MASS 2 , 10 year follow up study : A shot in the arm for CABG ?
Posted Oct 28 2010 10:15am
MASS 2 study , the 10 year follow-up results are just out in circulation september 2010 .
It is a rare study , where “one to one vs one” was compared ie the effect of medical, CABG , and PCI in chronic CAD .This was done in a single centre in Brazil, between 1995 -2000 . It was followed up till 2010. Interestingly , such a study may not be possible in the future , as many of us have prematurely glorified the PCI and CABG over medical therapy . Recruiting patients for medical therapy alone is becoming a difficult job even in developing countries. Even if we recruit , huge cross over is likely to PCI, CABG for all fancy reasons.
So , in MASS 2 we have a rare treasure on hand . . . Let us give three cheers to those Brazilians who did this study , and shall carefully analyse and interpret the results.
Highlights ( According to my interpretation)
A total of about 600 patients with 200 in each group.
The overall death at 10 years is not greatly different . (Around 25 % )
But ,cardiac deaths were distinctly higher by few percentages in pure medical arm
Need for crossover from medical to surgery and PCI to surgery was significant.
CABG tended to prevent future MI in this study . This could be most significant observation from this study ,( A revelation in fact ! ).It is against the popular belief created by CASS legacy.
What are the observed difference between MASS 2 - 5 year results , which was published in 2004 , and the 10 year follow-up , as on 2010 ?
At the end of 5 years in 2004 , the differences among the three groups were not obvious.The benefits of CABG mainly appeared after the 5th year and at 10 years it was significant.
Shortcoming of MASS 2
It is a single centre study .Numbers were less (600) .
It need to be emphasised CABG was done with pump in all patients . So the currently prevalent off pump CABG may not be really comparable with reference to outcome.
Only bare metal stents were used in PCI .(If only DES was used . . . Considering the host of issues for and against DES , it will be a wild guess to judge it’s implication . It could have tilted , either in favor or against the PCI limb .)
In medical limb , statins were not used in all. Further , the dose of statins were not aggressive.This makes medical therapy appear less effective.
When we say medical therapy is being compared with PCI and surgery , we are actually comparing ,
Medical therapy alone
Medical therapy+ PCI
Medical therapy + CABG .
Every patient in all three groups receive statin , antiplatelet and beta blocking drugs and so on. Even though statistics would vouch for additional benefit , over and above medical therapy , in a given CABG individual , how much of the the accrued benefit is contributed by co- administering medical therapy .It is beyond reasoning even with all gimmicks of statistics.
To exactly quantify the individual benefits and efficiency of PCI , CABG and medical therapy two more study limbs are necessary .
PCI without drugs.
CABG without drugs.
Such a study is possible only in a virtual world ! . Decision making in favor of CABG , especially in chronic stable angina , will continue , to be difficult in the absence of refractory angina .This is due to the modest benefit of CABG , that is expected, at an additional risk , cost and expertise.
Please remember, a person can survive , only with medical therapy for > 10 years but no one can ever live with PCI or CABG for that period of time without adjunct drugs . Guess which modality is going to win the race against CAD in the long run ?
If any one asks for conclusion of MASS 2 study , don’t ever say ”CABG is superior to medical therapy” . Please emphasize , “CABG + medical therapy could be , marginally superior to medical therapy alone in some of the patients with chronic stable angina. (Each word in the above statement is important !) .
So . . . MASS 2 : Is it a shot in the arm or shot in the head for CABG , we do not know !