Globally, breast cancer is the most prevalent cancer among women. Global breast cancer incidence was 47.8 cases per 100,000 women in 2018, as reported by the International Agency for Research on Cancer (IARC). Approximately 15% of all cancer patients globally lost their lives to breast cancer in 2020, with 684,996 females succumbing to the disease.1 Breast cancer is a disease that causes a relatively high number of fatalities in Indonesia.

Mastectomy is one of the most frequently performed breast cancer therapy options.2 Numerous complications may arise subsequent to a mastectomy, encompassing post-mastectomy pain syndrome (PMPS), which is characterized by persistent pain following the operation, seroma, infection, fat necrosis, wound dehiscence, venous thromboembolism, diminished tactile sensation, and wound necrosis. Post-mastectomy pain syndrome (PMPS) is a persistent neuropathic pain that is confined to the area surrounding the surgical scar. It may manifest either immediately or at some point after the procedure and persist for a duration exceeding three months. Patients may experience a decline in their quality of life as a result of the pain associated with this syndrome. Furthermore, its management is challenging due to the lack of sufficient research and the absence of a consensus regarding PMPS treatment.3 Currently, in Indonesia, there is still not enough data regarding PMPS. Therefore, the research aims to conduct descriptive research to obtain an overview of the characteristics of patients who experience PMPS.

The results of this study show that the age group most frequently diagnosed with breast cancer is the 50-59 year age group, followed by the 40-49 year age group. Gong et al. (2020) also stated that age ≤35 years was significantly associated with PMPS in univariate analysis (P<0.05), and multivariate analysis showed that age ≤35 years was an independent risk factor for PMPS. It is suggested that the mechanism for increasing the risk of PMPS at a younger age is due to the possibility of a higher histopathological tumor grade, the need for adjuvant chemotherapy, and increased recurrence rates, especially in breast cancer in younger women. Another possible factor is the difference in estrogen receptor status in young and old patients, with decreased pain receptor sensitivity in older patients.4-6

The BMI profile shows that the highest incidence of breast cancer is found in the overweight group (25-29.9 kg/m2). There was a trend of increasing frequency of PMPS as BMI increased from underweight to overweight; however, the number of PMPS patients who were obese was found to be the least, with a percentage of 12.2%. In research conducted by Gong et al. (2020) who conducted a study on the incidence of PMPS, the incidence of PMPS was greater in the BMI <30 kg/m2 group (96.8%) compared to the BMI ≥30 kg/m2 group (3.2%). These results are in line with the results of this study, where the incidence of PMPS was more common in the group with a BMI <30 kg/m2 (87.8%) compared to the group with a BMI ≥30 kg/m2 (12.2%).

Based on their occupation, most of the patients with PMPS in this study were housewives, and only 6.5% worked. This result is in contrast to the results of a study by Gong et al. (2020), which showed that PMPS is more common among women who have jobs (85.4%). However, the percentage of patients without PMPS who work has a similar value, namely 84.9%, which shows that there is no relationship between work and the occurrence of PMPS (P=0.88).7

A higher prevalence of PMPS was observed in the group (56.7%) that did not engage in regular exercise. The correlation between inflammation and pain in female patients diagnosed with breast cancer is supported by the findings of Calapai et al. (2023), showing that there is an elevation in pro-inflammatory cytokines, specifically C-reactive protein, within the body. Evidence shows that regular exercise has benefits for cancer patients, namely due to increased defense against endogenous antioxidants, resistance to oxidative stress, and resistance to cancer cell growth. Physical activity has been found to be correlated with a decrease in both the intensity of pain and the inflammatory response of the patient.8

It was observed that all participants in this research had a prior utilization of contraception, with the highest proportion (73%) having employed injectable contraceptives for a duration of three months. Patients who had previously used hormonal contraception had a significantly higher risk of developing breast cancer than those who had never used hormonal contraception (RR=1.20; 95% CI=1.14-1.26). Morch et al. (2017) found that the likelihood of developing breast cancer escalated in correlation with extended contraceptive use. Additionally, Beaber et al. (2014) observed that an increased risk of developing breast cancer was associated with the use of combined oral contraceptives within the previous 12 months (OR=1.5; 95% CI=1.3-1.9).

