Page 891 - Read Online

Page 2 of 12 Galvez et al. Mini-invasive Surg 2020;4:86 I http://dx.doi.org/10.20517/2574-1225.2020.86
[2]
stage I . Since the Lung Cancer Study Group (LCSG) in 1995, lobectomy became the standard pulmonary
[3]
resection for standard-risk surgical cases . Since then, several comparative studies have shown that
anatomical sublobar resections (SLR) in selected cases (early stage carcinoma less than 2 cm, in peripheral
location without nodal involvement, especially when ground-glass appearance or long duplication time
have been observed) shows similar outcomes to lobectomy in terms of disease-free survival (DFS) and
OS [4-8] , so the role of SLR is growing exponentially from the high-risk and inoperable patients to also
elective cases without pulmonary or cardiovascular compromise (i.e., intentional SLR). Stereotactic ablative
radiation therapy (SABR), also known as stereotactic body radiation therapy (SBRT), has also shown a role
for inoperable stage I NSCLC with acceptable survival outcomes [9-11] and better postoperative morbidity
profiles. However, there is still a lack of prospective randomized trials comparing specifically SLR with
[12]
SABR, so level 1 evidence is still missing . The aim of this review is to collect and discuss all the evidence
available regarding this controversial issue.

STEREOTACTIC ABLATIVE RADIATION THERAPY
SABR differentiates from conventional radiotherapy treatments in delivering larger doses of radiation per
session. A typical SABR course for stage I NSCLC consists of 1 to 5 treatments over a 1 to 2 week time
period with daily doses of 10 to 34 Gy, while a conventional daily dose of radiation therapy is 2 Gy, which
is typically given 5 days a week for approximately 6 weeks.

There are some studies comparing standard radiotherapy and SABR. The SPACE trial randomized 102
patients to receive SABR 66 Gy (3 fractions, 1 week) or three dimensional conformal radiation therapy
(3DCRT) 70 Gy (7 weeks). There were no significant differences in terms of OS and progression free
survival (PFS) between both arms, with a tendency of improved disease control rate in the SABR arm,
[13]
[14]
as well as less toxicity and better quality of life . Li et al. conducted a meta-analysis comparing
conventional radiotherapy to SABR in inoperable stage I NSCLC. They found better OS (HR = 0.66; P <
0.00001), PFS (HR = 0.34; P < 0.00001), and lung-cancer specific survival (HR = 0.42; P < 0.00001). SABR
showed lower rate of adverse events in terms of pneumonitis, esophagitis, and dyspnea. A systematic review
published in 2017 also found SABR to be better in terms of survival and local control compared to other
techniques of radiotherapy, as well as less toxic .
[15]

One advantage is the shorter treatment duration. The increased doses of radiation also make SABR more
[12]
potent and achieve higher rates of local tumor control in stage I NSCLC . Indeed, prospective studies
and propensity score comparisons have consistently shown 3-year local control rates of approximately 90%
with SABR for stage I NSCLC [11,16,17] . Toxicity is low after SABR, with symptomatic radiation pneumonitis
(grade ≥ 2) - usually consisting of mild fatigue - ranging between 7%-16% [18,19] , chest wall toxicity (pain and
rib fractures), decreased pulmonary function, and less commonly, esophagitis, skin irritation, and brachial
plexopathy in apical tumors.

One more potential advantage of SABR compared to surgical treatment is that overall quality of life is
usually not affected after the treatment. The use of less intense fraction schemes is recommended for more
central tumors to avoid more severe adverse effects such as hemoptysis, pneumonia, and respiratory failure.

As SABR induces lung damage and does not resect the tumor, surveillance requires careful imaging
tests to assess ground-glass opacities, consolidation, and nodular growth in relation to primary site, but
[12]
local control rates at 3 years are about 90% [11,17] . Intralobar failures after therapy are 15% and regional
[20]
recurrence 9.6% , with distant recurrence as the most common pattern of recurrence, raising up to 25% of
treated cases.