Children with solid tumours have 25% metastatic disease at initial diagnosis and another 20% develop metastases during or after treatment. The most common location of these metastases is the lung [4].

Pulmonary metastasectomy is currently indicated for patients with the following criteria: primary tumor controlled, possibility of complete resection verified by computed tomography (CT) of the chest, pulmonary function and performance status compatible with the proposed lung resection, and lack of another available treatment that would be more effective than the surgical procedure [9].

In the current study, most of the patients were diagnosed as Osteosarcoma (79.8℅) followed by Synovial sarcoma (9.1℅), then Rhabdomyosarcoma (3.6℅), Ewing Sarcoma (3.6℅), Germ cell tumors (3.6℅) and Wilm’s tumor (1.8℅). The 5-year overall survival of of the patients in the current study patients was (74.8%). The 5-year overall survival in Osteosarcoma patients was 68%.

The mean age of the studied patients was 15 years old ranging from (4.5- 23) years with males (54.5%) predominance over females (45.5%) There was no statistically significant difference between the age and gender of the patients and overall survival rates (5 year OS) P value (0.894) P value (0.648) respectively. This agrees with Erginel et al. (2016) Turkish study which retrospectively reviewed the medical records of 43 children who were operated on in the Pediatric Surgery Clinic between January 1988 and 2014,forty-three children (26 boys; 17 girls; mean age 10 ± 4.24 years, range (6 months–18 years) who underwent pulmonary metastasectomy, there was statistically significant difference regarding the age while insignificant regarding the gender of the patients and overall survival rates (p = 0.029 and p = 0.48, respectively) [12].

In the current study, all patients received chemotherapy as per protocol for the primary diseases. Tumour necrosis which represent response of primary disease to chemotherapy was less than 90% in 40 cases (72.2%) and more than 90% in only 8 cases (14.5%) while no comment was mentioned in the pathology report for the rest 7 cases of the study, the overall survival time in correlation with tumour necrosis of the primary tumour for patient > 90% compared with those < 90% was 88.7 and 52.2 months respectively with statistically significant p-value (0.017).This result was similar to the study done by [13] where histological response of the primary tumour to neoadjuvant chemotherapy was a well-recognized prognostic factor in patients with metastatic osteosarcoma. In another study where 77 pediatric patients diagnosed with metastatic osteosarcoma, they underwent pulmonary metastasectomy, chemonecrosis had a significant higher 5-year survival rate in patients > 90% when compared with those with chemonecrosis < 90% (p-value 0.008) [14]. The Livestrong Young Adult Alliance has conducted a meta-analysis of individual patient data from prospective neoadjuvant chemotherapy osteosarcoma studies and registries, the study was published by American Society of Clinical Oncology in which 4838 patients were included with median age 15 years old, data were collected from 5 international cooperative groups, the results revealed significant relation between survival and response to chemotherapy p = 0.001 [15].

On the other hand, an Irish study done by O'Kane et al. reviewed 97patients diagnosed with localized and metastatic osteosarcoma (lungs and other sites) with a median age 23 years old, the 33 patients who achieved ≥ 90% primary tumour necrosis, the 5-year OS was 82% while the 29 patients who had < 90% tumour necrosis, the 5-year OS was 68% with statistically insignificant impact of tumour necrosis on survival p = 0.15 [16].

Regarding pulmonary metastases, size of metastatic nodules in this study ranged from (0.5 to 10 cm) with a mean 3.4 cm, the 5-year overall survival in patients with pulmonary nodules 2 cm or less was 83.1% compared to 69.7% in patients with pulmonary nodules more than 2 cm with statistically insignificant p-value (0.22).This is similar to the study which was carried out in Japan, where data was gathered from 37 patients with pulmonary metastasis from osteosarcoma who underwent metastasectomy. They found no statistical significance between maximal diameter of the lung nodules and overall survival [17].

Regarding the number of pulmonary nodules, the number in our study was ranging from (1to 28) with a median of 4. The 5- year overall survival in patients with three pulmonary nodules or less was 77.2% compared to 71.8% in patients with pulmonary nodules more than three with statistical insignificance (p = 0.313). The International Registry of Lung Metastases retrospectively reviewed 575 patients who underwent 708 lung metastasectomies. They confirmed that completeness of surgery resection, histology, and DFI as independent prognostic factors while number of metastases, presence of lymph node metastases, surgical approach, and number of metastasectomies did not statistically influence long-term survival [18].

