* Q2 adj profit $2.91 per share vs est of $2.48 per share
* Raises 2017 profit forecast to $9.75-$10.05 per share
* Low cost trend likely to persist through the year-Piper Jaffray (Adds details, analyst comment)
Aug 4 (Reuters) - Cigna Corp raised its full-year earnings forecast on Friday and reported a better-than-expected quarterly profit, helped by strength in its commercial business and cost control.
The company's shares were up 3.4 percent at $182 in premarket trading.
Cigna joins other health insurers such as Humana Inc and Aetna Inc in beating estimates and providing a rosy forecast at a time when uncertainty in the healthcare industry remains.
Republican lawmakers have vowed to repeal and replace former President Barack Obama's signature healthcare law, often called Obamacare, but have not agreed on how to do so.
President Donald Trump last week renewed his threat to cut about $8 billion in subsidies next year.
Cigna said in June it will continue to offer individual coverage under Obamacare, adding it was keeping the option to stay in the seven states where it now sells plans, but would wait to make a final decision on its participation depending on how possible market changes shake out.
The company said total commercial medical care ratio came in at 78.7 percent reflecting strong performance and effective medical cost management.
Medical care ratio is the amount an insurer spends on medical claims compared with its income from premiums.
"The beat follows similar results from peers as we continue to see a low cost trend quarter that we believe will persist through the remainder of the year," Piper Jaffray analyst Sarah James said.
Cigna's net income rose to $813 million, or $3.15 per share, in the second quarter ended June 30, from $510 million, or $1.97 per share, a year earlier.
Excluding items, the company earned $2.91 per share, ahead of analysts' estimate of $2.48, according to Thomson Reuters I/B/E/S.
Operating revenue rose to $10.27 billion from $9.89 billion, in line with estimates.
The company said it expects 2017 adjusted income from operations to be in the range of $9.75 to $10.05 per share, up from its previous forecast of $9.35 to $9.85.
Evercore ISI analyst Michael Newshel noted Cigna rounded out the health insurance earnings season with another big utilization-aided earnings beat, adding he expects the stock to be up on an overall strong quarter. (Reporting by Ankur Banerjee in Bengaluru; Editing by Shounak Dasgupta)