Half of the sample experienced their first menstruation at the age of ≥14 years. Based on previous research, the risk of breast cancer increases significantly in patients with earlier onset of menarche (≤13 years) (OR = 1.60; 95% CI = 1.08-2.38).9 These results are consistent with other studies that found similar results.11,12

More than half of the sample (54%) had experienced menopause. Studies show an increase in the risk of breast cancer every 1 year of age at the time of menopause, but other studies have found no relationship between age at menopause and the incidence of breast cancer.9,12

In this study, it was found that 22% of the sample had a previous history of chronic pain, followed by a history of hypertension (11%), diabetes mellitus (10%), and autoimmune disease (4%). In research conducted by Gong et al. (2020), it was found that 15.9% of PMPS patients had a previous chronic history, while 15.4% had a history of comorbid diseases. Analysis in this study showed that a history of chronic pain was associated with the incidence of PMPS (P<0.001) but not with a history of comorbid diseases (P=0.186).7 Bivariate analysis in other studies showed that any previous history of pain was associated with PMPS (PR=1.39; 95% CI=1.12-1.74), and multivariate analysis showed that previous history of headache was significantly associated with PMPS (OR=1.92; 95% CI=1.10-3.34).6

Upon examining the prior breast surgical procedures, it is evident that the Modified Radical Mastectomy (MRM) is the most frequently performed procedure (92.7%) among the participants in this research sample. Only 7.2% underwent simple mastectomy. Previous research by Gong et al. (2020) provides support for the findings of this study, indicating that 87.1% of patients who presented with PMPS had a prior history of mastectomy. In the interim, BCS had been performed on a mere 12.9% of patients diagnosed with PMPS. The incidence of PMPS was found to be significantly associated with total mastectomy, as determined by univariate and multivariate analyses in this study.7

In this study, the sample that underwent surgery with the Stewart incision was the largest group (52.2%), followed by 47.7% with the Orr incision type. The study by Couceiro et al. (2013) reported that the incidence of PMPS was greater in quadrantectomy in both bivariate (PR=1.59; 95% CI=1.18-2.1) and multivariate analysis (OR=2.83; 95% CI=1.60-5.02). It is suspected that this is related to the axillary lymphadenectomy rather than the surgical technique itself, because in this study, all quadrantectomy procedures were always accompanied by an axillary lymphadenectomy procedure.6

TNM staging in this study sample showed that most PMPS patients had stages T3 (47.2%), N2 (50%), M0 (90%) before surgery, with post-operative stages T2 (71%), N1 (43.8%), M0 (84%). These results are slightly different from those of the previous research conducted by Gong et al. (2020), which shows that the majority of PMPS are found at advanced stages (58.4%) compared to early stages (41.6%).

This study demonstrates that chemotherapy, radiotherapy, and hormonal therapy have no bearing on the incidence of PMPS. For these three variables, the same findings (P>0.05) are seen in both univariate and multivariate analyses.7 These findings contrast with those of the Beyaz et al. (2016) study, which found a significant correlation (P=0.028) between postoperative radiation and the incidence of PMPS. According to Beyaz et al. (2016), 98.89% of the samples with PMPS had previously received postoperative radiation. Radiation to the axillary region and supraclavicular glands was found to produce more pain in the arms, shoulders, and breasts.4,13,14 Numerous studies have also reported radiation as a risk factor for chronic pain.

In this study, the quality of pain that elicited the highest number of complaints regarding PMPS pain characteristics was radiating pain (52.7%), followed by stinging (33.3%) and dullness (14%). Numbness was the most prevalent pain symptom in prior research (77.3%), followed by stabbing pain (50.9%), swelling pain (32.1%), and electric overstress pain (22.5%).7 According to Bruce et al. (2004), the pain was described by patients as stabbing, shooting, aching, and nagging. Comparable pain characteristics were also documented by Beyaz et al. (2016): stabbing (15%), shooting (12.8%), aching (12.8%), gnawing (10.5%), nagging (10.5%), annoying (9.8%), numb (9.8%), tiring (9.8%), and tight (9%).

This study showed that 94% of patients with PMPS complained of pain in the surgical area, while the remaining 6% felt pain in the ipsilateral arm. Previous studies on PMPS showed that pain often occurred in the ipsilateral axilla (63.6%), followed by the ipsilateral chest wall (43.4%), ipsilateral arm (28.2%), and other sites ( 4.1%) (Gong et al., 2020). Another study reported that the majority of pain was felt in the arm/axilla (39%), followed by scar tissue from surgery (29.9%), chest wall (12.3%), shoulder (11%), and a small percentage experienced phantom pain. (7.8%).15 Meanwhile, Stevens et al. (1995) reported that 84% of pain was felt in the axilla, followed by the medial upper arm (74%), anterior chest wall (58%), and shoulder (32%).