In the current study patients, 76.4% had bilateral metastatic nodules with 5-year OS 69.4% and 23.6% had unilateral nodules with 5-year OS 92.3% with statistical insignificant difference between overall survival and laterality (p = 0.076). In our patients, 76.4% had bilateral metastatic nodules with 5-year OS 69.4% and 23.6% had unilateral nodules with 5-year OS 92.3% with statistical insignificant difference between overall survival and laterality (p = 0.076). That was similar to studies done by (Harting and Blakely, 2006; Chen et al., 2009). In a more recent study done by Okiror et al. (2016) during the period between August 2007 and January 2014, a total of 80 pulmonary metastasectomies were performed on 66 patients with metastatic sarcoma, there were no postoperative in-hospital deaths, the median age was 51 years (range, 16–79), fourteen patients had bilateral lung operations and surgical access was by video-assisted thoracoscopic surgery in 48 (73%) cases, the median number of metastases resected was 3 (range, 1–9), there was no significant difference in survival between patients with high-grade versus low-grade tumors (p = 0.13), histological type (osteosarcoma vs. other soft tissue sarcoma types, p = 0.14), unilateral versus bilateral lung metastases (p = 0.48). On the other hand, Other investigators demonstrated that patients with bilateral lung metastases had reduced overall survival when compared to patients with unilateral disease [19, 20, 21], also the study done by Tronc et al. [3] in which 52 pediatric patients underwent PM, they concluded that there was a statistically significant difference in survival rates between patients with unilateral metastases and those with bilateral metastases (49% vs 7%, p = 0.001) [22,23,24].

About surgical margin of metastatic nodules in our study, 32.7% of patients were excised with negative margins, 34.5% were excised with positive margins and 32.7%were excised with close margins, the 5-year OS was 94% in negative margins, 62% in positive margins and 87% in close margins. In our study, there was a tendency towards longer survival in patients with negative margins compared to patients with close and positive margins but the difference between OS and surgical margin was not statistically significant (p = 0.08), This may be attributed to small number of the studied patients. Similar conclusion was reached by Tanju et al. study, which was carried out in Turkey, where they analysed the role of extended resections if it may be necessary to achieve tumour-free borders for secondary pulmonary malignancies, and they found no statistical significance [25]. In another Jordanian study, King Hussein Cancer Center, the patients with positive resection margins in any of the resected nodules did not have statistically significant differences in OS compared to patients with negative resection margins [26]. On the other hand, Kim et al. at Massachusetts General Hospital, Harvard Medical School, USA, they studied 97 patients who underwent pulmonary resection for metastatic sarcoma, they proved that tumour resectability for pulmonary metastasis for sarcoma can be associated with prolonged survival p value (0.004) [27].

According to the time of diagnosis of pulmonary metastasis of our participants: 23.6% of patients developed synchronous metastasis with 5 year OS 70%, 29.1% of patients developed metastasis during treatment with 5 year OS 52.9%, 32.7% of patients developed metastasis within the first year follow up after end of treatment with 5-year OS 67% and 14.5% presented with metastatic after the first year follow up with 5-year OS 100%. There was statistically significant difference between OS and metastatic free period in our study (p = 0.001). This agrees with the study which included seventy-seven pediatric patients with metastatic osteosarcoma were analysed, they reported that regarding timing of lung metastasis, both presence of lung metastases at diagnosis or during follow-up were found to correlate with overall survival P = 0.004 and P = 0.003 respectively [12]. In another study, they observed a significant association between the timing of detection of metastasis in relation to chemotherapy and survival P < 0.0001 [13].

Surgical approaches of pulmonary metastasectomy among the studied patients had the following distribution: 90.9% of patients did metastasectomy via thoracotomy, 3.6% of patients via VAT and 5.5% did both. Open thoracotomy is the most common surgical approach, this was reported [10].

Regarding the type of metastasectomy in the present study, (81.8%) of patients underwent metastatectomy (wedge resection), lobectomy was done in (14.5%) of patients and Only (3.6%) of patients underwent pneumonectomy, the 5 year OS was 77% in patients who did wedge resection and it was 64.8% in patients who did lobectomy and pneumonectomy with statistically insignificant p-value = 0.6. This is in agreement with the study done by MD Anderson Cancer Center published in Journal of Pediatric Surgery, which included 115 pediatric patients with pulmonary metastasis secondary to osteosarcoma, revealed that there was no significant difference in 3 year overall survival when comparing lobectomy to wedge resection (18% vs 30%) p = 0.91 [14].

In our study, some patients underwent repeated thoracotomies either sequential thoracotomy for bilateral lung metastases or for recurrent lung metastasis, the mean number of thoracotomies was 2, the number was ranging from 1 to 6 thoracotomies, there was no statistically significant correlation between survival and the number of thoracotomies p value 0. 097. This result was similar to the study done [28].

In our study, complications related to pulmonary metastasectomy were presented in 19 cases in the form of (lung collapse, pleural effusion, pneumothorax and surgical emphysema), there were no perioperative deaths.

The overall median survival time in our study was 64 months duration and the 5-year overall survival was (74.8%). The 5-year overall survival in our Osteosarcoma patients was 68%. By reviewing other studies we found a retrospective study included 68 patients of children and adults who underwent curative pulmonary resection for metastatic lung tumour from different solid tumours, it was published in European Journal of Cardio-thoracic surgery, the overall 5 year survival rate after pulmonary metastasectomy was 75.7% [29] which is similar to our results, Another study included 210 children and young adults with a diagnosis of metastatic bone and soft tissue sarcoma the 3-year estimates of OS of all 210 patients included in the study was 74.94.1% [30]. A recent European study which was published in Journal of Thoracic Diseases under the name of Metastasectomy in pediatric patients, the study mentioned that ranges of overall survival vary from 20 to 70% [31].