In this retrospective study of a nine-year period, 72 of 132 patients with unilateral PSP were found to have contralateral blebs by HRCT. The incidence (54.5%) in this study was comparable to the rate reported in the literature [3–5]. Studies disagree with regard to the predictability of a contralateral episode following a first occurrence of PSP. Some have found an association between HRCT detection of blebs/bullae in the contralateral lung after ipsilateral PSP and higher risk of contralateral recurrence, three studies reporting 26%, 26.7%, and 25.8% [3, 10, 11]. According to one recent large retrospective cohort study of 1055 PSP patients reported by Jang and colleagues [12], the 5-year cumulative incidence of contralateral recurrence reached 28.2% for the contralateral asymptomatic blebs/bullae. In that study, the authors suggested that preemptive surgery be considered particularly in patients with multiple blebs/bullae.
We weighed the advantages and disadvantages of unilateral VATS and bilateral VATS in patients with and without contralateral blebs. Group B + cb had longer operative times and greater blood loss due to the need for sequential bilateral procedures performed under the same anesthesia as well as higher postoperative pain scores and longer hospital stays. Despite these differences, there was no significant differences in postoperative complications rates among the three groups. Consequently, we consider it is safe for physiologically fit male adolescents to receive one-stage bilateral operations. The patients and their guardians were satisfied with the outcomes in respect of the prevention of recurrence. In our patients in whom contralateral blebs were detected, group B + cb had significantly lower contralateral recurrence than group U + cb (0% vs. 30%, P < 0.001). Our results were comparable to those of the above-mentioned studies reporting recurrence rates of asymptomatic contralateral blebs/bullae ranging 25–28% [3, 10–12]. To the best of our knowledge, our study is the first to take evaluate risk of recurrence and long-term outcomes of simultaneous treatment of contralateral blebs with bilateral VATS for pediatric PSP, especially in a male adolescent population.
Although VATS blebectomies with pleurodesis for pediatric PSP has been found to produce similar treatment outcomes in young adult patients, ipsilateral recurrence seems to be more prevalent in adolescents than in young adults even after surgery [8, 20, 21]. Similarly, this study found the cumulative incidence of ipsilateral recurrence to be comparable among the three groups (9%, 15%, and 16.7%; respectively). The recurrence rate was, however, much higher than what we found in a previous study in young adults (7.1%, 8.1%, and 8.5%; respectively) [13].
Another controversial issue is the correlation between risk factors and pneumothorax recurrence. Factors such as younger age, gender, smoking, prolonged air leakage, low BMI, and HRCT detection of blebs/bullae have been associated with recurrence [22–25]. Cardillo et al. found smoking to be significantly associated with PSP recurrence [26]. Huang and colleagues found contralateral blebs/bullae and underweightedness (BMI < 18.5) to be predictors of contralateral recurrence [3, 5]. Typically, PSP occurs in tall and thin young males with BMIs indicating underweightedness [27]. In this series, we included only adolescents under 19 years old and excluded 12 female patients initially, making our findings more relevant to a homogenous population. In addition, we did not find smoking or lower BMI have any statistical difference with regard to recurrence risk. Only 11.3% (15/132 patients) of our male adolescent patients with PSP were smokers, which can be explained by the lower prevalence of smoking in pediatric population compared to adults [28]. Thus, although smoking might play a role in recurrence, it does not factor in as much in the development of recurrence in adolescent PSP.
In both our univariate and multivariate analyses, younger age (< 16.5 years) and intervention group U + cb were the independent risk factors for overall recurrence (Table 2), a result consistent with the finding of high incidence of recurrence in adolescents in a nationwide population-based study [29]. Physical development has been shown to differ in individuals of ages belonging to adolescent period. For individuals younger than 16 years, growth rates are higher than those in 17- or 18-years-olds and remain steady in individuals over the age of 19 years [20]. The rapid increase in the vertical dimension of the thorax compared with the horizontal dimension could produce an increase in negative intrathoracic pressure at the apex of lung, which may lead to formation of subpleural blebs/bullae that can induce PSP upon rupturing [30]. This may also contribute to higher recurrence rates after surgery in younger patients. Therefore, some authors even suggest that surgery for pediatric PSP might be delayed in younger groups (age < 16) [20].
One key strength of our study is its long-term follow-up period (median, 80 months; IQR, 50–113 months). The age distribution among the three groups was also similar (median age 17 years old) (Fig. 2). The result of our Kaplan-Meier analysis revealed that over the half of contralateral recurrences (9/13; 69%) and ipsilateral recurrences (11/19; 58%) tended to occur during the first 2-years after surgery (Fig. 3 and Fig. 5). Notably, all the overall recurrences occurred within 5 years, except for one patient in group B + cb and another patient in group U-cb, who had ipsilateral recurrences at 68 and 62 months, respectively (Fig. 4). Hence, we suggest vigilant postoperative follow-ups throughout adolescence because there is a close relationship between this age range and potential physical development and chest dimension growth.
The main limitation of this study is that it is a retrospective study design with no randomization of subjects. Therefore, some selection bias dose unavoidably exist, including absence of HRCT interpretation for blebs/bullae or patient’s and/or their guardians’ viewpoint toward the preemptive contralateral surgery. In addition, we did not include the female PSP patients due to the small sample size.