing lymphedema during the first postoperative year[12]. It may be that neoadjuvant chemotherapy increased body fluid accumulation, and increased the incidence of AWS. But Fukushima KF [11] found there was no difference in AWS incidence, whether the patients received neoadjuvant chemotherapy or not.
Much research has shown that low BMI is associated with a higher risk of AWS [5, 15, 17]. Individuals with a lower BMI tend to have less body mass, and it has been suggested that it is easier to palpate and identify the cords in these patients. The literature suggests that difficulty palpating over adipose tissue could be a factor that inhibits detection of cords and may lead to underestimation of AWS [2, 9, 12]. BMI was not found to be a risk factor for AWS in our study. This could be because BMI was almost the same in the AWS (24.3 kg/m2) and non-AWS (24.6 kg/m2) groups. Our patients were thinner than those in other studies[9]. In our study, approximately 60% of the women were either normal or underweight. In other studies [9, 14], most participants were obese or overweight, no matter whether the AWS (25 kg/m2) or non-AWS (29 kg/m2) group.
The time between diagnosis of AWS and referral to PT was 26.3 days in our study, because BC patients must visit physiatrist clinics within the first postoperative month in our hospital. This was compatible with the findings of Yeung et al[1] and Ryans K[12]. Shoulder abduction ROM was significantly lower in the AWS group in the early postoperative period, which is consistent with Koehler LA’s result[15]. Patients with AWS could achieve full shoulder ROM and return to regular ADL after 14.8 PT sessions. This means that a 7-week PT program could lead to successful improvement in AWS and shoulder ROM. Our PT protocol consisted of a manual lymph-drainage technique to flexibilize the cords[14], mobilization of the shoulder and scapula to relieve shoulder adhesion, and strengthening exercises to stabilize the affected shoulder to prevent further injury. In our study, there was no AWS occurrence 40 days after surgery. This indicates that early intervention could effectively reduce the long-term incidence of AWS, as reported in Koehler LA[9] and Torres Lacomba M’s [14] studies. Although early intervention could effectively improve shoulder function, we should still encourage BC patients to pay attention to the affected shoulder, because, as Wernicke AG reported, the chronic complication of decreased ROM of the shoulder was found in 80.0% of ALND BC patients at a 10-year follow-up[4].
There were limitations to our study, as described below. 1). This was a retrospective analysis, even though the BC patient’s follow-up protocol is well established. 2). Follow-up should be extended to 2 years after surgery and the incidence of lymphedema in AWS recorded, since many studies have concluded that AWS patients have a greater risk of developing lymphedema[10, 12]. Patients who developed AWS within the first postoperative month were almost 3 times more likely to develop lymphedema[12] .