The VAS assessment in this study obtained the highest VAS score of 4 (69%), followed by score 3 (19%), and score 2 (11.7%). Research on 1983 patients conducted by Gong et al. (2020) showed that 28 cases (5.0%) experienced severe pain (numerical rating scale score ≥4).7 Another study by Couceiro et al. (2013) reported a median VAS of 5 (4-7) in patients with PMPS. Meanwhile, another study by Beza et al. (2016) reported that the majority of patients (78.6%) experienced pain with a VAS score of 0-3, and only the remaining 21.4% experienced moderate pain with a VAS score of 4-7.

This study shows that the majority of PMPS appear 9 months to 1 year after surgery, followed by <6 months after surgery. The results of this study differ from previous research by Stevens et al. (1995), who found that pain generally occurs within days to weeks after breast cancer surgery. Other studies also show that the onset of pain in PMPS varies from 2 weeks to 3 months after surgery. However, this study showed the same results as those found in this research, that most of the pain was felt to come and go.7 Meanwhile, a study by Stevens et al. (1995) reported a number that was not much different between intermittent pain (52%) and continuous pain (48%) in patients with PMPS. This study found that 86.7% of patients had a history of taking anti-pain medication to treat their PMPS. The study by Bezal et al. (2016) also reported that 89.9% of patients had tried one or more pain medications, most of which were over-the-counter medications or medications prescribed by general practitioners. Other patients try non-pharmacological therapies or a combination of both, such as physiotherapy, homeopathy, reflexology, acupuncture, massage, and counseling. Only 72.9% of PMPS patients said their pain had improved.15 These results contradict the results of this study, where the majority of patients (63.9%) did not feel any improvement in pain.

This study found that most patients with PMPS had a Karnofsky score <70 (65.6%). Prior research has indicated that post-mastectomy patients who experience severe pain have Karnofsky scores that are lower than those who do not experience pain (Miaskowski et al., 2012). An additional investigation conducted by Langford et al. (2014) corroborates these findings, revealing that individuals experiencing mild PMPS pain exhibited higher Karnofsky scores than those with moderate to severe PMPS pain.17

Arm edema, which is frequently observed in patients following mastectomy surgery, is a complication induced by lymphedema in the upper limbs.14 Overall, 11.1% of PMPS patients exhibited arm edema, according to the findings of this study. Patients with PMPS and lymphedema who underwent lymphedema surgery reported a reduction in pain, according to a study by Becker et al. (2008). Following surgery, it was observed that neuropathic pain resolved entirely, and all patients ceased the use of analgesic medications. According to Becker et al. (2008), the findings suggest that lymphedema in the upper extremities subsequent to mastectomy may be a contributing factor to PMP in affected individuals. In this study, the majority of patients complained of pain, especially with activity. These results are in line with the study by Beyaz et al. (2016) who reported pain that was aggravated by activity (54.5%), lying down (14.3%), cold weather (10.3%), rubbing of scars on clothes (10.3%), and waking up from sleep (10.3%). Activities such as lifting, carrying, and housework are generally found to aggravate pain. Some even complain of pain when walking, driving, and working.15 Another study also reported that all sample patients with PMPS said the pain was especially worse with movement and when tired.21

The use of a cross-sectional study design using monocentric data collected prospectively is the primary source of limitations in this study. It is necessary to understand our observations as both descriptive and exploratory. Caution must be exercised when extrapolating to another institution. This study did not identify all of the causes or contributing variables to PMPS in certain areas. It is necessary to conduct more research.

At the Tertiary Oncologic Centre in Surabaya, the majority of patients with post-mastectomy pain syndrome were older, had luminal A type, and were at higher TNM stages. Most people with a VAS score of 4 report having pain that radiates from the surgery site. Most patients with PMPS had a Karnofsky score of at least 70, and the pain usually manifests 9 months to a year after the surgery. Our research reveals no characteristics that PMPS patients share with previous studies in terms of their pain profile or demographics. These results might be specific to our neighborhood because PMPS is impacted by a wide range of internal and external variables. In the management of breast cancer, all stakeholders, particularly oncologic experts, ought to promote a more patient- and community-focused approach to PMPS research, prevention, and treatment in their local communities.

The ethics committee has approved this study with the code 1595/LOE/301.4.2/II/2024.