diagnosis, no one wants to join the club of “candidates for mesothelioma surgery,”
but after reviewing
treatment options many patients decide that surgery is their best choice. Doctors have to
balance the possibility of extending life with the risk that the patient
will die from aggressive and invasive surgery. They also have to balance
the possibility of extending life with the possibility that even after
successfully removing all visible tumor, the patient will quickly succumb
to the disease anyway.
Patients have to make a similar analysis. Will I die on the operating table
or shortly thereafter? Will surgery extend my life without making survival
so painful and debilitating that my quality of life and that of my family is nil?
The patient resolves those questions by consulting with the surgeon and
the family. The doctor, however, resolves them by looking at prognostic
factors. Those factors help the surgeon estimate the chance that the surgery
will do more good than harm. Before deciding on surgery, patients should
know what the factors are that most strongly influence the success or
failure of surgery.
Prognostic factors can help doctors and patients choose a treatment plan.
Patients in the best prognostic groups may decide to choose aggressive
or experimental therapy, or they may prefer a period of observation before
selecting a treatment option.
The earliest studies tried to come up with a list of factors that would
predict the best survival in meso patients who underwent surgery. In general,
the more a cancer tumor has progressed from its early stages to its late
stages, the worse the outcome for the patient. Mesothelioma surgeons needed
a way to measure, or stage the tumor so that they would have a uniform
system for describing the tumor’s progress, which in turn would
allow them to look at the tumor’s stage and assess its impact on
survival after surgery.
By 1995, the International Mesothelioma Interest Group had come up with
a proposed tumor
staging system in order to replace the scattered and inconsistent systems—five
of them—that had been around since 1976.
This staging system is based on the relationship between the size of the
tumor, the type of tumor, whether or not the nearby lymph nodes have become
cancerous, whether the cancer has metastasized to other regions, and how
these factors relate to the patient’s survival after surgery. However,
it’s very important to note that the IMIG staging system is useful
only for patients considering surgery. For patients only undergoing chemo or
radiation, factors such as poor performance status, non-epithelial tumor, male gender,
and other factors are more important for their prognostic value. In fact,
performance status, or the overall health of the patient as measured by
lung function and lung reserves, is the most important prognostic factor
for nonsurgical treatment of pleural mesothelioma.
Tumor Stage as a Prognostic Factor for Surgical Candidates
But back to surgery. For those who will undergo EPP or PD surgery, the
stage of the tumor as measured by the IMIG system does play a role in
predicting the outcome of the operation. How much of a role? One of the
earliest studies to evaluate the IMIG system found that tumor stage, tumor
type, and type of surgery were the only factors that had a significant
influence on overall survival.
In a follow up study, the same authors found that the significant factors
were tumor stage, type of tumor, gender, and whether some additional therapy
such as chemo or radiation had been tacked on to the surgery.
The IMIG tumor staging system works like this. It takes three factors,
the primary site tumor (T), the regional lymph nodes (N), and the presence/absence
of distant metastasis (M), and combines them to come up with a stage for
The tumor is assigned values ranging from T0, where there is no evidence
of primary tumor, to T4, where the tumor has invaded the chest wall and
involved ribs, the peritoneal cavity, spine, or heart. Lymph nodes are
assigned values ranging from N0, where there is no regional lymph node
involvement, to N3, where the cancer has involved the opposite side mediastinal,
internal mammary, or hilar lymph nodes and or same side or opposite side
supraclavicular or scalene lymph nodes. Distant metastasis is M0 or M1,
indicating presence or absence of spreading tumors remote from the primary
site. The complete descriptive list of T, N, M and their varying stages
is published in detail by the British Thoracic Society and Society of
Cardiothoracic Surgeons of Great Britain and Ireland Working Party.
The IMIG system then combines these factors to come up with a stage. For
example, Stage 1 is T1 N0 M0, which means that the tumor involves the
same side pleura of the chest wall, with or without focal involvement
of the pleura on the outer side of lung; there is no involvement of regional
lymph nodes; and there is no evidence of distant metastasis.
Stage I and II tumors “have a much more favorable survival than was
previously assumed for
malignant mesothelioma, and suggests that surgical resection and adjuvant therapy may improve
survival.” Recent surgical studies update some of these findings,
indicating that with regards to surgical outcomes, staging is a significant
independent prognostic factor.
When trying to decide whether or not to undergo PD or EPP, it is important
to know the staging of the tumor. However, other factors in addition to
the tumor’s stage can provide prognostic information about the outcome
of the surgery. And although tumor staging can be a significant prognostic
factor for surgery, it is a much less important predictive factor for