In this retrospective 9-year follow-up study, 72 of 132 patients with unilateral PSP were found by HRCT to have contralateral blebs. The incidence (54.5%) in this study was comparable to incidence rates reported in the literature [3,4,5]. Studies disagree about predictability of a contralateral episode following a first occurrence of PSP. Three studies have found an association between HRCT detection of blebs/bullae in the contralateral lung after ipsilateral PSP and higher risk of contralateral recurrence, 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 et al. [12], the 5-year cumulative incidence of contralateral recurrence reached 28.2% for contralateral asymptomatic blebs/bullae. In that study, the authors suggested that preemptive surgery be considered particularly for 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 were 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, the most important being 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 previously-mentioned studies reporting recurrence rates of asymptomatic contralateral blebs/bullae ranging 25–28% [3, 10,11,12]. To the best of our knowledge, our study is the first to 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 blebectomy 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]. Likewise, the current study found the cumulative incidence of ipsilateral recurrence to be comparable among the three groups (9%, 15%, and 16.7%; respectively). The recurrence rate in this study was, however, much higher than the rate we found in our previous study of 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, sex, smoking, prolonged air leakage, low BMI, and HRCT detection of blebs/bullae have been associated with recurrence [22,23,24,25]. Cardillo et al. found smoking to be significantly associated with PSP recurrence [26]. Huang et al. 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, making our findings more relevant to a homogenous population. In addition, we did not find smoking or lower BMI to be significantly associated with risk of recurrence. 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 is not as important in recurrence in adolescent PSP. Furthermore, it is noteworthy that group B+cb had higher smoking habit and lower ipsilateral recurrence rate than group U+cb. This result contradicts the report by Cardillo et al. but is consistent with the findings of by Uramoto and Tsuboshima et al. [29, 30], who reported a lower postoperative recurrence in PSP patients who smoked.
In both our univariate and multivariate analyses, younger age (< 16.5 years) and intervention group U+cb were 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 in Taiwan [31]. Physical development has been shown to differ among adolescents. For individuals younger than 16 years, growth rates are higher than they are for 17- or 18-years-olds and growth rates remain steady in individuals over the age of 19 years old [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 the formation of subpleural blebs/bullae able to induce PSP if they rupture [32]. This increase may also contribute to higher post-surgery recurrence rates in younger patients. Therefore, some authors suggest that surgery for 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 (Figs. 3, 5). Notably, all the overall recurrences occurred within five 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 and patients were not randomized. Therefore, the study has some unavoidable selection bias, including absence of HRCT interpretation for blebs/bullae, patient’s and/or their guardians’ viewpoint toward the preemptive contralateral surgery as well as exclusion of the female PSP patients. Another limitation of this cohort study is that HRCT for measuring reconstruction thickness and interval as well as its interpretation criteria might have changed during the nine-year period. Although surgery for the PSP at our institute always comprises blebectomy and mechanical pleurodesis, how surgeons perform the minimally invasive operative technique could vary.
